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Simplify double-nextstate optimisation
[perl5.git] / regcomp.c
index 3728798..ebda789 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -102,6 +102,9 @@ EXTERN_C const struct regexp_engine my_reg_engine;
 #define        STATIC  static
 #endif
 
+#ifndef MIN
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+#endif
 
 struct RExC_state_t {
     U32                flags;                  /* RXf_* are we folding, multilining? */
@@ -171,9 +174,11 @@ struct RExC_state_t {
     const char  *lastparse;
     I32         lastnum;
     AV          *paren_name_list;       /* idx -> name */
+    U32         study_chunk_recursed_count;
 #define RExC_lastparse (pRExC_state->lastparse)
 #define RExC_lastnum   (pRExC_state->lastnum)
 #define RExC_paren_name_list    (pRExC_state->paren_name_list)
+#define RExC_study_chunk_recursed_count    (pRExC_state->study_chunk_recursed_count)
 #endif
 };
 
@@ -495,7 +500,8 @@ static const scan_data_t zero_scan_data =
  * Simple_vFAIL -- like FAIL, but marks the current location in the scan
  */
 #define        Simple_vFAIL(m) STMT_START {                                    \
-    const IV offset = RExC_parse - RExC_precomp;                       \
+    const IV offset =                                                   \
+        (RExC_parse > RExC_end ? RExC_end : RExC_parse) - RExC_precomp; \
     Perl_croak(aTHX_ "%s" REPORT_LOCATION,                             \
            m, REPORT_LOCATION_ARGS(offset));   \
 } STMT_END
@@ -1438,6 +1444,71 @@ S_ssc_clear_locale(regnode_ssc *ssc)
     ANYOF_FLAGS(ssc) &= ~ANYOF_LOCALE_FLAGS;
 }
 
+#define NON_OTHER_COUNT   NON_OTHER_COUNT_FOR_USE_ONLY_BY_REGCOMP_DOT_C
+
+STATIC bool
+S_is_ssc_worth_it(const RExC_state_t * pRExC_state, const regnode_ssc * ssc)
+{
+    /* The synthetic start class is used to hopefully quickly winnow down
+     * places where a pattern could start a match in the target string.  If it
+     * doesn't really narrow things down that much, there isn't much point to
+     * having the overhead of using it.  This function uses some very crude
+     * heuristics to decide if to use the ssc or not.
+     *
+     * It returns TRUE if 'ssc' rules out more than half what it considers to
+     * be the "likely" possible matches, but of course it doesn't know what the
+     * actual things being matched are going to be; these are only guesses
+     *
+     * For /l matches, it assumes that the only likely matches are going to be
+     *      in the 0-255 range, uniformly distributed, so half of that is 127
+     * For /a and /d matches, it assumes that the likely matches will be just
+     *      the ASCII range, so half of that is 63
+     * For /u and there isn't anything matching above the Latin1 range, it
+     *      assumes that that is the only range likely to be matched, and uses
+     *      half that as the cut-off: 127.  If anything matches above Latin1,
+     *      it assumes that all of Unicode could match (uniformly), except for
+     *      non-Unicode code points and things in the General Category "Other"
+     *      (unassigned, private use, surrogates, controls and formats).  This
+     *      is a much large number. */
+
+    const U32 max_match = (LOC)
+                          ? 127
+                          : (! UNI_SEMANTICS)
+                            ? 63
+                            : (invlist_highest(ssc->invlist) < 256)
+                              ? 127
+                              : ((NON_OTHER_COUNT + 1) / 2) - 1;
+    U32 count = 0;      /* Running total of number of code points matched by
+                           'ssc' */
+    UV start, end;      /* Start and end points of current range in inversion
+                           list */
+
+    PERL_ARGS_ASSERT_IS_SSC_WORTH_IT;
+
+    invlist_iterinit(ssc->invlist);
+    while (invlist_iternext(ssc->invlist, &start, &end)) {
+
+        /* /u is the only thing that we expect to match above 255; so if not /u
+         * and even if there are matches above 255, ignore them.  This catches
+         * things like \d under /d which does match the digits above 255, but
+         * since the pattern is /d, it is not likely to be expecting them */
+        if (! UNI_SEMANTICS) {
+            if (start > 255) {
+                break;
+            }
+            end = MIN(end, 255);
+        }
+        count += end - start + 1;
+        if (count > max_match) {
+            invlist_iterfinish(ssc->invlist);
+            return FALSE;
+        }
+    }
+
+    return TRUE;
+}
+
+
 STATIC void
 S_ssc_finalize(pTHX_ RExC_state_t *pRExC_state, regnode_ssc *ssc)
 {
@@ -3636,6 +3707,9 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
 
 
   fake_study_recurse:
+    DEBUG_r(
+        RExC_study_chunk_recursed_count++;
+    );
     while ( scan && OP(scan) != END && scan < last ){
         UV min_subtract = 0;    /* How mmany chars to subtract from the minimum
                                    node length to get a real minimum (because
@@ -3645,8 +3719,9 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
         DEBUG_OPTIMISE_MORE_r(
         {
             PerlIO_printf(Perl_debug_log,
-                "%*sstudy_chunk stopparen=%ld depth=%lu recursed_depth=%lu ",
+                "%*sstudy_chunk stopparen=%ld recursed_count=%lu depth=%lu recursed_depth=%lu ",
                 ((int) depth*2), "", (long)stopparen,
+                (unsigned long)RExC_study_chunk_recursed_count,
                 (unsigned long)depth, (unsigned long)recursed_depth);
             if (recursed_depth) {
                 U32 i;
@@ -4158,7 +4233,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
            regnode *end;
             U32 my_recursed_depth= recursed_depth;
 
-           if (OP(scan) != SUSPEND) {
+            if (OP(scan) != SUSPEND) { /* GOSUB/GOSTART */
                 /* set the pointer */
                if (OP(scan) == GOSUB) {
                    paren = ARG(scan);
@@ -4170,10 +4245,43 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                     start = RExC_rxi->program + 1;
                     end   = RExC_opend;
                 }
-                if (!recursed_depth
+                /* this code is intended to handle expanding regex "subs" so
+                 * we can apply various optimizations. For instance with
+                 * /(?(DEFINE)(?<foo>foo)(?<bar>bar))(?&foo)(?&bar)/ we
+                 * want to recognize that the mandatory substr is going to be
+                 * "foobar".
+                 * However if we are not in SCF_DO_SUBSTR mode then there is
+                 * no point in doing this, and it can cause a serious slowdown.
+                 * See RT #122283.
+                 * Note also that this was a workaround for the core problem
+                 * which was that during compilation logic the excessive
+                 * recursion resulted in slowly consuming all the memory on
+                 * the box. Exactly what causes this is unclear. It does not
+                 * appear to be directly related to allocating the "visited"
+                 * bitmaps that is RExC_study_chunk_recursed.
+                 *
+                 * In reality study_chunk() does far far too much, and probably
+                 * this an other issues would go away if we split it into
+                 * multiple components.
+                 *
+                 * - Yves
+                 * */
+                if (flags & SCF_DO_SUBSTR) {
+                if (
+                    !recursed_depth
                     ||
                     !PAREN_TEST(RExC_study_chunk_recursed + ((recursed_depth-1) * RExC_study_chunk_recursed_bytes), paren)
                 ) {
+                    /* it is quite possible that there are more efficient ways
+                     * to do this. We maintain a bitmap per level of recursion
+                     * of which patterns we have entered so we can detect if a
+                     * pattern creates a possible infinite loop. When we
+                     * recurse down a level we copy the previous levels bitmap
+                     * down. When we are at recursion level 0 we zero the top
+                     * level bitmap. It would be nice to implement a different
+                     * more efficient way of doing this. In particular the top
+                     * level bitmap may be unnecessary.
+                     */
                     if (!recursed_depth) {
                         Zero(RExC_study_chunk_recursed, RExC_study_chunk_recursed_bytes, U8);
                     } else {
@@ -4199,6 +4307,7 @@ S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
                         ssc_anything(data->start_class);
                     flags &= ~SCF_DO_STCLASS;
                }
+                }
             } else {
                Newx(newframe,1,scan_frame);
                paren = stopparen;
@@ -6054,7 +6163,6 @@ S_compile_runtime_code(pTHX_ RExC_state_t * const pRExC_state,
 
        ENTER;
        SAVETMPS;
-       save_re_context();
        PUSHSTACKi(PERLSI_REQUIRE);
         /* G_RE_REPARSING causes the toker to collapse \\ into \ when
          * parsing qr''; normally only q'' does this. It also alters
@@ -6761,6 +6869,9 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
 reStudy:
     r->minlen = minlen = sawlookahead = sawplus = sawopen = sawminmod = 0;
+    DEBUG_r(
+        RExC_study_chunk_recursed_count= 0;
+    );
     Zero(r->substrs, 1, struct reg_substr_data);
     if (RExC_study_chunk_recursed)
         Zero(RExC_study_chunk_recursed,
@@ -6872,9 +6983,7 @@ reStudy:
        else if (PL_regkind[OP(first)] == BOL) {
             r->intflags |= (OP(first) == MBOL
                            ? PREGf_ANCH_MBOL
-                          : (OP(first) == SBOL
-                              ? PREGf_ANCH_SBOL
-                              : PREGf_ANCH_BOL));
+                           : PREGf_ANCH_SBOL);
            first = NEXTOPER(first);
            goto again;
        }
@@ -7028,7 +7137,7 @@ reStudy:
        if ((!(r->anchored_substr || r->anchored_utf8) || r->anchored_offset)
            && stclass_flag
             && ! (ANYOF_FLAGS(data.start_class) & SSC_MATCHES_EMPTY_STRING)
-           && !ssc_is_anything(data.start_class))
+           && is_ssc_worth_it(pRExC_state, data.start_class))
        {
            const U32 n = add_data(pRExC_state, STR_WITH_LEN("f"));
 
@@ -7108,7 +7217,7 @@ reStudy:
                = r->float_substr = r->float_utf8 = NULL;
 
         if (! (ANYOF_FLAGS(data.start_class) & SSC_MATCHES_EMPTY_STRING)
-            && ! ssc_is_anything(data.start_class))
+           && is_ssc_worth_it(pRExC_state, data.start_class))
         {
            const U32 n = add_data(pRExC_state, STR_WITH_LEN("f"));
 
@@ -7191,7 +7300,12 @@ reStudy:
 
         if (PL_regkind[fop] == NOTHING && nop == END)
             r->extflags |= RXf_NULL;
-        else if (PL_regkind[fop] == BOL && nop == END)
+        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;
         else if (fop == PLUS
                  && PL_regkind[nop] == POSIXD && FLAGS(next) == _CC_SPACE
@@ -7227,7 +7341,10 @@ reStudy:
     }
     Newxz(r->offs, RExC_npar, regexp_paren_pair);
     /* assume we don't need to swap parens around before we match */
-
+    DEBUG_TEST_r({
+        PerlIO_printf(Perl_debug_log,"study_chunk_recursed_count: %lu\n",
+            (unsigned long)RExC_study_chunk_recursed_count);
+    });
     DEBUG_DUMP_r({
         DEBUG_RExC_seen();
         PerlIO_printf(Perl_debug_log,"Final program:\n");
@@ -9275,6 +9392,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
     regex_charset cs;
     bool has_use_defaults = FALSE;
     const char* const seqstart = RExC_parse - 1; /* Point to the '?' */
+    int x_mod_count = 0;
 
     PERL_ARGS_ASSERT_PARSE_LPAREN_QUESTION_FLAGS;
 
@@ -9302,7 +9420,7 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
         switch (*RExC_parse) {
 
             /* Code for the imsx flags */
-            CASE_STD_PMMOD_FLAGS_PARSE_SET(flagsp);
+            CASE_STD_PMMOD_FLAGS_PARSE_SET(flagsp, x_mod_count);
 
             case LOCALE_PAT_MOD:
                 if (has_charset_modifier) {
@@ -9439,6 +9557,9 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
                 if (RExC_flags & RXf_PMf_FOLD) {
                     RExC_contains_i = 1;
                 }
+                if (PASS2) {
+                    STD_PMMOD_FLAGS_PARSE_X_WARN(x_mod_count);
+                }
                 return;
                 /*NOTREACHED*/
             default:
@@ -9452,6 +9573,10 @@ S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
 
         ++RExC_parse;
     }
+
+    if (PASS2) {
+        STD_PMMOD_FLAGS_PARSE_X_WARN(x_mod_count);
+    }
 }
 
 /*
@@ -9882,21 +10007,18 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     num = RExC_npar + num - 1;
                 }
 
-                ret = reganode(pRExC_state, GOSUB, num);
+                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");
                    }
-                   ARG2L_SET( ret, RExC_recurse_count++);
-                    RExC_emit++;
+                   RExC_recurse_count++;
                    DEBUG_OPTIMISE_MORE_r(PerlIO_printf(Perl_debug_log,
                        "Recurse #%"UVuf" to %"IVdf"\n",
                               (UV)ARG(ret), (IV)ARG2L(ret)));
-               } else {
-                   RExC_size++;
-               }
-                    RExC_seen |= REG_RECURSE_SEEN;
+                }
+                RExC_seen |= REG_RECURSE_SEEN;
                 Set_Node_Length(ret, 1 + regarglen[OP(ret)]); /* MJD */
                Set_Node_Offset(ret, parse_start); /* MJD */
 
@@ -9959,17 +10081,22 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                if (is_logical) {
                     regnode *eval;
                    ret = reg_node(pRExC_state, LOGICAL);
-                    eval = reganode(pRExC_state, EVAL, n);
+
+                    eval = reg2Lanode(pRExC_state, EVAL,
+                                       n,
+
+                                       /* for later propagation into (??{})
+                                        * return value */
+                                       RExC_flags & RXf_PMf_COMPILETIME
+                                      );
                    if (!SIZE_ONLY) {
                        ret->flags = 2;
-                        /* for later propagation into (??{}) return value */
-                        eval->flags = (U8) (RExC_flags & RXf_PMf_COMPILETIME);
                     }
                     REGTAIL(pRExC_state, ret, eval);
                     /* deal with the length of this later - MJD */
                    return ret;
                }
-               ret = reganode(pRExC_state, EVAL, n);
+               ret = reg2Lanode(pRExC_state, EVAL, n, 0);
                Set_Node_Length(ret, RExC_parse - parse_start + 1);
                Set_Node_Offset(ret, parse_start);
                return ret;
@@ -9977,6 +10104,7 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
            case '(':           /* (?(?{...})...) and (?(?=...)...) */
            {
                int is_define= 0;
+                const int DEFINE_len = sizeof("DEFINE") - 1;
                if (RExC_parse[0] == '?') {        /* (?(?...)) */
                    if (RExC_parse[1] == '=' || RExC_parse[1] == '!'
                        || RExC_parse[1] == '<'
@@ -10019,15 +10147,11 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                     ret = reganode(pRExC_state,NGROUPP,num);
                     goto insert_if_check_paren;
                }
-               else if (RExC_parse[0] == 'D' &&
-                        RExC_parse[1] == 'E' &&
-                        RExC_parse[2] == 'F' &&
-                        RExC_parse[3] == 'I' &&
-                        RExC_parse[4] == 'N' &&
-                        RExC_parse[5] == 'E')
-               {
+               else if (strnEQ(RExC_parse, "DEFINE",
+                                       MIN(DEFINE_len, RExC_end - RExC_parse)))
+                {
                    ret = reganode(pRExC_state,DEFINEP,0);
-                   RExC_parse +=;
+                   RExC_parse += DEFINE_len;
                    is_define = 1;
                    goto insert_if_check_paren;
                }
@@ -10106,8 +10230,12 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
                    }
                    else
                        lastbr = NULL;
-                   if (c != ')')
-                       vFAIL("Switch (?(condition)... contains too many branches");
+                    if (c != ')') {
+                        if (RExC_parse>RExC_end)
+                            vFAIL("Switch (?(condition)... not terminated");
+                        else
+                            vFAIL("Switch (?(condition)... contains too many branches");
+                    }
                    ender = reg_node(pRExC_state, TAIL);
                     REGTAIL(pRExC_state, br, ender);
                    if (lastbr) {
@@ -10887,7 +11015,7 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state, regnode** node_p,
     if (valuep && (substitute_parse || ! has_multiple_chars)) {
        STRLEN length_of_hex = (STRLEN)(endchar - RExC_parse);
        I32 grok_hex_flags = PERL_SCAN_ALLOW_UNDERSCORES
-           | PERL_SCAN_DISALLOW_PREFIX
+                           | PERL_SCAN_DISALLOW_PREFIX
 
                              /* No errors in the first pass (See [perl
                               * #122671].)  We let the code below find the
@@ -10902,22 +11030,22 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state, regnode** node_p,
          * bypass it by using single quoting, so check.  Don't do the check
          * here when there are multiple chars; we do it below anyway. */
         if (! has_multiple_chars) {
-       if (length_of_hex == 0
-           || length_of_hex != (STRLEN)(endchar - RExC_parse) )
-       {
-           RExC_parse += length_of_hex;        /* Includes all the valid */
-           RExC_parse += (RExC_orig_utf8)      /* point to after 1st invalid */
-                           ? UTF8SKIP(RExC_parse)
-                           : 1;
-           /* Guard against malformed utf8 */
-           if (RExC_parse >= endchar) {
-                RExC_parse = endchar;
+            if (length_of_hex == 0
+                || length_of_hex != (STRLEN)(endchar - RExC_parse) )
+            {
+                RExC_parse += length_of_hex;   /* Includes all the valid */
+                RExC_parse += (RExC_orig_utf8) /* point to after 1st invalid */
+                                ? UTF8SKIP(RExC_parse)
+                                : 1;
+                /* Guard against malformed utf8 */
+                if (RExC_parse >= endchar) {
+                    RExC_parse = endchar;
+                }
+                vFAIL("Invalid hexadecimal number in \\N{U+...}");
             }
-           vFAIL("Invalid hexadecimal number in \\N{U+...}");
-       }
 
-        RExC_parse = endbrace + 1;
-        return 1;
+            RExC_parse = endbrace + 1;
+            return 1;
         }
     }
 
@@ -10987,15 +11115,15 @@ S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state, regnode** node_p,
        RExC_override_recoding = 1;
 
         if (node_p) {
-       if (!(*node_p = reg(pRExC_state, 1, &flags, depth+1))) {
-            if (flags & RESTART_UTF8) {
-                *flagp = RESTART_UTF8;
-                return (STRLEN) -1;
+            if (!(*node_p = reg(pRExC_state, 1, &flags, depth+1))) {
+                if (flags & RESTART_UTF8) {
+                    *flagp = RESTART_UTF8;
+                    return (STRLEN) -1;
+                }
+                FAIL2("panic: reg returned NULL to grok_bslash_N, flags=%#"UVxf"",
+                    (UV) flags);
             }
-            FAIL2("panic: reg returned NULL to grok_bslash_N, flags=%#"UVxf"",
-                  (UV) flags);
-        }
-       *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
+            *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
         }
 
        RExC_parse = endbrace;
@@ -11330,10 +11458,8 @@ tryagain:
        nextchar(pRExC_state);
        if (RExC_flags & RXf_PMf_MULTILINE)
            ret = reg_node(pRExC_state, MBOL);
-       else if (RExC_flags & RXf_PMf_SINGLELINE)
-           ret = reg_node(pRExC_state, SBOL);
        else
-           ret = reg_node(pRExC_state, BOL);
+           ret = reg_node(pRExC_state, SBOL);
         Set_Node_Length(ret, 1); /* MJD */
        break;
     case '$':
@@ -11342,10 +11468,8 @@ tryagain:
            RExC_seen_zerolen++;
        if (RExC_flags & RXf_PMf_MULTILINE)
            ret = reg_node(pRExC_state, MEOL);
-       else if (RExC_flags & RXf_PMf_SINGLELINE)
-           ret = reg_node(pRExC_state, SEOL);
        else
-           ret = reg_node(pRExC_state, EOL);
+           ret = reg_node(pRExC_state, SEOL);
         Set_Node_Length(ret, 1); /* MJD */
        break;
     case '.':
@@ -11434,6 +11558,11 @@ tryagain:
        case 'A':
            RExC_seen_zerolen++;
            ret = reg_node(pRExC_state, SBOL);
+            /* 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;
            *flagp |= SIMPLE;
            goto finish_meta_pat;
        case 'G':
@@ -11494,7 +11623,7 @@ tryagain:
            ret = reg_node(pRExC_state, op);
            FLAGS(ret) = get_regex_charset(RExC_flags);
            *flagp |= SIMPLE;
-           if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+           if ((U8) *(RExC_parse + 1) == '{') {
                 /* diag_listed_as: Use "%s" instead of "%s" */
                vFAIL("Use \"\\b\\{\" instead of \"\\b{\"");
            }
@@ -11512,7 +11641,7 @@ tryagain:
            ret = reg_node(pRExC_state, op);
            FLAGS(ret) = get_regex_charset(RExC_flags);
            *flagp |= SIMPLE;
-           if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+           if ((U8) *(RExC_parse + 1) == '{') {
                 /* diag_listed_as: Use "%s" instead of "%s" */
                vFAIL("Use \"\\B\\{\" instead of \"\\B{\"");
            }
@@ -13328,6 +13457,53 @@ S_add_above_Latin1_folds(pTHX_ RExC_state_t *pRExC_state, const U8 cp, SV** invl
     }
 }
 
+STATIC AV *
+S_add_multi_match(pTHX_ AV* multi_char_matches, SV* multi_string, const STRLEN cp_count)
+{
+    /* This adds the string scalar <multi_string> to the array
+     * <multi_char_matches>.  <multi_string> is known to have exactly
+     * <cp_count> code points in it.  This is used when constructing a
+     * bracketed character class and we find something that needs to match more
+     * than a single character.
+     *
+     * <multi_char_matches> is actually an array of arrays.  Each top-level
+     * element is an array that contains all the strings known so far that are
+     * the same length.  And that length (in number of code points) is the same
+     * as the index of the top-level array.  Hence, the [2] element is an
+     * array, each element thereof is a string containing TWO code points;
+     * while element [3] is for strings of THREE characters, and so on.  Since
+     * this is for multi-char strings there can never be a [0] nor [1] element.
+     *
+     * When we rewrite the character class below, we will do so such that the
+     * longest strings are written first, so that it prefers the longest
+     * matching strings first.  This is done even if it turns out that any
+     * quantifier is non-greedy, out of this programmer's (khw) laziness.  Tom
+     * Christiansen has agreed that this is ok.  This makes the test for the
+     * ligature 'ffi' come before the test for 'ff', for example */
+
+    AV* this_array;
+    AV** this_array_ptr;
+
+    PERL_ARGS_ASSERT_ADD_MULTI_MATCH;
+
+    if (! multi_char_matches) {
+        multi_char_matches = newAV();
+    }
+
+    if (av_exists(multi_char_matches, cp_count)) {
+        this_array_ptr = (AV**) av_fetch(multi_char_matches, cp_count, FALSE);
+        this_array = *this_array_ptr;
+    }
+    else {
+        this_array = newAV();
+        av_store(multi_char_matches, cp_count,
+                 (SV*) this_array);
+    }
+    av_push(this_array, multi_string);
+
+    return multi_char_matches;
+}
+
 /* The names of properties whose definitions are not known at compile time are
  * stored in this SV, after a constant heading.  So if the length has been
  * changed since initialization, then there is a run-time definition. */
@@ -13556,7 +13732,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
         }
         else {
             /* Is a backslash; get the code point of the char after it */
-           if (UTF && ! UTF8_IS_INVARIANT(RExC_parse)) {
+           if (UTF && ! UTF8_IS_INVARIANT(UCHARAT(RExC_parse))) {
                value = utf8n_to_uvchr((U8*)RExC_parse,
                                   RExC_end - RExC_parse,
                                   &numlen, UTF8_ALLOW_DEFAULT);
@@ -13607,23 +13783,26 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                             }
                         }
                         else { /* cp_count > 1 */
-                            /* We only pay attention to the first char of
-                             * multichar strings being returned in char
-                             * classes. I kinda wonder if this makes sense as
-                             * it does change the behaviour from earlier
-                             * versions, OTOH that behaviour was broken as
-                             * well. XXX Solution is to recharacterize as
-                             * [rest-of-class]|multi1|multi2...  */
+                            if (! RExC_in_multi_char_class) {
+                                if (invert || range || *RExC_parse == '-') {
                                     if (strict) {
                                         RExC_parse--;
-                                        vFAIL("\\N{} in character class restricted to one character");
+                                        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");
                                     }
+                                }
+                                else {
+                                    multi_char_matches
+                                        = add_multi_match(multi_char_matches,
+                                                          as_text,
+                                                          cp_count);
+                                }
                                 break; /* <value> contains the first code
                                           point. Drop out of the switch to
                                           process it */
+                            }
                         } /* End of cp_count != 1 */
 
                         /* This element should not be processed further in this
@@ -13634,6 +13813,10 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                         continue;   /* Back to top of loop to get next char */
                     }
                     /* Here, is a single code point, and <value> contains it */
+#ifdef EBCDIC
+                    /* We consider named characters to be literal characters */
+                    literal_endpoint++;
+#endif
                 }
                 break;
            case 'p':
@@ -14196,44 +14379,17 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
                      * again.  Otherwise add this character to the list of
                      * multi-char folds. */
                     if (! RExC_in_multi_char_class) {
-                        AV** this_array_ptr;
-                        AV* this_array;
                         STRLEN cp_count = utf8_length(foldbuf,
                                                       foldbuf + foldlen);
                         SV* multi_fold = sv_2mortal(newSVpvs(""));
 
                         Perl_sv_catpvf(aTHX_ multi_fold, "\\x{%"UVXf"}", value);
 
+                        multi_char_matches
+                                        = add_multi_match(multi_char_matches,
+                                                          multi_fold,
+                                                          cp_count);
 
-                        if (! multi_char_matches) {
-                            multi_char_matches = newAV();
-                        }
-
-                        /* <multi_char_matches> is actually an array of arrays.
-                         * There will be one or two top-level elements: [2],
-                         * and/or [3].  The [2] element is an array, each
-                         * element thereof is a character which folds to TWO
-                         * characters; [3] is for folds to THREE characters.
-                         * (Unicode guarantees a maximum of 3 characters in any
-                         * fold.)  When we rewrite the character class below,
-                         * we will do so such that the longest folds are
-                         * written first, so that it prefers the longest
-                         * matching strings first.  This is done even if it
-                         * turns out that any quantifier is non-greedy, out of
-                         * programmer laziness.  Tom Christiansen has agreed
-                         * that this is ok.  This makes the test for the
-                         * ligature 'ffi' come before the test for 'ff' */
-                        if (av_exists(multi_char_matches, cp_count)) {
-                            this_array_ptr = (AV**) av_fetch(multi_char_matches,
-                                                             cp_count, FALSE);
-                            this_array = *this_array_ptr;
-                        }
-                        else {
-                            this_array = newAV();
-                            av_store(multi_char_matches, cp_count,
-                                     (SV*) this_array);
-                        }
-                        av_push(this_array, multi_fold);
                     }
 
                     /* This element should not be processed further in this
@@ -14264,19 +14420,20 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
              * included.  literal_endpoint==2 means both ends of the range used
              * a literal character, not \x{foo} */
            if (literal_endpoint == 2
-                && ((prevvalue >= 'a' && value <= 'z')
-                    || (prevvalue >= 'A' && value <= 'Z')))
+                && ((isLOWER_A(prevvalue) && isLOWER_A(value))
+                    || (isUPPER_A(prevvalue) && isUPPER_A(value))))
             {
                 _invlist_intersection(this_range, PL_XPosix_ptrs[_CC_ASCII],
                                       &this_range);
 
-                /* Since this above only contains ascii, the intersection of it
-                 * with anything will still yield only ascii */
+                /* Since 'this_range' now only contains ascii, the intersection
+                 * of it with anything will still yield only ascii */
                 _invlist_intersection(this_range, PL_XPosix_ptrs[_CC_ALPHA],
                                       &this_range);
             }
             _invlist_union(cp_foldable_list, this_range, &cp_foldable_list);
             literal_endpoint = 0;
+            SvREFCNT_dec_NN(this_range);
 #endif
         }
 
@@ -14347,6 +14504,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
        RExC_parse = SvPV(substitute_parse, len);
        RExC_end = RExC_parse + len;
         RExC_in_multi_char_class = 1;
+       RExC_override_recoding = 1;
         RExC_emit = (regnode *)orig_emit;
 
        ret = reg(pRExC_state, 1, &reg_flags, depth+1);
@@ -14356,6 +14514,7 @@ S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
        RExC_parse = save_parse;
        RExC_end = save_end;
        RExC_in_multi_char_class = 0;
+       RExC_override_recoding = 0;
         SvREFCNT_dec_NN(multi_char_matches);
         return ret;
     }
@@ -15337,21 +15496,23 @@ S_nextchar(pTHX_ RExC_state_t *pRExC_state)
     }
 }
 
-/*
-- reg_node - emit a node
-*/
-STATIC regnode *                       /* Location. */
-S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
+STATIC regnode *
+S_regnode_guts(pTHX_ RExC_state_t *pRExC_state, const U8 op, const STRLEN extra_size, const char* const name)
 {
-    regnode *ptr;
+    /* 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 */
+
     regnode * const ret = RExC_emit;
     GET_RE_DEBUG_FLAGS_DECL;
 
-    PERL_ARGS_ASSERT_REG_NODE;
+    PERL_ARGS_ASSERT_REGNODE_GUTS;
+
+    assert(extra_size >= regarglen[op]);
 
     if (SIZE_ONLY) {
        SIZE_ALIGN(RExC_size);
-       RExC_size += 1;
+       RExC_size += 1 + extra_size;
        return(ret);
     }
     if (RExC_emit >= RExC_emit_bound)
@@ -15359,13 +15520,13 @@ S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
                   op, (void*)RExC_emit, (void*)RExC_emit_bound);
 
     NODE_ALIGN_FILL(ret);
-    ptr = ret;
-    FILL_ADVANCE_NODE(ptr, op);
-#ifdef RE_TRACK_PATTERN_OFFSETS
+#ifndef RE_TRACK_PATTERN_OFFSETS
+    PERL_UNUSED_ARG(name);
+#else
     if (RExC_offsets) {         /* MJD */
        MJD_OFFSET_DEBUG(
               ("%s:%d: (op %s) %s %"UVuf" (len %"UVuf") (max %"UVuf").\n",
-              "reg_node", __LINE__,
+              name, __LINE__,
               PL_reg_name[op],
               (UV)(RExC_emit - RExC_emit_start) > RExC_offsets[0]
                ? "Overwriting end of array!\n" : "OK",
@@ -15375,7 +15536,26 @@ S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
        Set_Node_Offset(RExC_emit, RExC_parse + (op == END));
     }
 #endif
-    RExC_emit = ptr;
+    return(ret);
+}
+
+/*
+- reg_node - emit a node
+*/
+STATIC regnode *                       /* Location. */
+S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
+{
+    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reg_node");
+
+    PERL_ARGS_ASSERT_REG_NODE;
+
+    assert(regarglen[op] == 0);
+
+    if (PASS2) {
+        regnode *ptr = ret;
+        FILL_ADVANCE_NODE(ptr, op);
+        RExC_emit = ptr;
+    }
     return(ret);
 }
 
@@ -15385,54 +15565,36 @@ S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
 STATIC regnode *                       /* Location. */
 S_reganode(pTHX_ RExC_state_t *pRExC_state, U8 op, U32 arg)
 {
-    regnode *ptr;
-    regnode * const ret = RExC_emit;
-    GET_RE_DEBUG_FLAGS_DECL;
+    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reganode");
 
     PERL_ARGS_ASSERT_REGANODE;
 
-    if (SIZE_ONLY) {
-       SIZE_ALIGN(RExC_size);
-       RExC_size += 2;
-       /*
-          We can't do this:
+    assert(regarglen[op] == 1);
 
-          assert(2==regarglen[op]+1);
+    if (PASS2) {
+        regnode *ptr = ret;
+        FILL_ADVANCE_NODE_ARG(ptr, op, arg);
+        RExC_emit = ptr;
+    }
+    return(ret);
+}
 
-          Anything larger than this has to allocate the extra amount.
-          If we changed this to be:
+STATIC regnode *
+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 */
 
-          RExC_size += (1 + regarglen[op]);
+    regnode * const ret = regnode_guts(pRExC_state, op, regarglen[op], "reg2Lanode");
 
-          then it wouldn't matter. Its not clear what side effect
-          might come from that so its not done so far.
-          -- dmq
-       */
-       return(ret);
-    }
-    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);
+    PERL_ARGS_ASSERT_REG2LANODE;
 
-    NODE_ALIGN_FILL(ret);
-    ptr = ret;
-    FILL_ADVANCE_NODE_ARG(ptr, op, arg);
-#ifdef RE_TRACK_PATTERN_OFFSETS
-    if (RExC_offsets) {         /* MJD */
-       MJD_OFFSET_DEBUG(
-              ("%s(%d): (op %s) %s %"UVuf" <- %"UVuf" (max %"UVuf").\n",
-              "reganode",
-             __LINE__,
-             PL_reg_name[op],
-              (UV)(RExC_emit - RExC_emit_start) > RExC_offsets[0] ?
-              "Overwriting end of array!\n" : "OK",
-              (UV)(RExC_emit - RExC_emit_start),
-              (UV)(RExC_parse - RExC_start),
-              (UV)RExC_offsets[0]));
-       Set_Cur_Node_Offset;
+    assert(regarglen[op] == 2);
+
+    if (PASS2) {
+        regnode *ptr = ret;
+        FILL_ADVANCE_NODE_2L_ARG(ptr, op, arg1, arg2);
+        RExC_emit = ptr;
     }
-#endif
-    RExC_emit = ptr;
     return(ret);
 }
 
@@ -15826,8 +15988,6 @@ Perl_regdump(pTHX_ const regexp *r)
     }
     if (r->intflags & PREGf_ANCH) {
        PerlIO_printf(Perl_debug_log, "anchored");
-        if (r->intflags & PREGf_ANCH_BOL)
-           PerlIO_printf(Perl_debug_log, "(BOL)");
         if (r->intflags & PREGf_ANCH_MBOL)
            PerlIO_printf(Perl_debug_log, "(MBOL)");
         if (r->intflags & PREGf_ANCH_SBOL)
@@ -16189,6 +16349,8 @@ Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_
     }
     else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH))
        Perl_sv_catpvf(aTHX_ sv, "[%d]", -(o->flags));
+    else if (OP(o) == SBOL)
+        Perl_sv_catpvf(aTHX_ sv, " /%s/", o->flags ? "\\A" : "^");
 #else
     PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(sv);
@@ -16761,35 +16923,6 @@ S_re_croak2(pTHX_ bool utf8, const char* pat1,const char* pat2,...)
     Perl_croak(aTHX_ "%"UTF8f, UTF8fARG(utf8, l1-1, buf));
 }
 
-/* XXX Here's a total kludge.  But we need to re-enter for swash routines. */
-
-#ifndef PERL_IN_XSUB_RE
-void
-Perl_save_re_context(pTHX)
-{
-    /* Save $1..$n (#18107: UTF-8 s/(\w+)/uc($1)/e); AMS 20021106. */
-    if (PL_curpm) {
-       const REGEXP * const rx = PM_GETRE(PL_curpm);
-       if (rx) {
-           U32 i;
-           for (i = 1; i <= RX_NPARENS(rx); i++) {
-               char digits[TYPE_CHARS(long)];
-               const STRLEN len = my_snprintf(digits, sizeof(digits),
-                                               "%lu", (long)i);
-               GV *const *const gvp
-                   = (GV**)hv_fetch(PL_defstash, digits, len, 0);
-
-               if (gvp) {
-                   GV * const gv = *gvp;
-                   if (SvTYPE(gv) == SVt_PVGV && GvSV(gv))
-                       save_scalar(gv);
-               }
-           }
-       }
-    }
-}
-#endif
-
 #ifdef DEBUGGING
 /* Certain characters are output as a sequence with the first being a
  * backslash. */
@@ -16823,10 +16956,6 @@ S_put_code_point(pTHX_ SV *sv, UV c)
 
 #define MAX_PRINT_A MAX_PRINT_A_FOR_USE_ONLY_BY_REGCOMP_DOT_C
 
-#ifndef MIN
-#define MIN(a,b) ((a) < (b) ? (a) : (b))
-#endif
-
 STATIC void
 S_put_range(pTHX_ SV *sv, UV start, const UV end, const bool allow_literals)
 {