This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
regcomp.c: Add assertion
[perl5.git] / regcomp.c
index 548da6d..b8265a1 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -133,31 +133,40 @@ struct RExC_state_t {
     char       *start;                 /* Start of input for compile */
     char       *end;                   /* End of input for compile */
     char       *parse;                 /* Input-scan pointer. */
-    char        *adjusted_start;        /* 'start', adjusted.  See code use */
-    STRLEN      precomp_adj;            /* an offset beyond precomp.  See code use */
+    char        *copy_start;            /* start of copy of input within
+                                           constructed parse string */
+    char        *copy_start_in_input;   /* Position in input string
+                                           corresponding to copy_start */
     SSize_t    whilem_seen;            /* number of WHILEM in this expr */
     regnode    *emit_start;            /* Start of emitted-code area */
-    regnode    *emit_bound;            /* First regnode outside of the
-                                           allocated space */
-    regnode    *emit;                  /* Code-emit pointer; if = &emit_dummy,
-                                           implies compiling, so don't emit */
-    regnode_ssc        emit_dummy;             /* placeholder for emit to point to;
-                                           large enough for the largest
-                                           non-EXACTish node, so can use it as
-                                           scratch in pass1 */
+    regnode_offset emit;               /* Code-emit pointer */
     I32                naughty;                /* How bad is this pattern? */
     I32                sawback;                /* Did we see \1, ...? */
     U32                seen;
-    SSize_t    size;                   /* Code size. */
-    I32         npar;                   /* Capture buffer count, (OPEN) plus
-                                           one. ("par" 0 is the whole
-                                           pattern)*/
+    SSize_t    size;                   /* Number of regnode equivalents in
+                                           pattern */
+
+    /* position beyond 'precomp' of the warning message furthest away from
+     * 'precomp'.  During the parse, no warnings are raised for any problems
+     * earlier in the parse than this position.  This works if warnings are
+     * raised the first time a given spot is parsed, and if only one
+     * independent warning is raised for any given spot */
+    Size_t     latest_warn_offset;
+
+    I32         npar;                   /* Capture buffer count so far in the
+                                           parse, (OPEN) plus one. ("par" 0 is
+                                           the whole pattern)*/
+    I32         total_par;              /* During initial parse, is either 0,
+                                           or -1; the latter indicating a
+                                           reparse is needed.  After that pass,
+                                           it is what 'npar' became after the
+                                           pass.  Hence, it being > 0 indicates
+                                           we are in a reparse situation */
     I32                nestroot;               /* root parens we are in - used by
                                            accept */
-    I32                extralen;
     I32                seen_zerolen;
-    regnode    **open_parens;          /* pointers to open parens */
-    regnode    **close_parens;         /* pointers to close parens */
+    regnode_offset *open_parens;       /* offsets to open parens */
+    regnode_offset *close_parens;      /* offsets to close parens */
     regnode     *end_op;                /* END node in program */
     I32                utf8;           /* whether the pattern is utf8 or not */
     I32                orig_utf8;      /* whether the pattern was originally in utf8 */
@@ -169,7 +178,7 @@ struct RExC_state_t {
     HV         *paren_names;           /* Paren names */
 
     regnode    **recurse;              /* Recurse regops */
-    I32                recurse_count;                /* Number of recurse regops we have generated */
+    I32         recurse_count;          /* Number of recurse regops we have generated */
     U8          *study_chunk_recursed;  /* bitmap of which subs we have moved
                                            through */
     U32         study_chunk_recursed_bytes;  /* bytes in bitmap */
@@ -200,6 +209,7 @@ struct RExC_state_t {
     U32         study_chunk_recursed_count;
     SV          *mysv1;
     SV          *mysv2;
+
 #define RExC_lastparse (pRExC_state->lastparse)
 #define RExC_lastnum   (pRExC_state->lastnum)
 #define RExC_paren_name_list    (pRExC_state->paren_name_list)
@@ -213,13 +223,14 @@ struct RExC_state_t {
     bool        strict;
     bool        study_started;
     bool        in_script_run;
+    bool        use_BRANCHJ;
 };
 
 #define RExC_flags     (pRExC_state->flags)
 #define RExC_pm_flags  (pRExC_state->pm_flags)
 #define RExC_precomp   (pRExC_state->precomp)
-#define RExC_precomp_adj (pRExC_state->precomp_adj)
-#define RExC_adjusted_start  (pRExC_state->adjusted_start)
+#define RExC_copy_start_in_input (pRExC_state->copy_start_in_input)
+#define RExC_copy_start_in_constructed  (pRExC_state->copy_start)
 #define RExC_precomp_end (pRExC_state->precomp_end)
 #define RExC_rx_sv     (pRExC_state->rx_sv)
 #define RExC_rx                (pRExC_state->rx)
@@ -227,6 +238,7 @@ struct RExC_state_t {
 #define RExC_start     (pRExC_state->start)
 #define RExC_end       (pRExC_state->end)
 #define RExC_parse     (pRExC_state->parse)
+#define RExC_latest_warn_offset (pRExC_state->latest_warn_offset )
 #define RExC_whilem_seen       (pRExC_state->whilem_seen)
 
 /* Set during the sizing pass when there is a LATIN SMALL LETTER SHARP S in any
@@ -240,20 +252,18 @@ struct RExC_state_t {
 #define RExC_seen_unfolded_sharp_s (pRExC_state->seen_unfolded_sharp_s)
 
 #ifdef RE_TRACK_PATTERN_OFFSETS
-#define RExC_offsets   (pRExC_state->rxi->u.offsets) /* I am not like the
+#  define RExC_offsets (RExC_rxi->u.offsets) /* I am not like the
                                                          others */
 #endif
 #define RExC_emit      (pRExC_state->emit)
-#define RExC_emit_dummy        (pRExC_state->emit_dummy)
 #define RExC_emit_start        (pRExC_state->emit_start)
-#define RExC_emit_bound        (pRExC_state->emit_bound)
 #define RExC_sawback   (pRExC_state->sawback)
 #define RExC_seen      (pRExC_state->seen)
 #define RExC_size      (pRExC_state->size)
 #define RExC_maxlen        (pRExC_state->maxlen)
 #define RExC_npar      (pRExC_state->npar)
+#define RExC_total_parens      (pRExC_state->total_par)
 #define RExC_nestroot   (pRExC_state->nestroot)
-#define RExC_extralen  (pRExC_state->extralen)
 #define RExC_seen_zerolen      (pRExC_state->seen_zerolen)
 #define RExC_utf8      (pRExC_state->utf8)
 #define RExC_uni_semantics     (pRExC_state->uni_semantics)
@@ -280,6 +290,7 @@ struct RExC_state_t {
 #define RExC_study_started      (pRExC_state->study_started)
 #define RExC_warn_text (pRExC_state->warn_text)
 #define RExC_in_script_run      (pRExC_state->in_script_run)
+#define RExC_use_BRANCHJ        (pRExC_state->use_BRANCHJ)
 
 /* Heuristic check on the complexity of the pattern: if TOO_NAUGHTY, we set
  * a flag to disable back-off on the fixed/floating substrings - if it's
@@ -313,8 +324,8 @@ struct RExC_state_t {
 #define        SPSTART         0x04    /* Starts with * or + */
 #define POSTPONED      0x08    /* (?1),(?&name), (??{...}) or similar */
 #define TRYAGAIN       0x10    /* Weeded out a declaration. */
-#define RESTART_PASS1   0x20    /* Need to restart sizing pass */
-#define NEED_UTF8       0x40    /* In conjunction with RESTART_PASS1, need to
+#define RESTART_PARSE   0x20    /* Need to redo the parse */
+#define NEED_UTF8       0x40    /* In conjunction with RESTART_PARSE, need to
                                    calcuate sizes as UTF-8 */
 
 #define REG_NODE_NUM(x) ((x) ? (int)((x)-RExC_emit_start) : -1)
@@ -336,9 +347,8 @@ struct RExC_state_t {
 
 #define REQUIRE_UTF8(flagp) STMT_START {                                   \
                                      if (!UTF) {                           \
-                                         assert(PASS1);                    \
-                                         *flagp = RESTART_PASS1|NEED_UTF8; \
-                                         return NULL;                      \
+                                         *flagp = RESTART_PARSE|NEED_UTF8; \
+                                         return 0;                         \
                                      }                                     \
                              } STMT_END
 
@@ -349,43 +359,53 @@ struct RExC_state_t {
 #define REQUIRE_UNI_RULES(flagp, restart_retval)                            \
     STMT_START {                                                            \
             if (DEPENDS_SEMANTICS) {                                        \
-                assert(PASS1);                                              \
                 set_regex_charset(&RExC_flags, REGEX_UNICODE_CHARSET);      \
                 RExC_uni_semantics = 1;                                     \
-                if (RExC_seen_unfolded_sharp_s) {                           \
-                    *flagp |= RESTART_PASS1;                                \
+                    *flagp |= RESTART_PARSE;                                \
                     return restart_retval;                                  \
-                }                                                           \
             }                                                               \
     } STMT_END
 
+#define BRANCH_MAX_OFFSET   U16_MAX
+#define REQUIRE_BRANCHJ(flagp, restart_retval)                              \
+    STMT_START {                                                            \
+                RExC_use_BRANCHJ = 1;                                       \
+                *flagp |= RESTART_PARSE;                                    \
+                return restart_retval;                                      \
+    } STMT_END
+
+#define REQUIRE_PARENS_PASS                                                 \
+    STMT_START {                                                            \
+                    if (RExC_total_parens == 0) RExC_total_parens = -1;     \
+    } STMT_END
+
 /* Executes a return statement with the value 'X', if 'flags' contains any of
- * 'RESTART_PASS1', 'NEED_UTF8', or 'extra'.  If so, *flagp is set to those
+ * 'RESTART_PARSE', 'NEED_UTF8', or 'extra'.  If so, *flagp is set to those
  * flags */
 #define RETURN_X_ON_RESTART_OR_FLAGS(X, flags, flagp, extra)                \
     STMT_START {                                                            \
-            if ((flags) & (RESTART_PASS1|NEED_UTF8|(extra))) {              \
-                *(flagp) = (flags) & (RESTART_PASS1|NEED_UTF8|(extra));     \
+            if ((flags) & (RESTART_PARSE|NEED_UTF8|(extra))) {              \
+                *(flagp) = (flags) & (RESTART_PARSE|NEED_UTF8|(extra));     \
                 return X;                                                   \
             }                                                               \
     } STMT_END
 
-#define RETURN_NULL_ON_RESTART_OR_FLAGS(flags,flagp,extra)                  \
-                    RETURN_X_ON_RESTART_OR_FLAGS(NULL,flags,flagp,extra)
+#define RETURN_FAIL_ON_RESTART_OR_FLAGS(flags,flagp,extra)                  \
+                    RETURN_X_ON_RESTART_OR_FLAGS(0,flags,flagp,extra)
 
 #define RETURN_X_ON_RESTART(X, flags,flagp)                                 \
                         RETURN_X_ON_RESTART_OR_FLAGS( X, flags, flagp, 0)
 
 
-#define RETURN_NULL_ON_RESTART_FLAGP_OR_FLAGS(flagp,extra)                  \
-            if (*(flagp) & (RESTART_PASS1|(extra))) return NULL
+#define RETURN_FAIL_ON_RESTART_FLAGP_OR_FLAGS(flagp,extra)                  \
+            if (*(flagp) & (RESTART_PARSE|(extra))) return 0
 
-#define MUST_RESTART(flags) ((flags) & (RESTART_PASS1))
+#define MUST_RESTART(flags) ((flags) & (RESTART_PARSE))
 
-#define RETURN_NULL_ON_RESTART(flags,flagp)                                 \
-                                    RETURN_X_ON_RESTART(NULL, flags,flagp)
-#define RETURN_NULL_ON_RESTART_FLAGP(flagp)                                 \
-                            RETURN_NULL_ON_RESTART_FLAGP_OR_FLAGS(flagp,0)
+#define RETURN_FAIL_ON_RESTART(flags,flagp)                                 \
+                                    RETURN_X_ON_RESTART(0, flags,flagp)
+#define RETURN_FAIL_ON_RESTART_FLAGP(flagp)                                 \
+                            RETURN_FAIL_ON_RESTART_FLAGP_OR_FLAGS(flagp, 0)
 
 /* This converts the named class defined in regcomp.h to its equivalent class
  * number defined in handy.h. */
@@ -606,11 +626,11 @@ static const scan_data_t zero_scan_data = {
  * the form of something that is completely different from the input, or
  * something that uses the input as part of the alternate.  In the first case,
  * there should be no possibility of an error, as we are in complete control of
- * the alternate string.  But in the second case we don't control the input
- * portion, so there may be errors in that.  Here's an example:
+ * the alternate string.  But in the second case we don't completely control
+ * the input portion, so there may be errors in that.  Here's an example:
  *      /[abc\x{DF}def]/ui
  * is handled specially because \x{df} folds to a sequence of more than one
- * character, 'ss'.  What is done is to create and parse an alternate string,
+ * character: 'ss'.  What is done is to create and parse an alternate string,
  * which looks like this:
  *      /(?:\x{DF}|[abc\x{DF}def])/ui
  * where it uses the input unchanged in the middle of something it constructs,
@@ -619,60 +639,81 @@ static const scan_data_t zero_scan_data = {
  * class while in this substitute parse.) 'abc' and 'def' may have errors that
  * need to be reported.  The general situation looks like this:
  *
+ *                                       |<------- identical ------>|
  *              sI                       tI               xI       eI
- * Input:       ----------------------------------------------------
+ * Input:       ---------------------------------------------------------------
  * Constructed:         ---------------------------------------------------
  *                      sC               tC               xC       eC     EC
+ *                                       |<------- identical ------>|
  *
- * The input string sI..eI is the input pattern.  The string sC..EC is the
- * constructed substitute parse string.  The portions sC..tC and eC..EC are
- * constructed by us.  The portion tC..eC is an exact duplicate of the input
- * pattern tI..eI.  In the diagram, these are vertically aligned.  Suppose that
- * while parsing, we find an error at xC.  We want to display a message showing
- * the real input string.  Thus we need to find the point xI in it which
- * corresponds to xC.  xC >= tC, since the portion of the string sC..tC has
- * been constructed by us, and so shouldn't have errors.  We get:
- *
- *      xI = sI + (tI - sI) + (xC - tC)
+ * sI..eI   is the portion of the input pattern we are concerned with here.
+ * sC..EC   is the constructed substitute parse string.
+ *  sC..tC  is constructed by us
+ *  tC..eC  is an exact duplicate of the portion of the input pattern tI..eI.
+ *          In the diagram, these are vertically aligned.
+ *  eC..EC  is also constructed by us.
+ * xC       is the position in the substitute parse string where we found a
+ *          problem.
+ * xI       is the position in the original pattern corresponding to xC.
  *
- * and, the offset into sI is:
+ * We want to display a message showing the real input string.  Thus we need to
+ * translate from xC to xI.  We know that xC >= tC, since the portion of the
+ * string sC..tC has been constructed by us, and so shouldn't have errors.  We
+ * get:
+ *      xI = tI + (xC - tC)
  *
- *      (xI - sI) = (tI - sI) + (xC - tC)
+ * When the substitute parse is constructed, the code needs to set:
+ *      RExC_start (sC)
+ *      RExC_end (eC)
+ *      RExC_copy_start_in_input  (tI)
+ *      RExC_copy_start_in_constructed (tC)
+ * and restore them when done.
  *
- * When the substitute is constructed, we save (tI -sI) as RExC_precomp_adj,
- * and we save tC as RExC_adjusted_start.
- *
- * During normal processing of the input pattern, everything points to that,
- * with RExC_precomp_adj set to 0, and RExC_adjusted_start set to sI.
+ * During normal processing of the input pattern, both
+ * 'RExC_copy_start_in_input' and 'RExC_copy_start_in_constructed' are set to
+ * sI, so that xC equals xI.
  */
 
-#define tI_sI           RExC_precomp_adj
-#define tC              RExC_adjusted_start
-#define sC              RExC_precomp
-#define xI_offset(xC)   ((IV) (tI_sI + (xC - tC)))
-#define xI(xC)          (sC + xI_offset(xC))
-#define eC              RExC_precomp_end
+#define sI              RExC_precomp
+#define eI              RExC_precomp_end
+#define sC              RExC_start
+#define eC              RExC_end
+#define tI              RExC_copy_start_in_input
+#define tC              RExC_copy_start_in_constructed
+#define xI(xC)          (tI + (xC - tC))
+#define xI_offset(xC)   (xI(xC) - sI)
 
 #define REPORT_LOCATION_ARGS(xC)                                            \
     UTF8fARG(UTF,                                                           \
-             (xI(xC) > eC) /* Don't run off end */                          \
-              ? eC - sC   /* Length before the <--HERE */                   \
+             (xI(xC) > eI) /* Don't run off end */                          \
+              ? eI - sI   /* Length before the <--HERE */                   \
               : ((xI_offset(xC) >= 0)                                       \
                  ? xI_offset(xC)                                            \
                  : (Perl_croak(aTHX_ "panic: %s: %d: negative offset: %"    \
                                     IVdf " trying to output message for "   \
                                     " pattern %.*s",                        \
-                                    __FILE__, __LINE__, xI_offset(xC),      \
+                                    __FILE__, __LINE__, (IV) xI_offset(xC), \
                                     ((int) (eC - sC)), sC), 0)),            \
-             sC),         /* The input pattern printed up to the <--HERE */ \
+             sI),         /* The input pattern printed up to the <--HERE */ \
     UTF8fARG(UTF,                                                           \
-             (xI(xC) > eC) ? 0 : eC - xI(xC), /* Length after <--HERE */    \
-             (xI(xC) > eC) ? eC : xI(xC))     /* pattern after <--HERE */
+             (xI(xC) > eI) ? 0 : eI - xI(xC), /* Length after <--HERE */    \
+             (xI(xC) > eI) ? eI : xI(xC))     /* pattern after <--HERE */
 
 /* Used to point after bad bytes for an error message, but avoid skipping
  * past a nul byte. */
 #define SKIP_IF_CHAR(s) (!*(s) ? 0 : UTF ? UTF8SKIP(s) : 1)
 
+/* Set up to clean up after our imminent demise */
+#define PREPARE_TO_DIE                                                      \
+    STMT_START {                                                           \
+        if (RExC_rx_sv)                                                     \
+            SAVEFREESV(RExC_rx_sv);                                         \
+        if (RExC_open_parens)                                               \
+            SAVEFREEPV(RExC_open_parens);                                   \
+        if (RExC_close_parens)                                              \
+            SAVEFREEPV(RExC_close_parens);                                  \
+    } STMT_END
+
 /*
  * Calls SAVEDESTRUCTOR_X if needed, then calls Perl_croak with the given
  * arg. Show regex, up to a maximum length. If it's too long, chop and add
@@ -680,10 +721,9 @@ static const scan_data_t zero_scan_data = {
  */
 #define _FAIL(code) STMT_START {                                       \
     const char *ellipses = "";                                         \
-    IV len = RExC_precomp_end - RExC_precomp;                                  \
+    IV len = RExC_precomp_end - RExC_precomp;                          \
                                                                        \
-    if (!SIZE_ONLY)                                                    \
-       SAVEFREESV(RExC_rx_sv);                                         \
+    PREPARE_TO_DIE;                                                    \
     if (len > RegexLengthToShowInErrorMessages) {                      \
        /* chop 10 shorter than the max, to ensure meaning of "..." */  \
        len = RegexLengthToShowInErrorMessages - 10;                    \
@@ -712,8 +752,7 @@ static const scan_data_t zero_scan_data = {
  * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL()
  */
 #define        vFAIL(m) STMT_START {                           \
-    if (!SIZE_ONLY)                                    \
-       SAVEFREESV(RExC_rx_sv);                         \
+    PREPARE_TO_DIE;                                     \
     Simple_vFAIL(m);                                   \
 } STMT_END
 
@@ -729,8 +768,7 @@ static const scan_data_t zero_scan_data = {
  * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL2().
  */
 #define        vFAIL2(m,a1) STMT_START {                       \
-    if (!SIZE_ONLY)                                    \
-       SAVEFREESV(RExC_rx_sv);                         \
+    PREPARE_TO_DIE;                                     \
     Simple_vFAIL2(m, a1);                              \
 } STMT_END
 
@@ -747,8 +785,7 @@ static const scan_data_t zero_scan_data = {
  * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL3().
  */
 #define        vFAIL3(m,a1,a2) STMT_START {                    \
-    if (!SIZE_ONLY)                                    \
-       SAVEFREESV(RExC_rx_sv);                         \
+    PREPARE_TO_DIE;                                     \
     Simple_vFAIL3(m, a1, a2);                          \
 } STMT_END
 
@@ -761,115 +798,154 @@ static const scan_data_t zero_scan_data = {
 } STMT_END
 
 #define        vFAIL4(m,a1,a2,a3) STMT_START {                 \
-    if (!SIZE_ONLY)                                    \
-       SAVEFREESV(RExC_rx_sv);                         \
+    PREPARE_TO_DIE;                                     \
     Simple_vFAIL4(m, a1, a2, a3);                      \
 } STMT_END
 
 /* A specialized version of vFAIL2 that works with UTF8f */
 #define vFAIL2utf8f(m, a1) STMT_START {             \
-    if (!SIZE_ONLY)                                 \
-        SAVEFREESV(RExC_rx_sv);                     \
+    PREPARE_TO_DIE;                                 \
     S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1,  \
             REPORT_LOCATION_ARGS(RExC_parse));      \
 } STMT_END
 
 #define vFAIL3utf8f(m, a1, a2) STMT_START {             \
-    if (!SIZE_ONLY)                                     \
-        SAVEFREESV(RExC_rx_sv);                         \
+    PREPARE_TO_DIE;                                     \
     S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1, a2,  \
             REPORT_LOCATION_ARGS(RExC_parse));          \
 } STMT_END
 
-/* These have asserts in them because of [perl #122671] Many warnings in
- * regcomp.c can occur twice.  If they get output in pass1 and later in that
- * pass, the pattern has to be converted to UTF-8 and the pass restarted, they
- * would get output again.  So they should be output in pass2, and these
- * asserts make sure new warnings follow that paradigm. */
+/* Setting this to NULL is a signal to not output warnings */
+#define TURN_OFF_WARNINGS_IN_SUBSTITUTE_PARSE RExC_copy_start_in_constructed = NULL
+#define RESTORE_WARNINGS RExC_copy_start_in_constructed = RExC_precomp
+
+/* Since a warning can be generated multiple times as the input is reparsed, we
+ * output it the first time we come to that point in the parse, but suppress it
+ * otherwise.  'RExC_copy_start_in_constructed' being NULL is a flag to not
+ * generate any warnings */
+#define TO_OUTPUT_WARNINGS(loc)                                         \
+  (   RExC_copy_start_in_constructed                                    \
+   && ((xI(loc)) - RExC_precomp) > (Ptrdiff_t) RExC_latest_warn_offset)
+
+/* After we've emitted a warning, we save the position in the input so we don't
+ * output it again */
+#define UPDATE_WARNINGS_LOC(loc)                                        \
+    STMT_START {                                                        \
+        if (TO_OUTPUT_WARNINGS(loc)) {                                  \
+            RExC_latest_warn_offset = (xI(loc)) - RExC_precomp;         \
+        }                                                               \
+    } STMT_END
+
+/* 'warns' is the output of the packWARNx macro used in 'code' */
+#define _WARN_HELPER(loc, warns, code)                                  \
+    STMT_START {                                                        \
+        if (! RExC_copy_start_in_constructed) {                         \
+            Perl_croak( aTHX_ "panic! %s: %d: Tried to warn when none"  \
+                              " expected at '%s'",                      \
+                              __FILE__, __LINE__, loc);                 \
+        }                                                               \
+        if (TO_OUTPUT_WARNINGS(loc)) {                                  \
+            if (ckDEAD(warns))                                          \
+                PREPARE_TO_DIE;                                         \
+            code;                                                       \
+            UPDATE_WARNINGS_LOC(loc);                                   \
+        }                                                               \
+    } STMT_END
 
 /* m is not necessarily a "literal string", in this macro */
-#define reg_warn_non_literal_string(loc, m) STMT_START {                \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_REGEXP),           \
+#define reg_warn_non_literal_string(loc, m)                             \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_warner(aTHX_ packWARN(WARN_REGEXP),          \
                                        "%s" REPORT_LOCATION,            \
-                                  m, REPORT_LOCATION_ARGS(loc));        \
-} STMT_END
+                                  m, REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARNreg(loc,m) STMT_START {                                   \
-    __ASSERT_(PASS2) Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),        \
+#define        ckWARNreg(loc,m)                                                \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),       \
                                           m REPORT_LOCATION,           \
-                                         REPORT_LOCATION_ARGS(loc));   \
-} STMT_END
+                                         REPORT_LOCATION_ARGS(loc)))
 
-#define        vWARN(loc, m) STMT_START {                                      \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_REGEXP),           \
+#define        vWARN(loc, m)                                                   \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_warner(aTHX_ packWARN(WARN_REGEXP),          \
                                        m REPORT_LOCATION,               \
-                                       REPORT_LOCATION_ARGS(loc));      \
-} STMT_END
+                                       REPORT_LOCATION_ARGS(loc)))      \
 
-#define        vWARN_dep(loc, m) STMT_START {                                  \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_DEPRECATED),       \
+#define        vWARN_dep(loc, m)                                               \
+    _WARN_HELPER(loc, packWARN(WARN_DEPRECATED),                        \
+                      Perl_warner(aTHX_ packWARN(WARN_DEPRECATED),      \
                                        m REPORT_LOCATION,               \
-                                      REPORT_LOCATION_ARGS(loc));      \
-} STMT_END
+                                      REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARNdep(loc,m) STMT_START {                                   \
-    __ASSERT_(PASS2) Perl_ck_warner_d(aTHX_ packWARN(WARN_DEPRECATED),  \
+#define        ckWARNdep(loc,m)                                                \
+    _WARN_HELPER(loc, packWARN(WARN_DEPRECATED),                        \
+                      Perl_ck_warner_d(aTHX_ packWARN(WARN_DEPRECATED), \
                                            m REPORT_LOCATION,          \
-                                           REPORT_LOCATION_ARGS(loc)); \
-} STMT_END
+                                           REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARNregdep(loc,m) STMT_START {                                    \
-    __ASSERT_(PASS2) Perl_ck_warner_d(aTHX_ packWARN2(WARN_DEPRECATED,      \
+#define        ckWARNregdep(loc,m)                                                 \
+    _WARN_HELPER(loc, packWARN2(WARN_DEPRECATED, WARN_REGEXP),              \
+                      Perl_ck_warner_d(aTHX_ packWARN2(WARN_DEPRECATED,     \
                                                       WARN_REGEXP),         \
                                             m REPORT_LOCATION,             \
-                                            REPORT_LOCATION_ARGS(loc));    \
-} STMT_END
+                                            REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARN2reg_d(loc,m, a1) STMT_START {                                \
-    __ASSERT_(PASS2) Perl_ck_warner_d(aTHX_ packWARN(WARN_REGEXP),          \
+#define        ckWARN2reg_d(loc,m, a1)                                             \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                                \
+                      Perl_ck_warner_d(aTHX_ packWARN(WARN_REGEXP),         \
                                            m REPORT_LOCATION,              \
-                                           a1, REPORT_LOCATION_ARGS(loc)); \
-} STMT_END
+                                           a1, REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARN2reg(loc, m, a1) STMT_START {                                 \
-    __ASSERT_(PASS2) Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),            \
+#define        ckWARN2reg(loc, m, a1)                                              \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                                \
+                      Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),           \
                                           m REPORT_LOCATION,               \
-                                          a1, REPORT_LOCATION_ARGS(loc));   \
-} STMT_END
+                                          a1, REPORT_LOCATION_ARGS(loc)))
 
-#define        vWARN3(loc, m, a1, a2) STMT_START {                                 \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_REGEXP),               \
+#define        vWARN3(loc, m, a1, a2)                                              \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                                \
+                      Perl_warner(aTHX_ packWARN(WARN_REGEXP),              \
                                        m REPORT_LOCATION,                   \
-                                      a1, a2, REPORT_LOCATION_ARGS(loc));  \
-} STMT_END
+                                      a1, a2, REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARN3reg(loc, m, a1, a2) STMT_START {                             \
-    __ASSERT_(PASS2) Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),            \
+#define        ckWARN3reg(loc, m, a1, a2)                                          \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                                \
+                      Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),           \
                                           m REPORT_LOCATION,                \
                                          a1, a2,                           \
-                                          REPORT_LOCATION_ARGS(loc));       \
-} STMT_END
+                                          REPORT_LOCATION_ARGS(loc)))
 
-#define        vWARN4(loc, m, a1, a2, a3) STMT_START {                         \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_REGEXP),           \
+#define        vWARN4(loc, m, a1, a2, a3)                                      \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_warner(aTHX_ packWARN(WARN_REGEXP),          \
                                        m REPORT_LOCATION,               \
                                       a1, a2, a3,                      \
-                                       REPORT_LOCATION_ARGS(loc));      \
-} STMT_END
+                                       REPORT_LOCATION_ARGS(loc)))
 
-#define        ckWARN4reg(loc, m, a1, a2, a3) STMT_START {                     \
-    __ASSERT_(PASS2) Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),        \
+#define        ckWARN4reg(loc, m, a1, a2, a3)                                  \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),       \
                                           m REPORT_LOCATION,            \
                                          a1, a2, a3,                   \
-                                          REPORT_LOCATION_ARGS(loc));   \
-} STMT_END
+                                          REPORT_LOCATION_ARGS(loc)))
 
-#define        vWARN5(loc, m, a1, a2, a3, a4) STMT_START {                     \
-    __ASSERT_(PASS2) Perl_warner(aTHX_ packWARN(WARN_REGEXP),           \
+#define        vWARN5(loc, m, a1, a2, a3, a4)                                  \
+    _WARN_HELPER(loc, packWARN(WARN_REGEXP),                            \
+                      Perl_warner(aTHX_ packWARN(WARN_REGEXP),          \
                                        m REPORT_LOCATION,              \
                                       a1, a2, a3, a4,                  \
-                                       REPORT_LOCATION_ARGS(loc));      \
-} STMT_END
+                                       REPORT_LOCATION_ARGS(loc)))
+
+#define        ckWARNexperimental(loc, class, m)                               \
+    _WARN_HELPER(loc, packWARN(class),                                  \
+                      Perl_ck_warner_d(aTHX_ packWARN(class),           \
+                                            m REPORT_LOCATION,          \
+                                            REPORT_LOCATION_ARGS(loc)))
+
+/* Convert between a pointer to a node and its offset from the beginning of the
+ * program */
+#define REGNODE_p(offset)    (RExC_emit_start + (offset))
+#define REGNODE_OFFSET(node) ((node) - RExC_emit_start)
 
 /* Macros for recording node offsets.   20001227 mjd@plover.com
  * Nodes are numbered 1, 2, 3, 4.  Node #n's position is recorded in
@@ -878,7 +954,7 @@ static const scan_data_t zero_scan_data = {
  * Position is 1 indexed.
  */
 #ifndef RE_TRACK_PATTERN_OFFSETS
-#define Set_Node_Offset_To_R(node,byte)
+#define Set_Node_Offset_To_R(offset,byte)
 #define Set_Node_Offset(node,byte)
 #define Set_Cur_Node_Offset
 #define Set_Node_Length_To_R(node,len)
@@ -889,28 +965,26 @@ static const scan_data_t zero_scan_data = {
 #define Set_Node_Offset_Length(node,offset,len)
 #define ProgLen(ri) ri->u.proglen
 #define SetProgLen(ri,x) ri->u.proglen = x
+#define Track_Code(code)
 #else
 #define ProgLen(ri) ri->u.offsets[0]
 #define SetProgLen(ri,x) ri->u.offsets[0] = x
-#define Set_Node_Offset_To_R(node,byte) STMT_START {                   \
-    if (! SIZE_ONLY) {                                                 \
+#define Set_Node_Offset_To_R(offset,byte) STMT_START {                 \
        MJD_OFFSET_DEBUG(("** (%d) offset of node %d is %d.\n",         \
-                   __LINE__, (int)(node), (int)(byte)));               \
-       if((node) < 0) {                                                \
+                   __LINE__, (int)(offset), (int)(byte)));             \
+       if((offset) < 0) {                                              \
            Perl_croak(aTHX_ "value of node is %d in Offset macro",     \
-                                         (int)(node));                  \
+                                         (int)(offset));                \
        } else {                                                        \
-           RExC_offsets[2*(node)-1] = (byte);                          \
+            RExC_offsets[2*(offset)-1] = (byte);                       \
        }                                                               \
-    }                                                                  \
 } STMT_END
 
-#define Set_Node_Offset(node,byte) \
-    Set_Node_Offset_To_R((node)-RExC_emit_start, (byte)-RExC_start)
+#define Set_Node_Offset(node,byte)                                      \
+    Set_Node_Offset_To_R(REGNODE_OFFSET(node), (byte)-RExC_start)
 #define Set_Cur_Node_Offset Set_Node_Offset(RExC_emit, RExC_parse)
 
 #define Set_Node_Length_To_R(node,len) STMT_START {                    \
-    if (! SIZE_ONLY) {                                                 \
        MJD_OFFSET_DEBUG(("** (%d) size of node %d is %d.\n",           \
                __LINE__, (int)(node), (int)(len)));                    \
        if((node) < 0) {                                                \
@@ -919,22 +993,23 @@ static const scan_data_t zero_scan_data = {
        } else {                                                        \
            RExC_offsets[2*(node)] = (len);                             \
        }                                                               \
-    }                                                                  \
 } STMT_END
 
 #define Set_Node_Length(node,len) \
-    Set_Node_Length_To_R((node)-RExC_emit_start, len)
+    Set_Node_Length_To_R(REGNODE_OFFSET(node), len)
 #define Set_Node_Cur_Length(node, start)                \
     Set_Node_Length(node, RExC_parse - start)
 
 /* Get offsets and lengths */
-#define Node_Offset(n) (RExC_offsets[2*((n)-RExC_emit_start)-1])
-#define Node_Length(n) (RExC_offsets[2*((n)-RExC_emit_start)])
+#define Node_Offset(n) (RExC_offsets[2*(REGNODE_OFFSET(n))-1])
+#define Node_Length(n) (RExC_offsets[2*(REGNODE_OFFSET(n))])
 
 #define Set_Node_Offset_Length(node,offset,len) STMT_START {   \
-    Set_Node_Offset_To_R((node)-RExC_emit_start, (offset));    \
-    Set_Node_Length_To_R((node)-RExC_emit_start, (len));       \
+    Set_Node_Offset_To_R(REGNODE_OFFSET(node), (offset));      \
+    Set_Node_Length_To_R(REGNODE_OFFSET(node), (len)); \
 } STMT_END
+
+#define Track_Code(code) STMT_START { code } STMT_END
 #endif
 
 #if PERL_ENABLE_EXPERIMENTAL_REGEX_OPTIMISATIONS
@@ -972,39 +1047,39 @@ Perl_re_indentf(pTHX_ const char *fmt, U32 depth, ...)
 
 #define DEBUG_RExC_seen()                                                   \
         DEBUG_OPTIMISE_MORE_r({                                             \
-            Perl_re_printf( aTHX_ "RExC_seen: ");                                       \
+            Perl_re_printf( aTHX_ "RExC_seen: ");                           \
                                                                             \
             if (RExC_seen & REG_ZERO_LEN_SEEN)                              \
-                Perl_re_printf( aTHX_ "REG_ZERO_LEN_SEEN ");                            \
+                Perl_re_printf( aTHX_ "REG_ZERO_LEN_SEEN ");                \
                                                                             \
             if (RExC_seen & REG_LOOKBEHIND_SEEN)                            \
-                Perl_re_printf( aTHX_ "REG_LOOKBEHIND_SEEN ");                          \
+                Perl_re_printf( aTHX_ "REG_LOOKBEHIND_SEEN ");              \
                                                                             \
             if (RExC_seen & REG_GPOS_SEEN)                                  \
-                Perl_re_printf( aTHX_ "REG_GPOS_SEEN ");                                \
+                Perl_re_printf( aTHX_ "REG_GPOS_SEEN ");                    \
                                                                             \
             if (RExC_seen & REG_RECURSE_SEEN)                               \
-                Perl_re_printf( aTHX_ "REG_RECURSE_SEEN ");                             \
+                Perl_re_printf( aTHX_ "REG_RECURSE_SEEN ");                 \
                                                                             \
             if (RExC_seen & REG_TOP_LEVEL_BRANCHES_SEEN)                    \
-                Perl_re_printf( aTHX_ "REG_TOP_LEVEL_BRANCHES_SEEN ");                  \
+                Perl_re_printf( aTHX_ "REG_TOP_LEVEL_BRANCHES_SEEN ");      \
                                                                             \
             if (RExC_seen & REG_VERBARG_SEEN)                               \
-                Perl_re_printf( aTHX_ "REG_VERBARG_SEEN ");                             \
+                Perl_re_printf( aTHX_ "REG_VERBARG_SEEN ");                 \
                                                                             \
             if (RExC_seen & REG_CUTGROUP_SEEN)                              \
-                Perl_re_printf( aTHX_ "REG_CUTGROUP_SEEN ");                            \
+                Perl_re_printf( aTHX_ "REG_CUTGROUP_SEEN ");                \
                                                                             \
             if (RExC_seen & REG_RUN_ON_COMMENT_SEEN)                        \
-                Perl_re_printf( aTHX_ "REG_RUN_ON_COMMENT_SEEN ");                      \
+                Perl_re_printf( aTHX_ "REG_RUN_ON_COMMENT_SEEN ");          \
                                                                             \
             if (RExC_seen & REG_UNFOLDED_MULTI_SEEN)                        \
-                Perl_re_printf( aTHX_ "REG_UNFOLDED_MULTI_SEEN ");                      \
+                Perl_re_printf( aTHX_ "REG_UNFOLDED_MULTI_SEEN ");          \
                                                                             \
             if (RExC_seen & REG_UNBOUNDED_QUANTIFIER_SEEN)                  \
-                Perl_re_printf( aTHX_ "REG_UNBOUNDED_QUANTIFIER_SEEN ");                \
+                Perl_re_printf( aTHX_ "REG_UNBOUNDED_QUANTIFIER_SEEN ");    \
                                                                             \
-            Perl_re_printf( aTHX_ "\n");                                                \
+            Perl_re_printf( aTHX_ "\n");                                    \
         });
 
 #define DEBUG_SHOW_STUDY_FLAG(flags,flag) \
@@ -1150,7 +1225,7 @@ typedef struct dictionary item;
 
 
 PERL_STATIC_INLINE item*
-push(UV key,item* curr)
+push(UV key, item* curr)
 {
     item* head;
     Newx(head, 1, item);
@@ -1176,7 +1251,7 @@ find(item* head, UV key)
 }
 
 PERL_STATIC_INLINE item*
-uniquePush(item* head,UV key)
+uniquePush(item* head, UV key)
 {
     item* iterator = head;
 
@@ -1187,7 +1262,7 @@ uniquePush(item* head,UV key)
         iterator = iterator->next;
     }
 
-    return push(key,head);
+    return push(key, head);
 }
 
 PERL_STATIC_INLINE void
@@ -1216,7 +1291,7 @@ S_edit_distance(const UV* src,
 )
 {
     item *head = NULL;
-    UV swapCount,swapScore,targetCharCount,i,j;
+    UV swapCount, swapScore, targetCharCount, i, j;
     UV *scores;
     UV score_ceil = x + y;
 
@@ -1228,14 +1303,14 @@ S_edit_distance(const UV* src,
     scores[1 * (y + 2) + 0] = score_ceil;
     scores[0 * (y + 2) + 1] = score_ceil;
     scores[1 * (y + 2) + 1] = 0;
-    head = uniquePush(uniquePush(head,src[0]),tgt[0]);
+    head = uniquePush(uniquePush(head, src[0]), tgt[0]);
 
     /* work loops    */
     /* i = src index */
     /* j = tgt index */
     for (i=1;i<=x;i++) {
         if (i < x)
-            head = uniquePush(head,src[i]);
+            head = uniquePush(head, src[i]);
         scores[(i+1) * (y + 2) + 1] = i;
         scores[(i+1) * (y + 2) + 0] = score_ceil;
         swapCount = 0;
@@ -1243,12 +1318,12 @@ S_edit_distance(const UV* src,
         for (j=1;j<=y;j++) {
             if (i == 1) {
                 if(j < y)
-                head = uniquePush(head,tgt[j]);
+                head = uniquePush(head, tgt[j]);
                 scores[1 * (y + 2) + (j + 1)] = j;
                 scores[0 * (y + 2) + (j + 1)] = score_ceil;
             }
 
-            targetCharCount = find(head,tgt[j-1])->value;
+            targetCharCount = find(head, tgt[j-1])->value;
             swapScore = scores[targetCharCount * (y + 2) + swapCount] + i - targetCharCount - 1 + j - swapCount;
 
             if (src[i-1] != tgt[j-1]){
@@ -1260,7 +1335,7 @@ S_edit_distance(const UV* src,
             }
         }
 
-        find(head,src[i-1])->value = i;
+        find(head, src[i-1])->value = i;
     }
 
     {
@@ -1500,7 +1575,7 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
         assert(RExC_rxi->data->what[n] == 's');
 
         if (ary[1] && ary[1] != &PL_sv_undef) { /* Has compile-time swash */
-            invlist = sv_2mortal(invlist_clone(_get_swash_invlist(ary[1])));
+            invlist = sv_2mortal(invlist_clone(_get_swash_invlist(ary[1]), NULL));
         }
         else if (ary[0] && ary[0] != &PL_sv_undef) {
 
@@ -1513,7 +1588,7 @@ S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
 
             /* Here no compile-time swash, and no run-time only data.  Use the
              * node's inversion list */
-            invlist = sv_2mortal(invlist_clone(ary[3]));
+            invlist = sv_2mortal(invlist_clone(ary[3], NULL));
         }
 
         /* Get the code points valid only under UTF-8 locales */
@@ -2002,7 +2077,7 @@ S_ssc_finalize(pTHX_ RExC_state_t *pRExC_state, regnode_ssc *ssc)
      * ANYOF node, with the first NUM_ANYOF_CODE_POINTS code points in a bit
      * map */
 
-    SV* invlist = invlist_clone(ssc->invlist);
+    SV* invlist = invlist_clone(ssc->invlist, NULL);
 
     PERL_ARGS_ASSERT_SSC_FINALIZE;
 
@@ -2026,9 +2101,9 @@ S_ssc_finalize(pTHX_ RExC_state_t *pRExC_state, regnode_ssc *ssc)
 
     if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
         ANYOF_FLAGS(ssc) |= ANYOF_MATCHES_POSIXL;
+        OP(ssc) = ANYOFPOSIXL;
     }
-
-    if (RExC_contains_locale) {
+    else if (RExC_contains_locale) {
         OP(ssc) = ANYOFL;
     }
 
@@ -2134,7 +2209,7 @@ S_dump_trie(pTHX_ const struct _reg_trie_data *trie, HV *widecharmap,
                     (UV)trie->trans[ base + ofs - trie->uniquecharcount ].next
                    );
                 } else {
-                    Perl_re_printf( aTHX_  "%*s",colwidth,"   ." );
+                    Perl_re_printf( aTHX_  "%*s", colwidth,"   ." );
                 }
             }
 
@@ -2190,7 +2265,7 @@ S_dump_trie_interim_list(pTHX_ const struct _reg_trie_data *trie,
         }
         for( charid = 1 ; charid <= TRIE_LIST_USED( state ) ; charid++ ) {
            SV ** const tmp = av_fetch( revcharmap,
-                                        TRIE_LIST_ITEM(state,charid).forid, 0);
+                                        TRIE_LIST_ITEM(state, charid).forid, 0);
            if ( tmp ) {
                 Perl_re_printf( aTHX_  "%*s:%3X=%4" UVXf " | ",
                     colwidth,
@@ -2200,8 +2275,8 @@ S_dump_trie_interim_list(pTHX_ const struct _reg_trie_data *trie,
                               (SvUTF8(*tmp) ? PERL_PV_ESCAPE_UNI : 0)
                               | PERL_PV_ESCAPE_FIRSTCHAR
                     ) ,
-                    TRIE_LIST_ITEM(state,charid).forid,
-                    (UV)TRIE_LIST_ITEM(state,charid).newstate
+                    TRIE_LIST_ITEM(state, charid).forid,
+                    (UV)TRIE_LIST_ITEM(state, charid).newstate
                 );
                 if (!(charid % 10))
                     Perl_re_printf( aTHX_  "\n%*s| ",
@@ -2612,7 +2687,7 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
         Perl_re_indentf( aTHX_
           "make_trie start==%d, first==%d, last==%d, tail==%d depth=%d\n",
           depth+1,
-          REG_NODE_NUM(startbranch),REG_NODE_NUM(first),
+          REG_NODE_NUM(startbranch), REG_NODE_NUM(first),
           REG_NODE_NUM(last), REG_NODE_NUM(tail), (int)depth);
     });
 
@@ -3387,14 +3462,14 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                                     SV ** const tmp = av_fetch( revcharmap, first_ofs, 0);
                                    const U8 * const ch = (U8*)SvPV_nolen_const( *tmp );
 
-                                    TRIE_BITMAP_SET_FOLDED(trie,*ch,folder);
+                                    TRIE_BITMAP_SET_FOLDED(trie,*ch, folder);
                                     DEBUG_OPTIMISE_r(
                                         Perl_re_printf( aTHX_  "%s", (char*)ch)
                                     );
                                }
                            }
                             /* store the current firstchar in the bitmap */
-                            TRIE_BITMAP_SET_FOLDED(trie,*ch,folder);
+                            TRIE_BITMAP_SET_FOLDED(trie,*ch, folder);
                             DEBUG_OPTIMISE_r(Perl_re_printf( aTHX_ "%s", ch));
                        }
                         first_ofs = ofs;
@@ -3455,7 +3530,9 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
                    ) {
                    regnode *fix = convert;
                    U32 word = trie->wordcount;
+#ifdef RE_TRACK_PATTERN_OFFSETS
                    mjd_nodelen++;
+#endif
                    Set_Node_Offset_Length(convert, mjd_offset, state - 1);
                    while( ++fix < n ) {
                        Set_Node_Offset_Length(fix, 0, 0);
@@ -3522,19 +3599,19 @@ S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
             regnode *opt = convert;
 
             while ( ++opt < optimize) {
-                Set_Node_Offset_Length(opt,0,0);
+                Set_Node_Offset_Length(opt, 0, 0);
             }
             /*
                 Try to clean up some of the debris left after the
                 optimisation.
              */
             while( optimize < jumper ) {
-                mjd_nodelen += Node_Length((optimize));
+                Track_Code( mjd_nodelen += Node_Length((optimize)); );
                 OP( optimize ) = OPTIMIZED;
-                Set_Node_Offset_Length(optimize,0,0);
+                Set_Node_Offset_Length(optimize, 0, 0);
                 optimize++;
             }
-            Set_Node_Offset_Length(convert,mjd_offset,mjd_nodelen);
+            Set_Node_Offset_Length(convert, mjd_offset, mjd_nodelen);
         });
     } /* end node insert */
 
@@ -3638,12 +3715,12 @@ S_construct_ahocorasick_from_trie(pTHX_ RExC_state_t *pRExC_state, regnode *sour
     if ( OP(source) == TRIE ) {
         struct regnode_1 *op = (struct regnode_1 *)
             PerlMemShared_calloc(1, sizeof(struct regnode_1));
-        StructCopy(source,op,struct regnode_1);
+        StructCopy(source, op, struct regnode_1);
         stclass = (regnode *)op;
     } else {
         struct regnode_charclass *op = (struct regnode_charclass *)
             PerlMemShared_calloc(1, sizeof(struct regnode_charclass));
-        StructCopy(source,op,struct regnode_charclass);
+        StructCopy(source, op, struct regnode_charclass);
         stclass = (regnode *)op;
     }
     OP(stclass)+=2; /* convert the TRIE type to its AHO-CORASICK equivalent */
@@ -3844,12 +3921,12 @@ S_construct_ahocorasick_from_trie(pTHX_ RExC_state_t *pRExC_state, regnode *sour
 
 #define JOIN_EXACT(scan,min_subtract,unfolded_multi_char, flags) \
     if (PL_regkind[OP(scan)] == EXACT) \
-        join_exact(pRExC_state,(scan),(min_subtract),unfolded_multi_char, (flags),NULL,depth+1)
+        join_exact(pRExC_state,(scan),(min_subtract),unfolded_multi_char, (flags), NULL, depth+1)
 
 STATIC U32
 S_join_exact(pTHX_ RExC_state_t *pRExC_state, regnode *scan,
                    UV *min_subtract, bool *unfolded_multi_char,
-                   U32 flags,regnode *val, U32 depth)
+                   U32 flags, regnode *val, U32 depth)
 {
     /* Merge several consecutive EXACTish nodes into one. */
     regnode *n = regnext(scan);
@@ -4163,7 +4240,7 @@ S_join_exact(pTHX_ RExC_state_t *pRExC_state, regnode *scan,
 
 #define INIT_AND_WITHP \
     assert(!and_withp); \
-    Newx(and_withp,1, regnode_ssc); \
+    Newx(and_withp, 1, regnode_ssc); \
     SAVEFREEPV(and_withp)
 
 
@@ -4238,7 +4315,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
             U32 i;
             U32 j;
             for ( j = 0 ; j < recursed_depth ; j++ ) {
-                for ( i = 0 ; i < (U32)RExC_npar ; i++ ) {
+                for ( i = 0 ; i < (U32)RExC_total_parens ; i++ ) {
                     if (
                         PAREN_TEST(RExC_study_chunk_recursed +
                                    ( j * RExC_study_chunk_recursed_bytes), i )
@@ -4393,7 +4470,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                     /* recurse study_chunk() for each BRANCH in an alternation */
                    minnext = study_chunk(pRExC_state, &scan, minlenp,
                                       &deltanext, next, &data_fake, stopparen,
-                                      recursed_depth, NULL, f,depth+1);
+                                      recursed_depth, NULL, f, depth+1);
 
                    if (min1 > minnext)
                        min1 = minnext;
@@ -4539,7 +4616,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                             Perl_re_indentf( aTHX_  "%s %" UVuf ":%s\n",
                               depth+1,
                               "Looking for TRIE'able sequences. Tail node is ",
-                              (UV)(tail - RExC_emit_start),
+                              (UV) REGNODE_OFFSET(tail),
                               SvPV_nolen_const( RExC_mysv )
                             );
                         });
@@ -4738,7 +4815,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                         DEBUG_TRIE_COMPILE_r({
                             regprop(RExC_rx, RExC_mysv, cur, NULL, pRExC_state);
                             Perl_re_indentf( aTHX_  "- %s (%d) <SCAN FINISHED> ",
-                              depth+1, SvPV_nolen_const( RExC_mysv ),REG_NODE_NUM(cur));
+                              depth+1, SvPV_nolen_const( RExC_mysv ), REG_NODE_NUM(cur));
                             Perl_re_printf( aTHX_  "(First==%d, Last==%d, Cur==%d, tt==%s)\n",
                                REG_NODE_NUM(first), REG_NODE_NUM(last), REG_NODE_NUM(cur),
                                PL_reg_name[trietype]
@@ -4781,7 +4858,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                                         regprop(RExC_rx, RExC_mysv, cur, NULL, pRExC_state);
                                         Perl_re_indentf( aTHX_  "- %s (%d) <NOTHING BRANCH SEQUENCE>\n",
                                           depth+1,
-                                          SvPV_nolen_const( RExC_mysv ),REG_NODE_NUM(cur));
+                                          SvPV_nolen_const( RExC_mysv ), REG_NODE_NUM(cur));
 
                                     });
                                     OP(startbranch)= NOTHING;
@@ -4814,8 +4891,8 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                  * study_chunk(). */
                 paren = ARG(scan);
                 RExC_recurse[ARG2L(scan)] = scan;
-                start = RExC_open_parens[paren];
-                end   = RExC_close_parens[paren];
+                start = REGNODE_p(RExC_open_parens[paren]);
+                end   = REGNODE_p(RExC_close_parens[paren]);
 
                 /* NOTE we MUST always execute the above code, even
                  * if we do nothing with a GOSUB */
@@ -4899,7 +4976,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                     RExC_frame_head= newframe;
                     RExC_frame_count++;
                 } else if (!RExC_frame_last->next_frame) {
-                    Newxz(newframe,1,scan_frame);
+                    Newxz(newframe, 1, scan_frame);
                     RExC_frame_last->next_frame= newframe;
                     newframe->prev_frame= RExC_frame_last;
                     RExC_frame_count++;
@@ -5171,15 +5248,13 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                     && maxcount <= REG_INFTY/3) /* Complement check for big
                                                    count */
                {
-                   /* Fatal warnings may leak the regexp without this: */
-                   SAVEFREESV(RExC_rx_sv);
-                   Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),
-                       "Quantifier unexpected on zero-length expression "
-                       "in regex m/%" UTF8f "/",
-                        UTF8fARG(UTF, RExC_precomp_end - RExC_precomp,
-                                 RExC_precomp));
-                   (void)ReREFCNT_inc(RExC_rx_sv);
-               }
+                   _WARN_HELPER(RExC_precomp_end, packWARN(WARN_REGEXP),
+                        Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP),
+                            "Quantifier unexpected on zero-length expression "
+                            "in regex m/%" UTF8f "/",
+                            UTF8fARG(UTF, RExC_precomp_end - RExC_precomp,
+                                 RExC_precomp)));
+                }
 
                min += minnext * mincount;
                is_inf_internal |= deltanext == SSize_t_MAX
@@ -5216,8 +5291,12 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                    if (OP(nxt) != CLOSE)
                        goto nogo;
                    if (RExC_open_parens) {
-                        RExC_open_parens[ARG(nxt1)]=oscan; /*open->CURLYM*/
-                        RExC_close_parens[ARG(nxt1)]=nxt+2; /*close->while*/
+
+                        /*open->CURLYM*/
+                        RExC_open_parens[ARG(nxt1)] = REGNODE_OFFSET(oscan);
+
+                        /*close->while*/
+                        RExC_close_parens[ARG(nxt1)] = REGNODE_OFFSET(nxt) + 2;
                    }
                    /* Now we know that nxt2 is the only contents: */
                    oscan->flags = (U8)ARG(nxt);
@@ -5263,8 +5342,12 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
 
                        oscan->flags = (U8)ARG(nxt);
                        if (RExC_open_parens) {
-                            RExC_open_parens[ARG(nxt1)]=oscan; /*open->CURLYM*/
-                            RExC_close_parens[ARG(nxt1)]=nxt2+1; /*close->NOTHING*/
+                             /*open->CURLYM*/
+                            RExC_open_parens[ARG(nxt1)] = REGNODE_OFFSET(oscan);
+
+                            /*close->NOTHING*/
+                            RExC_close_parens[ARG(nxt1)] = REGNODE_OFFSET(nxt2)
+                                                         + 1;
                        }
                        OP(nxt1) = OPTIMIZED;   /* was OPEN. */
                        OP(nxt) = OPTIMIZED;    /* was CLOSE. */
@@ -5292,7 +5375,8 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                        /* Optimize again: */
                         /* recurse study_chunk() on optimised CURLYX => CURLYM */
                        study_chunk(pRExC_state, &nxt1, minlenp, &deltanext, nxt,
-                                    NULL, stopparen, recursed_depth, NULL, 0,depth+1);
+                                    NULL, stopparen, recursed_depth, NULL, 0,
+                                    depth+1);
                    }
                    else
                        oscan->flags = 0;
@@ -5542,6 +5626,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
 
                 case ANYOFD:
                 case ANYOFL:
+                case ANYOFPOSIXL:
                 case ANYOF:
                    if (flags & SCF_DO_STCLASS_AND)
                        ssc_and(pRExC_state, data->start_class,
@@ -5616,7 +5701,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                     invert = 1;
                     /* FALLTHROUGH */
                case ASCII:
-                    my_invlist = invlist_clone(PL_Posix_ptrs[_CC_ASCII]);
+                    my_invlist = invlist_clone(PL_Posix_ptrs[_CC_ASCII], NULL);
 
                     /* This can be handled as a Posix class */
                     goto join_posix_and_ascii;
@@ -5627,7 +5712,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                     /* FALLTHROUGH */
                case POSIXA:
                     assert(FLAGS(scan) != _CC_ASCII);
-                    my_invlist = invlist_clone(PL_Posix_ptrs[FLAGS(scan)]);
+                    my_invlist = invlist_clone(PL_Posix_ptrs[FLAGS(scan)], NULL);
                     goto join_posix_and_ascii;
 
                case NPOSIXD:
@@ -5636,7 +5721,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                     /* FALLTHROUGH */
                case POSIXD:
                case POSIXU:
-                    my_invlist = invlist_clone(PL_XPosix_ptrs[FLAGS(scan)]);
+                    my_invlist = invlist_clone(PL_XPosix_ptrs[FLAGS(scan)], NULL);
 
                     /* NPOSIXD matches all upper Latin1 code points unless the
                      * target string being matched is UTF-8, which is
@@ -5803,7 +5888,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                 *minnextp = study_chunk(pRExC_state, &nscan, minnextp,
                                         &deltanext, last, &data_fake,
                                         stopparen, recursed_depth, NULL,
-                                        f,depth+1);
+                                        f, depth+1);
                 if (scan->flags) {
                     if (deltanext) {
                        FAIL("Variable length lookbehind not implemented");
@@ -5964,7 +6049,7 @@ Perl_re_printf( aTHX_  "LHS=%" UVuf " RHS=%" UVuf "\n",
                         /* optimise study_chunk() for TRIE */
                         minnext = study_chunk(pRExC_state, &scan, minlenp,
                             &deltanext, (regnode *)nextbranch, &data_fake,
-                            stopparen, recursed_depth, NULL, f,depth+1);
+                            stopparen, recursed_depth, NULL, f, depth+1);
                     }
                     if (nextbranch && PL_regkind[OP(nextbranch)]==BRANCH)
                         nextbranch= regnext((regnode*)nextbranch);
@@ -6204,7 +6289,7 @@ Perl_current_re_engine(pTHX)
        ptr = hv_fetchs(table, "regcomp", FALSE);
        if ( !(ptr && SvIOK(*ptr) && SvIV(*ptr)))
            return &PL_core_reg_engine;
-       return INT2PTR(regexp_engine*,SvIV(*ptr));
+       return INT2PTR(regexp_engine*, SvIV(*ptr));
     }
     else {
        SV *ptr;
@@ -6213,7 +6298,7 @@ Perl_current_re_engine(pTHX)
        ptr = cop_hints_fetch_pvs(PL_curcop, "regcomp", 0);
        if ( !(ptr && SvIOK(ptr) && SvIV(ptr)))
            return &PL_core_reg_engine;
-       return INT2PTR(regexp_engine*,SvIV(ptr));
+       return INT2PTR(regexp_engine*, SvIV(ptr));
     }
 }
 
@@ -6264,8 +6349,10 @@ S_free_codeblocks(pTHX_ struct reg_code_blocks *cbs)
         return;
     for (n = 0; n < cbs->count; n++) {
         REGEXP *rx = cbs->cb[n].src_regex;
-        cbs->cb[n].src_regex = NULL;
-        SvREFCNT_dec(rx);
+        if (rx) {
+            cbs->cb[n].src_regex = NULL;
+            SvREFCNT_dec_NN(rx);
+        }
     }
     Safefree(cbs->cb);
     Safefree(cbs);
@@ -6309,7 +6396,8 @@ S_pat_upgrade_to_utf8(pTHX_ RExC_state_t * const pRExC_state,
     DEBUG_PARSE_r(Perl_re_printf( aTHX_
         "UTF8 mismatch! Converting to utf8 for resizing and compile\n"));
 
-    Newx(dst, *plen_p * 2 + 1, U8);
+    /* 1 for each byte + 1 for each byte that expands to two, + trailing NUL */
+    Newx(dst, *plen_p + variant_under_utf8_count(src, src + *plen_p) + 1, U8);
     d = dst;
 
     while (s < *plen_p) {
@@ -6591,7 +6679,7 @@ S_has_runtime_code(pTHX_ RExC_state_t * const pRExC_state,
 {
     int n = 0;
     STRLEN s;
-    
+
     PERL_UNUSED_CONTEXT;
 
     for (s = 0; s < plen; s++) {
@@ -6703,7 +6791,7 @@ S_compile_runtime_code(pTHX_ RExC_state_t * const pRExC_state,
        DEBUG_COMPILE_r({
             Perl_re_printf( aTHX_
                "%sre-parsing pattern for runtime code:%s %s\n",
-               PL_colors[4],PL_colors[5],newpat);
+               PL_colors[4], PL_colors[5], newpat);
        });
 
        sv = newSVpvn_flags(newpat, p-newpat-1, RExC_utf8 ? SVf_UTF8 : 0);
@@ -6872,6 +6960,95 @@ S_setup_longest(pTHX_ RExC_state_t *pRExC_state,
     return TRUE;
 }
 
+STATIC void
+S_set_regex_pv(pTHX_ RExC_state_t *pRExC_state, REGEXP *Rx)
+{
+    /* Calculates and sets in the compiled pattern 'Rx' the string to compile,
+     * properly wrapped with the right modifiers */
+
+    bool has_p     = ((RExC_rx->extflags & RXf_PMf_KEEPCOPY) == RXf_PMf_KEEPCOPY);
+    bool has_charset = RExC_utf8 || (get_regex_charset(RExC_rx->extflags)
+                                                != REGEX_DEPENDS_CHARSET);
+
+    /* The caret is output if there are any defaults: if not all the STD
+        * flags are set, or if no character set specifier is needed */
+    bool has_default =
+                (((RExC_rx->extflags & RXf_PMf_STD_PMMOD) != RXf_PMf_STD_PMMOD)
+                || ! has_charset);
+    bool has_runon = ((RExC_seen & REG_RUN_ON_COMMENT_SEEN)
+                                                == REG_RUN_ON_COMMENT_SEEN);
+    U8 reganch = (U8)((RExC_rx->extflags & RXf_PMf_STD_PMMOD)
+                        >> RXf_PMf_STD_PMMOD_SHIFT);
+    const char *fptr = STD_PAT_MODS;        /*"msixxn"*/
+    char *p;
+    STRLEN pat_len = RExC_precomp_end - RExC_precomp;
+
+    /* We output all the necessary flags; we never output a minus, as all
+        * those are defaults, so are
+        * covered by the caret */
+    const STRLEN wraplen = pat_len + has_p + has_runon
+        + has_default       /* If needs a caret */
+        + PL_bitcount[reganch] /* 1 char for each set standard flag */
+
+            /* If needs a character set specifier */
+        + ((has_charset) ? MAX_CHARSET_NAME_LENGTH : 0)
+        + (sizeof("(?:)") - 1);
+
+    PERL_ARGS_ASSERT_SET_REGEX_PV;
+
+    /* make sure PL_bitcount bounds not exceeded */
+    assert(sizeof(STD_PAT_MODS) <= 8);
+
+    p = sv_grow(MUTABLE_SV(Rx), wraplen + 1); /* +1 for the ending NUL */
+    SvPOK_on(Rx);
+    if (RExC_utf8)
+        SvFLAGS(Rx) |= SVf_UTF8;
+    *p++='('; *p++='?';
+
+    /* If a default, cover it using the caret */
+    if (has_default) {
+        *p++= DEFAULT_PAT_MOD;
+    }
+    if (has_charset) {
+        STRLEN len;
+        const char* name;
+
+        name = get_regex_charset_name(RExC_rx->extflags, &len);
+        if strEQ(name, DEPENDS_PAT_MODS) {  /* /d under UTF-8 => /u */
+            assert(RExC_utf8);
+            name = UNICODE_PAT_MODS;
+            len = sizeof(UNICODE_PAT_MODS) - 1;
+        }
+        Copy(name, p, len, char);
+        p += len;
+    }
+    if (has_p)
+        *p++ = KEEPCOPY_PAT_MOD; /*'p'*/
+    {
+        char ch;
+        while((ch = *fptr++)) {
+            if(reganch & 1)
+                *p++ = ch;
+            reganch >>= 1;
+        }
+    }
+
+    *p++ = ':';
+    Copy(RExC_precomp, p, pat_len, char);
+    assert ((RX_WRAPPED(Rx) - p) < 16);
+    RExC_rx->pre_prefix = p - RX_WRAPPED(Rx);
+    p += pat_len;
+
+    /* Adding a trailing \n causes this to compile properly:
+            my $R = qr / A B C # D E/x; /($R)/
+        Otherwise the parens are considered part of the comment */
+    if (has_runon)
+        *p++ = '\n';
+    *p++ = ')';
+    *p = 0;
+    SvCUR_set(Rx, p - RX_WRAPPED(Rx));
+}
+
 /*
  * Perl_re_op_compile - the perl internal RE engine's function to compile a
  * regular expression into internal code.
@@ -6919,11 +7096,9 @@ S_setup_longest(pTHX_ RExC_state_t *pRExC_state,
 REGEXP *
 Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
                    OP *expr, const regexp_engine* eng, REGEXP *old_re,
-                    bool *is_bare_re, U32 orig_rx_flags, U32 pm_flags)
+                    bool *is_bare_re, const U32 orig_rx_flags, const U32 pm_flags)
 {
-    REGEXP *rx;
-    struct regexp *r;
-    regexp_internal *ri;
+    REGEXP *Rx;         /* Capital 'R' means points to a REGEXP */
     STRLEN plen;
     char *exp;
     regnode *scan;
@@ -7087,7 +7262,9 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     /* ignore the utf8ness if the pattern is 0 length */
     RExC_utf8 = RExC_orig_utf8 = (plen == 0 || IN_BYTES) ? 0 : SvUTF8(pat);
 
-    RExC_uni_semantics = 0;
+    RExC_uni_semantics = RExC_utf8; /* UTF-8 implies unicode semantics;
+                                       otherwise we may find later this should
+                                       be 1 */
     RExC_seen_unfolded_sharp_s = 0;
     RExC_contains_locale = 0;
     RExC_strict = cBOOL(pm_flags & RXf_PMf_STRICT);
@@ -7097,19 +7274,29 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     RExC_frame_head= NULL;
     RExC_frame_last= NULL;
     RExC_frame_count= 0;
+    RExC_latest_warn_offset = 0;
+    RExC_use_BRANCHJ = 0;
+    RExC_total_parens = 0;
+    RExC_open_parens = NULL;
+    RExC_close_parens = NULL;
+    RExC_paren_names = NULL;
+    RExC_size = 0;
+#ifdef DEBUGGING
+    RExC_paren_name_list = NULL;
+#endif
 
     DEBUG_r({
         RExC_mysv1= sv_newmortal();
         RExC_mysv2= sv_newmortal();
     });
+
     DEBUG_COMPILE_r({
             SV *dsv= sv_newmortal();
             RE_PV_QUOTED_DECL(s, RExC_utf8, dsv, exp, plen, PL_dump_re_max_len);
             Perl_re_printf( aTHX_  "%sCompiling REx%s %s\n",
-                          PL_colors[4],PL_colors[5],s);
+                          PL_colors[4], PL_colors[5], s);
         });
 
-  redo_first_pass:
     /* we jump here if we have to recompile, e.g., from upgrading the pattern
      * to utf8 */
 
@@ -7120,6 +7307,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     )
        runtime_code = S_has_runtime_code(aTHX_ pRExC_state, exp, plen);
 
+  redo_parse:
     /* return old regex if pattern hasn't changed */
     /* XXX: note in the below we have to check the flags as well as the
      * pattern.
@@ -7139,10 +7327,16 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
         return old_re;
     }
 
+    /* Allocate the pattern's SV */
+    RExC_rx_sv = Rx = (REGEXP*) newSV_type(SVt_REGEXP);
+    RExC_rx = ReANY(Rx);
+    if ( RExC_rx == NULL )
+        FAIL("Regexp out of space");
+
     rx_flags = orig_rx_flags;
 
     if (   initial_charset == REGEX_DEPENDS_CHARSET
-        && (RExC_utf8 ||RExC_uni_semantics))
+        && (RExC_uni_semantics))
     {
 
        /* Set to use unicode semantics if the pattern is in utf8 and has the
@@ -7150,9 +7344,6 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
        set_regex_charset(&rx_flags, REGEX_UNICODE_CHARSET);
     }
 
-    RExC_precomp = exp;
-    RExC_precomp_adj = 0;
-    RExC_flags = rx_flags;
     RExC_pm_flags = pm_flags;
 
     if (runtime_code) {
@@ -7165,7 +7356,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
             * got compiled as utf8. Try again with a utf8 pattern */
             S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &exp, &plen,
                 pRExC_state->code_blocks ? pRExC_state->code_blocks->count : 0);
-            goto redo_first_pass;
+            goto redo_parse;
        }
     }
     assert(!pRExC_state->runtime_code_qr);
@@ -7176,36 +7367,83 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     RExC_maxlen = 0;
     RExC_in_lookbehind = 0;
     RExC_seen_zerolen = *exp == '^' ? -1 : 0;
-    RExC_extralen = 0;
 #ifdef EBCDIC
     RExC_recode_x_to_native = 0;
 #endif
     RExC_in_multi_char_class = 0;
 
-    /* First pass: determine size, legality. */
-    RExC_parse = exp;
-    RExC_start = RExC_adjusted_start = exp;
-    RExC_end = exp + plen;
-    RExC_precomp_end = RExC_end;
-    RExC_naughty = 0;
-    RExC_npar = 1;
+    RExC_start = RExC_copy_start_in_constructed = RExC_copy_start_in_input = RExC_precomp = exp;
+    RExC_precomp_end = RExC_end = exp + plen;
     RExC_nestroot = 0;
-    RExC_size = 0L;
-    RExC_emit = (regnode *) &RExC_emit_dummy;
     RExC_whilem_seen = 0;
-    RExC_open_parens = NULL;
-    RExC_close_parens = NULL;
     RExC_end_op = NULL;
-    RExC_paren_names = NULL;
-#ifdef DEBUGGING
-    RExC_paren_name_list = NULL;
-#endif
     RExC_recurse = NULL;
     RExC_study_chunk_recursed = NULL;
     RExC_study_chunk_recursed_bytes= 0;
     RExC_recurse_count = 0;
     pRExC_state->code_index = 0;
 
+    /* Initialize the string in the compiled pattern.  This is so that there is
+     * something to output if necessary */
+    set_regex_pv(pRExC_state, Rx);
+
+    DEBUG_PARSE_r({
+        Perl_re_printf( aTHX_
+            "Starting parse and generation\n");
+        RExC_lastnum=0;
+        RExC_lastparse=NULL;
+    });
+
+    /* Allocate space and zero-initialize. Note, the two step process
+       of zeroing when in debug mode, thus anything assigned has to
+       happen after that */
+    if (!  RExC_size) {
+
+        /* On the first pass of the parse, we guess how big this will be.  Then
+         * we grow in one operation to that amount and then give it back.  As
+         * we go along, we re-allocate what we need.
+         *
+         * XXX Currently the guess is essentially that the pattern will be an
+         * EXACT node with one byte input, one byte output.  This is crude, and
+         * better heuristics are welcome.
+         *
+         * On any subsequent passes, we guess what we actually computed in the
+         * latest earlier pass.  Such a pass probably didn't complete so is
+         * missing stuff.  We could improve those guesses by knowing where the
+         * parse stopped, and use the length so far plus apply the above
+         * assumption to what's left. */
+        RExC_size = STR_SZ(RExC_end - RExC_start);
+    }
+
+    Newxc(RExC_rxi, sizeof(regexp_internal) + RExC_size, char, regexp_internal);
+    if ( RExC_rxi == NULL )
+        FAIL("Regexp out of space");
+
+    Zero(RExC_rxi, sizeof(regexp_internal) + RExC_size, char);
+    RXi_SET( RExC_rx, RExC_rxi );
+
+    /* We start from 0 (over from 0 in the case this is a reparse.  The first
+     * node parsed will give back any excess memory we have allocated so far).
+     * */
+    RExC_size = 0;
+
+    /* non-zero initialization begins here */
+    RExC_rx->engine= eng;
+    RExC_rx->extflags = rx_flags;
+    RXp_COMPFLAGS(RExC_rx) = orig_rx_flags & RXf_PMf_FLAGCOPYMASK;
+
+    if (pm_flags & PMf_IS_QR) {
+       RExC_rxi->code_blocks = pRExC_state->code_blocks;
+        if (RExC_rxi->code_blocks) {
+            RExC_rxi->code_blocks->refcnt++;
+        }
+    }
+
+    RExC_rx->intflags = 0;
+
+    RExC_flags = rx_flags;     /* don't let top level (?i) bleed */
+    RExC_parse = exp;
+
     /* This NUL is guaranteed because the pattern comes from an SV*, and the sv
      * code makes sure the final byte is an uncounted NUL.  But should this
      * ever not be the case, lots of things could read beyond the end of the
@@ -7215,13 +7453,34 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
      * etc.  So it is worth noting. */
     assert(*RExC_end == '\0');
 
-    DEBUG_PARSE_r(
-        Perl_re_printf( aTHX_  "Starting first pass (sizing)\n");
-        RExC_lastnum=0;
-        RExC_lastparse=NULL;
-    );
+    RExC_naughty = 0;
+    RExC_npar = 1;
+    RExC_emit_start = RExC_rxi->program;
+    pRExC_state->code_index = 0;
+
+    *((char*) RExC_emit_start) = (char) REG_MAGIC;
+    RExC_emit = 1;
+
+    /* Do the parse */
+    if (reg(pRExC_state, 0, &flags, 1)) {
+
+        /* Success!, But if RExC_total_parens < 0, we need to redo the parse
+         * knowing how many parens there actually are */
+        if (RExC_total_parens < 0) {
+            flags |= RESTART_PARSE;
+        }
+
+        /* We have that number in RExC_npar */
+        RExC_total_parens = RExC_npar;
+    }
+    else if (! MUST_RESTART(flags)) {
+       ReREFCNT_dec(Rx);
+        Perl_croak(aTHX_ "panic: reg returned failure to re_op_compile, flags=%#" UVxf, (UV) flags);
+    }
+
+    /* Here, we either have success, or we have to redo the parse for some reason */
+    if (MUST_RESTART(flags)) {
 
-    if (reg(pRExC_state, 0, &flags,1) == NULL) {
         /* It's possible to write a regexp in ascii that represents Unicode
         codepoints outside of the byte range, such as via \x{100}. If we
         detect such a sequence we have to convert the entire pattern to utf8
@@ -7230,230 +7489,130 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
         at least some part of the pattern, and therefore must convert the whole
         thing.
         -- dmq */
-        if (MUST_RESTART(flags)) {
-            if (flags & NEED_UTF8) {
-                S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &exp, &plen,
-                pRExC_state->code_blocks ? pRExC_state->code_blocks->count : 0);
-                DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo pass 1 after upgrade\n"));
-            }
-            else {
-                DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo pass 1\n"));
+        if (flags & NEED_UTF8) {
+
+            /* We have stored the offset of the final warning output so far.
+             * That must be adjusted.  Any variant characters between the start
+             * of the pattern and this warning count for 2 bytes in the final,
+             * so just add them again */
+            if (UNLIKELY(RExC_latest_warn_offset > 0)) {
+                RExC_latest_warn_offset +=
+                            variant_under_utf8_count((U8 *) exp, (U8 *) exp
+                                                + RExC_latest_warn_offset);
             }
+            S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &exp, &plen,
+            pRExC_state->code_blocks ? pRExC_state->code_blocks->count : 0);
+            DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo parse after upgrade\n"));
+        }
+        else {
+            DEBUG_PARSE_r(Perl_re_printf( aTHX_ "Need to redo parse\n"));
+        }
 
-            goto redo_first_pass;
+        if (RExC_total_parens > 0) {
+            /* Make enough room for all the known parens, and zero it */
+            Renew(RExC_open_parens, RExC_total_parens, regnode_offset);
+            Zero(RExC_open_parens, RExC_total_parens, regnode_offset);
+            RExC_open_parens[0] = 1;    /* +1 for REG_MAGIC */
+
+            Renew(RExC_close_parens, RExC_total_parens, regnode_offset);
+            Zero(RExC_close_parens, RExC_total_parens, regnode_offset);
+        }
+        else { /* Parse did not complete.  Reinitialize the parentheses
+                  structures */
+            RExC_total_parens = 0;
+            if (RExC_open_parens) {
+                Safefree(RExC_open_parens);
+                RExC_open_parens = NULL;
+            }
+            if (RExC_close_parens) {
+                Safefree(RExC_close_parens);
+                RExC_close_parens = NULL;
+            }
         }
-        Perl_croak(aTHX_ "panic: reg returned NULL to re_op_compile for sizing pass, flags=%#" UVxf, (UV) flags);
-    }
 
-    DEBUG_PARSE_r({
-        Perl_re_printf( aTHX_
-            "Required size %" IVdf " nodes\n"
-            "Starting second pass (creation)\n",
-            (IV)RExC_size);
-        RExC_lastnum=0;
-        RExC_lastparse=NULL;
-    });
+        /* Clean up what we did in this parse */
+        SvREFCNT_dec_NN(RExC_rx_sv);
 
-    /* The first pass could have found things that force Unicode semantics */
-    if ((RExC_utf8 || RExC_uni_semantics)
-        && get_regex_charset(rx_flags) == REGEX_DEPENDS_CHARSET)
-    {
-       set_regex_charset(&rx_flags, REGEX_UNICODE_CHARSET);
+        goto redo_parse;
     }
 
-    /* Small enough for pointer-storage convention?
-       If extralen==0, this means that we will not need long jumps. */
-    if (RExC_size >= 0x10000L && RExC_extralen)
-        RExC_size += RExC_extralen;
-    else
-       RExC_extralen = 0;
-    if (RExC_whilem_seen > 15)
-       RExC_whilem_seen = 15;
-
-    /* Allocate space and zero-initialize. Note, the two step process
-       of zeroing when in debug mode, thus anything assigned has to
-       happen after that */
-    rx = (REGEXP*) newSV_type(SVt_REGEXP);
-    r = ReANY(rx);
-    Newxc(ri, sizeof(regexp_internal) + (unsigned)RExC_size * sizeof(regnode),
-        char, regexp_internal);
-    if ( r == NULL || ri == NULL )
-       FAIL("Regexp out of space");
-#ifdef DEBUGGING
-    /* avoid reading uninitialized memory in DEBUGGING code in study_chunk() */
-    Zero(ri, sizeof(regexp_internal) + (unsigned)RExC_size * sizeof(regnode),
-         char);
-#else
-    /* bulk initialize base fields with 0. */
-    Zero(ri, sizeof(regexp_internal), char);
-#endif
+    /* In a stable state, as here, this must be true */
+    assert(RExC_size = RExC_emit + 1);
 
-    /* non-zero initialization begins here */
-    RXi_SET( r, ri );
-    r->engine= eng;
-    r->extflags = rx_flags;
-    RXp_COMPFLAGS(r) = orig_rx_flags & RXf_PMf_FLAGCOPYMASK;
+    /* Here, we have successfully parsed and generated the pattern's program
+     * for the regex engine.  We are ready to finish things up and look for
+     * optimizations. */
 
-    if (pm_flags & PMf_IS_QR) {
-       ri->code_blocks = pRExC_state->code_blocks;
-       if (ri->code_blocks)
-            ri->code_blocks->refcnt++;
-    }
+    /* Update the string to compile, with correct modifiers, etc */
+    set_regex_pv(pRExC_state, Rx);
 
-    {
-        bool has_p     = ((r->extflags & RXf_PMf_KEEPCOPY) == RXf_PMf_KEEPCOPY);
-        bool has_charset = (get_regex_charset(r->extflags)
-                                                    != REGEX_DEPENDS_CHARSET);
-
-        /* The caret is output if there are any defaults: if not all the STD
-         * flags are set, or if no character set specifier is needed */
-        bool has_default =
-                    (((r->extflags & RXf_PMf_STD_PMMOD) != RXf_PMf_STD_PMMOD)
-                    || ! has_charset);
-        bool has_runon = ((RExC_seen & REG_RUN_ON_COMMENT_SEEN)
-                                                   == REG_RUN_ON_COMMENT_SEEN);
-       U8 reganch = (U8)((r->extflags & RXf_PMf_STD_PMMOD)
-                           >> RXf_PMf_STD_PMMOD_SHIFT);
-       const char *fptr = STD_PAT_MODS;        /*"msixxn"*/
-       char *p;
-
-        /* We output all the necessary flags; we never output a minus, as all
-         * those are defaults, so are
-         * covered by the caret */
-       const STRLEN wraplen = plen + has_p + has_runon
-            + has_default       /* If needs a caret */
-            + PL_bitcount[reganch] /* 1 char for each set standard flag */
-
-               /* If needs a character set specifier */
-           + ((has_charset) ? MAX_CHARSET_NAME_LENGTH : 0)
-            + (sizeof("(?:)") - 1);
-
-        /* make sure PL_bitcount bounds not exceeded */
-        assert(sizeof(STD_PAT_MODS) <= 8);
-
-        p = sv_grow(MUTABLE_SV(rx), wraplen + 1); /* +1 for the ending NUL */
-        SvPOK_on(rx);
-       if (RExC_utf8)
-           SvFLAGS(rx) |= SVf_UTF8;
-        *p++='('; *p++='?';
-
-        /* If a default, cover it using the caret */
-        if (has_default) {
-            *p++= DEFAULT_PAT_MOD;
-        }
-        if (has_charset) {
-           STRLEN len;
-           const char* const name = get_regex_charset_name(r->extflags, &len);
-           Copy(name, p, len, char);
-           p += len;
-        }
-        if (has_p)
-            *p++ = KEEPCOPY_PAT_MOD; /*'p'*/
-        {
-            char ch;
-            while((ch = *fptr++)) {
-                if(reganch & 1)
-                    *p++ = ch;
-                reganch >>= 1;
-            }
-        }
+    RExC_rx->nparens = RExC_total_parens - 1;
 
-        *p++ = ':';
-        Copy(RExC_precomp, p, plen, char);
-       assert ((RX_WRAPPED(rx) - p) < 16);
-       r->pre_prefix = p - RX_WRAPPED(rx);
-        p += plen;
-        if (has_runon)
-            *p++ = '\n';
-        *p++ = ')';
-        *p = 0;
-       SvCUR_set(rx, p - RX_WRAPPED(rx));
-    }
+    /* Uses the upper 4 bits of the FLAGS field, so keep within that size */
+    if (RExC_whilem_seen > 15)
+        RExC_whilem_seen = 15;
 
-    r->intflags = 0;
-    r->nparens = RExC_npar - 1;        /* set early to validate backrefs */
+    DEBUG_PARSE_r({
+        Perl_re_printf( aTHX_
+            "Required size %" IVdf " nodes\n", (IV)RExC_size);
+        RExC_lastnum=0;
+        RExC_lastparse=NULL;
+    });
 
-    /* Useful during FAIL. */
 #ifdef RE_TRACK_PATTERN_OFFSETS
-    Newxz(ri->u.offsets, 2*RExC_size+1, U32); /* MJD 20001228 */
     DEBUG_OFFSETS_r(Perl_re_printf( aTHX_
                           "%s %" UVuf " bytes for offset annotations.\n",
-                          ri->u.offsets ? "Got" : "Couldn't get",
-                          (UV)((2*RExC_size+1) * sizeof(U32))));
-#endif
-    SetProgLen(ri,RExC_size);
-    RExC_rx_sv = rx;
-    RExC_rx = r;
-    RExC_rxi = ri;
+                          RExC_offsets ? "Got" : "Couldn't get",
+                          (UV)((RExC_offsets[0] * 2 + 1))));
+    DEBUG_OFFSETS_r(if (RExC_offsets) {
+        const STRLEN len = RExC_offsets[0];
+        STRLEN i;
+        GET_RE_DEBUG_FLAGS_DECL;
+        Perl_re_printf( aTHX_
+                      "Offsets: [%" UVuf "]\n\t", (UV)RExC_offsets[0]);
+        for (i = 1; i <= len; i++) {
+            if (RExC_offsets[i*2-1] || RExC_offsets[i*2])
+                Perl_re_printf( aTHX_  "%" UVuf ":%" UVuf "[%" UVuf "] ",
+                (UV)i, (UV)RExC_offsets[i*2-1], (UV)RExC_offsets[i*2]);
+        }
+        Perl_re_printf( aTHX_  "\n");
+    });
 
-    /* Second pass: emit code. */
-    RExC_flags = rx_flags;     /* don't let top level (?i) bleed */
-    RExC_pm_flags = pm_flags;
-    RExC_parse = exp;
-    RExC_end = exp + plen;
-    RExC_naughty = 0;
-    RExC_emit_start = ri->program;
-    RExC_emit = ri->program;
-    RExC_emit_bound = ri->program + RExC_size + 1;
-    pRExC_state->code_index = 0;
+#else
+    SetProgLen(RExC_rxi,RExC_size);
+#endif
 
-    *((char*) RExC_emit++) = (char) REG_MAGIC;
-    /* setup various meta data about recursion, this all requires
-     * RExC_npar to be correctly set, and a bit later on we clear it */
-    if (RExC_seen & REG_RECURSE_SEEN) {
-        DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
-            "%*s%*s Setting up open/close parens\n",
-                  22, "|    |", (int)(0 * 2 + 1), ""));
-
-        /* setup RExC_open_parens, which holds the address of each
-         * OPEN tag, and to make things simpler for the 0 index
-         * the start of the program - this is used later for offsets */
-        Newxz(RExC_open_parens, RExC_npar,regnode *);
-        SAVEFREEPV(RExC_open_parens);
-        RExC_open_parens[0] = RExC_emit;
-
-        /* setup RExC_close_parens, which holds the address of each
-         * CLOSE tag, and to make things simpler for the 0 index
-         * the end of the program - this is used later for offsets */
-        Newxz(RExC_close_parens, RExC_npar,regnode *);
-        SAVEFREEPV(RExC_close_parens);
-        /* we dont know where end op starts yet, so we dont
-         * need to set RExC_close_parens[0] like we do RExC_open_parens[0] above */
-
-        /* Note, RExC_npar is 1 + the number of parens in a pattern.
-         * So its 1 if there are no parens. */
-        RExC_study_chunk_recursed_bytes= (RExC_npar >> 3) +
-                                         ((RExC_npar & 0x07) != 0);
-        Newx(RExC_study_chunk_recursed,
-             RExC_study_chunk_recursed_bytes * RExC_npar, U8);
-        SAVEFREEPV(RExC_study_chunk_recursed);
-    }
-    RExC_npar = 1;
-    if (reg(pRExC_state, 0, &flags,1) == NULL) {
-       ReREFCNT_dec(rx);
-        Perl_croak(aTHX_ "panic: reg returned NULL to re_op_compile for generation pass, flags=%#" UVxf, (UV) flags);
-    }
     DEBUG_OPTIMISE_r(
         Perl_re_printf( aTHX_  "Starting post parse optimization\n");
     );
 
     /* XXXX To minimize changes to RE engine we always allocate
        3-units-long substrs field. */
-    Newx(r->substrs, 1, struct reg_substr_data);
+    Newx(RExC_rx->substrs, 1, struct reg_substr_data);
     if (RExC_recurse_count) {
-        Newx(RExC_recurse,RExC_recurse_count,regnode *);
+        Newx(RExC_recurse, RExC_recurse_count, regnode *);
         SAVEFREEPV(RExC_recurse);
     }
 
+    if (RExC_seen & REG_RECURSE_SEEN) {
+        /* Note, RExC_total_parens is 1 + the number of parens in a pattern.
+         * So its 1 if there are no parens. */
+        RExC_study_chunk_recursed_bytes= (RExC_total_parens >> 3) +
+                                         ((RExC_total_parens & 0x07) != 0);
+        Newx(RExC_study_chunk_recursed,
+             RExC_study_chunk_recursed_bytes * RExC_total_parens, U8);
+        SAVEFREEPV(RExC_study_chunk_recursed);
+    }
+
   reStudy:
-    r->minlen = minlen = sawlookahead = sawplus = sawopen = sawminmod = 0;
+    RExC_rx->minlen = minlen = sawlookahead = sawplus = sawopen = sawminmod = 0;
     DEBUG_r(
         RExC_study_chunk_recursed_count= 0;
     );
-    Zero(r->substrs, 1, struct reg_substr_data);
+    Zero(RExC_rx->substrs, 1, struct reg_substr_data);
     if (RExC_study_chunk_recursed) {
         Zero(RExC_study_chunk_recursed,
-             RExC_study_chunk_recursed_bytes * RExC_npar, U8);
+             RExC_study_chunk_recursed_bytes * RExC_total_parens, U8);
     }
 
 
@@ -7477,15 +7636,15 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 #endif
 
     /* Dig out information for optimizations. */
-    r->extflags = RExC_flags; /* was pm_op */
+    RExC_rx->extflags = RExC_flags; /* was pm_op */
     /*dmq: removed as part of de-PMOP: pm->op_pmflags = RExC_flags; */
 
     if (UTF)
-       SvUTF8_on(rx);  /* Unicode in it? */
-    ri->regstclass = NULL;
+       SvUTF8_on(Rx);  /* Unicode in it? */
+    RExC_rxi->regstclass = NULL;
     if (RExC_naughty >= TOO_NAUGHTY)   /* Probably an expensive pattern. */
-       r->intflags |= PREGf_NAUGHTY;
-    scan = ri->program + 1;            /* First BRANCH. */
+       RExC_rx->intflags |= PREGf_NAUGHTY;
+    scan = RExC_rxi->program + 1;              /* First BRANCH. */
 
     /* testing for BRANCH here tells us whether there is "must appear"
        data in the pattern. If there is then we can use it for optimisations */
@@ -7547,30 +7706,30 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
            if (OP(first) == EXACT || OP(first) == EXACTL)
                NOOP;   /* Empty, get anchored substr later. */
            else
-               ri->regstclass = first;
+               RExC_rxi->regstclass = first;
        }
 #ifdef TRIE_STCLASS
        else if (PL_regkind[OP(first)] == TRIE &&
-               ((reg_trie_data *)ri->data->data[ ARG(first) ])->minlen>0)
+               ((reg_trie_data *)RExC_rxi->data->data[ ARG(first) ])->minlen>0)
        {
             /* this can happen only on restudy */
-            ri->regstclass = construct_ahocorasick_from_trie(pRExC_state, (regnode *)first, 0);
+            RExC_rxi->regstclass = construct_ahocorasick_from_trie(pRExC_state, (regnode *)first, 0);
        }
 #endif
        else if (REGNODE_SIMPLE(OP(first)))
-           ri->regstclass = first;
+           RExC_rxi->regstclass = first;
        else if (PL_regkind[OP(first)] == BOUND ||
                 PL_regkind[OP(first)] == NBOUND)
-           ri->regstclass = first;
+           RExC_rxi->regstclass = first;
        else if (PL_regkind[OP(first)] == BOL) {
-            r->intflags |= (OP(first) == MBOL
+            RExC_rx->intflags |= (OP(first) == MBOL
                            ? PREGf_ANCH_MBOL
                            : PREGf_ANCH_SBOL);
            first = NEXTOPER(first);
            goto again;
        }
        else if (OP(first) == GPOS) {
-            r->intflags |= PREGf_ANCH_GPOS;
+            RExC_rx->intflags |= PREGf_ANCH_GPOS;
            first = NEXTOPER(first);
            goto again;
        }
@@ -7578,14 +7737,14 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
             !sawlookahead &&
            (OP(first) == STAR &&
            PL_regkind[OP(NEXTOPER(first))] == REG_ANY) &&
-            !(r->intflags & PREGf_ANCH) && !pRExC_state->code_blocks)
+            !(RExC_rx->intflags & PREGf_ANCH) && !pRExC_state->code_blocks)
        {
            /* turn .* into ^.* with an implied $*=1 */
            const int type =
                (OP(NEXTOPER(first)) == REG_ANY)
                     ? PREGf_ANCH_MBOL
                     : PREGf_ANCH_SBOL;
-            r->intflags |= (type | PREGf_IMPLICIT);
+            RExC_rx->intflags |= (type | PREGf_IMPLICIT);
            first = NEXTOPER(first);
            goto again;
        }
@@ -7593,7 +7752,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
             && (!sawopen || !RExC_sawback)
            && !pRExC_state->code_blocks) /* May examine pos and $& */
            /* x+ must match at the 1st pos of run of x's */
-           r->intflags |= PREGf_SKIP;
+           RExC_rx->intflags |= PREGf_SKIP;
 
        /* Scan is after the zeroth branch, first is atomic matcher. */
 #ifdef TRIE_STUDY_OPT
@@ -7631,7 +7790,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
        SAVEFREESV(data.substrs[1].str);
        SAVEFREESV(data.last_found);
        first = scan;
-       if (!ri->regstclass) {
+       if (!RExC_rxi->regstclass) {
            ssc_init(pRExC_state, &ch_class);
            data.start_class = &ch_class;
            stclass_flag = SCF_DO_STCLASS_AND;
@@ -7655,15 +7814,15 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
         CHECK_RESTUDY_GOTO_butfirst(LEAVE_with_name("study_chunk"));
 
 
-       if ( RExC_npar == 1 && !data.cur_is_floating
+       if ( RExC_total_parens == 1 && !data.cur_is_floating
             && data.last_start_min == 0 && data.last_end > 0
             && !RExC_seen_zerolen
              && !(RExC_seen & REG_VERBARG_SEEN)
              && !(RExC_seen & REG_GPOS_SEEN)
         ){
-           r->extflags |= RXf_CHECK_ALL;
+           RExC_rx->extflags |= RXf_CHECK_ALL;
         }
-       scan_commit(pRExC_state, &data,&minlen,0);
+       scan_commit(pRExC_state, &data,&minlen, 0);
 
 
         /* XXX this is done in reverse order because that's the way the
@@ -7680,34 +7839,34 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
                         == SvCUR(data.substrs[1].str)
                     )
                 && S_setup_longest (aTHX_ pRExC_state,
-                                        &(r->substrs->data[i]),
+                                        &(RExC_rx->substrs->data[i]),
                                         &(data.substrs[i]),
                                         longest_length[i]))
             {
-                r->substrs->data[i].min_offset =
+                RExC_rx->substrs->data[i].min_offset =
                         data.substrs[i].min_offset - data.substrs[i].lookbehind;
 
-                r->substrs->data[i].max_offset = data.substrs[i].max_offset;
+                RExC_rx->substrs->data[i].max_offset = data.substrs[i].max_offset;
                 /* Don't offset infinity */
                 if (data.substrs[i].max_offset < SSize_t_MAX)
-                    r->substrs->data[i].max_offset -= data.substrs[i].lookbehind;
+                    RExC_rx->substrs->data[i].max_offset -= data.substrs[i].lookbehind;
                 SvREFCNT_inc_simple_void_NN(data.substrs[i].str);
             }
             else {
-                r->substrs->data[i].substr      = NULL;
-                r->substrs->data[i].utf8_substr = NULL;
+                RExC_rx->substrs->data[i].substr      = NULL;
+                RExC_rx->substrs->data[i].utf8_substr = NULL;
                 longest_length[i] = 0;
             }
         }
 
        LEAVE_with_name("study_chunk");
 
-       if (ri->regstclass
-           && (OP(ri->regstclass) == REG_ANY || OP(ri->regstclass) == SANY))
-           ri->regstclass = NULL;
+       if (RExC_rxi->regstclass
+           && (OP(RExC_rxi->regstclass) == REG_ANY || OP(RExC_rxi->regstclass) == SANY))
+           RExC_rxi->regstclass = NULL;
 
-       if ((!(r->substrs->data[0].substr || r->substrs->data[0].utf8_substr)
-              || r->substrs->data[0].min_offset)
+       if ((!(RExC_rx->substrs->data[0].substr || RExC_rx->substrs->data[0].utf8_substr)
+              || RExC_rx->substrs->data[0].min_offset)
            && stclass_flag
             && ! (ANYOF_FLAGS(data.start_class) & SSC_MATCHES_EMPTY_STRING)
            && is_ssc_worth_it(pRExC_state, data.start_class))
@@ -7720,10 +7879,10 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
            StructCopy(data.start_class,
                       (regnode_ssc*)RExC_rxi->data->data[n],
                       regnode_ssc);
-           ri->regstclass = (regnode*)RExC_rxi->data->data[n];
-           r->intflags &= ~PREGf_SKIP; /* Used in find_byclass(). */
+           RExC_rxi->regstclass = (regnode*)RExC_rxi->data->data[n];
+           RExC_rx->intflags &= ~PREGf_SKIP;   /* Used in find_byclass(). */
            DEBUG_COMPILE_r({ SV *sv = sv_newmortal();
-                      regprop(r, sv, (regnode*)data.start_class, NULL, pRExC_state);
+                      regprop(RExC_rx, sv, (regnode*)data.start_class, NULL, pRExC_state);
                       Perl_re_printf( aTHX_
                                    "synthetic stclass \"%s\".\n",
                                    SvPVX_const(sv));});
@@ -7733,19 +7892,19 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
         /* A temporary algorithm prefers floated substr to fixed one of
          * same length to dig more info. */
        i = (longest_length[0] <= longest_length[1]);
-        r->substrs->check_ix = i;
-        r->check_end_shift  = r->substrs->data[i].end_shift;
-        r->check_substr     = r->substrs->data[i].substr;
-        r->check_utf8       = r->substrs->data[i].utf8_substr;
-        r->check_offset_min = r->substrs->data[i].min_offset;
-        r->check_offset_max = r->substrs->data[i].max_offset;
-        if (!i && (r->intflags & (PREGf_ANCH_SBOL|PREGf_ANCH_GPOS)))
-            r->intflags |= PREGf_NOSCAN;
-
-       if ((r->check_substr || r->check_utf8) ) {
-           r->extflags |= RXf_USE_INTUIT;
-           if (SvTAIL(r->check_substr ? r->check_substr : r->check_utf8))
-               r->extflags |= RXf_INTUIT_TAIL;
+        RExC_rx->substrs->check_ix = i;
+        RExC_rx->check_end_shift  = RExC_rx->substrs->data[i].end_shift;
+        RExC_rx->check_substr     = RExC_rx->substrs->data[i].substr;
+        RExC_rx->check_utf8       = RExC_rx->substrs->data[i].utf8_substr;
+        RExC_rx->check_offset_min = RExC_rx->substrs->data[i].min_offset;
+        RExC_rx->check_offset_max = RExC_rx->substrs->data[i].max_offset;
+        if (!i && (RExC_rx->intflags & (PREGf_ANCH_SBOL|PREGf_ANCH_GPOS)))
+            RExC_rx->intflags |= PREGf_NOSCAN;
+
+       if ((RExC_rx->check_substr || RExC_rx->check_utf8) ) {
+           RExC_rx->extflags |= RXf_USE_INTUIT;
+           if (SvTAIL(RExC_rx->check_substr ? RExC_rx->check_substr : RExC_rx->check_utf8))
+               RExC_rx->extflags |= RXf_INTUIT_TAIL;
        }
 
        /* XXX Unneeded? dmq (shouldn't as this is handled elsewhere)
@@ -7763,7 +7922,7 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
         DEBUG_PARSE_r(Perl_re_printf( aTHX_  "\nMulti Top Level\n"));
 
-       scan = ri->program + 1;
+       scan = RExC_rxi->program + 1;
        ssc_init(pRExC_state, &ch_class);
        data.start_class = &ch_class;
        data.last_closep = &last_close;
@@ -7782,12 +7941,12 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
         CHECK_RESTUDY_GOTO_butfirst(NOOP);
 
-       r->check_substr = NULL;
-        r->check_utf8 = NULL;
-        r->substrs->data[0].substr      = NULL;
-        r->substrs->data[0].utf8_substr = NULL;
-        r->substrs->data[1].substr      = NULL;
-        r->substrs->data[1].utf8_substr = NULL;
+       RExC_rx->check_substr = NULL;
+        RExC_rx->check_utf8 = NULL;
+        RExC_rx->substrs->data[0].substr      = NULL;
+        RExC_rx->substrs->data[0].utf8_substr = NULL;
+        RExC_rx->substrs->data[1].substr      = NULL;
+        RExC_rx->substrs->data[1].utf8_substr = NULL;
 
         if (! (ANYOF_FLAGS(data.start_class) & SSC_MATCHES_EMPTY_STRING)
            && is_ssc_worth_it(pRExC_state, data.start_class))
@@ -7800,10 +7959,10 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
            StructCopy(data.start_class,
                       (regnode_ssc*)RExC_rxi->data->data[n],
                       regnode_ssc);
-           ri->regstclass = (regnode*)RExC_rxi->data->data[n];
-           r->intflags &= ~PREGf_SKIP; /* Used in find_byclass(). */
+           RExC_rxi->regstclass = (regnode*)RExC_rxi->data->data[n];
+           RExC_rx->intflags &= ~PREGf_SKIP;   /* Used in find_byclass(). */
            DEBUG_COMPILE_r({ SV* sv = sv_newmortal();
-                      regprop(r, sv, (regnode*)data.start_class, NULL, pRExC_state);
+                      regprop(RExC_rx, sv, (regnode*)data.start_class, NULL, pRExC_state);
                       Perl_re_printf( aTHX_
                                    "synthetic stclass \"%s\".\n",
                                    SvPVX_const(sv));});
@@ -7812,52 +7971,52 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     }
 
     if (RExC_seen & REG_UNBOUNDED_QUANTIFIER_SEEN) {
-        r->extflags |= RXf_UNBOUNDED_QUANTIFIER_SEEN;
-        r->maxlen = REG_INFTY;
+        RExC_rx->extflags |= RXf_UNBOUNDED_QUANTIFIER_SEEN;
+        RExC_rx->maxlen = REG_INFTY;
     }
     else {
-        r->maxlen = RExC_maxlen;
+        RExC_rx->maxlen = RExC_maxlen;
     }
 
     /* Guard against an embedded (?=) or (?<=) with a longer minlen than
        the "real" pattern. */
     DEBUG_OPTIMISE_r({
-        Perl_re_printf( aTHX_ "minlen: %" IVdf " r->minlen:%" IVdf " maxlen:%" IVdf "\n",
-                      (IV)minlen, (IV)r->minlen, (IV)RExC_maxlen);
+        Perl_re_printf( aTHX_ "minlen: %" IVdf " RExC_rx->minlen:%" IVdf " maxlen:%" IVdf "\n",
+                      (IV)minlen, (IV)RExC_rx->minlen, (IV)RExC_maxlen);
     });
-    r->minlenret = minlen;
-    if (r->minlen < minlen)
-        r->minlen = minlen;
+    RExC_rx->minlenret = minlen;
+    if (RExC_rx->minlen < minlen)
+        RExC_rx->minlen = minlen;
 
     if (RExC_seen & REG_RECURSE_SEEN ) {
-        r->intflags |= PREGf_RECURSE_SEEN;
-        Newx(r->recurse_locinput, r->nparens + 1, char *);
+        RExC_rx->intflags |= PREGf_RECURSE_SEEN;
+        Newx(RExC_rx->recurse_locinput, RExC_rx->nparens + 1, char *);
     }
     if (RExC_seen & REG_GPOS_SEEN)
-        r->intflags |= PREGf_GPOS_SEEN;
+        RExC_rx->intflags |= PREGf_GPOS_SEEN;
     if (RExC_seen & REG_LOOKBEHIND_SEEN)
-        r->extflags |= RXf_NO_INPLACE_SUBST; /* inplace might break the
+        RExC_rx->extflags |= RXf_NO_INPLACE_SUBST; /* inplace might break the
                                                 lookbehind */
     if (pRExC_state->code_blocks)
-       r->extflags |= RXf_EVAL_SEEN;
+       RExC_rx->extflags |= RXf_EVAL_SEEN;
     if (RExC_seen & REG_VERBARG_SEEN)
     {
-       r->intflags |= PREGf_VERBARG_SEEN;
-        r->extflags |= RXf_NO_INPLACE_SUBST; /* don't understand this! Yves */
+       RExC_rx->intflags |= PREGf_VERBARG_SEEN;
+        RExC_rx->extflags |= RXf_NO_INPLACE_SUBST; /* don't understand this! Yves */
     }
     if (RExC_seen & REG_CUTGROUP_SEEN)
-       r->intflags |= PREGf_CUTGROUP_SEEN;
+       RExC_rx->intflags |= PREGf_CUTGROUP_SEEN;
     if (pm_flags & PMf_USE_RE_EVAL)
-       r->intflags |= PREGf_USE_RE_EVAL;
+       RExC_rx->intflags |= PREGf_USE_RE_EVAL;
     if (RExC_paren_names)
-        RXp_PAREN_NAMES(r) = MUTABLE_HV(SvREFCNT_inc(RExC_paren_names));
+        RXp_PAREN_NAMES(RExC_rx) = MUTABLE_HV(SvREFCNT_inc(RExC_paren_names));
     else
-        RXp_PAREN_NAMES(r) = NULL;
+        RXp_PAREN_NAMES(RExC_rx) = NULL;
 
     /* If we have seen an anchor in our pattern then we set the extflag RXf_IS_ANCHORED
      * so it can be used in pp.c */
-    if (r->intflags & PREGf_ANCH)
-        r->extflags |= RXf_IS_ANCHORED;
+    if (RExC_rx->intflags & PREGf_ANCH)
+        RExC_rx->extflags |= RXf_IS_ANCHORED;
 
 
     {
@@ -7868,45 +8027,45 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
          * we avoid weird issues with equivalent patterns resulting in different behavior,
          * AND we allow non Perl engines to get the same optimizations by the setting the
          * flags appropriately - Yves */
-        regnode *first = ri->program + 1;
+        regnode *first = RExC_rxi->program + 1;
         U8 fop = OP(first);
         regnode *next = regnext(first);
         U8 nop = OP(next);
 
         if (PL_regkind[fop] == NOTHING && nop == END)
-            r->extflags |= RXf_NULL;
+            RExC_rx->extflags |= RXf_NULL;
         else if ((fop == MBOL || (fop == SBOL && !first->flags)) && nop == END)
             /* when fop is SBOL first->flags will be true only when it was
              * produced by parsing /\A/, and not when parsing /^/. This is
              * very important for the split code as there we want to
              * treat /^/ as /^/m, but we do not want to treat /\A/ as /^/m.
              * See rt #122761 for more details. -- Yves */
-            r->extflags |= RXf_START_ONLY;
+            RExC_rx->extflags |= RXf_START_ONLY;
         else if (fop == PLUS
                  && PL_regkind[nop] == POSIXD && FLAGS(next) == _CC_SPACE
                  && nop == END)
-            r->extflags |= RXf_WHITE;
-        else if ( r->extflags & RXf_SPLIT
+            RExC_rx->extflags |= RXf_WHITE;
+        else if ( RExC_rx->extflags & RXf_SPLIT
                   && (fop == EXACT || fop == EXACTL)
                   && STR_LEN(first) == 1
                   && *(STRING(first)) == ' '
                   && nop == END )
-            r->extflags |= (RXf_SKIPWHITE|RXf_WHITE);
+            RExC_rx->extflags |= (RXf_SKIPWHITE|RXf_WHITE);
 
     }
 
     if (RExC_contains_locale) {
-        RXp_EXTFLAGS(r) |= RXf_TAINTED;
+        RXp_EXTFLAGS(RExC_rx) |= RXf_TAINTED;
     }
 
 #ifdef DEBUGGING
     if (RExC_paren_names) {
-        ri->name_list_idx = add_data( pRExC_state, STR_WITH_LEN("a"));
-        ri->data->data[ri->name_list_idx]
+        RExC_rxi->name_list_idx = add_data( pRExC_state, STR_WITH_LEN("a"));
+        RExC_rxi->data->data[RExC_rxi->name_list_idx]
                                    = (void*)SvREFCNT_inc(RExC_paren_name_list);
     } else
 #endif
-    ri->name_list_idx = 0;
+    RExC_rxi->name_list_idx = 0;
 
     while ( RExC_recurse_count > 0 ) {
         const regnode *scan = RExC_recurse[ --RExC_recurse_count ];
@@ -7922,10 +8081,10 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
          *
          */
         assert(scan && OP(scan) == GOSUB);
-        ARG2L_SET( scan, RExC_open_parens[ARG(scan)] - scan );
+        ARG2L_SET( scan, RExC_open_parens[ARG(scan)] - REGNODE_OFFSET(scan));
     }
 
-    Newxz(r->offs, RExC_npar, regexp_paren_pair);
+    Newxz(RExC_rx->offs, RExC_total_parens, regexp_paren_pair);
     /* assume we don't need to swap parens around before we match */
     DEBUG_TEST_r({
         Perl_re_printf( aTHX_ "study_chunk_recursed_count: %lu\n",
@@ -7934,32 +8093,26 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
     DEBUG_DUMP_r({
         DEBUG_RExC_seen();
         Perl_re_printf( aTHX_ "Final program:\n");
-        regdump(r);
-    });
-#ifdef RE_TRACK_PATTERN_OFFSETS
-    DEBUG_OFFSETS_r(if (ri->u.offsets) {
-        const STRLEN len = ri->u.offsets[0];
-        STRLEN i;
-        GET_RE_DEBUG_FLAGS_DECL;
-        Perl_re_printf( aTHX_
-                      "Offsets: [%" UVuf "]\n\t", (UV)ri->u.offsets[0]);
-        for (i = 1; i <= len; i++) {
-            if (ri->u.offsets[i*2-1] || ri->u.offsets[i*2])
-                Perl_re_printf( aTHX_  "%" UVuf ":%" UVuf "[%" UVuf "] ",
-                (UV)i, (UV)ri->u.offsets[i*2-1], (UV)ri->u.offsets[i*2]);
-            }
-        Perl_re_printf( aTHX_  "\n");
+        regdump(RExC_rx);
     });
-#endif
+
+    if (RExC_open_parens) {
+        Safefree(RExC_open_parens);
+        RExC_open_parens = NULL;
+    }
+    if (RExC_close_parens) {
+        Safefree(RExC_close_parens);
+        RExC_close_parens = NULL;
+    }
 
 #ifdef USE_ITHREADS
     /* under ithreads the ?pat? PMf_USED flag on the pmop is simulated
      * by setting the regexp SV to readonly-only instead. If the
      * pattern's been recompiled, the USEDness should remain. */
     if (old_re && SvREADONLY(old_re))
-        SvREADONLY_on(rx);
+        SvREADONLY_on(Rx);
 #endif
-    return rx;
+    return Rx;
 }
 
 
@@ -8030,7 +8183,7 @@ Perl_reg_named_buff_fetch(pTHX_ REGEXP * const r, SV * const namesv,
                     && rx->offs[nums[i]].end != -1)
                 {
                     ret = newSVpvs("");
-                    CALLREG_NUMBUF_FETCH(r,nums[i],ret);
+                    CALLREG_NUMBUF_FETCH(r, nums[i], ret);
                     if (!retarray)
                         return ret;
                 } else {
@@ -8099,7 +8252,7 @@ Perl_reg_named_buff_nextkey(pTHX_ REGEXP * const r, const U32 flags)
     if (rx && RXp_PAREN_NAMES(rx)) {
         HV *hv = RXp_PAREN_NAMES(rx);
         HE *temphe;
-        while ( (temphe = hv_iternext_flags(hv,0)) ) {
+        while ( (temphe = hv_iternext_flags(hv, 0)) ) {
             IV i;
             IV parno = 0;
             SV* sv_dat = HeVAL(temphe);
@@ -8161,7 +8314,7 @@ Perl_reg_named_buff_all(pTHX_ REGEXP * const r, const U32 flags)
         HV *hv= RXp_PAREN_NAMES(rx);
         HE *temphe;
         (void)hv_iterinit(hv);
-        while ( (temphe = hv_iternext_flags(hv,0)) ) {
+        while ( (temphe = hv_iternext_flags(hv, 0)) ) {
             IV i;
             IV parno = 0;
             SV* sv_dat = HeVAL(temphe);
@@ -8411,6 +8564,7 @@ STATIC SV*
 S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
 {
     char *name_start = RExC_parse;
+    SV* sv_name;
 
     PERL_ARGS_ASSERT_REG_SCAN_NAME;
 
@@ -8433,38 +8587,42 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
                          character */
         vFAIL("Group name must start with a non-digit word character");
     }
-    if ( flags ) {
-        SV* sv_name
-           = newSVpvn_flags(name_start, (int)(RExC_parse - name_start),
+    sv_name = newSVpvn_flags(name_start, (int)(RExC_parse - name_start),
                             SVs_TEMP | (UTF ? SVf_UTF8 : 0));
-        if ( flags == REG_RSN_RETURN_NAME)
-            return sv_name;
-        else if (flags==REG_RSN_RETURN_DATA) {
-            HE *he_str = NULL;
-            SV *sv_dat = NULL;
-            if ( ! sv_name )      /* should not happen*/
-                Perl_croak(aTHX_ "panic: no svname in reg_scan_name");
-            if (RExC_paren_names)
-                he_str = hv_fetch_ent( RExC_paren_names, sv_name, 0, 0 );
-            if ( he_str )
-                sv_dat = HeVAL(he_str);
-            if ( ! sv_dat )
+    if ( flags == REG_RSN_RETURN_NAME)
+        return sv_name;
+    else if (flags==REG_RSN_RETURN_DATA) {
+        HE *he_str = NULL;
+        SV *sv_dat = NULL;
+        if ( ! sv_name )      /* should not happen*/
+            Perl_croak(aTHX_ "panic: no svname in reg_scan_name");
+        if (RExC_paren_names)
+            he_str = hv_fetch_ent( RExC_paren_names, sv_name, 0, 0 );
+        if ( he_str )
+            sv_dat = HeVAL(he_str);
+        if ( ! sv_dat ) {   /* Didn't find group */
+
+            /* It might be a forward reference; we can't fail until we
+                * know, by completing the parse to get all the groups, and
+                * then reparsing */
+            if (RExC_total_parens > 0)  {
                 vFAIL("Reference to nonexistent named group");
-            return sv_dat;
-        }
-        else {
-            Perl_croak(aTHX_ "panic: bad flag %lx in reg_scan_name",
-                      (unsigned long) flags);
+            }
+            else {
+                REQUIRE_PARENS_PASS;
+            }
         }
-        NOT_REACHED; /* NOTREACHED */
+        return sv_dat;
     }
-    return NULL;
+
+    Perl_croak(aTHX_ "panic: bad flag %lx in reg_scan_name",
+                     (unsigned long) flags);
 }
 
 #define DEBUG_PARSE_MSG(funcname)     DEBUG_PARSE_r({           \
     int num;                                                    \
     if (RExC_lastparse!=RExC_parse) {                           \
-        Perl_re_printf( aTHX_  "%s",                                        \
+        Perl_re_printf( aTHX_  "%s",                            \
             Perl_pv_pretty(aTHX_ RExC_mysv1, RExC_parse,        \
                 RExC_end - RExC_parse, 16,                      \
                 "", "",                                         \
@@ -8476,17 +8634,14 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
             )                                                   \
         );                                                      \
     } else                                                      \
-        Perl_re_printf( aTHX_ "%16s","");                                   \
+        Perl_re_printf( aTHX_ "%16s","");                       \
                                                                 \
-    if (SIZE_ONLY)                                              \
-       num = RExC_size + 1;                                     \
-    else                                                        \
-       num=REG_NODE_NUM(RExC_emit);                             \
+    num=REG_NODE_NUM(REGNODE_p(RExC_emit));                     \
     if (RExC_lastnum!=num)                                      \
-       Perl_re_printf( aTHX_ "|%4d",num);                                   \
+       Perl_re_printf( aTHX_ "|%4d", num);                      \
     else                                                        \
-       Perl_re_printf( aTHX_ "|%4s","");                                    \
-    Perl_re_printf( aTHX_ "|%*s%-4s",                                       \
+       Perl_re_printf( aTHX_ "|%4s","");                        \
+    Perl_re_printf( aTHX_ "|%*s%-4s",                           \
         (int)((depth*2)), "",                                   \
         (funcname)                                              \
     );                                                          \
@@ -8591,8 +8746,6 @@ S__invlist_array_init(SV* const invlist, const bool will_have_0)
     return zero_addr + *offset;
 }
 
-#endif
-
 PERL_STATIC_INLINE void
 S_invlist_set_len(pTHX_ SV* const invlist, const UV len, const bool offset)
 {
@@ -8601,7 +8754,7 @@ S_invlist_set_len(pTHX_ SV* const invlist, const UV len, const bool offset)
     PERL_UNUSED_CONTEXT;
     PERL_ARGS_ASSERT_INVLIST_SET_LEN;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     SvCUR_set(invlist,
               (len == 0)
@@ -8610,8 +8763,6 @@ S_invlist_set_len(pTHX_ SV* const invlist, const UV len, const bool offset)
     assert(SvLEN(invlist) == 0 || SvCUR(invlist) <= SvLEN(invlist));
 }
 
-#ifndef PERL_IN_XSUB_RE
-
 STATIC void
 S_invlist_replace_list_destroys_src(pTHX_ SV * dest, SV * src)
 {
@@ -8629,8 +8780,8 @@ S_invlist_replace_list_destroys_src(pTHX_ SV * dest, SV * src)
 
     PERL_ARGS_ASSERT_INVLIST_REPLACE_LIST_DESTROYS_SRC;
 
-    assert(SvTYPE(src) == SVt_INVLIST);
-    assert(SvTYPE(dest) == SVt_INVLIST);
+    assert(is_invlist(src));
+    assert(is_invlist(dest));
     assert(! invlist_is_iterating(src));
     assert(SvCUR(src) == 0 || SvCUR(src) < SvLEN(src));
 
@@ -8665,7 +8816,7 @@ S_get_invlist_previous_index_addr(SV* invlist)
      * */
     PERL_ARGS_ASSERT_GET_INVLIST_PREVIOUS_INDEX_ADDR;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     return &(((XINVLIST*) SvANY(invlist))->prev_index);
 }
@@ -8703,7 +8854,7 @@ S_invlist_trim(SV* invlist)
 
     PERL_ARGS_ASSERT_INVLIST_TRIM;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     SvPV_renew(invlist, MAX(min_size, SvCUR(invlist) + 1));
 }
@@ -8713,7 +8864,7 @@ S_invlist_clear(pTHX_ SV* invlist)    /* Empty the inversion list */
 {
     PERL_ARGS_ASSERT_INVLIST_CLEAR;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     invlist_set_len(invlist, 0, 0);
     invlist_trim(invlist);
@@ -8739,7 +8890,7 @@ S_invlist_max(SV* const invlist)
 
     PERL_ARGS_ASSERT_INVLIST_MAX;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     /* Assumes worst case, in which the 0 element is not counted in the
      * inversion list, so subtracts 1 for that */
@@ -8747,6 +8898,23 @@ S_invlist_max(SV* const invlist)
            ? FROM_INTERNAL_SIZE(SvCUR(invlist)) - 1
            : FROM_INTERNAL_SIZE(SvLEN(invlist)) - 1;
 }
+
+STATIC void
+S_initialize_invlist_guts(pTHX_ SV* invlist, const Size_t initial_size)
+{
+    PERL_ARGS_ASSERT_INITIALIZE_INVLIST_GUTS;
+
+    /* First 1 is in case the zero element isn't in the list; second 1 is for
+     * trailing NUL */
+    SvGROW(invlist, TO_INTERNAL_SIZE(initial_size + 1) + 1);
+    invlist_set_len(invlist, 0, 0);
+
+    /* Force iterinit() to be used to get iteration to work */
+    invlist_iterfinish(invlist);
+
+    *get_invlist_previous_index_addr(invlist) = 0;
+}
+
 SV*
 Perl__new_invlist(pTHX_ IV initial_size)
 {
@@ -8764,15 +8932,7 @@ Perl__new_invlist(pTHX_ IV initial_size)
     /* Allocate the initial space */
     new_list = newSV_type(SVt_INVLIST);
 
-    /* First 1 is in case the zero element isn't in the list; second 1 is for
-     * trailing NUL */
-    SvGROW(new_list, TO_INTERNAL_SIZE(initial_size + 1) + 1);
-    invlist_set_len(new_list, 0, 0);
-
-    /* Force iterinit() to be used to get iteration to work */
-    *get_invlist_iter_addr(new_list) = (STRLEN) UV_MAX;
-
-    *get_invlist_previous_index_addr(new_list) = 0;
+    initialize_invlist_guts(new_list, initial_size);
 
     return new_list;
 }
@@ -8840,7 +9000,7 @@ S_invlist_extend(pTHX_ SV* const invlist, const UV new_max)
 
     PERL_ARGS_ASSERT_INVLIST_EXTEND;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     /* Add one to account for the zero element at the beginning which may not
      * be counted by the calling parameters */
@@ -9164,7 +9324,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
 
     PERL_ARGS_ASSERT__INVLIST_UNION_MAYBE_COMPLEMENT_2ND;
     assert(a != b);
-    assert(*output == NULL || SvTYPE(*output) == SVt_INVLIST);
+    assert(*output == NULL || is_invlist(*output));
 
     len_b = _invlist_len(b);
     if (len_b == 0) {
@@ -9206,7 +9366,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
          * union.  We can just return a copy of 'a' if '*output' doesn't point
          * to an existing list */
         if (*output == NULL) {
-            *output = invlist_clone(a);
+            *output = invlist_clone(a, NULL);
             return;
         }
 
@@ -9217,7 +9377,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
         }
 
         /* Here, '*output' is to be overwritten by 'a' */
-        u = invlist_clone(a);
+        u = invlist_clone(a, NULL);
         invlist_replace_list_destroys_src(*output, u);
         SvREFCNT_dec_NN(u);
 
@@ -9234,7 +9394,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
          * the clone */
 
         SV ** dest = (*output == NULL) ? output : &u;
-        *dest = invlist_clone(b);
+        *dest = invlist_clone(b, NULL);
         if (complement_b) {
             _invlist_invert(*dest);
         }
@@ -9442,7 +9602,7 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
 
     PERL_ARGS_ASSERT__INVLIST_INTERSECTION_MAYBE_COMPLEMENT_2ND;
     assert(a != b);
-    assert(*i == NULL || SvTYPE(*i) == SVt_INVLIST);
+    assert(*i == NULL || is_invlist(*i));
 
     /* Special case if either one is empty */
     len_a = (a == NULL) ? 0 : _invlist_len(a);
@@ -9459,11 +9619,11 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
             }
 
             if (*i == NULL) {
-                *i = invlist_clone(a);
+                *i = invlist_clone(a, NULL);
                 return;
             }
 
-            r = invlist_clone(a);
+            r = invlist_clone(a, NULL);
             invlist_replace_list_destroys_src(*i, r);
             SvREFCNT_dec_NN(r);
             return;
@@ -9953,30 +10113,38 @@ Perl__invlist_invert(pTHX_ SV* const invlist)
     *get_invlist_offset_addr(invlist) = ! *get_invlist_offset_addr(invlist);
 }
 
-#endif
-
-PERL_STATIC_INLINE SV*
-S_invlist_clone(pTHX_ SV* const invlist)
+SV*
+Perl_invlist_clone(pTHX_ SV* const invlist, SV* new_invlist)
 {
 
     /* Return a new inversion list that is a copy of the input one, which is
      * unchanged.  The new list will not be mortal even if the old one was. */
 
-    /* Need to allocate extra space to accommodate Perl's addition of a
-     * trailing NUL to SvPV's, since it thinks they are always strings */
-    SV* new_invlist = _new_invlist(_invlist_len(invlist) + 1);
-    STRLEN physical_length = SvCUR(invlist);
-    bool offset = *(get_invlist_offset_addr(invlist));
+    const STRLEN nominal_length = _invlist_len(invlist);    /* Why not +1 XXX */
+    const STRLEN physical_length = SvCUR(invlist);
+    const bool offset = *(get_invlist_offset_addr(invlist));
 
     PERL_ARGS_ASSERT_INVLIST_CLONE;
 
+    /* Need to allocate extra space to accommodate Perl's addition of a
+     * trailing NUL to SvPV's, since it thinks they are always strings */
+    if (new_invlist == NULL) {
+        new_invlist = _new_invlist(nominal_length);
+    }
+    else {
+        sv_upgrade(new_invlist, SVt_INVLIST);
+        initialize_invlist_guts(new_invlist, nominal_length);
+    }
+
     *(get_invlist_offset_addr(new_invlist)) = offset;
-    invlist_set_len(new_invlist, _invlist_len(invlist), offset);
+    invlist_set_len(new_invlist, nominal_length, offset);
     Copy(SvPVX(invlist), SvPVX(new_invlist), physical_length, char);
 
     return new_invlist;
 }
 
+#endif
+
 PERL_STATIC_INLINE STRLEN*
 S_get_invlist_iter_addr(SV* invlist)
 {
@@ -9985,7 +10153,7 @@ S_get_invlist_iter_addr(SV* invlist)
 
     PERL_ARGS_ASSERT_GET_INVLIST_ITER_ADDR;
 
-    assert(SvTYPE(invlist) == SVt_INVLIST);
+    assert(is_invlist(invlist));
 
     return &(((XINVLIST*) SvANY(invlist))->iterator);
 }
@@ -10416,14 +10584,14 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
         RExC_parse++;
         has_use_defaults = TRUE;
         STD_PMMOD_FLAGS_CLEAR(&RExC_flags);
-        set_regex_charset(&RExC_flags, (RExC_utf8 || RExC_uni_semantics)
+        set_regex_charset(&RExC_flags, (RExC_uni_semantics)
                                         ? REGEX_UNICODE_CHARSET
                                         : REGEX_DEPENDS_CHARSET);
     }
 
     cs = get_regex_charset(RExC_flags);
     if (cs == REGEX_DEPENDS_CHARSET
-        && (RExC_utf8 || RExC_uni_semantics))
+        && (RExC_uni_semantics))
     {
         cs = REGEX_UNICODE_CHARSET;
     }
@@ -10488,7 +10656,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                  * pattern (or target, not known until runtime) are
                  * utf8, or something in the pattern indicates unicode
                  * semantics */
-                cs = (RExC_utf8 || RExC_uni_semantics)
+                cs = (RExC_uni_semantics)
                      ? REGEX_UNICODE_CHARSET
                      : REGEX_DEPENDS_CHARSET;
                 has_charset_modifier = DEPENDS_PAT_MOD;
@@ -10513,7 +10681,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 NOT_REACHED; /*NOTREACHED*/
             case ONCE_PAT_MOD: /* 'o' */
             case GLOBAL_PAT_MOD: /* 'g' */
-                if (PASS2 && ckWARN(WARN_REGEXP)) {
+                if (ckWARN(WARN_REGEXP)) {
                     const I32 wflagbit = *RExC_parse == 'o'
                                          ? WASTED_O
                                          : WASTED_G;
@@ -10533,7 +10701,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 break;
 
             case CONTINUE_PAT_MOD: /* 'c' */
-                if (PASS2 && ckWARN(WARN_REGEXP)) {
+                if (ckWARN(WARN_REGEXP)) {
                     if (! (wastedflags & WASTED_C) ) {
                         wastedflags |= WASTED_GC;
                        /* diag_listed_as: Useless (?-%s) - don't use /%s modifier in regex; marked by <-- HERE in m/%s/ */
@@ -10548,8 +10716,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 break;
             case KEEPCOPY_PAT_MOD: /* 'p' */
                 if (flagsp == &negflags) {
-                    if (PASS2)
-                        ckWARNreg(RExC_parse + 1,"Useless use of (?-p)");
+                    ckWARNreg(RExC_parse + 1,"Useless use of (?-p)");
                 } else {
                     *flagsp |= RXf_PMf_KEEPCOPY;
                 }
@@ -10611,32 +10778,30 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
 #define REGTAIL_STUDY(x,y,z) regtail((x),(y),(z),depth+1)
 #endif
 
-PERL_STATIC_INLINE regnode *
+PERL_STATIC_INLINE regnode_offset
 S_handle_named_backref(pTHX_ RExC_state_t *pRExC_state,
                              I32 *flagp,
                              char * parse_start,
                              char ch
                       )
 {
-    regnode *ret;
+    regnode_offset ret;
     char* name_start = RExC_parse;
     U32 num = 0;
-    SV *sv_dat = reg_scan_name(pRExC_state, SIZE_ONLY
-                                            ? REG_RSN_RETURN_NULL
-                                            : REG_RSN_RETURN_DATA);
+    SV *sv_dat = reg_scan_name(pRExC_state, REG_RSN_RETURN_DATA);
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_HANDLE_NAMED_BACKREF;
 
     if (RExC_parse == name_start || *RExC_parse != ch) {
         /* diag_listed_as: Sequence \%s... not terminated in regex; marked by <-- HERE in m/%s/ */
-        vFAIL2("Sequence %.3s... not terminated",parse_start);
+        vFAIL2("Sequence %.3s... not terminated", parse_start);
     }
 
-    if (!SIZE_ONLY) {
+    if (sv_dat) {
         num = add_data( pRExC_state, STR_WITH_LEN("S"));
         RExC_rxi->data->data[num]=(void*)sv_dat;
-        SvREFCNT_inc_simple_void(sv_dat);
+        SvREFCNT_inc_simple_void_NN(sv_dat);
     }
     RExC_sawback = 1;
     ret = reganode(pRExC_state,
@@ -10652,29 +10817,33 @@ S_handle_named_backref(pTHX_ RExC_state_t *pRExC_state,
                     num);
     *flagp |= HASWIDTH;
 
-    Set_Node_Offset(ret, parse_start+1);
-    Set_Node_Cur_Length(ret, parse_start);
+    Set_Node_Offset(REGNODE_p(ret), parse_start+1);
+    Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
 
     nextchar(pRExC_state);
     return ret;
 }
 
-/* Returns NULL, setting *flagp to TRYAGAIN at the end of (?) that only sets
-   flags. Returns NULL, setting *flagp to RESTART_PASS1 if the sizing scan
-   needs to be restarted, or'd with NEED_UTF8 if the pattern needs to be
-   upgraded to UTF-8.  Otherwise would only return NULL if regbranch() returns
-   NULL, which cannot happen.  */
-STATIC regnode *
-S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
+/* On success, returns the offset at which any next node should be placed into
+ * the regex engine program being compiled.
+ *
+ * Returns 0 otherwise, with *flagp set to indicate why:
+ *  TRYAGAIN        at the end of (?) that only sets flags.
+ *  RESTART_PARSE   if the sizing scan needs to be restarted, or'd with
+ *                  NEED_UTF8 if the pattern needs to be upgraded to UTF-8.
+ *  Otherwise would only return 0 if regbranch() returns 0, which cannot
+ *  happen.  */
+STATIC regnode_offset
+S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp, U32 depth)
     /* paren: Parenthesized? 0=top; 1,2=inside '(': changed to letter.
      * 2 is like 1, but indicates that nextchar() has been called to advance
      * RExC_parse beyond the '('.  Things like '(?' are indivisible tokens, and
      * this flag alerts us to the need to check for that */
 {
-    regnode *ret = NULL;    /* Will be the head of the group. */
-    regnode *br;
-    regnode *lastbr;
-    regnode *ender = NULL;
+    regnode_offset ret = 0;    /* Will be the head of the group. */
+    regnode_offset br;
+    regnode_offset lastbr;
+    regnode_offset ender = 0;
     I32 parno = 0;
     I32 flags;
     U32 oregflags = RExC_flags;
@@ -10790,38 +10959,38 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
 
            switch ( *start_verb ) {
             case 'A':  /* (*ACCEPT) */
-                if ( memEQs(start_verb,verb_len,"ACCEPT") ) {
+                if ( memEQs(start_verb, verb_len,"ACCEPT") ) {
                    op = ACCEPT;
                    internal_argval = RExC_nestroot;
                }
                break;
             case 'C':  /* (*COMMIT) */
-                if ( memEQs(start_verb,verb_len,"COMMIT") )
+                if ( memEQs(start_verb, verb_len,"COMMIT") )
                     op = COMMIT;
                 break;
             case 'F':  /* (*FAIL) */
-                if ( verb_len==1 || memEQs(start_verb,verb_len,"FAIL") ) {
+                if ( verb_len==1 || memEQs(start_verb, verb_len,"FAIL") ) {
                    op = OPFAIL;
                }
                break;
             case ':':  /* (*:NAME) */
            case 'M':  /* (*MARK:NAME) */
-               if ( verb_len==0 || memEQs(start_verb,verb_len,"MARK") ) {
+               if ( verb_len==0 || memEQs(start_verb, verb_len,"MARK") ) {
                     op = MARKPOINT;
                     arg_required = 1;
                 }
                 break;
             case 'P':  /* (*PRUNE) */
-                if ( memEQs(start_verb,verb_len,"PRUNE") )
+                if ( memEQs(start_verb, verb_len,"PRUNE") )
                     op = PRUNE;
                 break;
             case 'S':   /* (*SKIP) */
-                if ( memEQs(start_verb,verb_len,"SKIP") )
+                if ( memEQs(start_verb, verb_len,"SKIP") )
                     op = SKIP;
                 break;
             case 'T':  /* (*THEN) */
                 /* [19:06] <TimToady> :: is then */
-                if ( memEQs(start_verb,verb_len,"THEN") ) {
+                if ( memEQs(start_verb, verb_len,"THEN") ) {
                     op = CUTGROUP;
                     RExC_seen |= REG_CUTGROUP_SEEN;
                 }
@@ -10870,14 +11039,14 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                 if (   memEQs(start_verb, verb_len, "sr")
                     || memEQs(start_verb, verb_len, "script_run"))
                 {
-                    regnode * atomic;
+                    regnode_offset atomic;
 
                     paren = 's';
 
                    script_run:
 
                     /* This indicates Unicode rules. */
-                    REQUIRE_UNI_RULES(flagp, NULL);
+                    REQUIRE_UNI_RULES(flagp, 0);
 
                     if (! start_arg) {
                         goto no_colon;
@@ -10893,7 +11062,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                          *  side effects, but that is explicitly documented as
                          *  undefined behavior. */
 
-                        ret = NULL;
+                        ret = 0;
 
                         if (paren == 's') {
                             paren = ':';
@@ -10909,13 +11078,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
 
                     /* By doing this here, we avoid extra warnings for nested
                      * script runs */
-                    if (PASS2) {
-                        Perl_ck_warner_d(aTHX_
-                            packWARN(WARN_EXPERIMENTAL__SCRIPT_RUN),
-                            "The script_run feature is experimental"
-                            REPORT_LOCATION, REPORT_LOCATION_ARGS(RExC_parse));
-
-                    }
+                    ckWARNexperimental(RExC_parse,
+                        WARN_EXPERIMENTAL__SCRIPT_RUN,
+                        "The script_run feature is experimental");
 
                     if (paren == 's') {
                         /* Here, we're starting a new regular script run */
@@ -10934,9 +11099,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     RExC_in_script_run = 1;
 
                     atomic = reg(pRExC_state, 'r', &flags, depth);
-                    if (flags & (RESTART_PASS1|NEED_UTF8)) {
-                        *flagp = flags & (RESTART_PASS1|NEED_UTF8);
-                        return NULL;
+                    if (flags & (RESTART_PARSE|NEED_UTF8)) {
+                        *flagp = flags & (RESTART_PARSE|NEED_UTF8);
+                        return 0;
                     }
 
                     REGTAIL(pRExC_state, ret, atomic);
@@ -10956,13 +11121,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                 /*FALLTHROUGH*/
 
             alpha_assertions:
-
-                if (PASS2) {
-                    Perl_ck_warner_d(aTHX_
-                        packWARN(WARN_EXPERIMENTAL__ALPHA_ASSERTIONS),
-                        "The alpha_assertions feature is experimental"
-                        REPORT_LOCATION, REPORT_LOCATION_ARGS(RExC_parse));
-                }
+                ckWARNexperimental(RExC_parse,
+                        WARN_EXPERIMENTAL__ALPHA_ASSERTIONS,
+                        "The alpha_assertions feature is experimental");
 
                 RExC_seen_zerolen++;
 
@@ -11013,20 +11174,18 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                 ret = reg2Lanode(pRExC_state, op, 0, internal_argval);
             }
             RExC_seen |= REG_VERBARG_SEEN;
-            if ( ! SIZE_ONLY ) {
-                if (start_arg) {
-                    SV *sv = newSVpvn( start_arg,
-                                       RExC_parse - start_arg);
-                    ARG(ret) = add_data( pRExC_state,
-                                         STR_WITH_LEN("S"));
-                    RExC_rxi->data->data[ARG(ret)]=(void*)sv;
-                    ret->flags = 1;
-                } else {
-                    ret->flags = 0;
-                }
-                if ( internal_argval != -1 )
-                    ARG2L_SET(ret, internal_argval);
+            if (start_arg) {
+                SV *sv = newSVpvn( start_arg,
+                                    RExC_parse - start_arg);
+                ARG(REGNODE_p(ret)) = add_data( pRExC_state,
+                                        STR_WITH_LEN("S"));
+                RExC_rxi->data->data[ARG(REGNODE_p(ret))]=(void*)sv;
+                FLAGS(REGNODE_p(ret)) = 1;
+            } else {
+                FLAGS(REGNODE_p(ret)) = 0;
             }
+            if ( internal_argval != -1 )
+                ARG2L_SET(REGNODE_p(ret), internal_argval);
            nextchar(pRExC_state);
            return ret;
         }
@@ -11046,7 +11205,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
             if (RExC_parse > RExC_end) {
                 paren = '\0';
             }
-           ret = NULL;                 /* For look-ahead/behind. */
+           ret = 0;                    /* For look-ahead/behind. */
            switch (paren) {
 
            case 'P':   /* (?P...) variants for those used to PCRE/Python */
@@ -11087,10 +11246,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                 /* FALLTHROUGH */
             case '\'':          /* (?'...') */
                     name_start = RExC_parse;
-                    svname = reg_scan_name(pRExC_state,
-                        SIZE_ONLY    /* reverse test from the others */
-                        ? REG_RSN_RETURN_NAME
-                        : REG_RSN_RETURN_NULL);
+                    svname = reg_scan_name(pRExC_state, REG_RSN_RETURN_NAME);
                    if (   RExC_parse == name_start
                         || RExC_parse >= RExC_end
                         || *RExC_parse != paren)
@@ -11098,7 +11254,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                        vFAIL2("Sequence (?%c... not terminated",
                            paren=='>' ? '<' : paren);
                     }
-                   if (SIZE_ONLY) {
+                   {
                        HE *he_str;
                        SV *sv_dat = NULL;
                         if (!svname) /* shouldn't happen */
@@ -11142,7 +11298,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                                 SvIV_set(sv_dat, SvIVX(sv_dat) + 1);
                             }
                         } else {
-                            (void)SvUPGRADE(sv_dat,SVt_PVNV);
+                            (void)SvUPGRADE(sv_dat, SVt_PVNV);
                             sv_setpvn(sv_dat, (char *)&(RExC_npar),
                                                                 sizeof(I32));
                             SvIOK_on(sv_dat);
@@ -11152,7 +11308,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                         /* Yes this does cause a memory leak in debugging Perls
                          * */
                         if (!av_store(RExC_paren_name_list,
-                                      RExC_npar, SvREFCNT_inc(svname)))
+                                      RExC_npar, SvREFCNT_inc_NN(svname)))
                             SvREFCNT_dec_NN(svname);
 #endif
 
@@ -11190,6 +11346,11 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                   buffers in alternations share the same numbers */
                paren = ':';
                after_freeze = freeze_paren = RExC_npar;
+
+                /* XXX This construct currently requires an extra pass.
+                 * Investigation would be required to see if that could be
+                 * changed */
+                REQUIRE_PARENS_PASS;
                break;
            case ':':           /* (?:...) */
            case '>':           /* (?>...) */
@@ -11204,6 +11365,11 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                    FAIL("Sequence (?R) not terminated");
                 num = 0;
                 RExC_seen |= REG_RECURSE_SEEN;
+
+                /* XXX These constructs currently require an extra pass.
+                 * It probably could be changed */
+                REQUIRE_PARENS_PASS;
+
                *flagp |= POSTPONED;
                 goto gen_recurse_regop;
                /*notreached*/
@@ -11212,9 +11378,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                 parse_start = RExC_parse - 1;
               named_recursion:
                 {
-                   SV *sv_dat = reg_scan_name(pRExC_state,
-                       SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
-                    num = sv_dat ? *((I32 *)SvPVX(sv_dat)) : 0;
+                    SV *sv_dat = reg_scan_name(pRExC_state,
+                                               REG_RSN_RETURN_DATA);
+                   num = sv_dat ? *((I32 *)SvPVX(sv_dat)) : 0;
                 }
                 if (RExC_parse >= RExC_end || *RExC_parse != ')')
                     vFAIL("Sequence (?&... not terminated");
@@ -11276,8 +11442,17 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     */
                     num = RExC_npar + num;
                     if (num < 1)  {
-                        RExC_parse++;
-                        vFAIL("Reference to nonexistent group");
+
+                        /* It might be a forward reference; we can't fail until
+                         * we know, by completing the parse to get all the
+                         * groups, and then reparsing */
+                        if (RExC_total_parens > 0)  {
+                            RExC_parse++;
+                            vFAIL("Reference to nonexistent group");
+                        }
+                        else {
+                            REQUIRE_PARENS_PASS;
+                        }
                     }
                 } else if ( paren == '+' ) {
                     num = RExC_npar + num - 1;
@@ -11292,21 +11467,32 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                  */
 
                 ret = reg2Lanode(pRExC_state, GOSUB, num, RExC_recurse_count);
-                if (!SIZE_ONLY) {
-                   if (num > (I32)RExC_rx->nparens) {
-                       RExC_parse++;
-                       vFAIL("Reference to nonexistent group");
-                   }
-                   RExC_recurse_count++;
-                    DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
-                        "%*s%*s Recurse #%" UVuf " to %" IVdf "\n",
-                              22, "|    |", (int)(depth * 2 + 1), "",
-                              (UV)ARG(ret), (IV)ARG2L(ret)));
+                if (num >= RExC_npar) {
+
+                    /* It might be a forward reference; we can't fail until we
+                     * know, by completing the parse to get all the groups, and
+                     * then reparsing */
+                    if (RExC_total_parens > 0)  {
+                        if (num >= RExC_total_parens) {
+                            RExC_parse++;
+                            vFAIL("Reference to nonexistent group");
+                        }
+                    }
+                    else {
+                        REQUIRE_PARENS_PASS;
+                    }
                 }
+                RExC_recurse_count++;
+                DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
+                    "%*s%*s Recurse #%" UVuf " to %" IVdf "\n",
+                            22, "|    |", (int)(depth * 2 + 1), "",
+                            (UV)ARG(REGNODE_p(ret)),
+                            (IV)ARG2L(REGNODE_p(ret))));
                 RExC_seen |= REG_RECURSE_SEEN;
 
-                Set_Node_Length(ret, 1 + regarglen[OP(ret)]); /* MJD */
-               Set_Node_Offset(ret, parse_start); /* MJD */
+                Set_Node_Length(REGNODE_p(ret),
+                                1 + regarglen[OP(REGNODE_p(ret))]); /* MJD */
+               Set_Node_Offset(REGNODE_p(ret), parse_start); /* MJD */
 
                 *flagp |= POSTPONED;
                 assert(*RExC_parse == ')');
@@ -11333,6 +11519,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
            {
                U32 n = 0;
                struct reg_code_block *cb;
+                OP * o;
 
                RExC_seen_zerolen++;
 
@@ -11350,25 +11537,23 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                /* this is a pre-compiled code block (?{...}) */
                cb = &pRExC_state->code_blocks->cb[pRExC_state->code_index];
                RExC_parse = RExC_start + cb->end;
-               if (!SIZE_ONLY) {
-                   OP *o = cb->block;
-                   if (cb->src_regex) {
-                       n = add_data(pRExC_state, STR_WITH_LEN("rl"));
-                       RExC_rxi->data->data[n] =
-                           (void*)SvREFCNT_inc((SV*)cb->src_regex);
-                       RExC_rxi->data->data[n+1] = (void*)o;
-                   }
-                   else {
-                       n = add_data(pRExC_state,
-                              (RExC_pm_flags & PMf_HAS_CV) ? "L" : "l", 1);
-                       RExC_rxi->data->data[n] = (void*)o;
-                   }
-               }
+               o = cb->block;
+                if (cb->src_regex) {
+                    n = add_data(pRExC_state, STR_WITH_LEN("rl"));
+                    RExC_rxi->data->data[n] =
+                        (void*)SvREFCNT_inc((SV*)cb->src_regex);
+                    RExC_rxi->data->data[n+1] = (void*)o;
+                }
+                else {
+                    n = add_data(pRExC_state,
+                            (RExC_pm_flags & PMf_HAS_CV) ? "L" : "l", 1);
+                    RExC_rxi->data->data[n] = (void*)o;
+                }
                pRExC_state->code_index++;
                nextchar(pRExC_state);
 
                if (is_logical) {
-                    regnode *eval;
+                    regnode_offset eval;
                    ret = reg_node(pRExC_state, LOGICAL);
 
                     eval = reg2Lanode(pRExC_state, EVAL,
@@ -11378,16 +11563,14 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                                         * return value */
                                        RExC_flags & RXf_PMf_COMPILETIME
                                       );
-                   if (!SIZE_ONLY) {
-                       ret->flags = 2;
-                    }
+                    FLAGS(REGNODE_p(ret)) = 2;
                     REGTAIL(pRExC_state, ret, eval);
                     /* deal with the length of this later - MJD */
                    return ret;
                }
                ret = reg2Lanode(pRExC_state, EVAL, n, 0);
-               Set_Node_Length(ret, RExC_parse - parse_start + 1);
-               Set_Node_Offset(ret, parse_start);
+               Set_Node_Length(REGNODE_p(ret), RExC_parse - parse_start + 1);
+               Set_Node_Offset(REGNODE_p(ret), parse_start);
                return ret;
            }
            case '(':           /* (?(?{...})...) and (?(?=...)...) */
@@ -11427,14 +11610,13 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                                          "negative_lookbehind:"))))
                 ) { /* Lookahead or eval. */
                     I32 flag;
-                    regnode *tail;
+                    regnode_offset tail;
 
                     ret = reg_node(pRExC_state, LOGICAL);
-                    if (!SIZE_ONLY)
-                        ret->flags = 1;
+                    FLAGS(REGNODE_p(ret)) = 1;
 
                     tail = reg(pRExC_state, 1, &flag, depth+1);
-                    RETURN_NULL_ON_RESTART(flag,flagp);
+                    RETURN_FAIL_ON_RESTART(flag, flagp);
                     REGTAIL(pRExC_state, ret, tail);
                     goto insert_if;
                 }
@@ -11444,8 +11626,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                    char ch = RExC_parse[0] == '<' ? '>' : '\'';
                    char *name_start= RExC_parse++;
                    U32 num = 0;
-                   SV *sv_dat=reg_scan_name(pRExC_state,
-                       SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
+                   SV *sv_dat=reg_scan_name(pRExC_state, REG_RSN_RETURN_DATA);
                    if (   RExC_parse == name_start
                         || RExC_parse >= RExC_end
                         || *RExC_parse != ch)
@@ -11454,19 +11635,19 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                             (ch == '>' ? '<' : ch));
                     }
                     RExC_parse++;
-                   if (!SIZE_ONLY) {
+                    if (sv_dat) {
                         num = add_data( pRExC_state, STR_WITH_LEN("S"));
                         RExC_rxi->data->data[num]=(void*)sv_dat;
-                        SvREFCNT_inc_simple_void(sv_dat);
+                        SvREFCNT_inc_simple_void_NN(sv_dat);
                     }
-                    ret = reganode(pRExC_state,NGROUPP,num);
+                    ret = reganode(pRExC_state, NGROUPP, num);
                     goto insert_if_check_paren;
                }
                else if (memBEGINs(RExC_parse,
                                    (STRLEN) (RExC_end - RExC_parse),
                                    "DEFINE"))
                 {
-                   ret = reganode(pRExC_state,DEFINEP,0);
+                   ret = reganode(pRExC_state, DEFINEP, 0);
                    RExC_parse += DEFINE_len;
                    is_define = 1;
                    goto insert_if_check_paren;
@@ -11496,24 +11677,11 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                        SV *sv_dat;
                        RExC_parse++;
                        sv_dat = reg_scan_name(pRExC_state,
-                            SIZE_ONLY
-                            ? REG_RSN_RETURN_NULL
-                            : REG_RSN_RETURN_DATA);
-
-                        /* we should only have a false sv_dat when
-                         * SIZE_ONLY is true, and we always have false
-                         * sv_dat when SIZE_ONLY is true.
-                         * reg_scan_name() will VFAIL() if the name is
-                         * unknown when SIZE_ONLY is false, and otherwise
-                         * will return something, and when SIZE_ONLY is
-                         * true, reg_scan_name() just parses the string,
-                         * and doesnt return anything. (in theory) */
-                        assert(SIZE_ONLY ? !sv_dat : !!sv_dat);
-
+                                               REG_RSN_RETURN_DATA);
                         if (sv_dat)
                             parno = 1 + *((I32 *)SvPVX(sv_dat));
                    }
-                   ret = reganode(pRExC_state,INSUBP,parno);
+                   ret = reganode(pRExC_state, INSUBP, parno);
                    goto insert_if_check_paren;
                }
                else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
@@ -11540,10 +11708,10 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                    nextchar(pRExC_state);
                  insert_if:
                     REGTAIL(pRExC_state, ret, reganode(pRExC_state, IFTHEN, 0));
-                    br = regbranch(pRExC_state, &flags, 1,depth+1);
-                   if (br == NULL) {
-                        RETURN_NULL_ON_RESTART(flags,flagp);
-                        FAIL2("panic: regbranch returned NULL, flags=%#" UVxf,
+                    br = regbranch(pRExC_state, &flags, 1, depth+1);
+                   if (br == 0) {
+                        RETURN_FAIL_ON_RESTART(flags,flagp);
+                        FAIL2("panic: regbranch returned failure, flags=%#" UVxf,
                               (UV) flags);
                     } else
                         REGTAIL(pRExC_state, br, reganode(pRExC_state,
@@ -11559,9 +11727,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                         /* Fake one for optimizer.  */
                         lastbr = reganode(pRExC_state, IFTHEN, 0);
 
-                        if (!regbranch(pRExC_state, &flags, 1,depth+1)) {
-                            RETURN_NULL_ON_RESTART(flags,flagp);
-                            FAIL2("panic: regbranch returned NULL, flags=%#" UVxf,
+                        if (!regbranch(pRExC_state, &flags, 1, depth+1)) {
+                            RETURN_FAIL_ON_RESTART(flags, flagp);
+                            FAIL2("panic: regbranch returned failure, flags=%#" UVxf,
                                   (UV) flags);
                         }
                         REGTAIL(pRExC_state, ret, lastbr);
@@ -11571,7 +11739,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                         nextchar(pRExC_state);
                    }
                    else
-                       lastbr = NULL;
+                       lastbr = 0;
                     if (c != ')') {
                         if (RExC_parse >= RExC_end)
                             vFAIL("Switch (?(condition)... not terminated");
@@ -11582,13 +11750,18 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     REGTAIL(pRExC_state, br, ender);
                    if (lastbr) {
                         REGTAIL(pRExC_state, lastbr, ender);
-                        REGTAIL(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender);
+                        REGTAIL(pRExC_state, REGNODE_OFFSET(
+                                                NEXTOPER(
+                                                NEXTOPER(REGNODE_p(lastbr)))),
+                                             ender);
                    }
                    else
                         REGTAIL(pRExC_state, ret, ender);
+#if 0  /* Removing this doesn't cause failures in the test suite -- khw */
                     RExC_size++; /* XXX WHY do we need this?!!
                                     For large programs it seems to be required
                                     but I can't figure out why. -- dmq*/
+#endif
                    return ret;
                }
                 RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
@@ -11609,16 +11782,16 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     if (RExC_parse < RExC_end)
                         nextchar(pRExC_state);
                     *flagp = TRYAGAIN;
-                    return NULL;
+                    return 0;
                 }
                 paren = ':';
                 nextchar(pRExC_state);
-                ret = NULL;
+                ret = 0;
                 goto parse_rest;
             } /* end switch */
        }
        else {
-            if (*RExC_parse == '{' && PASS2) {
+            if (*RExC_parse == '{') {
                 ckWARNregdep(RExC_parse + 1,
                             "Unescaped left brace in regex is "
                             "deprecated here (and will be fatal "
@@ -11630,56 +11803,83 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
          capturing_parens:
            parno = RExC_npar;
            RExC_npar++;
+            if (RExC_total_parens <= 0) {
+                /* If we are in our first pass through (and maybe only pass),
+                 * we  need to allocate memory for the capturing parentheses
+                 * data structures.  Since we start at npar=1, when it reaches
+                 * 2, for the first time it has something to put in it.  Above
+                 * 2 means we extend what we already have */
+                if (RExC_npar == 2) {
+                    /* setup RExC_open_parens, which holds the address of each
+                     * OPEN tag, and to make things simpler for the 0 index the
+                     * start of the program - this is used later for offsets */
+                    Newxz(RExC_open_parens, RExC_npar, regnode_offset);
+                    RExC_open_parens[0] = 1;    /* +1 for REG_MAGIC */
+
+                    /* setup RExC_close_parens, which holds the address of each
+                     * CLOSE tag, and to make things simpler for the 0 index
+                     * the end of the program - this is used later for offsets
+                     * */
+                    Newxz(RExC_close_parens, RExC_npar, regnode_offset);
+                    /* we dont know where end op starts yet, so we dont need to
+                     * set RExC_close_parens[0] like we do RExC_open_parens[0]
+                     * above */
+                }
+                else {
+                    Renew(RExC_open_parens, RExC_npar, regnode_offset);
+                    Zero(RExC_open_parens + RExC_npar - 1, 1, regnode_offset);
+
+                    Renew(RExC_close_parens, RExC_npar, regnode_offset);
+                    Zero(RExC_close_parens + RExC_npar - 1, 1, regnode_offset);
+                }
+            }
 
            ret = reganode(pRExC_state, OPEN, parno);
-           if (!SIZE_ONLY ){
-               if (!RExC_nestroot)
-                   RExC_nestroot = parno;
-                if (RExC_open_parens && !RExC_open_parens[parno])
-               {
-                    DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
-                        "%*s%*s Setting open paren #%" IVdf " to %d\n",
-                        22, "|    |", (int)(depth * 2 + 1), "",
-                       (IV)parno, REG_NODE_NUM(ret)));
-                    RExC_open_parens[parno]= ret;
-               }
-           }
-            Set_Node_Length(ret, 1); /* MJD */
-            Set_Node_Offset(ret, RExC_parse); /* MJD */
+            if (!RExC_nestroot)
+                RExC_nestroot = parno;
+            if (RExC_open_parens && !RExC_open_parens[parno])
+            {
+                DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
+                    "%*s%*s Setting open paren #%" IVdf " to %d\n",
+                    22, "|    |", (int)(depth * 2 + 1), "",
+                    (IV)parno, REG_NODE_NUM(REGNODE_p(ret))));
+                RExC_open_parens[parno]= ret;
+            }
+
+            Set_Node_Length(REGNODE_p(ret), 1); /* MJD */
+            Set_Node_Offset(REGNODE_p(ret), RExC_parse); /* MJD */
            is_open = 1;
        } else {
             /* with RXf_PMf_NOCAPTURE treat (...) as (?:...) */
             paren = ':';
-           ret = NULL;
+           ret = 0;
        }
         }
     }
     else                        /* ! paren */
-       ret = NULL;
+       ret = 0;
 
    parse_rest:
     /* Pick up the branches, linking them together. */
     parse_start = RExC_parse;   /* MJD */
-    br = regbranch(pRExC_state, &flags, 1,depth+1);
+    br = regbranch(pRExC_state, &flags, 1, depth+1);
 
     /*     branch_len = (paren != 0); */
 
-    if (br == NULL) {
-        RETURN_NULL_ON_RESTART(flags,flagp);
-        FAIL2("panic: regbranch returned NULL, flags=%#" UVxf, (UV) flags);
+    if (br == 0) {
+        RETURN_FAIL_ON_RESTART(flags, flagp);
+        FAIL2("panic: regbranch returned failure, flags=%#" UVxf, (UV) flags);
     }
     if (*RExC_parse == '|') {
-       if (!SIZE_ONLY && RExC_extralen) {
+       if (RExC_use_BRANCHJ) {
            reginsert(pRExC_state, BRANCHJ, br, depth+1);
        }
        else {                  /* MJD */
            reginsert(pRExC_state, BRANCH, br, depth+1);
-            Set_Node_Length(br, paren != 0);
-            Set_Node_Offset_To_R(br-RExC_emit_start, parse_start-RExC_start);
+            Set_Node_Length(REGNODE_p(br), paren != 0);
+            Set_Node_Offset_To_R(br, parse_start-RExC_start);
         }
        have_branch = 1;
-       if (SIZE_ONLY)
-           RExC_extralen += 1;         /* For BRANCHJ-BRANCH. */
     }
     else if (paren == ':') {
        *flagp |= flags&SIMPLE;
@@ -11692,14 +11892,14 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
     *flagp |= flags & (SPSTART | HASWIDTH | POSTPONED);
     lastbr = br;
     while (*RExC_parse == '|') {
-       if (!SIZE_ONLY && RExC_extralen) {
-           ender = reganode(pRExC_state, LONGJMP,0);
+       if (RExC_use_BRANCHJ) {
+           ender = reganode(pRExC_state, LONGJMP, 0);
 
             /* Append to the previous. */
-            REGTAIL(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender);
+            REGTAIL(pRExC_state,
+                    REGNODE_OFFSET(NEXTOPER(NEXTOPER(REGNODE_p(lastbr)))),
+                    ender);
        }
-       if (SIZE_ONLY)
-           RExC_extralen += 2;         /* Account for LONGJMP. */
        nextchar(pRExC_state);
        if (freeze_paren) {
            if (RExC_npar > after_freeze)
@@ -11708,9 +11908,9 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
         }
         br = regbranch(pRExC_state, &flags, 0, depth+1);
 
-       if (br == NULL) {
-            RETURN_NULL_ON_RESTART(flags,flagp);
-            FAIL2("panic: regbranch returned NULL, flags=%#" UVxf, (UV) flags);
+       if (br == 0) {
+            RETURN_FAIL_ON_RESTART(flags, flagp);
+            FAIL2("panic: regbranch returned failure, flags=%#" UVxf, (UV) flags);
         }
         REGTAIL(pRExC_state, lastbr, br);               /* BRANCH -> BRANCH. */
        lastbr = br;
@@ -11718,6 +11918,8 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
     }
 
     if (have_branch || paren != ':') {
+        regnode * br;
+
        /* Make a closing node, and hook it on the end. */
        switch (paren) {
        case ':':
@@ -11728,13 +11930,14 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
             if ( RExC_close_parens ) {
                 DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
                         "%*s%*s Setting close paren #%" IVdf " to %d\n",
-                        22, "|    |", (int)(depth * 2 + 1), "", (IV)parno, REG_NODE_NUM(ender)));
+                        22, "|    |", (int)(depth * 2 + 1), "",
+                        (IV)parno, REG_NODE_NUM(REGNODE_p(ender))));
                 RExC_close_parens[parno]= ender;
                if (RExC_nestroot == parno)
                    RExC_nestroot = 0;
            }
-            Set_Node_Offset(ender,RExC_parse+1); /* MJD */
-            Set_Node_Length(ender,1); /* MJD */
+            Set_Node_Offset(REGNODE_p(ender), RExC_parse+1); /* MJD */
+            Set_Node_Length(REGNODE_p(ender), 1); /* MJD */
            break;
        case 's':
            ender = reg_node(pRExC_state, SRCLOSE);
@@ -11756,79 +11959,87 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
            break;
        case 0:
            ender = reg_node(pRExC_state, END);
-           if (!SIZE_ONLY) {
-                assert(!RExC_end_op); /* there can only be one! */
-                RExC_end_op = ender;
-                if (RExC_close_parens) {
-                    DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
-                        "%*s%*s Setting close paren #0 (END) to %d\n",
-                        22, "|    |", (int)(depth * 2 + 1), "", REG_NODE_NUM(ender)));
+            assert(!RExC_end_op); /* there can only be one! */
+            RExC_end_op = REGNODE_p(ender);
+            if (RExC_close_parens) {
+                DEBUG_OPTIMISE_MORE_r(Perl_re_printf( aTHX_
+                    "%*s%*s Setting close paren #0 (END) to %d\n",
+                    22, "|    |", (int)(depth * 2 + 1), "",
+                    REG_NODE_NUM(REGNODE_p(ender))));
 
-                    RExC_close_parens[0]= ender;
-                }
+                RExC_close_parens[0]= ender;
             }
            break;
        }
-        DEBUG_PARSE_r(if (!SIZE_ONLY) {
+        DEBUG_PARSE_r(
             DEBUG_PARSE_MSG("lsbr");
-            regprop(RExC_rx, RExC_mysv1, lastbr, NULL, pRExC_state);
-            regprop(RExC_rx, RExC_mysv2, ender, NULL, pRExC_state);
+            regprop(RExC_rx, RExC_mysv1, REGNODE_p(lastbr), NULL, pRExC_state);
+            regprop(RExC_rx, RExC_mysv2, REGNODE_p(ender), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ tying lastbr %s (%" IVdf ") to ender %s (%" IVdf ") offset %" IVdf "\n",
                           SvPV_nolen_const(RExC_mysv1),
-                          (IV)REG_NODE_NUM(lastbr),
+                          (IV)REG_NODE_NUM(REGNODE_p(lastbr)),
                           SvPV_nolen_const(RExC_mysv2),
-                          (IV)REG_NODE_NUM(ender),
+                          (IV)REG_NODE_NUM(REGNODE_p(ender)),
                           (IV)(ender - lastbr)
             );
-        });
+        );
         REGTAIL(pRExC_state, lastbr, ender);
 
-       if (have_branch && !SIZE_ONLY) {
+       if (have_branch) {
             char is_nothing= 1;
            if (depth==1)
                 RExC_seen |= REG_TOP_LEVEL_BRANCHES_SEEN;
 
            /* Hook the tails of the branches to the closing node. */
-           for (br = ret; br; br = regnext(br)) {
+           for (br = REGNODE_p(ret); br; br = regnext(br)) {
                const U8 op = PL_regkind[OP(br)];
                if (op == BRANCH) {
-                    REGTAIL_STUDY(pRExC_state, NEXTOPER(br), ender);
+                    REGTAIL_STUDY(pRExC_state,
+                                  REGNODE_OFFSET(NEXTOPER(br)),
+                                  ender);
                     if ( OP(NEXTOPER(br)) != NOTHING
-                         || regnext(NEXTOPER(br)) != ender)
+                         || regnext(NEXTOPER(br)) != REGNODE_p(ender))
                         is_nothing= 0;
                }
                else if (op == BRANCHJ) {
-                    REGTAIL_STUDY(pRExC_state, NEXTOPER(NEXTOPER(br)), ender);
+                    REGTAIL_STUDY(pRExC_state,
+                                  REGNODE_OFFSET(NEXTOPER(NEXTOPER(br))),
+                                  ender);
                     /* for now we always disable this optimisation * /
                     if ( OP(NEXTOPER(NEXTOPER(br))) != NOTHING
-                         || regnext(NEXTOPER(NEXTOPER(br))) != ender)
+                         || regnext(NEXTOPER(NEXTOPER(br))) != REGNODE_p(ender))
                     */
                         is_nothing= 0;
                }
            }
             if (is_nothing) {
-                br= PL_regkind[OP(ret)] != BRANCH ? regnext(ret) : ret;
-                DEBUG_PARSE_r(if (!SIZE_ONLY) {
+                regnode * ret_as_regnode = REGNODE_p(ret);
+                br= PL_regkind[OP(ret_as_regnode)] != BRANCH
+                               ? regnext(ret_as_regnode)
+                               : ret_as_regnode;
+                DEBUG_PARSE_r(
                     DEBUG_PARSE_MSG("NADA");
-                    regprop(RExC_rx, RExC_mysv1, ret, NULL, pRExC_state);
-                    regprop(RExC_rx, RExC_mysv2, ender, NULL, pRExC_state);
+                    regprop(RExC_rx, RExC_mysv1, ret_as_regnode,
+                                     NULL, pRExC_state);
+                    regprop(RExC_rx, RExC_mysv2, REGNODE_p(ender),
+                                     NULL, pRExC_state);
                     Perl_re_printf( aTHX_  "~ converting ret %s (%" IVdf ") to ender %s (%" IVdf ") offset %" IVdf "\n",
                                   SvPV_nolen_const(RExC_mysv1),
-                                  (IV)REG_NODE_NUM(ret),
+                                  (IV)REG_NODE_NUM(ret_as_regnode),
                                   SvPV_nolen_const(RExC_mysv2),
-                                  (IV)REG_NODE_NUM(ender),
+                                  (IV)REG_NODE_NUM(REGNODE_p(ender)),
                                   (IV)(ender - ret)
                     );
-                });
+                );
                 OP(br)= NOTHING;
-                if (OP(ender) == TAIL) {
+                if (OP(REGNODE_p(ender)) == TAIL) {
                     NEXT_OFF(br)= 0;
-                    RExC_emit= br + 1;
+                    RExC_emit= REGNODE_OFFSET(br) + 1;
                 } else {
                     regnode *opt;
-                    for ( opt= br + 1; opt < ender ; opt++ )
+                    for ( opt= br + 1; opt < REGNODE_p(ender) ; opt++ )
                         OP(opt)= OPTIMIZED;
-                    NEXT_OFF(br)= ender - br;
+                    NEXT_OFF(br)= REGNODE_p(ender) - br;
                 }
             }
        }
@@ -11848,10 +12059,10 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                node = SUSPEND, flag = 0;
             }
 
-           reginsert(pRExC_state, node,ret, depth+1);
-            Set_Node_Cur_Length(ret, parse_start);
-           Set_Node_Offset(ret, parse_start + 1);
-           ret->flags = flag;
+           reginsert(pRExC_state, node, ret, depth+1);
+            Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
+           Set_Node_Offset(REGNODE_p(ret), parse_start + 1);
+           FLAGS(REGNODE_p(ret)) = flag;
             REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL));
        }
     }
@@ -11893,15 +12104,19 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
  *
  * Implements the concatenation operator.
  *
- * Returns NULL, setting *flagp to RESTART_PASS1 if the sizing scan needs to be
- * restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to UTF-8
+ * On success, returns the offset at which any next node should be placed into
+ * the regex engine program being compiled.
+ *
+ * Returns 0 otherwise, setting flagp to RESTART_PARSE if the sizing scan needs
+ * to be restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to
+ * UTF-8
  */
-STATIC regnode *
+STATIC regnode_offset
 S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
 {
-    regnode *ret;
-    regnode *chain = NULL;
-    regnode *latest;
+    regnode_offset ret;
+    regnode_offset chain = 0;
+    regnode_offset latest;
     I32 flags = 0, c = 0;
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -11910,49 +12125,51 @@ S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
     DEBUG_PARSE("brnc");
 
     if (first)
-       ret = NULL;
+       ret = 0;
     else {
-       if (!SIZE_ONLY && RExC_extralen)
-           ret = reganode(pRExC_state, BRANCHJ,0);
+       if (RExC_use_BRANCHJ)
+           ret = reganode(pRExC_state, BRANCHJ, 0);
        else {
            ret = reg_node(pRExC_state, BRANCH);
-            Set_Node_Length(ret, 1);
+            Set_Node_Length(REGNODE_p(ret), 1);
         }
     }
 
-    if (!first && SIZE_ONLY)
-       RExC_extralen += 1;                     /* BRANCHJ */
-
     *flagp = WORST;                    /* Tentatively. */
 
     skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                             FALSE /* Don't force to /x */ );
     while (RExC_parse < RExC_end && *RExC_parse != '|' && *RExC_parse != ')') {
        flags &= ~TRYAGAIN;
-        latest = regpiece(pRExC_state, &flags,depth+1);
-       if (latest == NULL) {
+        latest = regpiece(pRExC_state, &flags, depth+1);
+       if (latest == 0) {
            if (flags & TRYAGAIN)
                continue;
-            RETURN_NULL_ON_RESTART(flags,flagp);
-            FAIL2("panic: regpiece returned NULL, flags=%#" UVxf, (UV) flags);
+            RETURN_FAIL_ON_RESTART(flags, flagp);
+            FAIL2("panic: regpiece returned failure, flags=%#" UVxf, (UV) flags);
        }
-       else if (ret == NULL)
+       else if (ret == 0)
             ret = latest;
        *flagp |= flags&(HASWIDTH|POSTPONED);
-       if (chain == NULL)      /* First piece. */
+       if (chain == 0)         /* First piece. */
            *flagp |= flags&SPSTART;
        else {
            /* FIXME adding one for every branch after the first is probably
             * excessive now we have TRIE support. (hv) */
            MARK_NAUGHTY(1);
+            if (     chain > (SSize_t) BRANCH_MAX_OFFSET
+                && ! RExC_use_BRANCHJ)
+            {
+                REQUIRE_BRANCHJ(flagp, 0);
+            }
             REGTAIL(pRExC_state, chain, latest);
        }
        chain = latest;
        c++;
     }
-    if (chain == NULL) {       /* Loop ran zero times. */
+    if (chain == 0) {  /* Loop ran zero times. */
        chain = reg_node(pRExC_state, NOTHING);
-       if (ret == NULL)
+       if (ret == 0)
            ret = chain;
     }
     if (c == 1) {
@@ -11971,15 +12188,18 @@ S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
  * It might seem that this node could be dispensed with entirely, but the
  * endmarker role is not redundant.
  *
- * Returns NULL, setting *flagp to TRYAGAIN if regatom() returns NULL with
- * TRYAGAIN.
- * Returns NULL, setting *flagp to RESTART_PASS1 if the sizing scan needs to be
- * restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to UTF-8
+ * On success, returns the offset at which any next node should be placed into
+ * the regex engine program being compiled.
+ *
+ * Returns 0 otherwise, with *flagp set to indicate why:
+ *  TRYAGAIN        if regatom() returns 0 with TRYAGAIN.
+ *  RESTART_PARSE   if the sizing scan needs to be restarted, or'd with
+ *                  NEED_UTF8 if the pattern needs to be upgraded to UTF-8.
  */
-STATIC regnode *
+STATIC regnode_offset
 S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 {
-    regnode *ret;
+    regnode_offset ret;
     char op;
     char *next;
     I32 flags;
@@ -11993,7 +12213,7 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
     UV uv;
 
     /* Save the original in case we change the emitted regop to a FAIL. */
-    regnode * const orig_emit = RExC_emit;
+    const regnode_offset orig_emit = RExC_emit;
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -12001,10 +12221,10 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 
     DEBUG_PARSE("piec");
 
-    ret = regatom(pRExC_state, &flags,depth+1);
-    if (ret == NULL) {
-        RETURN_NULL_ON_RESTART_OR_FLAGS(flags,flagp,TRYAGAIN);
-        FAIL2("panic: regatom returned NULL, flags=%#" UVxf, (UV) flags);
+    ret = regatom(pRExC_state, &flags, depth+1);
+    if (ret == 0) {
+        RETURN_FAIL_ON_RESTART_OR_FLAGS(flags, flagp, TRYAGAIN);
+        FAIL2("panic: regatom returned failure, flags=%#" UVxf, (UV) flags);
     }
 
     op = *RExC_parse;
@@ -12058,19 +12278,16 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             if (max < min) {    /* If can't match, warn and optimize to fail
                                    unconditionally */
                 reginsert(pRExC_state, OPFAIL, orig_emit, depth+1);
-                if (PASS2) {
-                    ckWARNreg(RExC_parse, "Quantifier {n,m} with n > m can't match");
-                    NEXT_OFF(orig_emit)= regarglen[OPFAIL] + NODE_STEP_REGNODE;
-                }
+                ckWARNreg(RExC_parse, "Quantifier {n,m} with n > m can't match");
+                NEXT_OFF(REGNODE_p(orig_emit)) =
+                                    regarglen[OPFAIL] + NODE_STEP_REGNODE;
                 return ret;
             }
             else if (min == max && *RExC_parse == '?')
             {
-                if (PASS2) {
-                    ckWARN2reg(RExC_parse + 1,
-                               "Useless use of greediness modifier '%c'",
-                               *RExC_parse);
-                }
+                ckWARN2reg(RExC_parse + 1,
+                           "Useless use of greediness modifier '%c'",
+                           *RExC_parse);
             }
 
          do_curly:
@@ -12089,42 +12306,40 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 }
                 MARK_NAUGHTY_EXP(2, 2);
                reginsert(pRExC_state, CURLY, ret, depth+1);
-                Set_Node_Offset(ret, parse_start+1); /* MJD */
-                Set_Node_Cur_Length(ret, parse_start);
+                Set_Node_Offset(REGNODE_p(ret), parse_start+1); /* MJD */
+                Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
            }
            else {
-               regnode * const w = reg_node(pRExC_state, WHILEM);
+               const regnode_offset w = reg_node(pRExC_state, WHILEM);
 
-               w->flags = 0;
+               FLAGS(REGNODE_p(w)) = 0;
                 REGTAIL(pRExC_state, ret, w);
-               if (!SIZE_ONLY && RExC_extralen) {
-                   reginsert(pRExC_state, LONGJMP,ret, depth+1);
-                   reginsert(pRExC_state, NOTHING,ret, depth+1);
-                   NEXT_OFF(ret) = 3;  /* Go over LONGJMP. */
+               if (RExC_use_BRANCHJ) {
+                   reginsert(pRExC_state, LONGJMP, ret, depth+1);
+                   reginsert(pRExC_state, NOTHING, ret, depth+1);
+                   NEXT_OFF(REGNODE_p(ret)) = 3;       /* Go over LONGJMP. */
                }
-               reginsert(pRExC_state, CURLYX,ret, depth+1);
+               reginsert(pRExC_state, CURLYX, ret, depth+1);
                                 /* MJD hk */
-                Set_Node_Offset(ret, parse_start+1);
-                Set_Node_Length(ret,
+                Set_Node_Offset(REGNODE_p(ret), parse_start+1);
+                Set_Node_Length(REGNODE_p(ret),
                                 op == '{' ? (RExC_parse - parse_start) : 1);
 
-               if (!SIZE_ONLY && RExC_extralen)
-                   NEXT_OFF(ret) = 3;  /* Go over NOTHING to LONGJMP. */
+               if (RExC_use_BRANCHJ)
+                    NEXT_OFF(REGNODE_p(ret)) = 3;   /* Go over NOTHING to
+                                                       LONGJMP. */
                 REGTAIL(pRExC_state, ret, reg_node(pRExC_state, NOTHING));
-               if (SIZE_ONLY)
-                   RExC_whilem_seen++, RExC_extralen += 3;
+                RExC_whilem_seen++;
                 MARK_NAUGHTY_EXP(1, 4);     /* compound interest */
            }
-           ret->flags = 0;
+           FLAGS(REGNODE_p(ret)) = 0;
 
            if (min > 0)
                *flagp = WORST;
            if (max > 0)
                *flagp |= HASWIDTH;
-           if (!SIZE_ONLY) {
-               ARG1_SET(ret, (U16)min);
-               ARG2_SET(ret, (U16)max);
-           }
+            ARG1_SET(REGNODE_p(ret), (U16)min);
+            ARG2_SET(REGNODE_p(ret), (U16)max);
             if (max == REG_INFTY)
                 RExC_seen |= REG_UNBOUNDED_QUANTIFIER_SEEN;
 
@@ -12173,15 +12388,13 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
        goto do_curly;
     }
   nest_check:
-    if (!SIZE_ONLY && !(flags&(HASWIDTH|POSTPONED)) && max > REG_INFTY/3) {
-       SAVEFREESV(RExC_rx_sv); /* in case of fatal warnings */
+    if (!(flags&(HASWIDTH|POSTPONED)) && max > REG_INFTY/3) {
        ckWARN2reg(RExC_parse,
                   "%" UTF8f " matches null string many times",
                   UTF8fARG(UTF, (RExC_parse >= origparse
                                  ? RExC_parse - origparse
                                  : 0),
                   origparse));
-       (void)ReREFCNT_inc(RExC_rx_sv);
     }
 
     if (*RExC_parse == '?') {
@@ -12190,7 +12403,7 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
         REGTAIL(pRExC_state, ret, ret + NODE_STEP_REGNODE);
     }
     else if (*RExC_parse == '+') {
-        regnode *ender;
+        regnode_offset ender;
         nextchar(pRExC_state);
         ender = reg_node(pRExC_state, SUCCEED);
         REGTAIL(pRExC_state, ret, ender);
@@ -12209,7 +12422,7 @@ S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 
 STATIC bool
 S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
-                regnode ** node_p,
+                regnode_offset * node_p,
                 UV * code_point_p,
                 int * cp_count,
                 I32 * flagp,
@@ -12230,7 +12443,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * If <node_p> is not NULL, the context is expecting the result to be one of
   * the things representable by a regnode.  If this \N instance turns out to be
   * one such, the function generates the regnode, returns TRUE and sets *node_p
-  * to point to that regnode.
+  * to point to the offset of that regnode into the regex engine program being
+  * compiled.
   *
   * If this instance of \N isn't legal in any context, this function will
   * generate a fatal error and not return.
@@ -12263,7 +12477,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   *
   * The fourth possibility is that \N resolves to a sequence of more than one
   * code points.  *cp_count will be set to the number of code points in the
-  * sequence. *node_p will be set to a generated node returned by this
+  * sequence. *node_p will be set to a generated node returned by this
   * function calling S_reg().
   *
   * The final possibility is that it is premature to be calling this function;
@@ -12272,7 +12486,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
   * latter occurs only when the fourth possibility would otherwise be in
   * effect, and is because one of those code points requires the pattern to be
   * recompiled as UTF-8.  The function returns FALSE, and sets the
-  * RESTART_PASS1 and NEED_UTF8 flags in *flagp, as appropriate.  When this
+  * RESTART_PARSE and NEED_UTF8 flags in *flagp, as appropriate.  When this
   * happens, the caller needs to desist from continuing parsing, and return
   * this information to its caller.  This is not set for when there is only one
   * code point, as this can be called as part of an ANYOF node, and they can
@@ -12337,7 +12551,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
         *node_p = reg_node(pRExC_state, REG_ANY);
         *flagp |= HASWIDTH|SIMPLE;
         MARK_NAUGHTY(1);
-        Set_Node_Length(*node_p, 1); /* MJD */
+        Set_Node_Length(REGNODE_p(*(node_p)), 1); /* MJD */
         return TRUE;
     }
 
@@ -12373,7 +12587,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
             return FALSE;
         }
 
-        *node_p = reg_node(pRExC_state,NOTHING);
+        *node_p = reg_node(pRExC_state, NOTHING);
         return TRUE;
     }
 
@@ -12410,8 +12624,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
             /* Loop through the hex digits of the current code point */
             do {
                 /* Adding this digit will shift the result 4 bits.  If that
-                 * result would be above IV_MAX, it's overflow */
-                if (cp > IV_MAX >> 4) {
+                 * result would be above the legal max, it's overflow */
+                if (cp > MAX_LEGAL_CP >> 4) {
 
                     /* Find the end of the code point */
                     do {
@@ -12422,7 +12636,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
                      * in utf8.c */
                     vFAIL4("Use of code point 0x%.*s is not allowed; the"
                         " permissible max is 0x%" UVxf,
-                        (int) (RExC_parse - start_digit), start_digit, IV_MAX);
+                        (int) (RExC_parse - start_digit), start_digit,
+                        MAX_LEGAL_CP);
                 }
 
                 /* Accumulate this (valid) digit into the running total */
@@ -12524,16 +12739,20 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
      * constructs.  This can be called from within a substitute parse already.
      * The error reporting mechanism doesn't work for 2 levels of this, but the
      * code above has validated this new construct, so there should be no
-     * errors generated by the below.*/
+     * errors generated by the below.  And this isn' an exact copy, so the
+     * mechanism to seamlessly deal with this won't work, so turn off warnings
+     * during it */
     save_start = RExC_start;
     orig_end = RExC_end;
 
     RExC_parse = RExC_start = SvPVX(substitute_parse);
     RExC_end = RExC_parse + SvCUR(substitute_parse);
+    TURN_OFF_WARNINGS_IN_SUBSTITUTE_PARSE;
 
     *node_p = reg(pRExC_state, 1, &flags, depth+1);
 
     /* Restore the saved values */
+    RESTORE_WARNINGS;
     RExC_start = save_start;
     RExC_parse = endbrace;
     RExC_end = orig_end;
@@ -12544,8 +12763,8 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state,
     SvREFCNT_dec_NN(substitute_parse);
 
     if (! *node_p) {
-        RETURN_X_ON_RESTART(FALSE, flags,flagp);
-        FAIL2("panic: reg returned NULL to grok_bslash_N, flags=%#" UVxf,
+        RETURN_X_ON_RESTART(FALSE, flags, flagp);
+        FAIL2("panic: reg returned failure to grok_bslash_N, flags=%#" UVxf,
             (UV) flags);
     }
     *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
@@ -12580,8 +12799,8 @@ S_compute_EXACTish(RExC_state_t *pRExC_state)
 
 PERL_STATIC_INLINE void
 S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
-                         regnode *node, I32* flagp, STRLEN len, UV code_point,
-                         bool downgradable)
+                         regnode_offset node, I32* flagp, STRLEN len,
+                         UV code_point, bool downgradable)
 {
     /* This knows the details about sizing an EXACTish node, setting flags for
      * it (by setting <*flagp>, and potentially populating it with a single
@@ -12615,22 +12834,13 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
 
     PERL_ARGS_ASSERT_ALLOC_MAYBE_POPULATE_EXACT;
 
-    /* Don't bother to check for downgrading in PASS1, as it doesn't make any
-     * sizing difference, and is extra work that is thrown away */
-    if (downgradable && ! PASS2) {
-        downgradable = FALSE;
-    }
-
     if (! len_passed_in) {
         if (UTF) {
             if (UVCHR_IS_INVARIANT(code_point)) {
                 if (LOC || ! FOLD) {    /* /l defers folding until runtime */
                     *character = (U8) code_point;
                 }
-                else { /* Here is /i and not /l. (toFOLD() is defined on just
-                          ASCII, which isn't the same thing as INVARIANT on
-                          EBCDIC, but it works there, as the extra invariants
-                          fold to themselves) */
+                else { /* Here is /i and not /l. */
                     *character = toFOLD((U8) code_point);
 
                     /* We can downgrade to an EXACT node if this character
@@ -12642,7 +12852,7 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
                      *      || ASCII_FOLD_RESTRICTED))
                      */
                     if (downgradable && PL_fold[code_point] == code_point) {
-                        OP(node) = EXACT;
+                        OP(REGNODE_p(node)) = EXACT;
                     }
                 }
                 len = 1;
@@ -12664,7 +12874,7 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
                                                for those.  */
                     && ! _invlist_contains_cp(PL_utf8_foldable, code_point))
                 {
-                    OP(node) = (LOC)
+                    OP(REGNODE_p(node)) = (LOC)
                                ? EXACTL
                                : EXACT;
                 }
@@ -12705,7 +12915,7 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
                 && (! HAS_NONLATIN1_FOLD_CLOSURE(code_point)
                     || (isASCII(code_point) && ASCII_FOLD_RESTRICTED)))
             {
-                OP(node) = EXACT;
+                OP(REGNODE_p(node)) = EXACT;
             }
         } /* else is Sharp s.  May need to fold it */
         else if (AT_LEAST_UNI_SEMANTICS && ! ASCII_FOLD_RESTRICTED) {
@@ -12719,15 +12929,14 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
         }
     }
 
-    if (SIZE_ONLY) {
-        RExC_size += STR_SZ(len);
+    if (downgradable) {
+        change_engine_size(pRExC_state, STR_SZ(len));
     }
-    else {
-        RExC_emit += STR_SZ(len);
-        STR_LEN(node) = len;
-        if (! len_passed_in) {
-            Copy((char *) character, STRING(node), len, char);
-        }
+
+    RExC_emit += STR_SZ(len);
+    STR_LEN(REGNODE_p(node)) = len;
+    if (! len_passed_in) {
+        Copy((char *) character, STRING(REGNODE_p(node)), len, char);
     }
 
     *flagp |= HASWIDTH;
@@ -12745,8 +12954,7 @@ S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
         *flagp |= SIMPLE;
     }
 
-    /* The OP may not be well defined in PASS1 */
-    if (PASS2 && OP(node) == EXACTFL) {
+    if (OP(REGNODE_p(node)) == EXACTFL) {
         RExC_contains_locale = 1;
     }
 }
@@ -12826,7 +13034,13 @@ S_backref_value(char *p, char *e)
    and not to the whole string of literals.
 
    Once we have been able to handle whatever type of thing started the
-   sequence, we return.
+   sequence, we return the offset into the regex engine program being compiled
+   at which any  next regnode should be placed.
+
+   Returns 0, setting *flagp to TRYAGAIN if reg() returns 0 with TRYAGAIN.
+   Returns 0, setting *flagp to RESTART_PARSE if the sizing scan needs to be
+   restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to UTF-8
+   Otherwise does not return 0.
 
    Note: we have to be careful with escapes, as they can be both literal
    and special, and in the case of \10 and friends, context determines which.
@@ -12873,17 +13087,12 @@ S_backref_value(char *p, char *e)
    a dummy entry for all of the special escapes that are actually handled
    by the other.
 
-   Returns NULL, setting *flagp to TRYAGAIN if reg() returns NULL with
-   TRYAGAIN.
-   Returns NULL, setting *flagp to RESTART_PASS1 if the sizing scan needs to be
-   restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to UTF-8
-   Otherwise does not return NULL.
 */
 
-STATIC regnode *
+STATIC regnode_offset
 S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 {
-    regnode *ret = NULL;
+    regnode_offset ret = 0;
     I32 flags = 0;
     char *parse_start;
     U8 op;
@@ -12909,7 +13118,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            ret = reg_node(pRExC_state, MBOL);
        else
            ret = reg_node(pRExC_state, SBOL);
-        Set_Node_Length(ret, 1); /* MJD */
+        Set_Node_Length(REGNODE_p(ret), 1); /* MJD */
        break;
     case '$':
        nextchar(pRExC_state);
@@ -12919,7 +13128,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            ret = reg_node(pRExC_state, MEOL);
        else
            ret = reg_node(pRExC_state, SEOL);
-        Set_Node_Length(ret, 1); /* MJD */
+        Set_Node_Length(REGNODE_p(ret), 1); /* MJD */
        break;
     case '.':
        nextchar(pRExC_state);
@@ -12929,12 +13138,12 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            ret = reg_node(pRExC_state, REG_ANY);
        *flagp |= HASWIDTH|SIMPLE;
        MARK_NAUGHTY(1);
-        Set_Node_Length(ret, 1); /* MJD */
+        Set_Node_Length(REGNODE_p(ret), 1); /* MJD */
        break;
     case '[':
     {
        char * const oregcomp_parse = ++RExC_parse;
-        ret = regclass(pRExC_state, flagp,depth+1,
+        ret = regclass(pRExC_state, flagp, depth+1,
                        FALSE, /* means parse the whole char class */
                        TRUE, /* allow multi-char folds */
                        FALSE, /* don't silence non-portable warnings. */
@@ -12942,9 +13151,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                        TRUE, /* Allow an optimized regnode result */
                        NULL,
                        NULL);
-        if (ret == NULL) {
-            RETURN_NULL_ON_RESTART_FLAGP_OR_FLAGS(flagp,NEED_UTF8);
-            FAIL2("panic: regclass returned NULL to regatom, flags=%#" UVxf,
+        if (ret == 0) {
+            RETURN_FAIL_ON_RESTART_FLAGP_OR_FLAGS(flagp, NEED_UTF8);
+            FAIL2("panic: regclass returned failure to regatom, flags=%#" UVxf,
                   (UV) *flagp);
         }
        if (*RExC_parse != ']') {
@@ -12952,23 +13161,23 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            vFAIL("Unmatched [");
        }
        nextchar(pRExC_state);
-        Set_Node_Length(ret, RExC_parse - oregcomp_parse + 1); /* MJD */
+        Set_Node_Length(REGNODE_p(ret), RExC_parse - oregcomp_parse + 1); /* MJD */
        break;
     }
     case '(':
        nextchar(pRExC_state);
-        ret = reg(pRExC_state, 2, &flags,depth+1);
-       if (ret == NULL) {
+        ret = reg(pRExC_state, 2, &flags, depth+1);
+       if (ret == 0) {
                if (flags & TRYAGAIN) {
                    if (RExC_parse >= RExC_end) {
                         /* Make parent create an empty node if needed. */
                        *flagp |= TRYAGAIN;
-                       return(NULL);
+                       return(0);
                    }
                    goto tryagain;
                }
-                RETURN_NULL_ON_RESTART(flags,flagp);
-                FAIL2("panic: reg returned NULL to regatom, flags=%#" UVxf,
+                RETURN_FAIL_ON_RESTART(flags, flagp);
+                FAIL2("panic: reg returned failure to regatom, flags=%#" UVxf,
                                                                  (UV) flags);
        }
        *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
@@ -12977,7 +13186,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
     case ')':
        if (flags & TRYAGAIN) {
            *flagp |= TRYAGAIN;
-           return NULL;
+           return 0;
        }
        vFAIL("Internal urp");
                                /* Supposed to be caught earlier. */
@@ -13010,8 +13219,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             /* SBOL is shared with /^/ so we set the flags so we can tell
              * /\A/ from /^/ in split. We check ret because first pass we
              * have no regop struct to set the flags on. */
-            if (PASS2)
-                ret->flags = 1;
+            FLAGS(REGNODE_p(ret)) = 1;
            *flagp |= SIMPLE;
            goto finish_meta_pat;
        case 'G':
@@ -13071,9 +13279,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
            ret = reg_node(pRExC_state, op);
            *flagp |= SIMPLE;
            if (RExC_parse >= RExC_end || *(RExC_parse + 1) != '{') {
-                FLAGS(ret) = TRADITIONAL_BOUND;
-                if (PASS2 && op > BOUNDA) {  /* /aa is same as /a */
-                    OP(ret) = BOUNDA;
+                FLAGS(REGNODE_p(ret)) = TRADITIONAL_BOUND;
+                if (op > BOUNDA) {  /* /aa is same as /a */
+                    OP(REGNODE_p(ret)) = BOUNDA;
                 }
             }
             else {
@@ -13109,25 +13317,25 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         {
                             goto bad_bound_type;
                         }
-                        FLAGS(ret) = GCB_BOUND;
+                        FLAGS(REGNODE_p(ret)) = GCB_BOUND;
                         break;
                     case 'l':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(ret) = LB_BOUND;
+                        FLAGS(REGNODE_p(ret)) = LB_BOUND;
                         break;
                     case 's':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(ret) = SB_BOUND;
+                        FLAGS(REGNODE_p(ret)) = SB_BOUND;
                         break;
                     case 'w':
                         if (length != 2 || *(RExC_parse + 1) != 'b') {
                             goto bad_bound_type;
                         }
-                        FLAGS(ret) = WB_BOUND;
+                        FLAGS(REGNODE_p(ret)) = WB_BOUND;
                         break;
                     default:
                       bad_bound_type:
@@ -13138,10 +13346,10 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         NOT_REACHED; /*NOTREACHED*/
                 }
                 RExC_parse = endbrace;
-                REQUIRE_UNI_RULES(flagp, NULL);
+                REQUIRE_UNI_RULES(flagp, 0);
 
-                if (PASS2 && op >= BOUNDA) {  /* /aa is same as /a */
-                    OP(ret) = BOUNDU;
+                if (op >= BOUNDA) {  /* /aa is same as /a */
+                    OP(REGNODE_p(ret)) = BOUNDU;
                     length += 4;
 
                     /* Don't have to worry about UTF-8, in this message because
@@ -13156,8 +13364,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 }
            }
 
-            if (PASS2 && invert) {
-                OP(ret) += NBOUND - BOUND;
+            if (invert) {
+                OP(REGNODE_p(ret)) += NBOUND - BOUND;
             }
            goto finish_meta_pat;
           }
@@ -13221,9 +13429,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             }
 
            ret = reg_node(pRExC_state, op);
-            if (! SIZE_ONLY) {
-                FLAGS(ret) = namedclass_to_classnum(arg);
-            }
+            FLAGS(REGNODE_p(ret)) = namedclass_to_classnum(arg);
 
            *flagp |= HASWIDTH|SIMPLE;
             /* FALLTHROUGH */
@@ -13236,13 +13442,13 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 vFAIL("Unescaped left brace in regex is illegal here");
             }
            nextchar(pRExC_state);
-            Set_Node_Length(ret, 2); /* MJD */
+            Set_Node_Length(REGNODE_p(ret), 2); /* MJD */
            break;
        case 'p':
        case 'P':
             RExC_parse--;
 
-            ret = regclass(pRExC_state, flagp,depth+1,
+            ret = regclass(pRExC_state, flagp, depth+1,
                            TRUE, /* means just parse this element */
                            FALSE, /* don't allow multi-char folds */
                            FALSE, /* don't silence non-portable warnings.  It
@@ -13252,17 +13458,17 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                            TRUE, /* Allow an optimized regnode result */
                            NULL,
                            NULL);
-            RETURN_NULL_ON_RESTART_FLAGP(flagp);
-            /* regclass() can only return RESTART_PASS1 and NEED_UTF8 if
+            RETURN_FAIL_ON_RESTART_FLAGP(flagp);
+            /* regclass() can only return RESTART_PARSE and NEED_UTF8 if
              * multi-char folds are allowed.  */
             if (!ret)
-                FAIL2("panic: regclass returned NULL to regatom, flags=%#" UVxf,
+                FAIL2("panic: regclass returned failure to regatom, flags=%#" UVxf,
                       (UV) *flagp);
 
             RExC_parse--;
 
-            Set_Node_Offset(ret, parse_start);
-            Set_Node_Cur_Length(ret, parse_start - 2);
+            Set_Node_Offset(REGNODE_p(ret), parse_start);
+            Set_Node_Cur_Length(REGNODE_p(ret), parse_start - 2);
             nextchar(pRExC_state);
            break;
         case 'N':
@@ -13291,7 +13497,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 break;
             }
 
-            RETURN_NULL_ON_RESTART_FLAGP(flagp);
+            RETURN_FAIL_ON_RESTART_FLAGP(flagp);
 
             /* Here, evaluates to a single code point.  Go get that */
             RExC_parse = parse_start;
@@ -13308,7 +13514,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             {
                RExC_parse++;
                /* diag_listed_as: Sequence \%s... not terminated in regex; marked by <-- HERE in m/%s/ */
-               vFAIL2("Sequence %.2s... not terminated",parse_start);
+               vFAIL2("Sequence %.2s... not terminated", parse_start);
            } else {
                RExC_parse += 2;
                 ret = handle_named_backref(pRExC_state,
@@ -13385,10 +13591,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         && *RExC_parse != '8'
                         /* cannot be an octal escape it it starts with 9 */
                         && *RExC_parse != '9'
-                    )
-                    {
-                        /* Probably not a backref, instead likely to be an
-                         * octal character escape, e.g. \35 or \777.
+                    ) {
+                        /* Probably not meant to be a backref, instead likely
+                         * to be an octal character escape, e.g. \35 or \777.
                          * The above logic should make it obvious why using
                          * octal escapes in patterns is problematic. - Yves */
                         RExC_parse = parse_start;
@@ -13408,9 +13613,19 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         vFAIL("Unterminated \\g{...} pattern");
                     RExC_parse++;
                 }
-                if (!SIZE_ONLY) {
-                    if (num > (I32)RExC_rx->nparens)
-                        vFAIL("Reference to nonexistent group");
+                if (num >= (I32)RExC_npar) {
+
+                    /* It might be a forward reference; we can't fail until we
+                     * know, by completing the parse to get all the groups, and
+                     * then reparsing */
+                    if (RExC_total_parens > 0)  {
+                        if (num >= RExC_total_parens)  {
+                            vFAIL("Reference to nonexistent group");
+                        }
+                    }
+                    else {
+                        REQUIRE_PARENS_PASS;
+                    }
                 }
                 RExC_sawback = 1;
                 ret = reganode(pRExC_state,
@@ -13427,8 +13642,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                 *flagp |= HASWIDTH;
 
                 /* override incorrect value set in reganode MJD */
-                Set_Node_Offset(ret, parse_start);
-                Set_Node_Cur_Length(ret, parse_start-1);
+                Set_Node_Offset(REGNODE_p(ret), parse_start);
+                Set_Node_Cur_Length(REGNODE_p(ret), parse_start-1);
                 skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                         FALSE /* Don't force to /x */ );
            }
@@ -13476,7 +13691,6 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 /* This allows us to fill a node with just enough spare so that if the final
  * character folds, its expansion is guaranteed to fit */
 #define MAX_NODE_STRING_SIZE (255-UTF8_MAXBYTES_CASE)
-           char foldbuf[MAX_NODE_STRING_SIZE+UTF8_MAXBYTES_CASE+1];
 
            char *s0;
            U8 upper_parse = MAX_NODE_STRING_SIZE;
@@ -13492,6 +13706,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
              * created for the new category. */
             U8 node_type = EXACT;
 
+            /* Assume node will be fully used; the excess is given back at the end */
+            Ptrdiff_t initial_size = STR_SZ(256);
+
             bool next_is_quantifier;
             char * oldp = NULL;
 
@@ -13505,19 +13722,20 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
              * which don't participate in folds with Latin1-range characters,
              * as the latter's folds aren't known until runtime.  (We don't
              * need to figure this out until pass 2) */
-            bool maybe_exactfu = PASS2;
+            bool maybe_exactfu = TRUE;
 
             /* To see if RExC_uni_semantics changes during parsing of the node.
              * */
             bool uni_semantics_at_node_start;
 
-            /* The node_type may change below, but since the size of the node
-             * doesn't change, it works */
-           ret = reg_node(pRExC_state, node_type);
+            /* Allocate an EXACT node.  The node_type may change below to
+             * another EXACTish node, but since the size of the node doesn't
+             * change, it works */
+            ret = regnode_guts(pRExC_state, node_type, initial_size, "exact");
+            FILL_NODE(ret, node_type);
+            RExC_emit++;
 
-            /* In pass1, folded, we use a temporary buffer instead of the
-             * actual node, as the node doesn't exist yet */
-           s = (SIZE_ONLY && FOLD) ? foldbuf : STRING(ret);
+           s = STRING(REGNODE_p(ret));
 
             s0 = s;
 
@@ -13537,7 +13755,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                    || UTF8_IS_INVARIANT(UCHARAT(RExC_parse))
                    || UTF8_IS_START(UCHARAT(RExC_parse)));
 
-            uni_semantics_at_node_start = RExC_uni_semantics;
+            uni_semantics_at_node_start = cBOOL(RExC_uni_semantics);
 
             /* Here, we have a literal character.  Find the maximal string of
              * them in the input that we can fit into a single EXACTish node.
@@ -13580,6 +13798,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                    */
 
                    switch ((U8)*++p) {
+
                    /* These are all the special escapes. */
                    case 'A':             /* Start assertion */
                    case 'b': case 'B':   /* Word-boundary assertion*/
@@ -13622,7 +13841,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         ) {
                             if (*flagp & NEED_UTF8)
                                 FAIL("panic: grok_bslash_N set NEED_UTF8");
-                            RETURN_NULL_ON_RESTART_FLAGP(flagp);
+                            RETURN_FAIL_ON_RESTART_FLAGP(flagp);
 
                             /* Here, it wasn't a single code point.  Go close
                              * up this EXACTish node.  The switch() prior to
@@ -13665,7 +13884,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                                        RExC_end,
                                                       &result,
                                                       &error_msg,
-                                                      PASS2, /* out warnings */
+                                                      TO_OUTPUT_WARNINGS(p),
                                                        (bool) RExC_strict,
                                                        TRUE, /* Output warnings
                                                                 for non-
@@ -13676,6 +13895,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                                   to exact spot of failure */
                                vFAIL(error_msg);
                            }
+                            UPDATE_WARNINGS_LOC(p - 1);
                             ender = result;
                            if (ender > 0xff) {
                                REQUIRE_UTF8(flagp);
@@ -13692,7 +13912,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                                        RExC_end,
                                                       &result,
                                                       &error_msg,
-                                                      PASS2, /* out warnings */
+                                                       TO_OUTPUT_WARNINGS(p),
                                                        (bool) RExC_strict,
                                                        TRUE, /* Silence warnings
                                                                 for non-
@@ -13703,6 +13923,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                                   to exact spot of failure */
                                vFAIL(error_msg);
                            }
+                            UPDATE_WARNINGS_LOC(p - 1);
                             ender = result;
 
                             if (ender < 0x100) {
@@ -13719,7 +13940,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                        }
                    case 'c':
                        p++;
-                       ender = grok_bslash_c(*p++, PASS2);
+                       ender = grok_bslash_c(*p, TO_OUTPUT_WARNINGS(p));
+                        UPDATE_WARNINGS_LOC(p);
+                        p++;
                        break;
                     case '8': case '9': /* must be a backreference */
                         --p;
@@ -13743,8 +13966,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                          * pattern.  */
 
                         /* NOTE, RExC_npar is 1 more than the actual number of
-                         * parens we have seen so far, hence the < RExC_npar below. */
-
+                         * parens we have seen so far, hence the "<" as opposed
+                         * to "<=" */
                         if ( !isDIGIT(p[1]) || S_backref_value(p, RExC_end) < RExC_npar)
                         {  /* Not to be treated as an octal constant, go
                                    find backref */
@@ -13761,9 +13984,9 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                                REQUIRE_UTF8(flagp);
                            }
                            p += numlen;
-                            if (PASS2   /* like \08, \178 */
-                                && numlen < 3
-                                && isDIGIT(*p) && ckWARN(WARN_REGEXP))
+                            if (   isDIGIT(*p)  /* like \08, \178 */
+                                && ckWARN(WARN_REGEXP)
+                                && numlen < 3)
                             {
                                reg_warn_non_literal_string(
                                          p + 1,
@@ -13776,12 +13999,14 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                            FAIL("Trailing \\");
                        /* FALLTHROUGH */
                    default:
-                       if (!SIZE_ONLY&& isALPHANUMERIC(*p)) {
-                           /* Include any left brace following the alpha to emphasize
-                            * that it could be part of an escape at some point
-                            * in the future */
-                           int len = (isALPHA(*p) && *(p + 1) == '{') ? 2 : 1;
-                           ckWARN3reg(p + len, "Unrecognized escape \\%.*s passed through", len, p);
+                       if (isALPHANUMERIC(*p)) {
+                            /* An alpha followed by '{' is going to fail next
+                             * iteration, so don't output this warning in that
+                             * case */
+                            if (! isALPHA(*p) || *(p + 1) != '{') {
+                                ckWARN2reg(p + 1, "Unrecognized escape \\%.1s"
+                                                  " passed through", p);
+                            }
                        }
                        goto normal_default;
                    } /* End of switch on '\' */
@@ -13813,15 +14038,13 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                             vFAIL("Unescaped left brace in regex is "
                                   "illegal here");
                         }
-                        if (PASS2) {
-                            ckWARNreg(p + 1, "Unescaped left brace in regex is"
-                                             " passed through");
-                        }
+                        ckWARNreg(p + 1, "Unescaped left brace in regex is"
+                                         " passed through");
                    }
                    goto normal_default;
                 case '}':
                 case ']':
-                    if (PASS2 && p > RExC_parse && RExC_strict) {
+                    if (p > RExC_parse && RExC_strict) {
                         ckWARN2reg(p + 1, "Unescaped literal '%c'", *p);
                     }
                    /*FALLTHROUGH*/
@@ -13867,19 +14090,6 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
 
                 if (! FOLD) {  /* The simple case, just append the literal */
 
-                    /* In the sizing pass, we need only the size of the
-                     * character we are appending, hence we can delay getting
-                     * its representation until PASS2. */
-                    if (SIZE_ONLY) {
-                        if (UTF && ! UVCHR_IS_INVARIANT(ender)) {
-                            const STRLEN unilen = UVCHR_SKIP(ender);
-                            s += unilen;
-                            added_len = unilen;
-                        }
-                        else {
-                            s++;
-                        }
-                    } else { /* PASS2 */
                       not_fold_common:
                         if (UTF && ! UVCHR_IS_INVARIANT(ender)) {
                             U8 * new_s = uvchr_to_utf8((U8*)s, ender);
@@ -13889,7 +14099,6 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                         else {
                             *(s++) = (char) ender;
                         }
-                    }
                 }
                 else if (LOC && is_PROBLEMATIC_LOCALE_FOLD_cp(ender)) {
 
@@ -14268,20 +14477,22 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
           loopdone:   /* Jumped to when encounters something that shouldn't be
                          in the node */
 
+            change_engine_size(pRExC_state, - (initial_size - STR_SZ(len)));
+
             /* I (khw) don't know if you can get here with zero length, but the
              * old code handled this situation by creating a zero-length EXACT
              * node.  Might as well be NOTHING instead */
             if (len == 0) {
-                OP(ret) = NOTHING;
+                OP(REGNODE_p(ret)) = NOTHING;
             }
             else {
-                OP(ret) = node_type;
+                OP(REGNODE_p(ret)) = node_type;
 
                 /* If the node type is EXACT here, check to see if it
                  * should be EXACTL. */
                 if (node_type == EXACT) {
                     if (LOC) {
-                        OP(ret) = EXACTL;
+                        OP(REGNODE_p(ret)) = EXACTL;
                     }
                 }
 
@@ -14291,10 +14502,10 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
                      * target string (for /u), or depending on locale for /l */
                     if (maybe_exactfu) {
                         if (node_type == EXACTF) {
-                            OP(ret) = EXACTFU;
+                            OP(REGNODE_p(ret)) = EXACTFU;
                         }
                         else if (node_type == EXACTFL) {
-                            OP(ret) = EXACTFLU8;
+                            OP(REGNODE_p(ret)) = EXACTFLU8;
                         }
                     }
                 }
@@ -14308,7 +14519,7 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
             }
 
            RExC_parse = p - 1;
-            Set_Node_Cur_Length(ret, parse_start);
+            Set_Node_Cur_Length(REGNODE_p(ret), parse_start);
            RExC_parse = p;
            {
                /* len is STRLEN which is unsigned, need to copy to signed */
@@ -14324,8 +14535,8 @@ S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
     /* Position parse to next real character */
     skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                             FALSE /* Don't force to /x */ );
-    if (   PASS2 && *RExC_parse == '{'
-        && OP(ret) != SBOL && ! regcurly(RExC_parse))
+    if (   *RExC_parse == '{'
+        && OP(REGNODE_p(ret)) != SBOL && ! regcurly(RExC_parse))
     {
         if (RExC_strict || new_regcurly(RExC_parse, RExC_end)) {
             RExC_parse++;
@@ -14425,8 +14636,9 @@ S_populate_ANYOF_from_invlist(pTHX_ regnode *node, SV** invlist_ptr)
  * routine. q.v. */
 #define ADD_POSIX_WARNING(p, text)  STMT_START {                            \
         if (posix_warnings) {                                               \
-            if (! RExC_warn_text ) RExC_warn_text = (AV *) sv_2mortal((SV *) newAV()); \
-            av_push(RExC_warn_text, Perl_newSVpvf(aTHX_                          \
+            if (! RExC_warn_text ) RExC_warn_text =                         \
+                                         (AV *) sv_2mortal((SV *) newAV()); \
+            av_push(RExC_warn_text, Perl_newSVpvf(aTHX_                     \
                                              WARNING_PREFIX                 \
                                              text                           \
                                              REPORT_LOCATION,               \
@@ -15203,7 +15415,10 @@ S_handle_possible_posix(pTHX_ RExC_state_t *pRExC_state,
                 ADD_POSIX_WARNING(p, "there is no terminating ']'");
             }
 
-            if (posix_warnings && RExC_warn_text && av_top_index(RExC_warn_text) > -1) {
+            if (   posix_warnings
+                && RExC_warn_text
+                && av_top_index(RExC_warn_text) > -1)
+            {
                 *posix_warnings = RExC_warn_text;
             }
         }
@@ -15259,7 +15474,7 @@ S_regex_set_precedence(const U8 my_operator) {
     return 0;   /* Silence compiler warning */
 }
 
-STATIC regnode *
+STATIC regnode_offset
 S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
                     I32 *flagp, U32 depth,
                     char * const oregcomp_parse)
@@ -15282,12 +15497,11 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
                                        with left paren in stack is; -1 if none.
                                      */
     STRLEN len;                     /* Temporary */
-    regnode* node;                  /* Temporary, and final regnode returned by
+    regnode_offset node;                  /* Temporary, and final regnode returned by
                                        this function */
     const bool save_fold = FOLD;    /* Temporary */
     char *save_end, *save_parse;    /* Temporaries */
     const bool in_locale = LOC;     /* we turn off /l during processing */
-    AV* posix_warnings = NULL;
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -15299,127 +15513,13 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
         set_regex_charset(&RExC_flags, REGEX_UNICODE_CHARSET);
     }
 
-    REQUIRE_UNI_RULES(flagp, NULL);   /* The use of this operator implies /u.
-                                         This is required so that the compile
-                                         time values are valid in all runtime
-                                         cases */
-
-    /* This will return only an ANYOF regnode, or (unlikely) something smaller
-     * (such as EXACT).  Thus we can skip most everything if just sizing.  We
-     * call regclass to handle '[]' so as to not have to reinvent its parsing
-     * rules here (throwing away the size it computes each time).  And, we exit
-     * upon an unescaped ']' that isn't one ending a regclass.  To do both
-     * these things, we need to realize that something preceded by a backslash
-     * is escaped, so we have to keep track of backslashes */
-    if (SIZE_ONLY) {
-        UV nest_depth = 0; /* how many nested (?[...]) constructs */
-
-        while (RExC_parse < RExC_end) {
-            SV* current = NULL;
-
-            skip_to_be_ignored_text(pRExC_state, &RExC_parse,
-                                    TRUE /* Force /x */ );
+    /* The use of this operator implies /u.  This is required so that the
+     * compile time values are valid in all runtime cases */
+    REQUIRE_UNI_RULES(flagp, 0);
 
-            switch (*RExC_parse) {
-                case '(':
-                    if (RExC_parse[1] == '?' && RExC_parse[2] == '[')
-                        nest_depth++, RExC_parse+=2;
-                    /* FALLTHROUGH */
-                default:
-                    break;
-                case '\\':
-                    /* Skip past this, so the next character gets skipped, after
-                     * the switch */
-                    RExC_parse++;
-                    if (*RExC_parse == 'c') {
-                            /* Skip the \cX notation for control characters */
-                            RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
-                    }
-                    break;
-
-                case '[':
-                {
-                    /* See if this is a [:posix:] class. */
-                    bool is_posix_class = (OOB_NAMEDCLASS
-                            < handle_possible_posix(pRExC_state,
-                                                RExC_parse + 1,
-                                                NULL,
-                                                NULL,
-                                                TRUE /* checking only */));
-                    /* If it is a posix class, leave the parse pointer at the
-                     * '[' to fool regclass() into thinking it is part of a
-                     * '[[:posix:]]'. */
-                    if (! is_posix_class) {
-                        RExC_parse++;
-                    }
-
-                    /* regclass() can only return RESTART_PASS1 and NEED_UTF8
-                     * if multi-char folds are allowed.  */
-                    if (!regclass(pRExC_state, flagp,depth+1,
-                                  is_posix_class, /* parse the whole char
-                                                     class only if not a
-                                                     posix class */
-                                  FALSE, /* don't allow multi-char folds */
-                                  TRUE, /* silence non-portable warnings. */
-                                  TRUE, /* strict */
-                                  FALSE, /* Require return to be an ANYOF */
-                                  &current,
-                                  &posix_warnings
-                                 ))
-                        FAIL2("panic: regclass returned NULL to handle_sets, "
-                              "flags=%#" UVxf, (UV) *flagp);
-
-                    /* function call leaves parse pointing to the ']', except
-                     * if we faked it */
-                    if (is_posix_class) {
-                        RExC_parse--;
-                    }
-
-                    SvREFCNT_dec(current);   /* In case it returned something */
-                    break;
-                }
-
-                case ']':
-                    if (RExC_parse[1] == ')') {
-                        RExC_parse++;
-                        if (nest_depth--) break;
-                        node = reganode(pRExC_state, ANYOF, 0);
-                        RExC_size += ANYOF_SKIP;
-                        nextchar(pRExC_state);
-                        Set_Node_Length(node,
-                                RExC_parse - oregcomp_parse + 1); /* MJD */
-                        if (in_locale) {
-                            set_regex_charset(&RExC_flags, REGEX_LOCALE_CHARSET);
-                        }
-
-                        return node;
-                    }
-                    /* We output the messages even if warnings are off, because we'll fail
-                     * the very next thing, and these give a likely diagnosis for that */
-                    if (posix_warnings && av_tindex_skip_len_mg(posix_warnings) >= 0) {
-                        output_or_return_posix_warnings(pRExC_state, posix_warnings, NULL);
-                    }
-                    RExC_parse++;
-                    vFAIL("Unexpected ']' with no following ')' in (?[...");
-            }
-
-            RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
-        }
-
-        /* We output the messages even if warnings are off, because we'll fail
-         * the very next thing, and these give a likely diagnosis for that */
-        if (posix_warnings && av_tindex_skip_len_mg(posix_warnings) >= 0) {
-            output_or_return_posix_warnings(pRExC_state, posix_warnings, NULL);
-        }
-
-        vFAIL("Syntax error in (?[...])");
-    }
-
-    /* Pass 2 only after this. */
-    Perl_ck_warner_d(aTHX_
-        packWARN(WARN_EXPERIMENTAL__REGEX_SETS),
-        "The regex_sets feature is experimental" REPORT_LOCATION,
-        REPORT_LOCATION_ARGS(RExC_parse));
+    ckWARNexperimental(RExC_parse,
+                       WARN_EXPERIMENTAL__REGEX_SETS,
+                       "The regex_sets feature is experimental");
 
     /* Everything in this construct is a metacharacter.  Operands begin with
      * either a '\' (for an escape sequence), or a '[' for a bracketed
@@ -15509,8 +15609,8 @@ S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
 
         skip_to_be_ignored_text(pRExC_state, &RExC_parse,
                                 TRUE /* Force /x */ );
-        if (RExC_parse >= RExC_end) {
-            Perl_croak(aTHX_ "panic: Read past end of '(?[ ])'");
+        if (RExC_parse >= RExC_end) {   /* Fail */
+            break;
         }
 
         curchar = UCHARAT(RExC_parse);
@@ -15631,9 +15731,9 @@ redo_curchar:
                 break;
 
             case '\\':
-                /* regclass() can only return RESTART_PASS1 and NEED_UTF8 if
+                /* regclass() can only return RESTART_PARSE and NEED_UTF8 if
                  * multi-char folds are allowed.  */
-                if (!regclass(pRExC_state, flagp,depth+1,
+                if (!regclass(pRExC_state, flagp, depth+1,
                               TRUE, /* means parse just the next thing */
                               FALSE, /* don't allow multi-char folds */
                               FALSE, /* don't silence non-portable warnings.  */
@@ -15642,7 +15742,7 @@ redo_curchar:
                               &current,
                               NULL))
                 {
-                    FAIL2("panic: regclass returned NULL to handle_sets, "
+                    FAIL2("panic: regclass returned failure to handle_sets, "
                           "flags=%#" UVxf, (UV) *flagp);
                 }
 
@@ -15667,9 +15767,9 @@ redo_curchar:
                     RExC_parse++;
                 }
 
-                /* regclass() can only return RESTART_PASS1 and NEED_UTF8 if
+                /* regclass() can only return RESTART_PARSE and NEED_UTF8 if
                  * multi-char folds are allowed.  */
-                if (!regclass(pRExC_state, flagp,depth+1,
+                if (!regclass(pRExC_state, flagp, depth+1,
                                 is_posix_class, /* parse the whole char
                                                     class only if not a
                                                     posix class */
@@ -15681,10 +15781,14 @@ redo_curchar:
                                 NULL
                                 ))
                 {
-                    FAIL2("panic: regclass returned NULL to handle_sets, "
+                    FAIL2("panic: regclass returned failure to handle_sets, "
                           "flags=%#" UVxf, (UV) *flagp);
                 }
 
+                if (! current) {
+                    break;
+                }
+
                 /* function call leaves parse pointing to the ']', except if we
                  * faked it */
                 if (is_posix_class) {
@@ -15704,6 +15808,9 @@ redo_curchar:
 
             case ')':
                 if (av_tindex_skip_len_mg(fence_stack) < 0) {
+                    if (UCHARAT(RExC_parse - 1) == ']')  {
+                        break;
+                    }
                     RExC_parse++;
                     vFAIL("Unexpected ')'");
                 }
@@ -15890,6 +15997,9 @@ redo_curchar:
 
             default:
                 RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                if (RExC_parse >= RExC_end) {
+                    break;
+                }
                 vFAIL("Unexpected character");
 
           handle_operand:
@@ -15949,7 +16059,18 @@ redo_curchar:
         RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
     } /* End of loop parsing through the construct */
 
+    vFAIL("Syntax error in (?[...])");
+
   done:
+
+    if (RExC_parse >= RExC_end || RExC_parse[1] != ')') {
+        if (RExC_parse < RExC_end) {
+            RExC_parse++;
+        }
+
+        vFAIL("Unexpected ']' with no following ')' in (?[...");
+    }
+
     if (av_tindex_skip_len_mg(fence_stack) >= 0) {
         vFAIL("Unmatched (");
     }
@@ -15957,7 +16078,7 @@ redo_curchar:
     if (av_tindex_skip_len_mg(stack) < 0   /* Was empty */
         || ((final = av_pop(stack)) == NULL)
         || ! IS_OPERAND(final)
-        || SvTYPE(final) != SVt_INVLIST
+        || ! is_invlist(final)
         || av_tindex_skip_len_mg(stack) >= 0)  /* More left on stack */
     {
       bad_syntax:
@@ -15992,14 +16113,15 @@ redo_curchar:
     RExC_parse = SvPV(result_string, len);
     save_end = RExC_end;
     RExC_end = RExC_parse + len;
+    TURN_OFF_WARNINGS_IN_SUBSTITUTE_PARSE;
 
     /* We turn off folding around the call, as the class we have constructed
      * already has all folding taken into consideration, and we don't want
      * regclass() to add to that */
     RExC_flags &= ~RXf_PMf_FOLD;
-    /* regclass() can only return RESTART_PASS1 and NEED_UTF8 if multi-char
+    /* regclass() can only return RESTART_PARSE and NEED_UTF8 if multi-char
      * folds are allowed.  */
-    node = regclass(pRExC_state, flagp,depth+1,
+    node = regclass(pRExC_state, flagp, depth+1,
                     FALSE, /* means parse the whole char class */
                     FALSE, /* don't allow multi-char folds */
                     TRUE, /* silence non-portable warnings.  The above may very
@@ -16010,8 +16132,19 @@ redo_curchar:
                     NULL,
                     NULL
                 );
+
+    RESTORE_WARNINGS;
+    RExC_parse = save_parse + 1;
+    RExC_end = save_end;
+    SvREFCNT_dec_NN(final);
+    SvREFCNT_dec_NN(result_string);
+
+    if (save_fold) {
+        RExC_flags |= RXf_PMf_FOLD;
+    }
+
     if (!node)
-        FAIL2("panic: regclass returned NULL to handle_sets, flags=%#" UVxf,
+        FAIL2("panic: regclass returned failure to handle_sets, flags=%#" UVxf,
                     PTR2UV(flagp));
 
     /* Fix up the node type if we are in locale.  (We have pretended we are
@@ -16033,24 +16166,15 @@ redo_curchar:
     if (in_locale) {
         set_regex_charset(&RExC_flags, REGEX_LOCALE_CHARSET);
 
-        assert(OP(node) == ANYOF);
+        assert(OP(REGNODE_p(node)) == ANYOF);
 
-        OP(node) = ANYOFL;
-        ANYOF_FLAGS(node)
+        OP(REGNODE_p(node)) = ANYOFL;
+        ANYOF_FLAGS(REGNODE_p(node))
                 |= ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
     }
 
-    if (save_fold) {
-        RExC_flags |= RXf_PMf_FOLD;
-    }
-
-    RExC_parse = save_parse + 1;
-    RExC_end = save_end;
-    SvREFCNT_dec_NN(final);
-    SvREFCNT_dec_NN(result_string);
-
     nextchar(pRExC_state);
-    Set_Node_Length(node, RExC_parse - oregcomp_parse + 1); /* MJD */
+    Set_Node_Length(REGNODE_p(node), RExC_parse - oregcomp_parse + 1); /* MJD */
     return node;
 }
 
@@ -16177,11 +16301,9 @@ S_add_above_Latin1_folds(pTHX_ RExC_state_t *pRExC_state, const U8 cp, SV** invl
 
                 /* Use deprecated warning to increase the chances of this being
                  * output */
-                if (PASS2) {
-                    ckWARN2reg_d(RExC_parse,
+                ckWARN2reg_d(RExC_parse,
                         "Perl folding rules are not up-to-date for 0x%02X;"
                         " please use the perlbug utility to report;", cp);
-                }
             }
             else {
                 unsigned int i;
@@ -16228,14 +16350,21 @@ S_output_or_return_posix_warnings(pTHX_ RExC_state_t *pRExC_state, AV* posix_war
                                                array is mortal, but is a
                                                fail-safe */
                 (void) sv_2mortal(msg);
-                if (PASS2) {
-                    SAVEFREESV(RExC_rx_sv);
+                if (ckDEAD(packWARN(WARN_REGEXP))) {
+                    PREPARE_TO_DIE;
                 }
             }
-            Perl_warner(aTHX_ packWARN(WARN_REGEXP), "%s", SvPVX(msg));
+            if (TO_OUTPUT_WARNINGS(RExC_parse)) {
+                Perl_warner(aTHX_ packWARN(WARN_REGEXP), "%s",
+                                           SvPVX(msg));
+            }
             SvREFCNT_dec_NN(msg);
         }
     }
+
+    if (! return_posix_warnings) {
+        UPDATE_WARNINGS_LOC(RExC_parse);
+    }
 }
 
 STATIC AV *
@@ -16307,7 +16436,7 @@ S_add_multi_match(pTHX_ AV* multi_char_matches, SV* multi_string, const STRLEN c
         }                                                               \
     } STMT_END
 
-STATIC regnode *
+STATIC regnode_offset
 S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                  const bool stop_at_1,  /* Just parse the next thing, don't
                                            look for a full character class */
@@ -16343,15 +16472,18 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * are extra bits for \w, etc. in locale ANYOFs, as what these match is not
      * determinable at compile time
      *
-     * Returns NULL, setting *flagp to RESTART_PASS1 if the sizing scan needs
-     * to be restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded
-     * to UTF-8.  This can only happen if ret_invlist is non-NULL.
+     * On success, returns the offset at which any next node should be placed
+     * into the regex engine program being compiled.
+     *
+     * Returns 0 otherwise, setting flagp to RESTART_PARSE if the sizing scan needs
+     * to be restarted, or'd with NEED_UTF8 if the pattern needs to be upgraded to
+     * UTF-8
      */
 
     UV prevvalue = OOB_UNICODE, save_prevvalue = OOB_UNICODE;
     IV range = 0;
     UV value = OOB_UNICODE, save_value = OOB_UNICODE;
-    regnode *ret;
+    regnode_offset ret;
     STRLEN numlen;
     int namedclass = OOB_NAMEDCLASS;
     char *rangebegin = NULL;
@@ -16429,10 +16561,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
     bool warn_super = ALWAYS_WARN_SUPER;
 
-    regnode * const orig_emit = RExC_emit; /* Save the original RExC_emit in
+    const regnode_offset orig_emit = RExC_emit; /* Save the original RExC_emit in
         case we need to change the emitted regop to an EXACT. */
     const char * orig_parse = RExC_parse;
-    const SSize_t orig_size = RExC_size;
     bool posixl_matches_all = FALSE; /* Does /l class have both e.g. \W,\w ? */
 
     /* This variable is used to mark where the end in the input is of something
@@ -16443,8 +16574,12 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     char *not_posix_region_end = RExC_parse - 1;
 
     AV* posix_warnings = NULL;
-    const bool do_posix_warnings =     return_posix_warnings
-                                   || (PASS2 && ckWARN(WARN_REGEXP));
+    const bool do_posix_warnings = return_posix_warnings || ckWARN(WARN_REGEXP);
+    U8 op = END;    /* The returned node-type, initialized to an impossible
+                       one.  */
+    U8 anyof_flags = 0;   /* flag bits if the node is an ANYOF-type */
+    U32 posixl = 0;       /* bit field of posix classes matched under /l */
+    bool use_anyofd = FALSE; /* ? Is this to be an ANYOFD node */
 
     GET_RE_DEBUG_FLAGS_DECL;
 
@@ -16461,25 +16596,9 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     allow_multi_folds = FALSE;
 #endif
 
-    /* Assume we are going to generate an ANYOF node. */
-    ret = reganode(pRExC_state,
-                   (LOC)
-                    ? ANYOFL
-                    : ANYOF,
-                   0);
-
-    if (SIZE_ONLY) {
-       RExC_size += ANYOF_SKIP;
-       listsv = &PL_sv_undef; /* For code scanners: listsv always non-NULL. */
-    }
-    else {
-        ANYOF_FLAGS(ret) = 0;
-
-       RExC_emit += ANYOF_SKIP;
-       listsv = newSVpvs_flags("# comment\n", SVs_TEMP);
-       initial_listsv_len = SvCUR(listsv);
-        SvTEMP_off(listsv); /* Grr, TEMPs and mortals are conflated.  */
-    }
+    listsv = newSVpvs_flags("# comment\n", SVs_TEMP);
+    initial_listsv_len = SvCUR(listsv);
+    SvTEMP_off(listsv); /* Grr, TEMPs and mortals are conflated.  */
 
     SKIP_BRACKETED_WHITE_SPACE(skip_white, RExC_parse);
 
@@ -16500,8 +16619,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                                 &not_posix_region_end,
                                                 NULL,
                                                 TRUE /* checking only */);
-        if (PASS2 && maybe_class >= OOB_NAMEDCLASS && do_posix_warnings) {
-            SAVEFREESV(RExC_rx_sv);
+        if (maybe_class >= OOB_NAMEDCLASS && do_posix_warnings) {
             ckWARN4reg(not_posix_region_end,
                     "POSIX syntax [%c %c] belongs inside character classes%s",
                     *RExC_parse, *RExC_parse,
@@ -16511,7 +16629,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         : " (but this one isn't fully valid)")
                     : ""
                     );
-            (void)ReREFCNT_inc(RExC_rx_sv);
         }
     }
 
@@ -16672,16 +16789,14 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         if (*flagp & NEED_UTF8)
                             FAIL("panic: grok_bslash_N set NEED_UTF8");
 
-                        RETURN_NULL_ON_RESTART_FLAGP(flagp);
+                        RETURN_FAIL_ON_RESTART_FLAGP(flagp);
 
                         if (cp_count < 0) {
                             vFAIL("\\N in a character class must be a named character: \\N{...}");
                         }
                         else if (cp_count == 0) {
-                            if (PASS2) {
-                                ckWARNreg(RExC_parse,
-                                        "Ignoring zero length \\N{} in character class");
-                            }
+                            ckWARNreg(RExC_parse,
+                              "Ignoring zero length \\N{} in character class");
                         }
                         else { /* cp_count > 1 */
                             if (! RExC_in_multi_char_class) {
@@ -16690,9 +16805,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                         RExC_parse--;
                                         vFAIL("\\N{} in inverted character class or as a range end-point is restricted to one character");
                                     }
-                                    else if (PASS2) {
-                                        ckWARNreg(RExC_parse, "Using just the first character returned by \\N{} in character class");
-                                    }
+                                    ckWARNreg(RExC_parse, "Using just the first character returned by \\N{} in character class");
                                     break; /* <value> contains the first code
                                               point. Drop out of the switch to
                                               process it */
@@ -16726,7 +16839,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                char *e;
                 char *i;
 
-
                 /* We will handle any undefined properties ourselves */
                 U8 swash_init_flags = _CORE_SWASH_INIT_RETURN_IF_UNDEF
                                        /* And we actually would prefer to get
@@ -16736,6 +16848,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                       |_CORE_SWASH_INIT_ACCEPT_INVLIST;
 
                 SvREFCNT_dec(swash); /* Free any left-overs */
+
+               /* \p means they want Unicode semantics */
+               REQUIRE_UNI_RULES(flagp, 0);
+
                if (RExC_parse >= RExC_end)
                    vFAIL2("Empty \\%c", (U8)value);
                if (*RExC_parse == '{') {
@@ -16785,7 +16901,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                    e = RExC_parse;
                    n = 1;
                }
-               if (!SIZE_ONLY) {
+               {
                     char* name = RExC_parse;
                     char* base_name;    /* name after any packages are stripped */
                     char* lookup_name = NULL;
@@ -16927,7 +17043,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                         /* We don't know yet what this matches, so have to flag
                          * it */
-                        ANYOF_FLAGS(ret) |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
+                        anyof_flags |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
                     }
                     else {
 
@@ -16976,14 +17092,11 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                             }
                        }
                     }
-                } /* End of actually getting the values in pass 2 */
+                }
 
                RExC_parse = e + 1;
                 namedclass = ANYOF_UNIPROP;  /* no official name, but it's
                                                 named */
-
-               /* \p means they want Unicode semantics */
-               REQUIRE_UNI_RULES(flagp, NULL);
                }
                break;
            case 'n':   value = '\n';                   break;
@@ -17001,14 +17114,14 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                                RExC_end,
                                               &value,
                                               &error_msg,
-                                               PASS2,   /* warnings only in
-                                                           pass 2 */
+                                               TO_OUTPUT_WARNINGS(RExC_parse),
                                                strict,
                                                silence_non_portable,
                                                UTF);
                    if (! valid) {
                        vFAIL(error_msg);
                    }
+                    UPDATE_WARNINGS_LOC(RExC_parse - 1);
                }
                 non_portable_endpoint++;
                break;
@@ -17020,18 +17133,21 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                                RExC_end,
                                               &value,
                                               &error_msg,
-                                              PASS2, /* Output warnings */
+                                              TO_OUTPUT_WARNINGS(RExC_parse),
                                                strict,
                                                silence_non_portable,
                                                UTF);
                     if (! valid) {
                        vFAIL(error_msg);
                    }
+                    UPDATE_WARNINGS_LOC(RExC_parse - 1);
                }
                 non_portable_endpoint++;
                break;
            case 'c':
-               value = grok_bslash_c(*RExC_parse++, PASS2);
+               value = grok_bslash_c(*RExC_parse, TO_OUTPUT_WARNINGS(RExC_parse));
+                UPDATE_WARNINGS_LOC(RExC_parse);
+               RExC_parse++;
                 non_portable_endpoint++;
                break;
            case '0': case '1': case '2': case '3': case '4':
@@ -17047,17 +17163,14 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                             RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
                             vFAIL("Need exactly 3 octal digits");
                         }
-                        else if (! SIZE_ONLY /* like \08, \178 */
-                                 && numlen < 3
+                        else if (   numlen < 3 /* like \08, \178 */
                                  && RExC_parse < RExC_end
                                  && isDIGIT(*RExC_parse)
                                  && ckWARN(WARN_REGEXP))
                         {
-                            SAVEFREESV(RExC_rx_sv);
                             reg_warn_non_literal_string(
                                  RExC_parse + 1,
                                  form_short_octal_warning(RExC_parse, numlen));
-                            (void)ReREFCNT_inc(RExC_rx_sv);
                         }
                     }
                     non_portable_endpoint++;
@@ -17065,17 +17178,15 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                }
            default:
                /* Allow \_ to not give an error */
-               if (!SIZE_ONLY && isWORDCHAR(value) && value != '_') {
+               if (isWORDCHAR(value) && value != '_') {
                     if (strict) {
                         vFAIL2("Unrecognized escape \\%c in character class",
                                (int)value);
                     }
                     else {
-                        SAVEFREESV(RExC_rx_sv);
                         ckWARN2reg(RExC_parse,
                             "Unrecognized escape \\%c in character class passed through",
                             (int)value);
-                        (void)ReREFCNT_inc(RExC_rx_sv);
                     }
                }
                break;
@@ -17091,26 +17202,22 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             * literal, as is the character that began the false range, i.e.
             * the 'a' in the examples */
            if (range) {
-               if (!SIZE_ONLY) {
-                   const int w = (RExC_parse >= rangebegin)
-                                  ? RExC_parse - rangebegin
-                                  : 0;
-                    if (strict) {
-                        vFAIL2utf8f(
-                            "False [] range \"%" UTF8f "\"",
-                            UTF8fARG(UTF, w, rangebegin));
-                    }
-                    else {
-                        SAVEFREESV(RExC_rx_sv); /* in case of fatal warnings */
-                        ckWARN2reg(RExC_parse,
-                            "False [] range \"%" UTF8f "\"",
-                            UTF8fARG(UTF, w, rangebegin));
-                        (void)ReREFCNT_inc(RExC_rx_sv);
-                        cp_list = add_cp_to_invlist(cp_list, '-');
-                        cp_foldable_list = add_cp_to_invlist(cp_foldable_list,
-                                                             prevvalue);
-                    }
-               }
+                const int w = (RExC_parse >= rangebegin)
+                                ? RExC_parse - rangebegin
+                                : 0;
+                if (strict) {
+                    vFAIL2utf8f(
+                        "False [] range \"%" UTF8f "\"",
+                        UTF8fARG(UTF, w, rangebegin));
+                }
+                else {
+                    ckWARN2reg(RExC_parse,
+                        "False [] range \"%" UTF8f "\"",
+                        UTF8fARG(UTF, w, rangebegin));
+                    cp_list = add_cp_to_invlist(cp_list, '-');
+                    cp_foldable_list = add_cp_to_invlist(cp_foldable_list,
+                                                            prevvalue);
+                }
 
                range = 0; /* this was not a true range */
                 element_count += 2; /* So counts for three values */
@@ -17123,6 +17230,8 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                 && classnum != _CC_ASCII
 #endif
             ) {
+                SV* scratch_list = NULL;
+
                 /* What the Posix classes (like \w, [:space:]) match in locale
                  * isn't knowable under locale until actual match time.  Room
                  * must be reserved (one time per outer bracketed class) to
@@ -17132,14 +17241,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                  * by locale, and hence are dealt with separately */
                 if (! need_class) {
                     need_class = 1;
-                    if (SIZE_ONLY) {
-                        RExC_size += ANYOF_POSIXL_SKIP - ANYOF_SKIP;
-                    }
-                    else {
-                        RExC_emit += ANYOF_POSIXL_SKIP - ANYOF_SKIP;
-                    }
-                    ANYOF_FLAGS(ret) |= ANYOF_MATCHES_POSIXL;
-                    ANYOF_POSIXL_ZERO(ret);
+                    anyof_flags |= ANYOF_MATCHES_POSIXL;
 
                     /* We can't change this into some other type of node
                      * (unless this is the only element, in which case there
@@ -17150,15 +17252,15 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                 /* Coverity thinks it is possible for this to be negative; both
                  * jhi and khw think it's not, but be safer */
-                assert(! (ANYOF_FLAGS(ret) & ANYOF_MATCHES_POSIXL)
+                assert(! (anyof_flags & ANYOF_MATCHES_POSIXL)
                        || (namedclass + ((namedclass % 2) ? -1 : 1)) >= 0);
 
                 /* See if it already matches the complement of this POSIX
                  * class */
-                if ((ANYOF_FLAGS(ret) & ANYOF_MATCHES_POSIXL)
-                    && ANYOF_POSIXL_TEST(ret, namedclass + ((namedclass % 2)
-                                                            ? -1
-                                                            : 1)))
+                if (  (anyof_flags & ANYOF_MATCHES_POSIXL)
+                    && POSIXL_TEST(posixl, namedclass + ((namedclass % 2)
+                                                         ? -1
+                                                         : 1)))
                 {
                     posixl_matches_all = TRUE;
                     break;  /* No need to continue.  Since it matches both
@@ -17167,38 +17269,35 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                 }
 
                 /* Add this class to those that should be checked at runtime */
-                ANYOF_POSIXL_SET(ret, namedclass);
+                POSIXL_SET(posixl, namedclass);
 
                 /* The above-Latin1 characters are not subject to locale rules.
                  * Just add them, in the second pass, to the
                  * unconditionally-matched list */
-                if (! SIZE_ONLY) {
-                    SV* scratch_list = NULL;
-
-                    /* Get the list of the above-Latin1 code points this
-                     * matches */
-                    _invlist_intersection_maybe_complement_2nd(PL_AboveLatin1,
-                                          PL_XPosix_ptrs[classnum],
-
-                                          /* Odd numbers are complements, like
-                                           * NDIGIT, NASCII, ... */
-                                          namedclass % 2 != 0,
-                                          &scratch_list);
-                    /* Checking if 'cp_list' is NULL first saves an extra
-                     * clone.  Its reference count will be decremented at the
-                     * next union, etc, or if this is the only instance, at the
-                     * end of the routine */
-                    if (! cp_list) {
-                        cp_list = scratch_list;
-                    }
-                    else {
-                        _invlist_union(cp_list, scratch_list, &cp_list);
-                        SvREFCNT_dec_NN(scratch_list);
-                    }
-                    continue;   /* Go get next character */
+
+                /* Get the list of the above-Latin1 code points this
+                    * matches */
+                _invlist_intersection_maybe_complement_2nd(PL_AboveLatin1,
+                                        PL_XPosix_ptrs[classnum],
+
+                                        /* Odd numbers are complements, like
+                                        * NDIGIT, NASCII, ... */
+                                        namedclass % 2 != 0,
+                                        &scratch_list);
+                /* Checking if 'cp_list' is NULL first saves an extra
+                    * clone.  Its reference count will be decremented at the
+                    * next union, etc, or if this is the only instance, at the
+                    * end of the routine */
+                if (! cp_list) {
+                    cp_list = scratch_list;
+                }
+                else {
+                    _invlist_union(cp_list, scratch_list, &cp_list);
+                    SvREFCNT_dec_NN(scratch_list);
                 }
+                continue;   /* Go get next character */
             }
-            else if (! SIZE_ONLY) {
+            else {
 
                 /* Here, not in pass1 (in that pass we skip calculating the
                  * contents of this class), and is not /l, or is a POSIX class
@@ -17234,7 +17333,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         || (DEPENDS_SEMANTICS && (   classnum == _CC_DIGIT
                                                   || classnum == _CC_XDIGIT)))
                 {
-                    /* We usually have to worry about /d a affecting what POSIX
+                    /* We usually have to worry about /d affecting what POSIX
                      * classes match, with special code needed because we won't
                      * know until runtime what all matches.  But there is no
                      * extra work needed under /u and /a; and [:ascii:] is
@@ -17316,7 +17415,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
                     /* a bad range like \w-, [:word:]- ? */
                     if (namedclass > OOB_NAMEDCLASS) {
-                        if (strict || (PASS2 && ckWARN(WARN_REGEXP))) {
+                        if (strict || ckWARN(WARN_REGEXP)) {
                             const int w = RExC_parse >= rangebegin
                                           ?  RExC_parse - rangebegin
                                           : 0;
@@ -17324,15 +17423,13 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                 vFAIL4("False [] range \"%*.*s\"",
                                     w, w, rangebegin);
                             }
-                            else if (PASS2) {
+                            else {
                                 vWARN4(RExC_parse,
                                     "False [] range \"%*.*s\"",
                                     w, w, rangebegin);
                             }
                         }
-                        if (!SIZE_ONLY) {
-                            cp_list = add_cp_to_invlist(cp_list, '-');
-                        }
+                        cp_list = add_cp_to_invlist(cp_list, '-');
                         element_count++;
                     } else
                         range = 1;     /* yeah, it's a range! */
@@ -17352,7 +17449,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
        /* non-Latin1 code point implies unicode semantics.  Must be set in
         * pass1 so is there for the whole of pass 2 */
        if (value > 255) {
-            REQUIRE_UNI_RULES(flagp, NULL);
+            REQUIRE_UNI_RULES(flagp, 0);
        }
 
         /* Ready to process either the single value, or the completed range.
@@ -17418,7 +17515,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             }
         }
 
-        if (strict && PASS2 && ckWARN(WARN_REGEXP)) {
+        if (strict && ckWARN(WARN_REGEXP)) {
             if (range) {
 
                 /* If the range starts above 255, everything is portable and
@@ -17550,48 +17647,45 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         }
 
         /* Deal with this element of the class */
-       if (! SIZE_ONLY) {
 
 #ifndef EBCDIC
-            cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
-                                                     prevvalue, value);
+        cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
+                                                    prevvalue, value);
 #else
-            /* On non-ASCII platforms, for ranges that span all of 0..255, and
-             * ones that don't require special handling, we can just add the
-             * range like we do for ASCII platforms */
-            if ((UNLIKELY(prevvalue == 0) && value >= 255)
-                || ! (prevvalue < 256
-                      && (unicode_range
-                          || (! non_portable_endpoint
-                              && ((isLOWER_A(prevvalue) && isLOWER_A(value))
-                                  || (isUPPER_A(prevvalue)
-                                      && isUPPER_A(value)))))))
-            {
-                cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
-                                                         prevvalue, value);
+        /* On non-ASCII platforms, for ranges that span all of 0..255, and ones
+         * that don't require special handling, we can just add the range like
+         * we do for ASCII platforms */
+        if ((UNLIKELY(prevvalue == 0) && value >= 255)
+            || ! (prevvalue < 256
+                    && (unicode_range
+                        || (! non_portable_endpoint
+                            && ((isLOWER_A(prevvalue) && isLOWER_A(value))
+                                || (isUPPER_A(prevvalue)
+                                    && isUPPER_A(value)))))))
+        {
+            cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
+                                                        prevvalue, value);
+        }
+        else {
+            /* Here, requires special handling.  This can be because it is a
+             * range whose code points are considered to be Unicode, and so
+             * must be individually translated into native, or because its a
+             * subrange of 'A-Z' or 'a-z' which each aren't contiguous in
+             * EBCDIC, but we have defined them to include only the "expected"
+             * upper or lower case ASCII alphabetics.  Subranges above 255 are
+             * the same in native and Unicode, so can be added as a range */
+            U8 start = NATIVE_TO_LATIN1(prevvalue);
+            unsigned j;
+            U8 end = (value < 256) ? NATIVE_TO_LATIN1(value) : 255;
+            for (j = start; j <= end; j++) {
+                cp_foldable_list = add_cp_to_invlist(cp_foldable_list, LATIN1_TO_NATIVE(j));
             }
-            else {
-                /* Here, requires special handling.  This can be because it is
-                 * a range whose code points are considered to be Unicode, and
-                 * so must be individually translated into native, or because
-                 * its a subrange of 'A-Z' or 'a-z' which each aren't
-                 * contiguous in EBCDIC, but we have defined them to include
-                 * only the "expected" upper or lower case ASCII alphabetics.
-                 * Subranges above 255 are the same in native and Unicode, so
-                 * can be added as a range */
-                U8 start = NATIVE_TO_LATIN1(prevvalue);
-                unsigned j;
-                U8 end = (value < 256) ? NATIVE_TO_LATIN1(value) : 255;
-                for (j = start; j <= end; j++) {
-                    cp_foldable_list = add_cp_to_invlist(cp_foldable_list, LATIN1_TO_NATIVE(j));
-                }
-                if (value > 255) {
-                    cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
-                                                             256, value);
-                }
+            if (value > 255) {
+                cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
+                                                            256, value);
             }
-#endif
         }
+#endif
 
        range = 0; /* this range (if it was one) is done now */
     } /* End of loop through all the text within the brackets */
@@ -17612,15 +17706,16 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
        char *save_end = RExC_end;
        char *save_parse = RExC_parse;
        char *save_start = RExC_start;
-        STRLEN prefix_end = 0;      /* We copy the character class after a
-                                       prefix supplied here.  This is the size
-                                       + 1 of that prefix */
+        Size_t constructed_prefix_len = 0; /* This gives the length of the
+                                              constructed portion of the
+                                              substitute parse. */
         bool first_time = TRUE;     /* First multi-char occurrence doesn't get
                                        a "|" */
         I32 reg_flags;
 
         assert(! invert);
-        assert(RExC_precomp_adj == 0); /* Only one level of recursion allowed */
+        /* Only one level of recursion allowed */
+        assert(RExC_copy_start_in_constructed == RExC_precomp);
 
 #if 0   /* Have decided not to deal with multi-char folds in inverted classes,
            because too confusing */
@@ -17658,7 +17753,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
          * multi-character folds, have to include it in recursive parsing */
         if (element_count) {
             sv_catpvs(substitute_parse, "|[");
-            prefix_end = SvCUR(substitute_parse);
+            constructed_prefix_len = SvCUR(substitute_parse);
             sv_catpvn(substitute_parse, orig_parse, RExC_parse - orig_parse);
 
             /* Put in a closing ']' only if not going off the end, as otherwise
@@ -17681,21 +17776,19 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         /* Set up the data structure so that any errors will be properly
          * reported.  See the comments at the definition of
          * REPORT_LOCATION_ARGS for details */
-        RExC_precomp_adj = orig_parse - RExC_precomp;
-       RExC_start =  RExC_parse = SvPV(substitute_parse, len);
-        RExC_adjusted_start = RExC_start + prefix_end;
+        RExC_copy_start_in_input = (char *) orig_parse;
+       RExC_start = RExC_parse = SvPV(substitute_parse, len);
+        RExC_copy_start_in_constructed = RExC_start + constructed_prefix_len;
        RExC_end = RExC_parse + len;
         RExC_in_multi_char_class = 1;
-        RExC_emit = (regnode *)orig_emit;
 
        ret = reg(pRExC_state, 1, &reg_flags, depth+1);
 
-        *flagp |= reg_flags & (HASWIDTH|SIMPLE|SPSTART|POSTPONED|RESTART_PASS1|NEED_UTF8);
+        *flagp |= reg_flags & (HASWIDTH|SIMPLE|SPSTART|POSTPONED|RESTART_PARSE|NEED_UTF8);
 
         /* And restore so can parse the rest of the pattern */
         RExC_parse = save_parse;
-       RExC_start = RExC_adjusted_start = save_start;
-        RExC_precomp_adj = 0;
+       RExC_start = RExC_copy_start_in_constructed = RExC_copy_start_in_input = save_start;
        RExC_end = save_end;
        RExC_in_multi_char_class = 0;
         SvREFCNT_dec_NN(multi_char_matches);
@@ -17863,39 +17956,24 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
          * an optimization */
         if (op != END) {
 
-            /* Throw away this ANYOF regnode, and emit the calculated one,
+            /* Emit the calculated regnode,
              * which should correspond to the beginning, not current, state of
              * the parse */
             const char * cur_parse = RExC_parse;
             RExC_parse = (char *)orig_parse;
-            if ( SIZE_ONLY) {
-                if (! LOC) {
-
-                    /* To get locale nodes to not use the full ANYOF size would
-                     * require moving the code above that writes the portions
-                     * of it that aren't in other nodes to after this point.
-                     * e.g.  ANYOF_POSIXL_SET */
-                    RExC_size = orig_size;
+            if (PL_regkind[op] == POSIXD) {
+                if (op == POSIXL) {
+                    RExC_contains_locale = 1;
                 }
-            }
-            else {
-                RExC_emit = (regnode *)orig_emit;
-                if (PL_regkind[op] == POSIXD) {
-                    if (op == POSIXL) {
-                        RExC_contains_locale = 1;
-                    }
-                    if (invert) {
-                        op += NPOSIXD - POSIXD;
-                    }
+                if (invert) {
+                    op += NPOSIXD - POSIXD;
                 }
             }
 
             ret = reg_node(pRExC_state, op);
 
             if (PL_regkind[op] == POSIXD || PL_regkind[op] == NPOSIXD) {
-                if (! SIZE_ONLY) {
-                    FLAGS(ret) = arg;
-                }
+                FLAGS(REGNODE_p(ret)) = arg;
                 *flagp |= HASWIDTH|SIMPLE;
             }
             else if (PL_regkind[op] == EXACT) {
@@ -17918,10 +17996,6 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         }
     }
 
-    if (SIZE_ONLY)
-        return ret;
-    /****** !SIZE_ONLY (Pass 2) AFTER HERE *********/
-
     /* If folding, we calculate all characters that could fold to or from the
      * ones already on the list */
     if (cp_foldable_list) {
@@ -18100,7 +18174,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
              *
              * Handle the case where there something like \W separately */
             if (nposixes) {
-                SV* only_non_utf8_list = invlist_clone(PL_UpperLatin1);
+                SV* only_non_utf8_list = invlist_clone(PL_UpperLatin1, NULL);
 
                 /* A complemented posix class matches all upper Latin1
                  * characters if not in UTF-8.  And it matches just certain
@@ -18135,7 +18209,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                 _invlist_subtract(only_non_utf8_list, cp_list,
                                   &only_non_utf8_list);
                 if (_invlist_len(only_non_utf8_list) != 0) {
-                    ANYOF_FLAGS(ret) |= ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER;
+                    anyof_flags |= ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER;
                 }
                 SvREFCNT_dec_NN(only_non_utf8_list);
             }
@@ -18220,7 +18294,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         }
 
         if (warn_super) {
-            ANYOF_FLAGS(ret)
+            anyof_flags
              |= ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER;
 
             /* Because an ANYOF node is the only one that warns, this node
@@ -18258,24 +18332,24 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
             }
         }
         if (only_utf8_locale_list) {
-            ANYOF_FLAGS(ret)
-                 |=  ANYOFL_FOLD
-                    |ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
+            anyof_flags
+                 |= ANYOFL_FOLD
+                 |  ANYOFL_SHARED_UTF8_LOCALE_fold_HAS_MATCHES_nonfold_REQD;
         }
         else if (cp_list) { /* Look to see if a 0-255 code point is in list */
             UV start, end;
             invlist_iterinit(cp_list);
             if (invlist_iternext(cp_list, &start, &end) && start < 256) {
-                ANYOF_FLAGS(ret) |= ANYOFL_FOLD;
+                anyof_flags |= ANYOFL_FOLD;
             }
             invlist_iterfinish(cp_list);
         }
     }
     else if (   DEPENDS_SEMANTICS
              && (    has_upper_latin1_only_utf8_matches
-                 || (ANYOF_FLAGS(ret) & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER)))
+                 || (anyof_flags & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER)))
     {
-        OP(ret) = ANYOFD;
+        use_anyofd = TRUE;
         optimizable = FALSE;
     }
 
@@ -18284,10 +18358,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * at compile time.  Besides not inverting folded locale now, we can't
      * invert if there are things such as \w, which aren't known until runtime
      * */
-    if (cp_list
-        && invert
-        && OP(ret) != ANYOFD
-        && ! (ANYOF_FLAGS(ret) & (ANYOF_LOCALE_FLAGS))
+    if (     cp_list
+        &&   invert
+        && ! use_anyofd
+        && ! (anyof_flags & (ANYOF_LOCALE_FLAGS))
        && ! HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
     {
         _invlist_invert(cp_list);
@@ -18303,19 +18377,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
     }
 
     if (ret_invlist) {
-        assert(cp_list);
-
         *ret_invlist = cp_list;
         SvREFCNT_dec(swash);
 
-        /* Discard the generated node */
-        if (SIZE_ONLY) {
-            RExC_size = orig_size;
-        }
-        else {
-            RExC_emit = orig_emit;
-        }
-        return orig_emit;
+        return RExC_emit;
     }
 
     /* Some character classes are equivalent to other nodes.  Such nodes take
@@ -18580,7 +18645,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
         if (op != END) {
             RExC_parse = (char *)orig_parse;
-            RExC_emit = (regnode *)orig_emit;
+            RExC_emit = orig_emit;
 
             if (regarglen[op]) {
                 ret = reganode(pRExC_state, op, anode_arg);
@@ -18596,10 +18661,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                                           );
             }
             else if (PL_regkind[op] == POSIXD || PL_regkind[op] == NPOSIXD) {
-                FLAGS(ret) = posix_class;
+                FLAGS(REGNODE_p(ret)) = posix_class;
             }
             else if (PL_regkind[op] == ANYOFM) {
-                FLAGS(ret) = ANYOFM_mask;
+                FLAGS(REGNODE_p(ret)) = ANYOFM_mask;
             }
 
             SvREFCNT_dec_NN(cp_list);
@@ -18607,16 +18672,33 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         }
     }
 
+    /* It's going to be an ANYOF node. */
+    op = (use_anyofd)
+         ? ANYOFD
+         : ((posixl)
+            ? ANYOFPOSIXL
+            : ((LOC)
+               ? ANYOFL
+               : ANYOF));
+    ret = regnode_guts(pRExC_state, op, regarglen[op], "anyof");
+    FILL_NODE(ret, op);        /* We set the argument later */
+    RExC_emit += 1 + regarglen[op];
+    ANYOF_FLAGS(REGNODE_p(ret)) = anyof_flags;
+
     /* Here, <cp_list> contains all the code points we can determine at
      * compile time that match under all conditions.  Go through it, and
      * for things that belong in the bitmap, put them there, and delete from
      * <cp_list>.  While we are at it, see if everything above 255 is in the
      * list, and if so, set a flag to speed up execution */
 
-    populate_ANYOF_from_invlist(ret, &cp_list);
+    populate_ANYOF_from_invlist(REGNODE_p(ret), &cp_list);
+
+    if (posixl) {
+        ANYOF_POSIXL_SET_TO_BITMAP(REGNODE_p(ret), posixl);
+    }
 
     if (invert) {
-        ANYOF_FLAGS(ret) |= ANYOF_INVERT;
+        ANYOF_FLAGS(REGNODE_p(ret)) |= ANYOF_INVERT;
     }
 
     /* Here, the bitmap has been populated with all the Latin1 code points that
@@ -18633,7 +18715,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
        else {
            cp_list = has_upper_latin1_only_utf8_matches;
        }
-        ANYOF_FLAGS(ret) |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
+        ANYOF_FLAGS(REGNODE_p(ret)) |= ANYOF_SHARED_d_UPPER_LATIN1_UTF8_STRING_MATCHES_non_d_RUNTIME_USER_PROP;
     }
 
     /* If there is a swash and more than one element, we can't use the swash in
@@ -18647,7 +18729,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
      * the class doesn't have us change swash at all, so it can include things
      * that are also in the bitmap; otherwise we have purposely deleted that
      * duplicate information */
-    set_ANYOF_arg(pRExC_state, ret, cp_list,
+    set_ANYOF_arg(pRExC_state, REGNODE_p(ret), cp_list,
                   (HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
                    ? listsv : NULL,
                   only_utf8_locale_list,
@@ -18655,7 +18737,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
 
     *flagp |= HASWIDTH|SIMPLE;
 
-    if (ANYOF_FLAGS(ret) & ANYOF_LOCALE_FLAGS) {
+    if (ANYOF_FLAGS(REGNODE_p(ret)) & ANYOF_LOCALE_FLAGS) {
         RExC_contains_locale = 1;
     }
 
@@ -18777,7 +18859,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
     SV *si  = NULL;         /* Input swash initialization string */
     SV* invlist = NULL;
 
-    RXi_GET_DECL(prog,progi);
+    RXi_GET_DECL(prog, progi);
     const struct reg_data * const data = prog ? progi->data : NULL;
 
     PERL_ARGS_ASSERT__GET_REGCLASS_NONBITMAP_DATA;
@@ -18964,7 +19046,7 @@ Perl__get_regclass_nonbitmap_data(pTHX_ const regexp *prog,
                                                   ));
             }
             else if (! *output_invlist) {
-                *output_invlist = invlist_clone(invlist);
+                *output_invlist = invlist_clone(invlist, NULL);
             }
             else {
                 _invlist_union(*output_invlist, invlist, output_invlist);
@@ -19094,44 +19176,71 @@ S_nextchar(pTHX_ RExC_state_t *pRExC_state)
     }
 }
 
-STATIC regnode *
-S_regnode_guts(pTHX_ RExC_state_t *pRExC_state, const U8 op, const STRLEN extra_size, const char* const name)
+STATIC void
+S_change_engine_size(pTHX_ RExC_state_t *pRExC_state, const Ptrdiff_t size)
 {
-    /* Allocate a regnode for 'op' and returns it, with 'extra_size' extra
-     * space.  In pass1, it aligns and increments RExC_size; in pass2,
-     * RExC_emit */
+    PERL_ARGS_ASSERT_CHANGE_ENGINE_SIZE;
 
-    regnode * const ret = RExC_emit;
-    GET_RE_DEBUG_FLAGS_DECL;
+    RExC_size += size;
 
-    PERL_ARGS_ASSERT_REGNODE_GUTS;
+    Renewc(RExC_rxi,
+           sizeof(regexp_internal) + (RExC_size + 1) * sizeof(regnode),
+                                                /* +1 for REG_MAGIC */
+           char,
+           regexp_internal);
+    if ( RExC_rxi == NULL )
+       FAIL("Regexp out of space");
+    RXi_SET(RExC_rx, RExC_rxi);
 
-    assert(extra_size >= regarglen[op]);
+    RExC_emit_start = RExC_rxi->program;
+    if (size > 0) {
+        Zero(REGNODE_p(RExC_emit), size, regnode);
+    }
 
-    if (SIZE_ONLY) {
-       SIZE_ALIGN(RExC_size);
-       RExC_size += 1 + extra_size;
-       return(ret);
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    Renew(RExC_offsets, 2*RExC_size+1, U32);
+    if (size > 0) {
+        Zero(RExC_offsets + 2*(RExC_size - size) + 1, 2 * size, U32);
     }
-    if (RExC_emit >= RExC_emit_bound)
-        Perl_croak(aTHX_ "panic: reg_node overrun trying to emit %d, %p>=%p",
-                  op, (void*)RExC_emit, (void*)RExC_emit_bound);
+    RExC_offsets[0] = RExC_size;
+#endif
+}
+
+STATIC regnode_offset
+S_regnode_guts(pTHX_ RExC_state_t *pRExC_state, const U8 op, const STRLEN extra_size, const char* const name)
+{
+    /* Allocate a regnode for 'op', with 'extra_size' extra space.  In pass1,
+     * it aligns and increments RExC_size; in pass2, RExC_emit
+     *
+     * It returns the renode's offset into the regex engine program (meaningful
+     * only in pass2 */
 
-    NODE_ALIGN_FILL(ret);
+    const regnode_offset ret = RExC_emit;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGNODE_GUTS;
+
+    SIZE_ALIGN(RExC_size);
+    change_engine_size(pRExC_state, (Ptrdiff_t) 1 + extra_size);
+    NODE_ALIGN_FILL(REGNODE_p(ret));
 #ifndef RE_TRACK_PATTERN_OFFSETS
     PERL_UNUSED_ARG(name);
+    PERL_UNUSED_ARG(op);
 #else
+    assert(extra_size >= regarglen[op] || PL_regkind[op] == ANYOF);
+
     if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(
               ("%s:%d: (op %s) %s %" UVuf " (len %" UVuf ") (max %" UVuf ").\n",
               name, __LINE__,
               PL_reg_name[op],
-              (UV)(RExC_emit - RExC_emit_start) > RExC_offsets[0]
+              (UV)(RExC_emit) > RExC_offsets[0]
                ? "Overwriting end of array!\n" : "OK",
-              (UV)(RExC_emit - RExC_emit_start),
+              (UV)(RExC_emit),
               (UV)(RExC_parse - RExC_start),
               (UV)RExC_offsets[0]));
-       Set_Node_Offset(RExC_emit, RExC_parse + (op == END));
+       Set_Node_Offset(REGNODE_p(RExC_emit), RExC_parse + (op == END));
     }
 #endif
     return(ret);
@@ -19140,78 +19249,74 @@ S_regnode_guts(pTHX_ RExC_state_t *pRExC_state, const U8 op, const STRLEN extra_
 /*
 - reg_node - emit a node
 */
-STATIC regnode *                       /* Location. */
+STATIC regnode_offset /* Location. */
 S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
 {
-    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reg_node");
+    const regnode_offset ret = regnode_guts(pRExC_state, op, regarglen[op], "reg_node");
+    regnode_offset ptr = ret;
 
     PERL_ARGS_ASSERT_REG_NODE;
 
     assert(regarglen[op] == 0);
 
-    if (PASS2) {
-        regnode *ptr = ret;
-        FILL_ADVANCE_NODE(ptr, op);
-        RExC_emit = ptr;
-    }
+    FILL_ADVANCE_NODE(ptr, op);
+    RExC_emit = ptr;
     return(ret);
 }
 
 /*
 - reganode - emit a node with an argument
 */
-STATIC regnode *                       /* Location. */
+STATIC regnode_offset /* Location. */
 S_reganode(pTHX_ RExC_state_t *pRExC_state, U8 op, U32 arg)
 {
-    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reganode");
+    const regnode_offset ret = regnode_guts(pRExC_state, op, regarglen[op], "reganode");
+    regnode_offset ptr = ret;
 
     PERL_ARGS_ASSERT_REGANODE;
 
+    /* ANYOF are special cased to allow non-length 1 args */
     assert(regarglen[op] == 1);
 
-    if (PASS2) {
-        regnode *ptr = ret;
-        FILL_ADVANCE_NODE_ARG(ptr, op, arg);
-        RExC_emit = ptr;
-    }
+    FILL_ADVANCE_NODE_ARG(ptr, op, arg);
+    RExC_emit = ptr;
     return(ret);
 }
 
-STATIC regnode *
+STATIC regnode_offset
 S_reg2Lanode(pTHX_ RExC_state_t *pRExC_state, const U8 op, const U32 arg1, const I32 arg2)
 {
     /* emit a node with U32 and I32 arguments */
 
-    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reg2Lanode");
+    const regnode_offset ret = regnode_guts(pRExC_state, op, regarglen[op], "reg2Lanode");
+    regnode_offset ptr = ret;
 
     PERL_ARGS_ASSERT_REG2LANODE;
 
     assert(regarglen[op] == 2);
 
-    if (PASS2) {
-        regnode *ptr = ret;
-        FILL_ADVANCE_NODE_2L_ARG(ptr, op, arg1, arg2);
-        RExC_emit = ptr;
-    }
+    FILL_ADVANCE_NODE_2L_ARG(ptr, op, arg1, arg2);
+    RExC_emit = ptr;
     return(ret);
 }
 
 /*
 - reginsert - insert an operator in front of already-emitted operand
 *
-* Means relocating the operand.
+* That means that on exit 'operand' is the offset of the newly inserted
+* operator, and the original operand has been relocated.
 *
 * IMPORTANT NOTE - it is the *callers* responsibility to correctly
 * set up NEXT_OFF() of the inserted node if needed. Something like this:
 *
-* reginsert(pRExC, OPFAIL, orig_emit, depth+1);
-* if (PASS2)
-*     NEXT_OFF(orig_emit) = regarglen[OPFAIL] + NODE_STEP_REGNODE;
+*   reginsert(pRExC, OPFAIL, orig_emit, depth+1);
+*   NEXT_OFF(orig_emit) = regarglen[OPFAIL] + NODE_STEP_REGNODE;
 *
-* ALSO NOTE - operand->flags will be set to 0 as well.
+* ALSO NOTE - FLAGS(newly-inserted-operator) will be set to 0 as well.
 */
 STATIC void
-S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
+S_reginsert(pTHX_ RExC_state_t *pRExC_state, const U8 op,
+                  const regnode_offset operand, const U32 depth)
 {
     regnode *src;
     regnode *dst;
@@ -19224,17 +19329,14 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
     PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(depth);
 /* (PL_regkind[(U8)op] == CURLY ? EXTRA_STEP_2ARGS : 0); */
-    DEBUG_PARSE_FMT("inst"," - %s",PL_reg_name[op]);
-    if (SIZE_ONLY) {
-       RExC_size += size;
-       return;
-    }
+    DEBUG_PARSE_FMT("inst"," - %s", PL_reg_name[op]);
     assert(!RExC_study_started); /* I believe we should never use reginsert once we have started
                                     studying. If this is wrong then we need to adjust RExC_recurse
                                     below like we do with RExC_open_parens/RExC_close_parens. */
-    src = RExC_emit;
+    change_engine_size(pRExC_state, (Ptrdiff_t) size);
+    src = REGNODE_p(RExC_emit);
     RExC_emit += size;
-    dst = RExC_emit;
+    dst = REGNODE_p(RExC_emit);
     if (RExC_open_parens) {
         int paren;
         /*DEBUG_PARSE_FMT("inst"," - %" IVdf, (IV)RExC_npar);*/
@@ -19246,13 +19348,13 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
              * regex, it can't move. RExC_close_parens[0] is the end
              * of the regex, it *can* move. */
             if ( paren && RExC_open_parens[paren] >= operand ) {
-                /*DEBUG_PARSE_FMT("open"," - %d",size);*/
+                /*DEBUG_PARSE_FMT("open"," - %d", size);*/
                 RExC_open_parens[paren] += size;
             } else {
                 /*DEBUG_PARSE_FMT("open"," - %s","ok");*/
             }
             if ( RExC_close_parens[paren] >= operand ) {
-                /*DEBUG_PARSE_FMT("close"," - %d",size);*/
+                /*DEBUG_PARSE_FMT("close"," - %d", size);*/
                 RExC_close_parens[paren] += size;
             } else {
                 /*DEBUG_PARSE_FMT("close"," - %s","ok");*/
@@ -19262,27 +19364,27 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
     if (RExC_end_op)
         RExC_end_op += size;
 
-    while (src > operand) {
+    while (src > REGNODE_p(operand)) {
        StructCopy(--src, --dst, regnode);
 #ifdef RE_TRACK_PATTERN_OFFSETS
         if (RExC_offsets) {     /* MJD 20010112 */
            MJD_OFFSET_DEBUG(
                  ("%s(%d): (op %s) %s copy %" UVuf " -> %" UVuf " (max %" UVuf ").\n",
-                  "reg_insert",
+                  "reginsert",
                  __LINE__,
                  PL_reg_name[op],
-                  (UV)(dst - RExC_emit_start) > RExC_offsets[0]
+                  (UV)(REGNODE_OFFSET(dst)) > RExC_offsets[0]
                    ? "Overwriting end of array!\n" : "OK",
-                  (UV)(src - RExC_emit_start),
-                  (UV)(dst - RExC_emit_start),
+                  (UV)REGNODE_OFFSET(src),
+                  (UV)REGNODE_OFFSET(dst),
                   (UV)RExC_offsets[0]));
-           Set_Node_Offset_To_R(dst-RExC_emit_start, Node_Offset(src));
-           Set_Node_Length_To_R(dst-RExC_emit_start, Node_Length(src));
+           Set_Node_Offset_To_R(REGNODE_OFFSET(dst), Node_Offset(src));
+           Set_Node_Length_To_R(REGNODE_OFFSET(dst), Node_Length(src));
         }
 #endif
     }
 
-    place = operand;           /* Op node, where operand used to be. */
+    place = REGNODE_p(operand);        /* Op node, where operand used to be. */
 #ifdef RE_TRACK_PATTERN_OFFSETS
     if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(
@@ -19290,9 +19392,9 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
               "reginsert",
              __LINE__,
              PL_reg_name[op],
-              (UV)(place - RExC_emit_start) > RExC_offsets[0]
+              (UV)REGNODE_OFFSET(place) > RExC_offsets[0]
               ? "Overwriting end of array!\n" : "OK",
-              (UV)(place - RExC_emit_start),
+              (UV)REGNODE_OFFSET(place),
               (UV)(RExC_parse - RExC_start),
               (UV)RExC_offsets[0]));
        Set_Node_Offset(place, RExC_parse);
@@ -19300,8 +19402,10 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
     }
 #endif
     src = NEXTOPER(place);
-    place->flags = 0;
-    FILL_ADVANCE_NODE(place, op);
+    FLAGS(place) = 0;
+    FILL_NODE(operand, op);
+
+    /* Zero out any arguments in the new node */
     Zero(src, offset, regnode);
 }
 
@@ -19311,11 +19415,11 @@ S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *operand, U32 depth)
 */
 STATIC void
 S_regtail(pTHX_ RExC_state_t * pRExC_state,
-                const regnode * const p,
-                const regnode * const val,
+                const regnode_offset p,
+                const regnode_offset val,
                 const U32 depth)
 {
-    regnode *scan;
+    regnode_offset scan;
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_REGTAIL;
@@ -19323,32 +19427,29 @@ S_regtail(pTHX_ RExC_state_t * pRExC_state,
     PERL_UNUSED_ARG(depth);
 #endif
 
-    if (SIZE_ONLY)
-       return;
-
     /* Find last node. */
-    scan = (regnode *) p;
+    scan = (regnode_offset) p;
     for (;;) {
-       regnode * const temp = regnext(scan);
+       regnode * const temp = regnext(REGNODE_p(scan));
         DEBUG_PARSE_r({
             DEBUG_PARSE_MSG((scan==p ? "tail" : ""));
-            regprop(RExC_rx, RExC_mysv, scan, NULL, pRExC_state);
+            regprop(RExC_rx, RExC_mysv, REGNODE_p(scan), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ %s (%d) %s %s\n",
-                SvPV_nolen_const(RExC_mysv), REG_NODE_NUM(scan),
+                SvPV_nolen_const(RExC_mysv), REG_NODE_NUM(REGNODE_p(scan)),
                     (temp == NULL ? "->" : ""),
-                    (temp == NULL ? PL_reg_name[OP(val)] : "")
+                    (temp == NULL ? PL_reg_name[OP(REGNODE_p(val))] : "")
             );
         });
         if (temp == NULL)
             break;
-        scan = temp;
+        scan = REGNODE_OFFSET(temp);
     }
 
-    if (reg_off_by_arg[OP(scan)]) {
-        ARG_SET(scan, val - scan);
+    if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+        ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
-        NEXT_OFF(scan) = val - scan;
+        NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
 }
 
@@ -19370,10 +19471,10 @@ to control which is which.
 /* TODO: All four parms should be const */
 
 STATIC U8
-S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode *p,
-                      const regnode *val,U32 depth)
+S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode_offset p,
+                      const regnode_offset val, U32 depth)
 {
-    regnode *scan;
+    regnode_offset scan;
     U8 exact = PSEUDO;
 #ifdef EXPERIMENTAL_INPLACESCAN
     I32 min = 0;
@@ -19383,24 +19484,21 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode *p,
     PERL_ARGS_ASSERT_REGTAIL_STUDY;
 
 
-    if (SIZE_ONLY)
-        return exact;
-
     /* Find last node. */
 
     scan = p;
     for (;;) {
-        regnode * const temp = regnext(scan);
+        regnode * const temp = regnext(REGNODE_p(scan));
 #ifdef EXPERIMENTAL_INPLACESCAN
-        if (PL_regkind[OP(scan)] == EXACT) {
+        if (PL_regkind[OP(REGNODE_p(scan))] == EXACT) {
            bool unfolded_multi_char;   /* Unexamined in this routine */
             if (join_exact(pRExC_state, scan, &min,
-                           &unfolded_multi_char, 1, val, depth+1))
+                           &unfolded_multi_char, 1, REGNODE_p(val), depth+1))
                 return EXACT;
        }
 #endif
         if ( exact ) {
-            switch (OP(scan)) {
+            switch (OP(REGNODE_p(scan))) {
                 case EXACT:
                 case EXACTL:
                 case EXACTF:
@@ -19411,8 +19509,8 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode *p,
                 case EXACTFU_SS:
                 case EXACTFL:
                         if( exact == PSEUDO )
-                            exact= OP(scan);
-                        else if ( exact != OP(scan) )
+                            exact= OP(REGNODE_p(scan));
+                        else if ( exact != OP(REGNODE_p(scan)) )
                             exact= 0;
                 case NOTHING:
                     break;
@@ -19422,31 +19520,31 @@ S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode *p,
         }
         DEBUG_PARSE_r({
             DEBUG_PARSE_MSG((scan==p ? "tsdy" : ""));
-            regprop(RExC_rx, RExC_mysv, scan, NULL, pRExC_state);
+            regprop(RExC_rx, RExC_mysv, REGNODE_p(scan), NULL, pRExC_state);
             Perl_re_printf( aTHX_  "~ %s (%d) -> %s\n",
                 SvPV_nolen_const(RExC_mysv),
-                REG_NODE_NUM(scan),
+                REG_NODE_NUM(REGNODE_p(scan)),
                 PL_reg_name[exact]);
         });
        if (temp == NULL)
            break;
-       scan = temp;
+       scan = REGNODE_OFFSET(temp);
     }
     DEBUG_PARSE_r({
         DEBUG_PARSE_MSG("");
-        regprop(RExC_rx, RExC_mysv, val, NULL, pRExC_state);
+        regprop(RExC_rx, RExC_mysv, REGNODE_p(val), NULL, pRExC_state);
         Perl_re_printf( aTHX_
                       "~ attach to %s (%" IVdf ") offset to %" IVdf "\n",
                      SvPV_nolen_const(RExC_mysv),
-                     (IV)REG_NODE_NUM(val),
+                     (IV)REG_NODE_NUM(REGNODE_p(val)),
                      (IV)(val - scan)
         );
     });
-    if (reg_off_by_arg[OP(scan)]) {
-       ARG_SET(scan, val - scan);
+    if (reg_off_by_arg[OP(REGNODE_p(scan))]) {
+       ARG_SET(REGNODE_p(scan), val - scan);
     }
     else {
-       NEXT_OFF(scan) = val - scan;
+       NEXT_OFF(REGNODE_p(scan)) = val - scan;
     }
 
     return exact;
@@ -19499,15 +19597,15 @@ S_regdump_intflags(pTHX_ const char *lead, const U32 flags)
     for (bit=0; bit<REG_INTFLAGS_NAME_SIZE; bit++) {
         if (flags & (1<<bit)) {
             if (!set++ && lead)
-                Perl_re_printf( aTHX_  "%s",lead);
-            Perl_re_printf( aTHX_  "%s ",PL_reg_intflags_name[bit]);
+                Perl_re_printf( aTHX_  "%s", lead);
+            Perl_re_printf( aTHX_  "%s ", PL_reg_intflags_name[bit]);
         }
     }
     if (lead)  {
         if (set)
             Perl_re_printf( aTHX_  "\n");
         else
-            Perl_re_printf( aTHX_  "%s[none-set]\n",lead);
+            Perl_re_printf( aTHX_  "%s[none-set]\n", lead);
     }
 }
 
@@ -19526,13 +19624,13 @@ S_regdump_extflags(pTHX_ const char *lead, const U32 flags)
                continue;
            }
             if (!set++ && lead)
-                Perl_re_printf( aTHX_  "%s",lead);
-            Perl_re_printf( aTHX_  "%s ",PL_reg_extflags_name[bit]);
+                Perl_re_printf( aTHX_  "%s", lead);
+            Perl_re_printf( aTHX_  "%s ", PL_reg_extflags_name[bit]);
         }
     }
     if ((cs = get_regex_charset(flags)) != REGEX_DEPENDS_CHARSET) {
             if (!set++ && lead) {
-                Perl_re_printf( aTHX_  "%s",lead);
+                Perl_re_printf( aTHX_  "%s", lead);
             }
             switch (cs) {
                 case REGEX_UNICODE_CHARSET:
@@ -19556,7 +19654,7 @@ S_regdump_extflags(pTHX_ const char *lead, const U32 flags)
         if (set)
             Perl_re_printf( aTHX_  "\n");
         else
-            Perl_re_printf( aTHX_  "%s[none-set]\n",lead);
+            Perl_re_printf( aTHX_  "%s[none-set]\n", lead);
     }
 }
 #endif
@@ -19568,7 +19666,7 @@ Perl_regdump(pTHX_ const regexp *r)
     int i;
     SV * const sv = sv_newmortal();
     SV *dsv= sv_newmortal();
-    RXi_GET_DECL(r,ri);
+    RXi_GET_DECL(r, ri);
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_REGDUMP;
@@ -19643,8 +19741,8 @@ Perl_regdump(pTHX_ const regexp *r)
         Perl_re_printf( aTHX_  "with eval ");
     Perl_re_printf( aTHX_  "\n");
     DEBUG_FLAGS_r({
-        regdump_extflags("r->extflags: ",r->extflags);
-        regdump_intflags("r->intflags: ",r->intflags);
+        regdump_extflags("r->extflags: ", r->extflags);
+        regdump_intflags("r->intflags: ", r->intflags);
     });
 #else
     PERL_ARGS_ASSERT_REGDUMP;
@@ -19709,7 +19807,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
 {
 #ifdef DEBUGGING
     int k;
-    RXi_GET_DECL(prog,progi);
+    RXi_GET_DECL(prog, progi);
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_REGPROP;
@@ -19750,7 +19848,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
         const reg_trie_data * const trie
            = (reg_trie_data*)progi->data->data[!IS_TRIE_AC(op) ? n : ac->trie];
 
-        Perl_sv_catpvf(aTHX_ sv, "-%s",PL_reg_name[o->flags]);
+        Perl_sv_catpvf(aTHX_ sv, "-%s", PL_reg_name[o->flags]);
         DEBUG_TRIE_COMPILE_r({
           if (trie->jump)
             sv_catpvs(sv, "(JUMP)");
@@ -19874,7 +19972,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
 
         const bool inverted = flags & ANYOF_INVERT;
 
-       if (OP(o) == ANYOFL) {
+       if (OP(o) == ANYOFL || OP(o) == ANYOFPOSIXL) {
             if (ANYOFL_UTF8_LOCALE_REQD(flags)) {
                 sv_catpvs(sv, "{utf8-locale-reqd}");
             }
@@ -19942,7 +20040,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
                 sv_catpvs(sv, "{");
             }
             else if (do_sep) {
-                Perl_sv_catpvf(aTHX_ sv,"%s][%s",PL_colors[1],PL_colors[0]);
+                Perl_sv_catpvf(aTHX_ sv,"%s][%s", PL_colors[1], PL_colors[0]);
             }
             sv_catsv(sv, unresolved);
             if (inverted) {
@@ -19962,7 +20060,7 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
 
             /* This is output in a separate [] */
             if (do_sep) {
-                Perl_sv_catpvf(aTHX_ sv,"%s][%s",PL_colors[1],PL_colors[0]);
+                Perl_sv_catpvf(aTHX_ sv,"%s][%s", PL_colors[1], PL_colors[0]);
             }
 
             /* And, for easy of understanding, it is shown in the
@@ -20089,7 +20187,7 @@ Perl_re_intuit_string(pTHX_ REGEXP * const r)
                      "%sUsing REx %ssubstr:%s \"%s%.60s%s%s\"\n",
                      PL_colors[4],
                      RX_UTF8(r) ? "utf8 " : "",
-                     PL_colors[5],PL_colors[0],
+                     PL_colors[5], PL_colors[0],
                      s,
                      PL_colors[1],
                      (strlen(s) > PL_dump_re_max_len ? "..." : ""));
@@ -20126,6 +20224,9 @@ Perl_pregfree2(pTHX_ REGEXP *rx)
 
     PERL_ARGS_ASSERT_PREGFREE2;
 
+    if (! r)
+        return;
+
     if (r->mother_re) {
         ReREFCNT_dec(r->mother_re);
     } else {
@@ -20243,7 +20344,7 @@ Perl_reg_temp_copy(pTHX_ REGEXP *dsv, REGEXP *ssv)
     drx->mother_re = ReREFCNT_inc(srx->mother_re ? srx->mother_re : ssv);
     SvREFCNT_inc_void(drx->qr_anoncv);
     if (srx->recurse_locinput)
-        Newx(drx->recurse_locinput,srx->nparens + 1,char *);
+        Newx(drx->recurse_locinput, srx->nparens + 1, char *);
 
     return dsv;
 }
@@ -20266,11 +20367,15 @@ void
 Perl_regfree_internal(pTHX_ REGEXP * const rx)
 {
     struct regexp *const r = ReANY(rx);
-    RXi_GET_DECL(r,ri);
+    RXi_GET_DECL(r, ri);
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_REGFREE_INTERNAL;
 
+    if (! ri) {
+        return;
+    }
+
     DEBUG_COMPILE_r({
        if (!PL_colorset)
            reginitcolors();
@@ -20279,9 +20384,10 @@ Perl_regfree_internal(pTHX_ REGEXP * const rx)
             RE_PV_QUOTED_DECL(s, RX_UTF8(rx),
                 dsv, RX_PRECOMP(rx), RX_PRELEN(rx), PL_dump_re_max_len);
             Perl_re_printf( aTHX_ "%sFreeing REx:%s %s\n",
-                PL_colors[4],PL_colors[5],s);
+                PL_colors[4], PL_colors[5], s);
         }
     });
+
 #ifdef RE_TRACK_PATTERN_OFFSETS
     if (ri->u.offsets)
         Safefree(ri->u.offsets);             /* 20010421 MJD */
@@ -20374,9 +20480,9 @@ Perl_regfree_internal(pTHX_ REGEXP * const rx)
     Safefree(ri);
 }
 
-#define av_dup_inc(s,t)        MUTABLE_AV(sv_dup_inc((const SV *)s,t))
-#define hv_dup_inc(s,t)        MUTABLE_HV(sv_dup_inc((const SV *)s,t))
-#define SAVEPVN(p,n)   ((p) ? savepvn(p,n) : NULL)
+#define av_dup_inc(s, t)       MUTABLE_AV(sv_dup_inc((const SV *)s, t))
+#define hv_dup_inc(s, t)       MUTABLE_HV(sv_dup_inc((const SV *)s, t))
+#define SAVEPVN(p, n)  ((p) ? savepvn(p, n) : NULL)
 
 /*
    re_dup_guts - duplicate a regexp.
@@ -20453,10 +20559,10 @@ Perl_re_dup_guts(pTHX_ const REGEXP *sstr, REGEXP *dstr, CLONE_PARAMS *param)
     RXp_PAREN_NAMES(ret) = hv_dup_inc(RXp_PAREN_NAMES(ret), param);
     ret->qr_anoncv = MUTABLE_CV(sv_dup_inc((const SV *)ret->qr_anoncv, param));
     if (r->recurse_locinput)
-        Newx(ret->recurse_locinput,r->nparens + 1,char *);
+        Newx(ret->recurse_locinput, r->nparens + 1, char *);
 
     if (ret->pprivate)
-       RXi_SET(ret,CALLREGDUPE_PVT(dstr,param));
+       RXi_SET(ret, CALLREGDUPE_PVT(dstr, param));
 
     if (RX_MATCH_COPIED(dstr))
        ret->subbeg  = SAVEPVN(ret->subbeg, ret->sublen);
@@ -20498,7 +20604,7 @@ Perl_regdupe_internal(pTHX_ REGEXP * const rx, CLONE_PARAMS *param)
     struct regexp *const r = ReANY(rx);
     regexp_internal *reti;
     int len;
-    RXi_GET_DECL(r,ri);
+    RXi_GET_DECL(r, ri);
 
     PERL_ARGS_ASSERT_REGDUPE_INTERNAL;
 
@@ -20603,7 +20709,7 @@ Perl_regdupe_internal(pTHX_ REGEXP * const rx, CLONE_PARAMS *param)
         Copy(ri->u.offsets, reti->u.offsets, 2*len+1, U32);
     }
 #else
-    SetProgLen(reti,len);
+    SetProgLen(reti, len);
 #endif
 
     return (void*)reti;
@@ -20635,10 +20741,11 @@ Perl_regnext(pTHX_ regnode *p)
 
     return(p+offset);
 }
+
 #endif
 
 STATIC void
-S_re_croak2(pTHX_ bool utf8, const char* pat1,const char* pat2,...)
+S_re_croak2(pTHX_ bool utf8, const char* pat1, const char* pat2,...)
 {
     va_list args;
     STRLEN l1 = strlen(pat1);
@@ -20660,7 +20767,7 @@ S_re_croak2(pTHX_ bool utf8, const char* pat1,const char* pat2,...)
     va_start(args, pat2);
     msv = vmess(buf, &args);
     va_end(args);
-    message = SvPV_const(msv,l1);
+    message = SvPV_const(msv, l1);
     if (l1 > 512)
        l1 = 512;
     Copy(message, buf, l1 , char);
@@ -21119,7 +21226,7 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
      * don't change the caller's list) */
     if (nonbitmap_invlist) {
         assert(invlist_highest(nonbitmap_invlist) < NUM_ANYOF_CODE_POINTS);
-        invlist = invlist_clone(nonbitmap_invlist);
+        invlist = invlist_clone(nonbitmap_invlist, NULL);
     }
     else {  /* Worst case size is every other code point is matched */
         invlist = _new_invlist(NUM_ANYOF_CODE_POINTS / 2);
@@ -21140,10 +21247,10 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
             /* And this flag for matching all non-ASCII 0xFF and below */
             if (flags & ANYOF_SHARED_d_MATCHES_ALL_NON_UTF8_NON_ASCII_non_d_WARN_SUPER)
             {
-                not_utf8 = invlist_clone(PL_UpperLatin1);
+                not_utf8 = invlist_clone(PL_UpperLatin1, NULL);
             }
         }
-        else if (OP(node) == ANYOFL) {
+        else if (OP(node) == ANYOFL || OP(node) == ANYOFPOSIXL) {
 
             /* If either of these flags are set, what matches isn't
              * determinable except during execution, so don't know enough here
@@ -21159,7 +21266,7 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
 
                 posixes = newSVpvs("");
                 for (i = 0; i < ANYOF_POSIXL_MAX; i++) {
-                    if (ANYOF_POSIXL_TEST(node,i)) {
+                    if (ANYOF_POSIXL_TEST(node, i)) {
                         sv_catpv(posixes, anyofs[i]);
                     }
                 }
@@ -21196,7 +21303,7 @@ S_put_charclass_bitmap_innards(pTHX_ SV *sv,
 
         /* Since this list is passed in, we have to make a copy before
          * modifying it */
-        only_utf8_locale = invlist_clone(only_utf8_locale_invlist);
+        only_utf8_locale = invlist_clone(only_utf8_locale_invlist, NULL);
 
         _invlist_subtract(only_utf8_locale, invlist, &only_utf8_locale);
 
@@ -21326,14 +21433,14 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
     const regnode *next;
     const regnode *optstart= NULL;
 
-    RXi_GET_DECL(r,ri);
+    RXi_GET_DECL(r, ri);
     GET_RE_DEBUG_FLAGS_DECL;
 
     PERL_ARGS_ASSERT_DUMPUNTIL;
 
 #ifdef DEBUG_DUMPUNTIL
-    Perl_re_printf( aTHX_  "--- %d : %d - %d - %d\n",indent,node-start,
-        last ? last-start : 0,plast ? plast-start : 0);
+    Perl_re_printf( aTHX_  "--- %d : %d - %d - %d\n", indent, node-start,
+        last ? last-start : 0, plast ? plast-start : 0);
 #endif
 
     if (plast && plast < last)
@@ -21405,7 +21512,7 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
            I32 word_idx;
             SvPVCLEAR(sv);
            for (word_idx= 0; word_idx < (I32)trie->wordcount; word_idx++) {
-               SV ** const elem_ptr = av_fetch(trie_words,word_idx,0);
+               SV ** const elem_ptr = av_fetch(trie_words, word_idx, 0);
 
                 Perl_re_indentf( aTHX_  "%s ",
                     indent+3,
@@ -21452,13 +21559,6 @@ S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
        else if ( op == PLUS || op == STAR) {
            DUMPUNTIL(NEXTOPER(node), NEXTOPER(node) + 1);
        }
-       else if (PL_regkind[(U8)op] == ANYOF) {
-           /* arglen 1 + class block */
-           node += 1 + ((ANYOF_FLAGS(node) & ANYOF_MATCHES_POSIXL)
-                          ? ANYOF_POSIXL_SKIP
-                          : ANYOF_SKIP);
-           node = NEXTOPER(node);
-       }
        else if (PL_regkind[(U8)op] == EXACT) {
             /* Literal string, where present. */
            node += NODE_SZ_STR(node) - 1;
@@ -21510,7 +21610,7 @@ Perl_init_uniprops(pTHX)
     PL_Posix_ptrs[_CC_ALPHANUMERIC] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXALNUM]);
     PL_Posix_ptrs[_CC_ALPHA] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXALPHA]);
     PL_Posix_ptrs[_CC_BLANK] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXBLANK]);
-    PL_Posix_ptrs[_CC_CASED] =  _new_invlist_C_array(uni_prop_ptrs[UNI_CASED]);
+    PL_Posix_ptrs[_CC_CASED] = PL_Posix_ptrs[_CC_ALPHA];
     PL_Posix_ptrs[_CC_CNTRL] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXCNTRL]);
     PL_Posix_ptrs[_CC_DIGIT] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXDIGIT]);
     PL_Posix_ptrs[_CC_GRAPH] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXGRAPH]);
@@ -21519,7 +21619,7 @@ Perl_init_uniprops(pTHX)
     PL_Posix_ptrs[_CC_PUNCT] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXPUNCT]);
     PL_Posix_ptrs[_CC_SPACE] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXSPACE]);
     PL_Posix_ptrs[_CC_UPPER] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXUPPER]);
-    PL_Posix_ptrs[_CC_VERTSPACE] = _new_invlist_C_array(uni_prop_ptrs[UNI_VERTSPACE]);
+    PL_Posix_ptrs[_CC_VERTSPACE] = NULL;
     PL_Posix_ptrs[_CC_WORDCHAR] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXWORD]);
     PL_Posix_ptrs[_CC_XDIGIT] = _new_invlist_C_array(uni_prop_ptrs[UNI_POSIXXDIGIT]);
 
@@ -21604,13 +21704,13 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         /* These characters can be freely ignored in most situations.  Later it
          * may turn out we shouldn't have ignored them, and we have to reparse,
          * but we don't have enough information yet to make that decision */
-        if (cur == '-' || cur == '_' || isSPACE(cur)) {
+        if (cur == '-' || cur == '_' || isSPACE_A(cur)) {
             continue;
         }
 
         /* Case differences are also ignored.  Our lookup routine assumes
          * everything is lowercase */
-        if (isUPPER(cur)) {
+        if (isUPPER_A(cur)) {
             lookup_name[j++] = toLOWER(cur);
             continue;
         }
@@ -21646,7 +21746,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         /* Space immediately after the '=' is ignored */
         i++;
         for (; i < name_len; i++) {
-            if (! isSPACE(name[i])) {
+            if (! isSPACE_A(name[i])) {
                 break;
             }
         }
@@ -21700,7 +21800,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
              * rules.  So look for an alpha that signifys not-strict */
             stricter = TRUE;
             for (k = i; k < name_len; k++) {
-                if (   isALPHA(name[k])
+                if (   isALPHA_A(name[k])
                     && (! is_nv_type || ! isALPHA_FOLD_EQ(name[k], 'E')))
                 {
                     stricter = FALSE;
@@ -21726,7 +21826,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
              * digit */
             for (; i < name_len - 1; i++) {
                 if (   name[i] != '0'
-                    && (name[i] != '_' || ! isDIGIT(name[i+1])))
+                    && (name[i] != '_' || ! isDIGIT_A(name[i+1])))
                 {
                     break;
                 }
@@ -21758,7 +21858,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
 
         /* In all instances, case differences are ignored, and we normalize to
          * lowercase */
-        if (isUPPER(cur)) {
+        if (isUPPER_A(cur)) {
             lookup_name[j++] = toLOWER(cur);
             continue;
         }
@@ -21768,7 +21868,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         if (cur == '_') {
             if (    stricter
                 && (     i == 0 || (int) i == equals_pos || i == name_len- 1
-                    || ! isDIGIT(name[i-1]) || ! isDIGIT(name[i+1])))
+                    || ! isDIGIT_A(name[i-1]) || ! isDIGIT_A(name[i+1])))
             {
                 lookup_name[j++] = '_';
             }
@@ -21783,7 +21883,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
         /* XXX Bug in documentation.  It says white space skipped adjacent to
          * non-word char.  Maybe we should, but shouldn't skip it next to a dot
          * in a number */
-        if (isSPACE(cur) && ! stricter) {
+        if (isSPACE_A(cur) && ! stricter) {
             continue;
         }
 
@@ -21810,7 +21910,7 @@ Perl_parse_uniprop_string(pTHX_ const char * const name, const Size_t name_len,
             /* Skip leading zeros including underscores separating digits */
             for (; i < name_len - 1; i++) {
                 if (   name[i] != '0'
-                    && (name[i] != '_' || ! isDIGIT(name[i+1])))
+                    && (name[i] != '_' || ! isDIGIT_A(name[i+1])))
                 {
                     break;
                 }