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Define an _() macro for XS backcompat
[perl5.git] / pp_hot.c
index 810a5d1..558214d 100644 (file)
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -130,7 +130,7 @@ PP(pp_sassign)
     */
     SV *left = POPs; SV *right = TOPs;
 
-    if (PL_op->op_private & OPpASSIGN_BACKWARDS) {
+    if (PL_op->op_private & OPpASSIGN_BACKWARDS) { /* {or,and,dor}assign */
        SV * const temp = left;
        left = right; right = temp;
     }
@@ -231,11 +231,11 @@ PP(pp_sassign)
 PP(pp_cond_expr)
 {
     dSP;
+    SV *sv;
+
     PERL_ASYNC_CHECK();
-    if (SvTRUEx(POPs))
-       RETURNOP(cLOGOP->op_other);
-    else
-       RETURNOP(cLOGOP->op_next);
+    sv = POPs;
+    RETURNOP(SvTRUE_NN(sv) ? cLOGOP->op_other : cLOGOP->op_next);
 }
 
 PP(pp_unstack)
@@ -284,9 +284,12 @@ PP(pp_concat)
     }
     else { /* $l .= $r   and   left == TARG */
        if (!SvOK(left)) {
-           if (left == right && ckWARN(WARN_UNINITIALIZED)) /* $l .= $l */
-               report_uninit(right);
-           sv_setpvs(left, "");
+            if ((left == right                          /* $l .= $l */
+                 || (PL_op->op_private & OPpTARGET_MY)) /* $l = $l . $r */
+                && ckWARN(WARN_UNINITIALIZED)
+                )
+                report_uninit(left);
+            SvPVCLEAR(left);
        }
         else {
             SvPV_force_nomg_nolen(left);
@@ -318,11 +321,9 @@ PP(pp_concat)
 }
 
 /* push the elements of av onto the stack.
- * XXX Note that padav has similar code but without the mg_get().
- * I suspect that the mg_get is no longer needed, but while padav
- * differs, it can't share this function */
+ * Returns PL_op->op_next to allow tail-call optimisation of its callers */
 
-STATIC void
+STATIC OP*
 S_pushav(pTHX_ AV* const av)
 {
     dSP;
@@ -332,10 +333,7 @@ S_pushav(pTHX_ AV* const av)
         PADOFFSET i;
         for (i=0; i < (PADOFFSET)maxarg; i++) {
             SV ** const svp = av_fetch(av, i, FALSE);
-            /* See note in pp_helem, and bug id #27839 */
-            SP[i+1] = svp
-                ? SvGMAGICAL(*svp) ? (mg_get(*svp), *svp) : *svp
-                : &PL_sv_undef;
+            SP[i+1] = svp ? *svp : &PL_sv_undef;
         }
     }
     else {
@@ -347,6 +345,7 @@ S_pushav(pTHX_ AV* const av)
     }
     SP += maxarg;
     PUTBACK;
+    return NORMAL;
 }
 
 
@@ -357,16 +356,17 @@ PP(pp_padrange)
     dSP;
     PADOFFSET base = PL_op->op_targ;
     int count = (int)(PL_op->op_private) & OPpPADRANGE_COUNTMASK;
-    int i;
     if (PL_op->op_flags & OPf_SPECIAL) {
         /* fake the RHS of my ($x,$y,..) = @_ */
         PUSHMARK(SP);
-        S_pushav(aTHX_ GvAVn(PL_defgv));
+        (void)S_pushav(aTHX_ GvAVn(PL_defgv));
         SPAGAIN;
     }
 
     /* note, this is only skipped for compile-time-known void cxt */
     if ((PL_op->op_flags & OPf_WANT) != OPf_WANT_VOID) {
+        int i;
+
         EXTEND(SP, count);
         PUSHMARK(SP);
         for (i = 0; i <count; i++)
@@ -378,8 +378,11 @@ PP(pp_padrange)
                       (base << (OPpPADRANGE_COUNTSHIFT + SAVE_TIGHT_SHIFT))
                     | (count << SAVE_TIGHT_SHIFT)
                     | SAVEt_CLEARPADRANGE);
+        int i;
+
         STATIC_ASSERT_STMT(OPpPADRANGE_COUNTMASK + 1 == (1 << OPpPADRANGE_COUNTSHIFT));
-        assert((payload >> (OPpPADRANGE_COUNTSHIFT+SAVE_TIGHT_SHIFT)) == base);
+        assert((payload >> (OPpPADRANGE_COUNTSHIFT+SAVE_TIGHT_SHIFT))
+                == (Size_t)base);
         {
             dSS_ADD;
             SS_ADD_UV(payload);
@@ -426,6 +429,8 @@ PP(pp_padsv)
 PP(pp_readline)
 {
     dSP;
+    /* pp_coreargs pushes a NULL to indicate no args passed to
+     * CORE::readline() */
     if (TOPs) {
        SvGETMAGIC(TOPs);
        tryAMAGICunTARGETlist(iter_amg, 0);
@@ -441,10 +446,7 @@ PP(pp_readline)
            PUTBACK;
            Perl_pp_rv2gv(aTHX);
            PL_last_in_gv = MUTABLE_GV(*PL_stack_sp--);
-           if (PL_last_in_gv == (GV *)&PL_sv_undef)
-               PL_last_in_gv = NULL;
-           else
-               assert(isGV_with_GP(PL_last_in_gv));
+            assert((SV*)PL_last_in_gv == &PL_sv_undef || isGV_with_GP(PL_last_in_gv));
        }
     }
     return do_readline();
@@ -514,8 +516,10 @@ PP(pp_predec)
 PP(pp_or)
 {
     dSP;
+    SV *sv;
     PERL_ASYNC_CHECK();
-    if (SvTRUE(TOPs))
+    sv = TOPs;
+    if (SvTRUE_NN(sv))
        RETURN;
     else {
        if (PL_op->op_type == OP_OR)
@@ -816,13 +820,30 @@ PP(pp_aelemfast)
     AV * const av = PL_op->op_type == OP_AELEMFAST_LEX
        ? MUTABLE_AV(PAD_SV(PL_op->op_targ)) : GvAVn(cGVOP_gv);
     const U32 lval = PL_op->op_flags & OPf_MOD;
-    SV** const svp = av_fetch(av, (I8)PL_op->op_private, lval);
-    SV *sv = (svp ? *svp : &PL_sv_undef);
+    const I8 key   = (I8)PL_op->op_private;
+    SV** svp;
+    SV *sv;
 
-    if (UNLIKELY(!svp && lval))
-        DIE(aTHX_ PL_no_aelem, (int)(I8)PL_op->op_private);
+    assert(SvTYPE(av) == SVt_PVAV);
 
     EXTEND(SP, 1);
+
+    /* inlined av_fetch() for simple cases ... */
+    if (!SvRMAGICAL(av) && key >= 0 && key <= AvFILLp(av)) {
+        sv = AvARRAY(av)[key];
+        if (sv) {
+            PUSHs(sv);
+            RETURN;
+        }
+    }
+
+    /* ... else do it the hard way */
+    svp = av_fetch(av, key, lval);
+    sv = (svp ? *svp : &PL_sv_undef);
+
+    if (UNLIKELY(!svp && lval))
+        DIE(aTHX_ PL_no_aelem, (int)key);
+
     if (!lval && SvRMAGICAL(av) && SvGMAGICAL(sv)) /* see note in pp_helem() */
        mg_get(sv);
     PUSHs(sv);
@@ -839,25 +860,6 @@ PP(pp_join)
     RETURN;
 }
 
-PP(pp_pushre)
-{
-    dSP;
-#ifdef DEBUGGING
-    /*
-     * We ass_u_me that LvTARGOFF() comes first, and that two STRLENs
-     * will be enough to hold an OP*.
-     */
-    SV* const sv = sv_newmortal();
-    sv_upgrade(sv, SVt_PVLV);
-    LvTYPE(sv) = '/';
-    Copy(&PL_op, &LvTARGOFF(sv), 1, OP*);
-    XPUSHs(sv);
-#else
-    XPUSHs(MUTABLE_SV(PL_op));
-#endif
-    RETURN;
-}
-
 /* Oversized hot code. */
 
 /* also used for: pp_say() */
@@ -957,6 +959,171 @@ PP(pp_print)
 }
 
 
+/* do the common parts of pp_padhv() and pp_rv2hv()
+ * It assumes the caller has done EXTEND(SP, 1) or equivalent.
+ * 'is_keys' indicates the OPpPADHV_ISKEYS/OPpRV2HV_ISKEYS flag is set.
+ * 'has_targ' indicates that the op has a target - this should
+ * be a compile-time constant so that the code can constant-folded as
+ * appropriate
+ * */
+
+PERL_STATIC_INLINE OP*
+S_padhv_rv2hv_common(pTHX_ HV *hv, U8 gimme, bool is_keys, bool has_targ)
+{
+    bool is_tied;
+    bool is_bool;
+    MAGIC *mg;
+    dSP;
+    IV  i;
+    SV *sv;
+
+    assert(PL_op->op_type == OP_PADHV || PL_op->op_type == OP_RV2HV);
+
+    if (gimme == G_ARRAY) {
+        hv_pushkv(hv, 3);
+        return NORMAL;
+    }
+
+    if (is_keys)
+        /* 'keys %h' masquerading as '%h': reset iterator */
+        (void)hv_iterinit(hv);
+
+    if (gimme == G_VOID)
+        return NORMAL;
+
+    is_bool = (     PL_op->op_private & OPpTRUEBOOL
+              || (  PL_op->op_private & OPpMAYBE_TRUEBOOL
+                  && block_gimme() == G_VOID));
+    is_tied = SvRMAGICAL(hv) && (mg = mg_find(MUTABLE_SV(hv), PERL_MAGIC_tied));
+
+    if (UNLIKELY(is_tied)) {
+        if (is_keys && !is_bool) {
+            i = 0;
+            while (hv_iternext(hv))
+                i++;
+            goto push_i;
+        }
+        else {
+            sv = magic_scalarpack(hv, mg);
+            goto push_sv;
+        }
+    }
+    else {
+        i = HvUSEDKEYS(hv);
+        if (is_bool) {
+            sv = i ? &PL_sv_yes : &PL_sv_zero;
+          push_sv:
+            PUSHs(sv);
+        }
+        else {
+          push_i:
+            if (has_targ) {
+                dTARGET;
+                PUSHi(i);
+            }
+            else
+#ifdef PERL_OP_PARENT
+            if (is_keys) {
+                /* parent op should be an unused OP_KEYS whose targ we can
+                 * use */
+                dTARG;
+                OP *k;
+
+                assert(!OpHAS_SIBLING(PL_op));
+                k = PL_op->op_sibparent;
+                assert(k->op_type == OP_KEYS);
+                TARG = PAD_SV(k->op_targ);
+                PUSHi(i);
+            }
+            else
+#endif
+                mPUSHi(i);
+        }
+    }
+
+    PUTBACK;
+    return NORMAL;
+}
+
+
+/* This is also called directly by pp_lvavref.  */
+PP(pp_padav)
+{
+    dSP; dTARGET;
+    U8 gimme;
+    assert(SvTYPE(TARG) == SVt_PVAV);
+    if (UNLIKELY( PL_op->op_private & OPpLVAL_INTRO ))
+       if (LIKELY( !(PL_op->op_private & OPpPAD_STATE) ))
+           SAVECLEARSV(PAD_SVl(PL_op->op_targ));
+    EXTEND(SP, 1);
+
+    if (PL_op->op_flags & OPf_REF) {
+       PUSHs(TARG);
+       RETURN;
+    }
+    else if (PL_op->op_private & OPpMAYBE_LVSUB) {
+        const I32 flags = is_lvalue_sub();
+        if (flags && !(flags & OPpENTERSUB_INARGS)) {
+           if (GIMME_V == G_SCALAR)
+                /* diag_listed_as: Can't return %s to lvalue scalar context */
+                Perl_croak(aTHX_ "Can't return array to lvalue scalar context");
+            PUSHs(TARG);
+            RETURN;
+       }
+    }
+
+    gimme = GIMME_V;
+    if (gimme == G_ARRAY)
+        return S_pushav(aTHX_ (AV*)TARG);
+
+    if (gimme == G_SCALAR) {
+       const SSize_t maxarg = AvFILL(MUTABLE_AV(TARG)) + 1;
+        if (!maxarg)
+            PUSHs(&PL_sv_zero);
+        else if (PL_op->op_private & OPpTRUEBOOL)
+            PUSHs(&PL_sv_yes);
+        else
+            mPUSHi(maxarg);
+    }
+    RETURN;
+}
+
+
+PP(pp_padhv)
+{
+    dSP; dTARGET;
+    U8 gimme;
+
+    assert(SvTYPE(TARG) == SVt_PVHV);
+    if (UNLIKELY( PL_op->op_private & OPpLVAL_INTRO ))
+       if (LIKELY( !(PL_op->op_private & OPpPAD_STATE) ))
+           SAVECLEARSV(PAD_SVl(PL_op->op_targ));
+
+    EXTEND(SP, 1);
+
+    if (PL_op->op_flags & OPf_REF) {
+        PUSHs(TARG);
+       RETURN;
+    }
+    else if (PL_op->op_private & OPpMAYBE_LVSUB) {
+        const I32 flags = is_lvalue_sub();
+        if (flags && !(flags & OPpENTERSUB_INARGS)) {
+            if (GIMME_V == G_SCALAR)
+                /* diag_listed_as: Can't return %s to lvalue scalar context */
+                Perl_croak(aTHX_ "Can't return hash to lvalue scalar context");
+            PUSHs(TARG);
+            RETURN;
+        }
+    }
+
+    gimme = GIMME_V;
+
+    return S_padhv_rv2hv_common(aTHX_ (HV*)TARG, gimme,
+                        cBOOL(PL_op->op_private & OPpPADHV_ISKEYS),
+                        0 /* has_targ*/);
+}
+
+
 /* also used for: pp_rv2hv() */
 /* also called directly by pp_lvavref */
 
@@ -1015,35 +1182,29 @@ PP(pp_rv2av)
 
     if (is_pp_rv2av) {
        AV *const av = MUTABLE_AV(sv);
-       /* The guts of pp_rv2av  */
+
        if (gimme == G_ARRAY) {
             SP--;
             PUTBACK;
-            S_pushav(aTHX_ av);
-            SPAGAIN;
+            return S_pushav(aTHX_ av);
        }
-       else if (gimme == G_SCALAR) {
-           dTARGET;
+
+       if (gimme == G_SCALAR) {
            const SSize_t maxarg = AvFILL(av) + 1;
-           SETi(maxarg);
-       }
-    } else {
-       /* The guts of pp_rv2hv  */
-       if (gimme == G_ARRAY) { /* array wanted */
-           *PL_stack_sp = sv;
-           return Perl_do_kv(aTHX);
-       }
-       else if ((PL_op->op_private & OPpTRUEBOOL
-             || (  PL_op->op_private & OPpMAYBE_TRUEBOOL
-                && block_gimme() == G_VOID  ))
-             && (!SvRMAGICAL(sv) || !mg_find(sv, PERL_MAGIC_tied)))
-           SETs(HvUSEDKEYS(sv) ? &PL_sv_yes : sv_2mortal(newSViv(0)));
-       else if (gimme == G_SCALAR) {
-           dTARG;
-           TARG = Perl_hv_scalar(aTHX_ MUTABLE_HV(sv));
-           SETTARG;
+            if (PL_op->op_private & OPpTRUEBOOL)
+                SETs(maxarg ? &PL_sv_yes : &PL_sv_zero);
+            else {
+                dTARGET;
+                SETi(maxarg);
+            }
        }
     }
+    else {
+        SP--; PUTBACK;
+        return S_padhv_rv2hv_common(aTHX_ (HV*)sv, gimme,
+                        cBOOL(PL_op->op_private & OPpRV2HV_ISKEYS),
+                        1 /* has_targ*/);
+    }
     RETURN;
 
  croak_cant_return:
@@ -1161,8 +1322,7 @@ S_aassign_copy_common(pTHX_ SV **firstlelem, SV **lastlelem,
                 lcount = -1;
                 lelem--; /* no need to unmark this element */
             }
-            else if (!(do_rc1 && SvREFCNT(svl) == 1) && svl != &PL_sv_undef) {
-                assert(!SvIMMORTAL(svl));
+            else if (!(do_rc1 && SvREFCNT(svl) == 1) && !SvIMMORTAL(svl)) {
                 SvFLAGS(svl) |= SVf_BREAK;
                 marked = TRUE;
             }
@@ -1181,6 +1341,7 @@ S_aassign_copy_common(pTHX_ SV **firstlelem, SV **lastlelem,
         assert(svr);
 
         if (UNLIKELY(SvFLAGS(svr) & (SVf_BREAK|SVs_GMG) || copy_all)) {
+            U32 brk = (SvFLAGS(svr) & SVf_BREAK);
 
 #ifdef DEBUGGING
             if (fake) {
@@ -1216,7 +1377,7 @@ S_aassign_copy_common(pTHX_ SV **firstlelem, SV **lastlelem,
             /* ... but restore afterwards in case it's needed again,
              * e.g. ($a,$b,$c) = (1,$a,$a)
              */
-            SvFLAGS(svr) |= SVf_BREAK;
+            SvFLAGS(svr) |= brk;
         }
 
         if (!lcount)
@@ -1247,15 +1408,7 @@ PP(pp_aassign)
 
     SV **relem;
     SV **lelem;
-
-    SV *sv;
-    AV *ary;
-
     U8 gimme;
-    HV *hash;
-    SSize_t i;
-    int magic;
-    U32 lval;
     /* PL_delaymagic is restored by JUMPENV_POP on dieing, so we
      * only need to save locally, not on the save stack */
     U16 old_delaymagic = PL_delaymagic;
@@ -1284,7 +1437,7 @@ PP(pp_aassign)
             if (PL_op->op_private & OPpASSIGN_COMMON_RC1) {
                 /* skip the scan if all scalars have a ref count of 1 */
                 for (lelem = firstlelem; lelem <= lastlelem; lelem++) {
-                    sv = *lelem;
+                    SV *sv = *lelem;
                     if (!sv || SvREFCNT(sv) == 1)
                         continue;
                     if (SvTYPE(sv) != SVt_PVAV && SvTYPE(sv) != SVt_PVAV)
@@ -1316,241 +1469,483 @@ PP(pp_aassign)
 #endif
 
     gimme = GIMME_V;
-    lval = (gimme == G_ARRAY) ? (PL_op->op_flags & OPf_MOD || LVRET) : 0;
-
     relem = firstrelem;
     lelem = firstlelem;
-    ary = NULL;
-    hash = NULL;
 
+    if (relem > lastrelem)
+        goto no_relems;
+
+    /* first lelem loop while there are still relems */
     while (LIKELY(lelem <= lastlelem)) {
        bool alias = FALSE;
-       TAINT_NOT;              /* Each item stands on its own, taintwise. */
-       sv = *lelem++;
-       if (UNLIKELY(!sv)) {
+       SV *lsv = *lelem++;
+
+        TAINT_NOT; /* Each item stands on its own, taintwise. */
+
+        assert(relem <= lastrelem);
+       if (UNLIKELY(!lsv)) {
            alias = TRUE;
-           sv = *lelem++;
-           ASSUME(SvTYPE(sv) == SVt_PVAV);
+           lsv = *lelem++;
+           ASSUME(SvTYPE(lsv) == SVt_PVAV);
        }
-       switch (SvTYPE(sv)) {
-       case SVt_PVAV: {
-            bool already_copied = FALSE;
-           ary = MUTABLE_AV(sv);
-           magic = SvMAGICAL(ary) != 0;
-           ENTER;
-           SAVEFREESV(SvREFCNT_inc_simple_NN(sv));
-
-            /* We need to clear ary. The is a danger that if we do this,
-             * elements on the RHS may be prematurely freed, e.g.
-             *   @a = ($a[0]);
-             * In the case of possible commonality, make a copy of each
-             * RHS SV *before* clearing the array, and add a reference
-             * from the tmps stack, so that it doesn't leak on death.
-             * Otherwise, make a copy of each RHS SV only as we're storing
-             * it into the array - that way we don't have to worry about
-             * it being leaked if we die, but don't incur the cost of
-             * mortalising everything.
-             */
 
-            if (   (PL_op->op_private & OPpASSIGN_COMMON_AGG)
-                && (relem <= lastrelem)
-                && (magic || AvFILL(ary) != -1))
-            {
-                SV **svp;
-                EXTEND_MORTAL(lastrelem - relem + 1);
+       switch (SvTYPE(lsv)) {
+       case SVt_PVAV: {
+            SV **svp;
+            SSize_t i;
+            SSize_t tmps_base;
+            SSize_t nelems = lastrelem - relem + 1;
+            AV *ary = MUTABLE_AV(lsv);
+
+            /* Assigning to an aggregate is tricky. First there is the
+             * issue of commonality, e.g. @a = ($a[0]). Since the
+             * stack isn't refcounted, clearing @a prior to storing
+             * elements will free $a[0]. Similarly with
+             *    sub FETCH { $status[$_[1]] } @status = @tied[0,1];
+             *
+             * The way to avoid these issues is to make the copy of each
+             * SV (and we normally store a *copy* in the array) *before*
+             * clearing the array. But this has a problem in that
+             * if the code croaks during copying, the not-yet-stored copies
+             * could leak. One way to avoid this is to make all the copies
+             * mortal, but that's quite expensive.
+             *
+             * The current solution to these issues is to use a chunk
+             * of the tmps stack as a temporary refcounted-stack. SVs
+             * will be put on there during processing to avoid leaks,
+             * but will be removed again before the end of this block,
+             * so free_tmps() is never normally called. Also, the
+             * sv_refcnt of the SVs doesn't have to be manipulated, since
+             * the ownership of 1 reference count is transferred directly
+             * from the tmps stack to the AV when the SV is stored.
+             *
+             * We disarm slots in the temps stack by storing PL_sv_undef
+             * there: it doesn't matter if that SV's refcount is
+             * repeatedly decremented during a croak. But usually this is
+             * only an interim measure. By the end of this code block
+             * we try where possible to not leave any PL_sv_undef's on the
+             * tmps stack e.g. by shuffling newer entries down.
+             *
+             * There is one case where we don't copy: non-magical
+             * SvTEMP(sv)'s with a ref count of 1. The only owner of these
+             * is on the tmps stack, so its safe to directly steal the SV
+             * rather than copying. This is common in things like function
+             * returns, map etc, which all return a list of such SVs.
+             *
+             * Note however something like @a = (f())[0,0], where there is
+             * a danger of the same SV being shared:  this avoided because
+             * when the SV is stored as $a[0], its ref count gets bumped,
+             * so the RC==1 test fails and the second element is copied
+             * instead.
+             *
+             * We also use one slot in the tmps stack to hold an extra
+             * ref to the array, to ensure it doesn't get prematurely
+             * freed. Again, this is removed before the end of this block.
+             *
+             * Note that OPpASSIGN_COMMON_AGG is used to flag a possible
+             * @a = ($a[0]) case, but the current implementation uses the
+             * same algorithm regardless, so ignores that flag. (It *is*
+             * used in the hash branch below, however).
+            */
+
+            /* Reserve slots for ary, plus the elems we're about to copy,
+             * then protect ary and temporarily void the remaining slots
+             * with &PL_sv_undef */
+            EXTEND_MORTAL(nelems + 1);
+            PL_tmps_stack[++PL_tmps_ix] = SvREFCNT_inc_simple_NN(ary);
+            tmps_base = PL_tmps_ix + 1;
+            for (i = 0; i < nelems; i++)
+                PL_tmps_stack[tmps_base + i] = &PL_sv_undef;
+            PL_tmps_ix += nelems;
+
+            /* Make a copy of each RHS elem and save on the tmps_stack
+             * (or pass through where we can optimise away the copy) */
+
+            if (UNLIKELY(alias)) {
+                U32 lval = (gimme == G_ARRAY)
+                                ? (PL_op->op_flags & OPf_MOD || LVRET) : 0;
                 for (svp = relem; svp <= lastrelem; svp++) {
-                    /* see comment in S_aassign_copy_common about SV_NOSTEAL */
-                    *svp = sv_mortalcopy_flags(*svp,
-                            SV_GMAGIC|SV_DO_COW_SVSETSV|SV_NOSTEAL);
-                    TAINT_NOT;
+                    SV *rsv = *svp;
+
+                    SvGETMAGIC(rsv);
+                    if (!SvROK(rsv))
+                        DIE(aTHX_ "Assigned value is not a reference");
+                    if (SvTYPE(SvRV(rsv)) > SVt_PVLV)
+                   /* diag_listed_as: Assigned value is not %s reference */
+                        DIE(aTHX_
+                           "Assigned value is not a SCALAR reference");
+                    if (lval)
+                        *svp = rsv = sv_mortalcopy(rsv);
+                    /* XXX else check for weak refs?  */
+                    rsv = SvREFCNT_inc_NN(SvRV(rsv));
+                    assert(tmps_base <= PL_tmps_max);
+                    PL_tmps_stack[tmps_base++] = rsv;
                 }
-                already_copied = TRUE;
             }
+            else {
+                for (svp = relem; svp <= lastrelem; svp++) {
+                    SV *rsv = *svp;
 
-            av_clear(ary);
-           if (relem <= lastrelem)
-                av_extend(ary, lastrelem - relem);
-
-           i = 0;
-           while (relem <= lastrelem) {        /* gobble up all the rest */
-               SV **didstore;
-               if (LIKELY(!alias)) {
-                    if (already_copied)
-                        sv = *relem;
+                    if (SvTEMP(rsv) && !SvGMAGICAL(rsv) && SvREFCNT(rsv) == 1) {
+                        /* can skip the copy */
+                        SvREFCNT_inc_simple_void_NN(rsv);
+                        SvTEMP_off(rsv);
+                    }
                     else {
-                        if (LIKELY(*relem))
-                            /* before newSV, in case it dies */
-                            SvGETMAGIC(*relem);
-                        sv = newSV(0);
+                        SV *nsv;
+                        /* do get before newSV, in case it dies and leaks */
+                        SvGETMAGIC(rsv);
+                        nsv = newSV(0);
                         /* see comment in S_aassign_copy_common about
                          * SV_NOSTEAL */
-                        sv_setsv_flags(sv, *relem,
-                                    (SV_DO_COW_SVSETSV|SV_NOSTEAL));
-                        *relem = sv;
+                        sv_setsv_flags(nsv, rsv,
+                                (SV_DO_COW_SVSETSV|SV_NOSTEAL));
+                        rsv = *svp = nsv;
                     }
-               }
-               else {
-                    if (!already_copied)
-                        SvGETMAGIC(*relem);
-                   if (!SvROK(*relem))
-                       DIE(aTHX_ "Assigned value is not a reference");
-                   if (SvTYPE(SvRV(*relem)) > SVt_PVLV)
-                  /* diag_listed_as: Assigned value is not %s reference */
-                       DIE(aTHX_
-                          "Assigned value is not a SCALAR reference");
-                   if (lval && !already_copied)
-                       *relem = sv_mortalcopy(*relem);
-                   /* XXX else check for weak refs?  */
-                   sv = SvREFCNT_inc_NN(SvRV(*relem));
-               }
-               relem++;
-                if (already_copied)
-                    SvREFCNT_inc_simple_void_NN(sv); /* undo mortal free */
-               didstore = av_store(ary,i++,sv);
-               if (magic) {
-                   if (!didstore)
-                       sv_2mortal(sv);
-                   if (SvSMAGICAL(sv))
-                       mg_set(sv);
-               }
-               TAINT_NOT;
-           }
+
+                    assert(tmps_base <= PL_tmps_max);
+                    PL_tmps_stack[tmps_base++] = rsv;
+                }
+            }
+
+            if (SvRMAGICAL(ary) || AvFILLp(ary) >= 0) /* may be non-empty */
+                av_clear(ary);
+
+            /* store in the array, the SVs that are in the tmps stack */
+
+            tmps_base -= nelems;
+
+            if (SvMAGICAL(ary) || SvREADONLY(ary) || !AvREAL(ary)) {
+                /* for arrays we can't cheat with, use the official API */
+                av_extend(ary, nelems - 1);
+                for (i = 0; i < nelems; i++) {
+                    SV **svp = &(PL_tmps_stack[tmps_base + i]);
+                    SV *rsv = *svp;
+                    /* A tied store won't take ownership of rsv, so keep
+                     * the 1 refcnt on the tmps stack; otherwise disarm
+                     * the tmps stack entry */
+                    if (av_store(ary, i, rsv))
+                        *svp = &PL_sv_undef;
+                    /* av_store() may have added set magic to rsv */;
+                    SvSETMAGIC(rsv);
+                }
+                /* disarm ary refcount: see comments below about leak */
+                PL_tmps_stack[tmps_base - 1] = &PL_sv_undef;
+            }
+            else {
+                /* directly access/set the guts of the AV */
+                SSize_t fill = nelems - 1;
+                if (fill > AvMAX(ary))
+                    av_extend_guts(ary, fill, &AvMAX(ary), &AvALLOC(ary),
+                                    &AvARRAY(ary));
+                AvFILLp(ary) = fill;
+                Copy(&(PL_tmps_stack[tmps_base]), AvARRAY(ary), nelems, SV*);
+                /* Quietly remove all the SVs from the tmps stack slots,
+                 * since ary has now taken ownership of the refcnt.
+                 * Also remove ary: which will now leak if we die before
+                 * the SvREFCNT_dec_NN(ary) below */
+                if (UNLIKELY(PL_tmps_ix >= tmps_base + nelems))
+                    Move(&PL_tmps_stack[tmps_base + nelems],
+                         &PL_tmps_stack[tmps_base - 1],
+                         PL_tmps_ix - (tmps_base + nelems) + 1,
+                         SV*);
+                PL_tmps_ix -= (nelems + 1);
+            }
+
            if (UNLIKELY(PL_delaymagic & DM_ARRAY_ISA))
+                /* its assumed @ISA set magic can't die and leak ary */
                SvSETMAGIC(MUTABLE_SV(ary));
-           LEAVE;
-           break;
+            SvREFCNT_dec_NN(ary);
+
+            relem = lastrelem + 1;
+           goto no_relems;
         }
 
        case SVt_PVHV: {                                /* normal hash */
-               SV *tmpstr;
-                int odd;
-                int duplicates = 0;
-               SV** topelem = relem;
-                SV **firsthashrelem = relem;
-                bool already_copied = FALSE;
-
-               hash = MUTABLE_HV(sv);
-               magic = SvMAGICAL(hash) != 0;
-
-                odd = ((lastrelem - firsthashrelem)&1)? 0 : 1;
-                if (UNLIKELY(odd)) {
-                    do_oddball(lastrelem, firsthashrelem);
-                    /* we have firstlelem to reuse, it's not needed anymore
-                    */
-                    *(lastrelem+1) = &PL_sv_undef;
+
+            SV **svp;
+            bool dirty_tmps;
+            SSize_t i;
+            SSize_t tmps_base;
+            SSize_t nelems = lastrelem - relem + 1;
+            HV *hash = MUTABLE_HV(lsv);
+
+            if (UNLIKELY(nelems & 1)) {
+                do_oddball(lastrelem, relem);
+                /* we have firstlelem to reuse, it's not needed any more */
+                *++lastrelem = &PL_sv_undef;
+                nelems++;
+            }
+
+            /* See the SVt_PVAV branch above for a long description of
+             * how the following all works. The main difference for hashes
+             * is that we treat keys and values separately (and have
+             * separate loops for them): as for arrays, values are always
+             * copied (except for the SvTEMP optimisation), since they
+             * need to be stored in the hash; while keys are only
+             * processed where they might get prematurely freed or
+             * whatever. */
+
+            /* tmps stack slots:
+             * * reserve a slot for the hash keepalive;
+             * * reserve slots for the hash values we're about to copy;
+             * * preallocate for the keys we'll possibly copy or refcount bump
+             *   later;
+             * then protect hash and temporarily void the remaining
+             * value slots with &PL_sv_undef */
+            EXTEND_MORTAL(nelems + 1);
+
+             /* convert to number of key/value pairs */
+             nelems >>= 1;
+
+            PL_tmps_stack[++PL_tmps_ix] = SvREFCNT_inc_simple_NN(hash);
+            tmps_base = PL_tmps_ix + 1;
+            for (i = 0; i < nelems; i++)
+                PL_tmps_stack[tmps_base + i] = &PL_sv_undef;
+            PL_tmps_ix += nelems;
+
+            /* Make a copy of each RHS hash value and save on the tmps_stack
+             * (or pass through where we can optimise away the copy) */
+
+            for (svp = relem + 1; svp <= lastrelem; svp += 2) {
+                SV *rsv = *svp;
+
+                if (SvTEMP(rsv) && !SvGMAGICAL(rsv) && SvREFCNT(rsv) == 1) {
+                    /* can skip the copy */
+                    SvREFCNT_inc_simple_void_NN(rsv);
+                    SvTEMP_off(rsv);
+                }
+                else {
+                    SV *nsv;
+                    /* do get before newSV, in case it dies and leaks */
+                    SvGETMAGIC(rsv);
+                    nsv = newSV(0);
+                    /* see comment in S_aassign_copy_common about
+                     * SV_NOSTEAL */
+                    sv_setsv_flags(nsv, rsv,
+                            (SV_DO_COW_SVSETSV|SV_NOSTEAL));
+                    rsv = *svp = nsv;
                 }
 
-               ENTER;
-               SAVEFREESV(SvREFCNT_inc_simple_NN(sv));
+                assert(tmps_base <= PL_tmps_max);
+                PL_tmps_stack[tmps_base++] = rsv;
+            }
+            tmps_base -= nelems;
 
-                /* We need to clear hash. The is a danger that if we do this,
-                 * elements on the RHS may be prematurely freed, e.g.
-                 *   %h = (foo => $h{bar});
-                 * In the case of possible commonality, make a copy of each
-                 * RHS SV *before* clearing the hash, and add a reference
-                 * from the tmps stack, so that it doesn't leak on death.
-                 */
 
-                if (   (PL_op->op_private & OPpASSIGN_COMMON_AGG)
-                    && (relem <= lastrelem)
-                    && (magic || HvUSEDKEYS(hash)))
-                {
-                    SV **svp;
-                    EXTEND_MORTAL(lastrelem - relem + 1);
-                    for (svp = relem; svp <= lastrelem; svp++) {
+            /* possibly protect keys */
+
+            if (UNLIKELY(gimme == G_ARRAY)) {
+                /* handle e.g.
+                *     @a = ((%h = ($$r, 1)), $r = "x");
+                *     $_++ for %h = (1,2,3,4);
+                */
+                EXTEND_MORTAL(nelems);
+                for (svp = relem; svp <= lastrelem; svp += 2)
+                    *svp = sv_mortalcopy_flags(*svp,
+                                SV_GMAGIC|SV_DO_COW_SVSETSV|SV_NOSTEAL);
+            }
+            else if (PL_op->op_private & OPpASSIGN_COMMON_AGG) {
+                /* for possible commonality, e.g.
+                 *       %h = ($h{a},1)
+                 * avoid premature freeing RHS keys by mortalising
+                 * them.
+                 * For a magic element, make a copy so that its magic is
+                 * called *before* the hash is emptied (which may affect
+                 * a tied value for example).
+                 * In theory we should check for magic keys in all
+                 * cases, not just under OPpASSIGN_COMMON_AGG, but in
+                 * practice, !OPpASSIGN_COMMON_AGG implies only
+                 * constants or padtmps on the RHS.
+                 */
+                EXTEND_MORTAL(nelems);
+                for (svp = relem; svp <= lastrelem; svp += 2) {
+                    SV *rsv = *svp;
+                    if (UNLIKELY(SvGMAGICAL(rsv))) {
+                        SSize_t n;
                         *svp = sv_mortalcopy_flags(*svp,
                                 SV_GMAGIC|SV_DO_COW_SVSETSV|SV_NOSTEAL);
-                        TAINT_NOT;
+                        /* allow other branch to continue pushing
+                         * onto tmps stack without checking each time */
+                        n = (lastrelem - relem) >> 1;
+                        EXTEND_MORTAL(n);
                     }
-                    already_copied = TRUE;
+                    else
+                        PL_tmps_stack[++PL_tmps_ix] =
+                                    SvREFCNT_inc_simple_NN(rsv);
                 }
+            }
 
-               hv_clear(hash);
-
-               while (LIKELY(relem < lastrelem+odd)) { /* gobble up all the rest */
-                   HE *didstore;
-                    assert(*relem);
-                   /* Copy the key if aassign is called in lvalue context,
-                      to avoid having the next op modify our rhs.  Copy
-                      it also if it is gmagical, lest it make the
-                      hv_store_ent call below croak, leaking the value. */
-                   sv = (lval || SvGMAGICAL(*relem)) && !already_copied
-                        ? sv_mortalcopy(*relem)
-                        : *relem;
-                   relem++;
-                    assert(*relem);
-                    if (already_copied)
-                        tmpstr = *relem++;
-                    else {
-                        SvGETMAGIC(*relem);
-                        tmpstr = newSV(0);
-                        sv_setsv_nomg(tmpstr,*relem++);        /* value */
-                    }
+            if (SvRMAGICAL(hash) || HvUSEDKEYS(hash))
+                hv_clear(hash);
 
-                   if (gimme == G_ARRAY) {
-                       if (hv_exists_ent(hash, sv, 0))
-                           /* key overwrites an existing entry */
-                           duplicates += 2;
-                       else {
-                           /* copy element back: possibly to an earlier
-                            * stack location if we encountered dups earlier,
-                            * possibly to a later stack location if odd */
-                           *topelem++ = sv;
-                           *topelem++ = tmpstr;
-                       }
-                   }
-                    if (already_copied)
-                        SvREFCNT_inc_simple_void_NN(tmpstr); /* undo mortal free */
-                   didstore = hv_store_ent(hash,sv,tmpstr,0);
-                   if (magic) {
-                       if (!didstore) sv_2mortal(tmpstr);
-                       SvSETMAGIC(tmpstr);
+            /* now assign the keys and values to the hash */
+
+            dirty_tmps = FALSE;
+
+            if (UNLIKELY(gimme == G_ARRAY)) {
+                /* @a = (%h = (...)) etc */
+                SV **svp;
+                SV **topelem = relem;
+
+                for (i = 0, svp = relem; svp <= lastrelem; i++, svp++) {
+                    SV *key = *svp++;
+                    SV *val = *svp;
+                    /* remove duplicates from list we return */
+                    if (!hv_exists_ent(hash, key, 0)) {
+                        /* copy key back: possibly to an earlier
+                         * stack location if we encountered dups earlier,
+                         * The values will be updated later
+                         */
+                        *topelem = key;
+                        topelem += 2;
                     }
-                   TAINT_NOT;
-               }
-               LEAVE;
-                if (duplicates && gimme == G_ARRAY) {
+                    /* A tied store won't take ownership of val, so keep
+                     * the 1 refcnt on the tmps stack; otherwise disarm
+                     * the tmps stack entry */
+                    if (hv_store_ent(hash, key, val, 0))
+                        PL_tmps_stack[tmps_base + i] = &PL_sv_undef;
+                    else
+                        dirty_tmps = TRUE;
+                    /* hv_store_ent() may have added set magic to val */;
+                    SvSETMAGIC(val);
+                }
+                if (topelem < svp) {
                     /* at this point we have removed the duplicate key/value
                      * pairs from the stack, but the remaining values may be
                      * wrong; i.e. with (a 1 a 2 b 3) on the stack we've removed
                      * the (a 2), but the stack now probably contains
                      * (a <freed> b 3), because { hv_save(a,1); hv_save(a,2) }
                      * obliterates the earlier key. So refresh all values. */
-                    lastrelem -= duplicates;
-                    relem = firsthashrelem;
-                    while (relem < lastrelem+odd) {
+                    lastrelem = topelem - 1;
+                    while (relem < lastrelem) {
                         HE *he;
                         he = hv_fetch_ent(hash, *relem++, 0, 0);
                         *relem++ = (he ? HeVAL(he) : &PL_sv_undef);
                     }
                 }
-                if (odd && gimme == G_ARRAY) lastrelem++;
-           }
-           break;
+            }
+            else {
+                SV **svp;
+                for (i = 0, svp = relem; svp <= lastrelem; i++, svp++) {
+                    SV *key = *svp++;
+                    SV *val = *svp;
+                    if (hv_store_ent(hash, key, val, 0))
+                        PL_tmps_stack[tmps_base + i] = &PL_sv_undef;
+                    else
+                        dirty_tmps = TRUE;
+                    /* hv_store_ent() may have added set magic to val */;
+                    SvSETMAGIC(val);
+                }
+            }
+
+            if (dirty_tmps) {
+                /* there are still some 'live' recounts on the tmps stack
+                 * - usually caused by storing into a tied hash. So let
+                 * free_tmps() do the proper but slow job later.
+                 * Just disarm hash refcount: see comments below about leak
+                 */
+                PL_tmps_stack[tmps_base - 1] = &PL_sv_undef;
+            }
+            else {
+                /* Quietly remove all the SVs from the tmps stack slots,
+                 * since hash has now taken ownership of the refcnt.
+                 * Also remove hash: which will now leak if we die before
+                 * the SvREFCNT_dec_NN(hash) below */
+                if (UNLIKELY(PL_tmps_ix >= tmps_base + nelems))
+                    Move(&PL_tmps_stack[tmps_base + nelems],
+                         &PL_tmps_stack[tmps_base - 1],
+                         PL_tmps_ix - (tmps_base + nelems) + 1,
+                         SV*);
+                PL_tmps_ix -= (nelems + 1);
+            }
+
+            SvREFCNT_dec_NN(hash);
+
+            relem = lastrelem + 1;
+           goto no_relems;
+       }
+
        default:
-           if (SvIMMORTAL(sv)) {
-               if (relem <= lastrelem)
-                   relem++;
-               break;
-           }
-           if (relem <= lastrelem) {
-               if (UNLIKELY(
-                 SvTEMP(sv) && !SvSMAGICAL(sv) && SvREFCNT(sv) == 1 &&
-                 (!isGV_with_GP(sv) || SvFAKE(sv)) && ckWARN(WARN_MISC)
-               ))
-                   Perl_warner(aTHX_
-                      packWARN(WARN_MISC),
-                     "Useless assignment to a temporary"
-                   );
-               sv_setsv(sv, *relem);
-               *(relem++) = sv;
-           }
-           else
-               sv_setsv(sv, &PL_sv_undef);
-           SvSETMAGIC(sv);
+           if (!SvIMMORTAL(lsv)) {
+                SV *ref;
+
+                if (UNLIKELY(
+                  SvTEMP(lsv) && !SvSMAGICAL(lsv) && SvREFCNT(lsv) == 1 &&
+                  (!isGV_with_GP(lsv) || SvFAKE(lsv)) && ckWARN(WARN_MISC)
+                ))
+                    Perl_warner(aTHX_
+                       packWARN(WARN_MISC),
+                      "Useless assignment to a temporary"
+                    );
+
+                /* avoid freeing $$lsv if it might be needed for further
+                 * elements, e.g. ($ref, $foo) = (1, $$ref) */
+                if (   SvROK(lsv)
+                    && ( ((ref = SvRV(lsv)), SvREFCNT(ref)) == 1)
+                    && lelem <= lastlelem
+                ) {
+                    SSize_t ix;
+                    SvREFCNT_inc_simple_void_NN(ref);
+                    /* an unrolled sv_2mortal */
+                    ix = ++PL_tmps_ix;
+                    if (UNLIKELY(ix >= PL_tmps_max))
+                        /* speculatively grow enough to cover other
+                         * possible refs */
+                         (void)tmps_grow_p(ix + (lastlelem - lelem));
+                    PL_tmps_stack[ix] = ref;
+                }
+
+                sv_setsv(lsv, *relem);
+                *relem = lsv;
+                SvSETMAGIC(lsv);
+            }
+            if (++relem > lastrelem)
+                goto no_relems;
            break;
+        } /* switch */
+    } /* while */
+
+
+  no_relems:
+
+    /* simplified lelem loop for when there are no relems left */
+    while (LIKELY(lelem <= lastlelem)) {
+       SV *lsv = *lelem++;
+
+        TAINT_NOT; /* Each item stands on its own, taintwise. */
+
+       if (UNLIKELY(!lsv)) {
+           lsv = *lelem++;
+           ASSUME(SvTYPE(lsv) == SVt_PVAV);
        }
-    }
+
+       switch (SvTYPE(lsv)) {
+       case SVt_PVAV:
+            if (SvRMAGICAL(lsv) || AvFILLp((SV*)lsv) >= 0) {
+                av_clear((AV*)lsv);
+                if (UNLIKELY(PL_delaymagic & DM_ARRAY_ISA))
+                    SvSETMAGIC(lsv);
+            }
+            break;
+
+       case SVt_PVHV:
+            if (SvRMAGICAL(lsv) || HvUSEDKEYS((HV*)lsv))
+                hv_clear((HV*)lsv);
+            break;
+
+       default:
+           if (!SvIMMORTAL(lsv)) {
+                sv_set_undef(lsv);
+                SvSETMAGIC(lsv);
+                *relem++ = lsv;
+            }
+           break;
+        } /* switch */
+    } /* while */
+
+    TAINT_NOT; /* result of list assign isn't tainted */
+
     if (UNLIKELY(PL_delaymagic & ~DM_DELAY)) {
        /* Will be used to set PL_tainting below */
        Uid_t tmp_uid  = PerlProc_getuid();
@@ -1565,12 +1960,11 @@ PP(pp_aassign)
                setresuid((PL_delaymagic & DM_RUID) ? PL_delaymagic_uid  : (Uid_t)-1,
                          (PL_delaymagic & DM_EUID) ? PL_delaymagic_euid : (Uid_t)-1,
                          (Uid_t)-1));
-#else
-#  ifdef HAS_SETREUID
+#elif defined(HAS_SETREUID)
             PERL_UNUSED_RESULT(
                 setreuid((PL_delaymagic & DM_RUID) ? PL_delaymagic_uid  : (Uid_t)-1,
                          (PL_delaymagic & DM_EUID) ? PL_delaymagic_euid : (Uid_t)-1));
-#  else
+#else
 #    ifdef HAS_SETRUID
            if ((PL_delaymagic & DM_UID) == DM_RUID) {
                PERL_UNUSED_RESULT(setruid(PL_delaymagic_uid));
@@ -1588,7 +1982,6 @@ PP(pp_aassign)
                    DIE(aTHX_ "No setreuid available");
                PERL_UNUSED_RESULT(PerlProc_setuid(PL_delaymagic_uid));
            }
-#  endif /* HAS_SETREUID */
 #endif /* HAS_SETRESUID */
 
            tmp_uid  = PerlProc_getuid();
@@ -1601,12 +1994,11 @@ PP(pp_aassign)
                 setresgid((PL_delaymagic & DM_RGID) ? PL_delaymagic_gid  : (Gid_t)-1,
                           (PL_delaymagic & DM_EGID) ? PL_delaymagic_egid : (Gid_t)-1,
                           (Gid_t)-1));
-#else
-#  ifdef HAS_SETREGID
+#elif defined(HAS_SETREGID)
            PERL_UNUSED_RESULT(
                 setregid((PL_delaymagic & DM_RGID) ? PL_delaymagic_gid  : (Gid_t)-1,
                          (PL_delaymagic & DM_EGID) ? PL_delaymagic_egid : (Gid_t)-1));
-#  else
+#else
 #    ifdef HAS_SETRGID
            if ((PL_delaymagic & DM_GID) == DM_RGID) {
                PERL_UNUSED_RESULT(setrgid(PL_delaymagic_gid));
@@ -1624,7 +2016,6 @@ PP(pp_aassign)
                    DIE(aTHX_ "No setregid available");
                PERL_UNUSED_RESULT(PerlProc_setgid(PL_delaymagic_gid));
            }
-#  endif /* HAS_SETREGID */
 #endif /* HAS_SETRESGID */
 
            tmp_gid  = PerlProc_getgid();
@@ -1643,22 +2034,17 @@ PP(pp_aassign)
     if (gimme == G_VOID)
        SP = firstrelem - 1;
     else if (gimme == G_SCALAR) {
-       dTARGET;
        SP = firstrelem;
-       SETi(lastrelem - firstrelem + 1);
-    }
-    else {
-       if (ary || hash)
-           /* note that in this case *firstlelem may have been overwritten
-              by sv_undef in the odd hash case */
-           SP = lastrelem;
-       else {
-           SP = firstrelem + (lastlelem - firstlelem);
-            lelem = firstlelem + (relem - firstrelem);
-            while (relem <= SP)
-                *relem++ = (lelem <= lastlelem) ? *lelem++ : &PL_sv_undef;
+        EXTEND(SP,1);
+        if (PL_op->op_private & OPpASSIGN_TRUEBOOL)
+            SETs((firstlelem - firstrelem) ? &PL_sv_yes : &PL_sv_zero);
+        else {
+            dTARGET;
+            SETi(firstlelem - firstrelem);
         }
     }
+    else
+        SP = relem - 1;
 
     RETURN;
 }
@@ -1668,7 +2054,8 @@ PP(pp_qr)
     dSP;
     PMOP * const pm = cPMOP;
     REGEXP * rx = PM_GETRE(pm);
-    SV * const pkg = rx ? CALLREG_PACKAGE(rx) : NULL;
+    regexp *prog = ReANY(rx);
+    SV * const pkg = RXp_ENGINE(prog)->qr_package(aTHX_ (rx));
     SV * const rv = sv_newmortal();
     CV **cvp;
     CV *cv;
@@ -1695,7 +2082,7 @@ PP(pp_qr)
        (void)sv_bless(rv, stash);
     }
 
-    if (UNLIKELY(RX_ISTAINTED(rx))) {
+    if (UNLIKELY(RXp_ISTAINTED(prog))) {
         SvTAINTED_on(rv);
         SvTAINTED_on(SvRV(rv));
     }
@@ -1715,6 +2102,7 @@ PP(pp_match)
     U8 r_flags = 0;
     const char *truebase;                      /* Start of string  */
     REGEXP *rx = PM_GETRE(pm);
+    regexp *prog = ReANY(rx);
     bool rxtainted;
     const U8 gimme = GIMME_V;
     STRLEN len;
@@ -1724,23 +2112,25 @@ PP(pp_match)
 
     if (PL_op->op_flags & OPf_STACKED)
        TARG = POPs;
-    else if (ARGTARG)
-       GETTARGET;
     else {
-       TARG = DEFSV;
+        if (ARGTARG)
+            GETTARGET;
+        else {
+            TARG = DEFSV;
+        }
        EXTEND(SP,1);
     }
 
     PUTBACK;                           /* EVAL blocks need stack_sp. */
     /* Skip get-magic if this is a qr// clone, because regcomp has
        already done it. */
-    truebase = ReANY(rx)->mother_re
+    truebase = prog->mother_re
         ? SvPV_nomg_const(TARG, len)
         : SvPV_const(TARG, len);
     if (!truebase)
        DIE(aTHX_ "panic: pp_match");
     strend = truebase + len;
-    rxtainted = (RX_ISTAINTED(rx) ||
+    rxtainted = (RXp_ISTAINTED(prog) ||
                 (TAINT_get && (pm->op_pmflags & PMf_RETAINT)));
     TAINT_NOT;
 
@@ -1759,18 +2149,27 @@ PP(pp_match)
        goto nope;
     }
 
-    /* empty pattern special-cased to use last successful pattern if
-       possible, except for qr// */
-    if (!ReANY(rx)->mother_re && !RX_PRELEN(rx)
-     && PL_curpm) {
-       pm = PL_curpm;
-       rx = PM_GETRE(pm);
+    /* handle the empty pattern */
+    if (!RX_PRELEN(rx) && PL_curpm && !prog->mother_re) {
+        if (PL_curpm == PL_reg_curpm) {
+            if (PL_curpm_under) {
+                if (PL_curpm_under == PL_reg_curpm) {
+                    Perl_croak(aTHX_ "Infinite recursion via empty pattern");
+                } else {
+                    pm = PL_curpm_under;
+                }
+            }
+        } else {
+            pm = PL_curpm;
+        }
+        rx = PM_GETRE(pm);
+        prog = ReANY(rx);
     }
 
-    if (RX_MINLEN(rx) >= 0 && (STRLEN)RX_MINLEN(rx) > len) {
+    if (RXp_MINLEN(prog) >= 0 && (STRLEN)RXp_MINLEN(prog) > len) {
         DEBUG_r(PerlIO_printf(Perl_debug_log, "String shorter than min possible regex match (%"
-                                              UVuf" < %"IVdf")\n",
-                                              (UV)len, (IV)RX_MINLEN(rx)));
+                                              UVuf " < %" IVdf ")\n",
+                                              (UV)len, (IV)RXp_MINLEN(prog)));
        goto nope;
     }
 
@@ -1786,9 +2185,9 @@ PP(pp_match)
     }
 
 #ifdef PERL_SAWAMPERSAND
-    if (       RX_NPARENS(rx)
+    if (       RXp_NPARENS(prog)
             || PL_sawampersand
-            || (RX_EXTFLAGS(rx) & (RXf_EVAL_SEEN|RXf_PMf_KEEPCOPY))
+            || (RXp_EXTFLAGS(prog) & (RXf_EVAL_SEEN|RXf_PMf_KEEPCOPY))
             || (dynpm->op_pmflags & PMf_KEEPCOPY)
     )
 #endif
@@ -1826,22 +2225,22 @@ PP(pp_match)
 #endif
 
     if (rxtainted)
-       RX_MATCH_TAINTED_on(rx);
-    TAINT_IF(RX_MATCH_TAINTED(rx));
+       RXp_MATCH_TAINTED_on(prog);
+    TAINT_IF(RXp_MATCH_TAINTED(prog));
 
     /* update pos */
 
     if (global && (gimme != G_ARRAY || (dynpm->op_pmflags & PMf_CONTINUE))) {
         if (!mg)
             mg = sv_magicext_mglob(TARG);
-        MgBYTEPOS_set(mg, TARG, truebase, RX_OFFS(rx)[0].end);
-        if (RX_ZERO_LEN(rx))
+        MgBYTEPOS_set(mg, TARG, truebase, RXp_OFFS(prog)[0].end);
+        if (RXp_ZERO_LEN(prog))
             mg->mg_flags |= MGf_MINMATCH;
         else
             mg->mg_flags &= ~MGf_MINMATCH;
     }
 
-    if ((!RX_NPARENS(rx) && !global) || gimme != G_ARRAY) {
+    if ((!RXp_NPARENS(prog) && !global) || gimme != G_ARRAY) {
        LEAVE_SCOPE(oldsave);
        RETPUSHYES;
     }
@@ -1849,7 +2248,7 @@ PP(pp_match)
     /* push captures on stack */
 
     {
-       const I32 nparens = RX_NPARENS(rx);
+       const I32 nparens = RXp_NPARENS(prog);
        I32 i = (global && !nparens) ? 1 : 0;
 
        SPAGAIN;                        /* EVAL blocks could move the stack. */
@@ -1857,25 +2256,28 @@ PP(pp_match)
        EXTEND_MORTAL(nparens + i);
        for (i = !i; i <= nparens; i++) {
            PUSHs(sv_newmortal());
-           if (LIKELY((RX_OFFS(rx)[i].start != -1)
-                     && RX_OFFS(rx)[i].end   != -1 ))
+           if (LIKELY((RXp_OFFS(prog)[i].start != -1)
+                     && RXp_OFFS(prog)[i].end   != -1 ))
             {
-               const I32 len = RX_OFFS(rx)[i].end - RX_OFFS(rx)[i].start;
-               const char * const s = RX_OFFS(rx)[i].start + truebase;
-               if (UNLIKELY(RX_OFFS(rx)[i].end < 0 || RX_OFFS(rx)[i].start < 0
-                        || len < 0 || len > strend - s))
+               const I32 len = RXp_OFFS(prog)[i].end - RXp_OFFS(prog)[i].start;
+               const char * const s = RXp_OFFS(prog)[i].start + truebase;
+               if (UNLIKELY(  RXp_OFFS(prog)[i].end   < 0
+                            || RXp_OFFS(prog)[i].start < 0
+                            || len < 0
+                            || len > strend - s)
+                )
                    DIE(aTHX_ "panic: pp_match start/end pointers, i=%ld, "
-                       "start=%ld, end=%ld, s=%p, strend=%p, len=%"UVuf,
-                       (long) i, (long) RX_OFFS(rx)[i].start,
-                       (long)RX_OFFS(rx)[i].end, s, strend, (UV) len);
+                       "start=%ld, end=%ld, s=%p, strend=%p, len=%" UVuf,
+                       (long) i, (long) RXp_OFFS(prog)[i].start,
+                       (long)RXp_OFFS(prog)[i].end, s, strend, (UV) len);
                sv_setpvn(*SP, s, len);
                if (DO_UTF8(TARG) && is_utf8_string((U8*)s, len))
                    SvUTF8_on(*SP);
            }
        }
        if (global) {
-            curpos = (UV)RX_OFFS(rx)[0].end;
-           had_zerolen = RX_ZERO_LEN(rx);
+            curpos = (UV)RXp_OFFS(prog)[0].end;
+           had_zerolen = RXp_ZERO_LEN(prog);
            PUTBACK;                    /* EVAL blocks may use stack */
            r_flags |= REXEC_IGNOREPOS | REXEC_NOT_FIRST;
            goto play_it_again;
@@ -1963,7 +2365,7 @@ Perl_do_readline(pTHX)
        if (gimme == G_SCALAR) {
            /* undef TARG, and push that undefined value */
            if (type != OP_RCATLINE) {
-               sv_setsv(TARG,NULL);
+               sv_set_undef(TARG);
            }
            PUSHTARG;
        }
@@ -2155,7 +2557,7 @@ PP(pp_helem)
            RETURN;
        }
        if (localizing) {
-           if (HvNAME_get(hv) && isGV(*svp))
+           if (HvNAME_get(hv) && isGV_or_RVCV(*svp))
                save_gp(MUTABLE_GV(*svp), !(PL_op->op_flags & OPf_SPECIAL));
            else if (preeminent)
                save_helem_flags(hv, keysv, svp,
@@ -2323,7 +2725,7 @@ PP(pp_multideref)
                     if (UNLIKELY(SvROK(elemsv) && !SvGAMAGIC(elemsv)
                                             && ckWARN(WARN_MISC)))
                         Perl_warner(aTHX_ packWARN(WARN_MISC),
-                                "Use of reference \"%"SVf"\" as array index",
+                                "Use of reference \"%" SVf "\" as array index",
                                 SVfARG(elemsv));
                     /* the only time that S_find_uninit_var() needs this
                      * is to determine which index value triggered the
@@ -2591,7 +2993,7 @@ PP(pp_multideref)
                         }
                         else {
                             if (localizing) {
-                                if (HvNAME_get(hv) && isGV(sv))
+                                if (HvNAME_get(hv) && isGV_or_RVCV(sv))
                                     save_gp(MUTABLE_GV(sv),
                                         !(PL_op->op_flags & OPf_SPECIAL));
                                 else if (preeminent) {
@@ -2628,7 +3030,6 @@ PP(pp_iter)
     PERL_CONTEXT *cx;
     SV *oldsv;
     SV **itersvp;
-    SV *retsv;
 
     SV *sv;
     AV *av;
@@ -2649,6 +3050,8 @@ PP(pp_iter)
            It has SvPVX of "" and SvCUR of 0, which is what we want.  */
         STRLEN maxlen = 0;
         const char *max = SvPV_const(end, maxlen);
+        if (DO_UTF8(end) && IN_UNI_8_BIT)
+            maxlen = sv_len_utf8_nomg(end);
         if (UNLIKELY(SvNIOK(cur) || SvCUR(cur) > maxlen))
             goto retno;
 
@@ -2789,20 +3192,28 @@ PP(pp_iter)
        DIE(aTHX_ "panic: pp_iter, type=%u", CxTYPE(cx));
     }
 
-    retsv = &PL_sv_yes;
-    if (0) {
-      retno:
-        retsv = &PL_sv_no;
-    }
+    /* Bypass pushing &PL_sv_yes and calling pp_and(); instead
+     * jump straight to the AND op's op_other */
+    assert(PL_op->op_next->op_type == OP_AND);
+    assert(PL_op->op_next->op_ppaddr == Perl_pp_and);
+    return cLOGOPx(PL_op->op_next)->op_other;
+
+  retno:
+    /* Bypass pushing &PL_sv_no and calling pp_and(); instead
+     * jump straight to the AND op's op_next */
+    assert(PL_op->op_next->op_type == OP_AND);
+    assert(PL_op->op_next->op_ppaddr == Perl_pp_and);
     /* pp_enteriter should have pre-extended the stack */
-    assert(PL_stack_sp < PL_stack_max);
-    *++PL_stack_sp =retsv;
-
-    return PL_op->op_next;
-
-
+    EXTEND_SKIP(PL_stack_sp, 1);
+    /* we only need this for the rare case where the OP_AND isn't
+     * in void context, e.g. $x = do { for (..) {...} };
+     * but its cheaper to just push it rather than testing first
+     */
+    *++PL_stack_sp = &PL_sv_no;
+    return PL_op->op_next->op_next;
 }
 
+
 /*
 A description of how taint works in pattern matching and substitution.
 
@@ -2888,13 +3299,14 @@ PP(pp_subst)
     char *orig;
     U8 r_flags;
     REGEXP *rx = PM_GETRE(pm);
+    regexp *prog = ReANY(rx);
     STRLEN len;
     int force_on_match = 0;
     const I32 oldsave = PL_savestack_ix;
     STRLEN slen;
     bool doutf8 = FALSE; /* whether replacement is in utf8 */
 #ifdef PERL_ANY_COW
-    bool is_cow;
+    bool was_cow;
 #endif
     SV *nsv = NULL;
     /* known replacement string? */
@@ -2904,33 +3316,36 @@ PP(pp_subst)
 
     if (PL_op->op_flags & OPf_STACKED)
        TARG = POPs;
-    else if (ARGTARG)
-       GETTARGET;
     else {
-       TARG = DEFSV;
+        if (ARGTARG)
+            GETTARGET;
+        else {
+            TARG = DEFSV;
+        }
        EXTEND(SP,1);
     }
 
     SvGETMAGIC(TARG); /* must come before cow check */
 #ifdef PERL_ANY_COW
-    /* Awooga. Awooga. "bool" types that are actually char are dangerous,
-       because they make integers such as 256 "false".  */
-    is_cow = SvIsCOW(TARG) ? TRUE : FALSE;
-#else
-    if (SvIsCOW(TARG))
-       sv_force_normal_flags(TARG,0);
+    /* note that a string might get converted to COW during matching */
+    was_cow = cBOOL(SvIsCOW(TARG));
+#endif
+    if (!(rpm->op_pmflags & PMf_NONDESTRUCT)) {
+#ifndef PERL_ANY_COW
+       if (SvIsCOW(TARG))
+           sv_force_normal_flags(TARG,0);
 #endif
-    if (!(rpm->op_pmflags & PMf_NONDESTRUCT)
-       && (SvREADONLY(TARG)
-           || ( ((SvTYPE(TARG) == SVt_PVGV && isGV_with_GP(TARG))
-                 || SvTYPE(TARG) > SVt_PVLV)
-                && !(SvTYPE(TARG) == SVt_PVGV && SvFAKE(TARG)))))
-       Perl_croak_no_modify();
+       if ((SvREADONLY(TARG)
+               || ( ((SvTYPE(TARG) == SVt_PVGV && isGV_with_GP(TARG))
+                     || SvTYPE(TARG) > SVt_PVLV)
+                    && !(SvTYPE(TARG) == SVt_PVGV && SvFAKE(TARG)))))
+           Perl_croak_no_modify();
+    }
     PUTBACK;
 
     orig = SvPV_nomg(TARG, len);
     /* note we don't (yet) force the var into being a string; if we fail
-     * to match, we leave as-is; on successful match howeverm, we *will*
+     * to match, we leave as-is; on successful match however, we *will*
      * coerce into a string, then repeat the match */
     if (!SvPOKp(TARG) || SvTYPE(TARG) == SVt_PVGV || SvVOK(TARG))
        force_on_match = 1;
@@ -2942,7 +3357,7 @@ PP(pp_subst)
     if (TAINTING_get) {
        rxtainted  = (
            (SvTAINTED(TARG) ? SUBST_TAINT_STR : 0)
-         | (RX_ISTAINTED(rx) ? SUBST_TAINT_PAT : 0)
+         | (RXp_ISTAINTED(prog) ? SUBST_TAINT_PAT : 0)
          | ((pm->op_pmflags & PMf_RETAINT) ? SUBST_TAINT_RETAINT : 0)
          | ((once && !(rpm->op_pmflags & PMf_NONDESTRUCT))
                ? SUBST_TAINT_BOOLRET : 0));
@@ -2959,16 +3374,27 @@ PP(pp_subst)
                                   position, once with zero-length,
                                   second time with non-zero. */
 
-    if (!RX_PRELEN(rx) && PL_curpm
-     && !ReANY(rx)->mother_re) {
-       pm = PL_curpm;
-       rx = PM_GETRE(pm);
+    /* handle the empty pattern */
+    if (!RX_PRELEN(rx) && PL_curpm && !prog->mother_re) {
+        if (PL_curpm == PL_reg_curpm) {
+            if (PL_curpm_under) {
+                if (PL_curpm_under == PL_reg_curpm) {
+                    Perl_croak(aTHX_ "Infinite recursion via empty pattern");
+                } else {
+                    pm = PL_curpm_under;
+                }
+            }
+        } else {
+            pm = PL_curpm;
+        }
+        rx = PM_GETRE(pm);
+        prog = ReANY(rx);
     }
 
 #ifdef PERL_SAWAMPERSAND
-    r_flags = (    RX_NPARENS(rx)
+    r_flags = (    RXp_NPARENS(prog)
                 || PL_sawampersand
-                || (RX_EXTFLAGS(rx) & (RXf_EVAL_SEEN|RXf_PMf_KEEPCOPY))
+                || (RXp_EXTFLAGS(prog) & (RXf_EVAL_SEEN|RXf_PMf_KEEPCOPY))
                 || (rpm->op_pmflags & PMf_KEEPCOPY)
               )
           ? REXEC_COPY_STR
@@ -2992,10 +3418,7 @@ PP(pp_subst)
        if (DO_UTF8(TARG) && !doutf8) {
             nsv = sv_newmortal();
             SvSetSV(nsv, dstr);
-            if (IN_ENCODING)
-                 sv_recode_to_utf8(nsv, _get_encoding());
-            else
-                 sv_utf8_upgrade(nsv);
+            sv_utf8_upgrade(nsv);
             c = SvPV_const(nsv, clen);
             doutf8 = TRUE;
        }
@@ -3015,19 +3438,20 @@ PP(pp_subst)
     /* can do inplace substitution? */
     if (c
 #ifdef PERL_ANY_COW
-       && !is_cow
+       && !was_cow
 #endif
-        && (I32)clen <= RX_MINLENRET(rx)
+        && (I32)clen <= RXp_MINLENRET(prog)
         && (  once
            || !(r_flags & REXEC_COPY_STR)
-           || (!SvGMAGICAL(dstr) && !(RX_EXTFLAGS(rx) & RXf_EVAL_SEEN))
+           || (!SvGMAGICAL(dstr) && !(RXp_EXTFLAGS(prog) & RXf_EVAL_SEEN))
            )
-        && !(RX_EXTFLAGS(rx) & RXf_NO_INPLACE_SUBST)
+        && !(RXp_EXTFLAGS(prog) & RXf_NO_INPLACE_SUBST)
        && (!doutf8 || SvUTF8(TARG))
        && !(rpm->op_pmflags & PMf_NONDESTRUCT))
     {
 
 #ifdef PERL_ANY_COW
+        /* string might have got converted to COW since we set was_cow */
        if (SvIsCOW(TARG)) {
          if (!force_on_match)
            goto have_a_cow;
@@ -3044,10 +3468,10 @@ PP(pp_subst)
 
        if (once) {
             char *d, *m;
-           if (RX_MATCH_TAINTED(rx)) /* run time pattern taint, eg locale */
+           if (RXp_MATCH_TAINTED(prog)) /* run time pattern taint, eg locale */
                rxtainted |= SUBST_TAINT_PAT;
-           m = orig + RX_OFFS(rx)[0].start;
-           d = orig + RX_OFFS(rx)[0].end;
+           m = orig + RXp_OFFS(prog)[0].start;
+           d = orig + RXp_OFFS(prog)[0].end;
            s = orig;
            if (m - s > strend - d) {  /* faster to shorten from end */
                 I32 i;
@@ -3077,14 +3501,15 @@ PP(pp_subst)
        }
        else {
             char *d, *m;
-            d = s = RX_OFFS(rx)[0].start + orig;
+            d = s = RXp_OFFS(prog)[0].start + orig;
            do {
                 I32 i;
                if (UNLIKELY(iters++ > maxiters))
                    DIE(aTHX_ "Substitution loop");
-               if (UNLIKELY(RX_MATCH_TAINTED(rx))) /* run time pattern taint, eg locale */
+                /* run time pattern taint, eg locale */
+               if (UNLIKELY(RXp_MATCH_TAINTED(prog)))
                    rxtainted |= SUBST_TAINT_PAT;
-               m = RX_OFFS(rx)[0].start + orig;
+               m = RXp_OFFS(prog)[0].start + orig;
                if ((i = m - s)) {
                    if (s != d)
                        Move(s, d, i, char);
@@ -3094,7 +3519,7 @@ PP(pp_subst)
                    Copy(c, d, clen, char);
                    d += clen;
                }
-               s = RX_OFFS(rx)[0].end + orig;
+               s = RXp_OFFS(prog)[0].end + orig;
            } while (CALLREGEXEC(rx, s, strend, orig,
                                 s == m, /* don't match same null twice */
                                 TARG, NULL,
@@ -3105,7 +3530,10 @@ PP(pp_subst)
                Move(s, d, i+1, char);          /* include the NUL */
            }
            SPAGAIN;
-           mPUSHi(iters);
+            if (PL_op->op_private & OPpTRUEBOOL)
+                PUSHs(iters ? &PL_sv_yes : &PL_sv_zero);
+            else
+                mPUSHi(iters);
        }
     }
     else {
@@ -3130,10 +3558,10 @@ PP(pp_subst)
 #ifdef PERL_ANY_COW
       have_a_cow:
 #endif
-       if (RX_MATCH_TAINTED(rx)) /* run time pattern taint, eg locale */
+       if (RXp_MATCH_TAINTED(prog)) /* run time pattern taint, eg locale */
            rxtainted |= SUBST_TAINT_PAT;
        repl = dstr;
-        s = RX_OFFS(rx)[0].start + orig;
+        s = RXp_OFFS(prog)[0].start + orig;
        dstr = newSVpvn_flags(orig, s-orig,
                     SVs_TEMP | (DO_UTF8(TARG) ? SVf_UTF8 : 0));
        if (!c) {
@@ -3152,20 +3580,20 @@ PP(pp_subst)
        do {
            if (UNLIKELY(iters++ > maxiters))
                DIE(aTHX_ "Substitution loop");
-           if (UNLIKELY(RX_MATCH_TAINTED(rx)))
+           if (UNLIKELY(RXp_MATCH_TAINTED(prog)))
                rxtainted |= SUBST_TAINT_PAT;
-           if (RX_MATCH_COPIED(rx) && RX_SUBBEG(rx) != orig) {
+           if (RXp_MATCH_COPIED(prog) && RXp_SUBBEG(prog) != orig) {
                char *old_s    = s;
                char *old_orig = orig;
-                assert(RX_SUBOFFSET(rx) == 0);
+                assert(RXp_SUBOFFSET(prog) == 0);
 
-               orig = RX_SUBBEG(rx);
+               orig = RXp_SUBBEG(prog);
                s = orig + (old_s - old_orig);
                strend = s + (strend - old_s);
            }
-           m = RX_OFFS(rx)[0].start + orig;
+           m = RXp_OFFS(prog)[0].start + orig;
            sv_catpvn_nomg_maybeutf8(dstr, s, m - s, DO_UTF8(TARG));
-           s = RX_OFFS(rx)[0].end + orig;
+           s = RXp_OFFS(prog)[0].end + orig;
            if (first) {
                /* replacement already stringified */
              if (clen)
@@ -3173,13 +3601,7 @@ PP(pp_subst)
              first = FALSE;
            }
            else {
-               if (IN_ENCODING) {
-                   if (!nsv) nsv = sv_newmortal();
-                   sv_copypv(nsv, repl);
-                   if (!DO_UTF8(nsv)) sv_recode_to_utf8(nsv, _get_encoding());
-                   sv_catsv(dstr, nsv);
-               }
-               else sv_catsv(dstr, repl);
+               sv_catsv(dstr, repl);
                if (UNLIKELY(SvTAINTED(repl)))
                    rxtainted |= SUBST_TAINT_REPL;
            }
@@ -3233,7 +3655,7 @@ PP(pp_subst)
            ((rxtainted & (SUBST_TAINT_STR|SUBST_TAINT_RETAINT)) ==
                                (SUBST_TAINT_STR|SUBST_TAINT_RETAINT))
        )
-           (RX_MATCH_TAINTED_on(rx)); /* taint $1 et al */
+           (RXp_MATCH_TAINTED_on(prog)); /* taint $1 et al */
 
        if (!(rxtainted & SUBST_TAINT_BOOLRET)
            && (rxtainted & (SUBST_TAINT_STR|SUBST_TAINT_PAT))
@@ -3257,8 +3679,9 @@ PP(pp_subst)
 PP(pp_grepwhile)
 {
     dSP;
+    dPOPss;
 
-    if (SvTRUEx(POPs))
+    if (SvTRUE_NN(sv))
        PL_stack_base[PL_markstack_ptr[-1]++] = PL_stack_base[*PL_markstack_ptr];
     ++*PL_markstack_ptr;
     FREETMPS;
@@ -3275,8 +3698,12 @@ PP(pp_grepwhile)
        (void)POPMARK;                          /* pop dst */
        SP = PL_stack_base + POPMARK;           /* pop original mark */
        if (gimme == G_SCALAR) {
+            if (PL_op->op_private & OPpTRUEBOOL)
+                PUSHs(items ? &PL_sv_yes : &PL_sv_zero);
+            else {
                dTARGET;
-               XPUSHi(items);
+               PUSHi(items);
+            }
        }
        else if (gimme == G_ARRAY)
            SP += items;
@@ -3623,6 +4050,8 @@ Perl_leave_adjust_stacks(pTHX_ SV **from_sp, SV **to_sp, U8 gimme, int pass)
 }
 
 
+/* also tail-called by pp_return */
+
 PP(pp_leavesub)
 {
     U8 gimme;
@@ -3782,6 +4211,7 @@ PP(pp_entersub)
 
     /* these two fields are in a union. If they ever become separate,
      * we have to test for both of them being null below */
+    assert(cv);
     assert((void*)&CvROOT(cv) == (void*)&CvXSUB(cv));
     while (UNLIKELY(!CvROOT(cv))) {
        GV* autogv;
@@ -3789,7 +4219,7 @@ PP(pp_entersub)
 
        /* anonymous or undef'd function leaves us no recourse */
        if (CvLEXICAL(cv) && CvHASGV(cv))
-           DIE(aTHX_ "Undefined subroutine &%"SVf" called",
+           DIE(aTHX_ "Undefined subroutine &%" SVf " called",
                       SVfARG(cv_name(cv, NULL, 0)));
        if (CvANON(cv) || !CvHASGV(cv)) {
            DIE(aTHX_ "Undefined subroutine called");
@@ -3803,13 +4233,16 @@ PP(pp_entersub)
        else {
           try_autoload:
            autogv = gv_autoload_pvn(GvSTASH(gv), GvNAME(gv), GvNAMELEN(gv),
-                                  GvNAMEUTF8(gv) ? SVf_UTF8 : 0);
+                                     (GvNAMEUTF8(gv) ? SVf_UTF8 : 0)
+                                    |(PL_op->op_flags & OPf_REF
+                                       ? GV_AUTOLOAD_ISMETHOD
+                                       : 0));
             cv = autogv ? GvCV(autogv) : NULL;
        }
        if (!cv) {
             sub_name = sv_newmortal();
             gv_efullname3(sub_name, gv, NULL);
-            DIE(aTHX_ "Undefined subroutine &%"SVf" called", SVfARG(sub_name));
+            DIE(aTHX_ "Undefined subroutine &%" SVf " called", SVfARG(sub_name));
         }
     }
 
@@ -3887,18 +4320,19 @@ PP(pp_entersub)
             items = SP - MARK;
            if (UNLIKELY(items - 1 > AvMAX(av))) {
                 SV **ary = AvALLOC(av);
-                AvMAX(av) = items - 1;
                 Renew(ary, items, SV*);
+                AvMAX(av) = items - 1;
                 AvALLOC(av) = ary;
                 AvARRAY(av) = ary;
             }
 
-           Copy(MARK+1,AvARRAY(av),items,SV*);
+            if (items)
+                Copy(MARK+1,AvARRAY(av),items,SV*);
            AvFILLp(av) = items - 1;
        }
        if (UNLIKELY((cx->blk_u16 & OPpENTERSUB_LVAL_MASK) == OPpLVAL_INTRO &&
            !CvLVALUE(cv)))
-            DIE(aTHX_ "Can't modify non-lvalue subroutine call of &%"SVf,
+            DIE(aTHX_ "Can't modify non-lvalue subroutine call of &%" SVf,
                 SVfARG(cv_name(cv, NULL, 0)));
        /* warning must come *after* we fully set up the context
         * stuff so that __WARN__ handlers can safely dounwind()
@@ -3925,7 +4359,7 @@ PP(pp_entersub)
               & CX_PUSHSUB_GET_LVALUE_MASK(Perl_is_lvalue_sub)
              ) & OPpENTERSUB_LVAL_MASK) == OPpLVAL_INTRO &&
            !CvLVALUE(cv)))
-            DIE(aTHX_ "Can't modify non-lvalue subroutine call of &%"SVf,
+            DIE(aTHX_ "Can't modify non-lvalue subroutine call of &%" SVf,
                 SVfARG(cv_name(cv, NULL, 0)));
 
        if (UNLIKELY(!(PL_op->op_flags & OPf_STACKED) && GvAV(PL_defgv))) {
@@ -3983,6 +4417,21 @@ PP(pp_entersub)
        assert(CvXSUB(cv));
        CvXSUB(cv)(aTHX_ cv);
 
+#if defined DEBUGGING && !defined DEBUGGING_RE_ONLY
+        /* This duplicates the check done in runops_debug(), but provides more
+         * information in the common case of the fault being with an XSUB.
+         *
+         * It should also catch an XSUB pushing more than it extends
+         * in scalar context.
+        */
+        if (PL_curstackinfo->si_stack_hwm < PL_stack_sp - PL_stack_base)
+            Perl_croak_nocontext(
+                "panic: XSUB %s::%s (%s) failed to extend arg stack: "
+                "base=%p, sp=%p, hwm=%p\n",
+                    HvNAME(GvSTASH(CvGV(cv))), GvNAME(CvGV(cv)), CvFILE(cv),
+                    PL_stack_base, PL_stack_sp,
+                    PL_stack_base + PL_curstackinfo->si_stack_hwm);
+#endif
        /* Enforce some sanity in scalar context. */
        if (is_scalar) {
             SV **svp = PL_stack_base + markix + 1;
@@ -4004,11 +4453,33 @@ Perl_sub_crush_depth(pTHX_ CV *cv)
     if (CvANON(cv))
        Perl_warner(aTHX_ packWARN(WARN_RECURSION), "Deep recursion on anonymous subroutine");
     else {
-       Perl_warner(aTHX_ packWARN(WARN_RECURSION), "Deep recursion on subroutine \"%"SVf"\"",
+       Perl_warner(aTHX_ packWARN(WARN_RECURSION), "Deep recursion on subroutine \"%" SVf "\"",
                    SVfARG(cv_name(cv,NULL,0)));
     }
 }
 
+
+
+/* like croak, but report in context of caller */
+
+void
+Perl_croak_caller(const char *pat, ...)
+{
+    dTHX;
+    va_list args;
+    const PERL_CONTEXT *cx = caller_cx(0, NULL);
+
+    /* make error appear at call site */
+    assert(cx);
+    PL_curcop = cx->blk_oldcop;
+
+    va_start(args, pat);
+    vcroak(pat, &args);
+    NOT_REACHED; /* NOTREACHED */
+    va_end(args);
+}
+
+
 PP(pp_aelem)
 {
     dSP;
@@ -4024,7 +4495,7 @@ PP(pp_aelem)
 
     if (UNLIKELY(SvROK(elemsv) && !SvGAMAGIC(elemsv) && ckWARN(WARN_MISC)))
        Perl_warner(aTHX_ packWARN(WARN_MISC),
-                   "Use of reference \"%"SVf"\" as array index",
+                   "Use of reference \"%" SVf "\" as array index",
                    SVfARG(elemsv));
     if (UNLIKELY(SvTYPE(av) != SVt_PVAV))
        RETPUSHUNDEF;
@@ -4129,7 +4600,7 @@ S_opmethod_stash(pTHX_ SV* meth)
     HV* stash;
 
     SV* const sv = PL_stack_base + TOPMARK == PL_stack_sp
-       ? (Perl_croak(aTHX_ "Can't call method \"%"SVf"\" without a "
+       ? (Perl_croak(aTHX_ "Can't call method \"%" SVf "\" without a "
                            "package or object reference", SVfARG(meth)),
           (SV *)NULL)
        : *(PL_stack_base + TOPMARK + 1);
@@ -4138,7 +4609,7 @@ S_opmethod_stash(pTHX_ SV* meth)
 
     if (UNLIKELY(!sv))
        undefined:
-       Perl_croak(aTHX_ "Can't call method \"%"SVf"\" on an undefined value",
+       Perl_croak(aTHX_ "Can't call method \"%" SVf "\" on an undefined value",
                   SVfARG(meth));
 
     if (UNLIKELY(SvGMAGICAL(sv))) mg_get(sv);
@@ -4152,7 +4623,7 @@ S_opmethod_stash(pTHX_ SV* meth)
     else if (!SvOK(sv)) goto undefined;
     else if (isGV_with_GP(sv)) {
        if (!GvIO(sv))
-           Perl_croak(aTHX_ "Can't call method \"%"SVf"\" "
+           Perl_croak(aTHX_ "Can't call method \"%" SVf "\" "
                             "without a package or object reference",
                              SVfARG(meth));
        ob = sv;
@@ -4180,7 +4651,7 @@ S_opmethod_stash(pTHX_ SV* meth)
            /* this isn't the name of a filehandle either */
            if (!packlen)
            {
-               Perl_croak(aTHX_ "Can't call method \"%"SVf"\" "
+               Perl_croak(aTHX_ "Can't call method \"%" SVf "\" "
                                 "without a package or object reference",
                                  SVfARG(meth));
            }
@@ -4199,8 +4670,8 @@ S_opmethod_stash(pTHX_ SV* meth)
                     && (ob = MUTABLE_SV(GvIO((const GV *)ob)))
                     && SvOBJECT(ob))))
     {
-       Perl_croak(aTHX_ "Can't call method \"%"SVf"\" on unblessed reference",
-                  SVfARG((SvSCREAM(meth) && strEQ(SvPV_nolen_const(meth),"isa"))
+       Perl_croak(aTHX_ "Can't call method \"%" SVf "\" on unblessed reference",
+                  SVfARG((SvPOK(meth) && SvPVX(meth) == PL_isa_DOES)
                                         ? newSVpvs_flags("DOES", SVs_TEMP)
                                         : meth));
     }