OP_AELEMFASTLEX_STORE - combined sassign/aelemfast_lex

This commit introduces a new OP to replace simple cases of OP_SASSIGN
and OP_AELEMFAST_LEX. (Similar concept to GH #19943)

For example, `my @ary; $ary[0] = "boo"` is currently implemented as:
    7     <2> sassign vKS/2 ->8
    5        <$> const[PV "boo"] s ->6
    -        <1> ex-aelem sKRM*/2 ->7
    6           <0> aelemfast_lex[@ary:1,2] sRM ->7
    -           <0> ex-const s ->-

But now will be turned into:
    6     <1> aelemfastlex_store[@ary:1,2] vKS ->7
    5        <$> const(PV "boo") s ->6
    -        <1> ex-aelem sKRM*/2 ->6
    -           <0> ex-aelemfast_lex sRM ->6
    -           <0> ex-const s ->-

This is intended to be a transparent performance optimization.
It should be applicable for RHS optrees of varying complexity.

1 files changed, 50 insertions, 0 deletions

diff --git a/pp_hot.c b/pp_hot.c
index cb76dda568..e64dbd093d 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -169,6 +169,56 @@ PP(pp_padsv_store)
     RETURN;
 }
 
+/* A mashup of simplified AELEMFAST_LEX + SASSIGN OPs */
+
+PP(pp_aelemfastlex_store)
+{
+    dSP;
+    OP * const op = PL_op;
+    SV* const val = TOPs; /* RHS value to assign */
+    AV * const av = MUTABLE_AV(PAD_SV(op->op_targ));
+    const I8 key   = (I8)PL_op->op_private;
+    SV * targ = NULL;
+
+    /* !OPf_STACKED is not handled by this OP */
+    assert(op->op_flags & OPf_STACKED);
+
+    /* Inlined, simplified pp_aelemfast here */
+    assert(SvTYPE(av) == SVt_PVAV);
+    assert(key >= 0);
+
+    /* inlined av_fetch() for simple cases ... */
+    if (!SvRMAGICAL(av) && key <= AvFILLp(av)) {
+        targ = AvARRAY(av)[key];
+    }
+    /* ... else do it the hard way */
+    if (!targ) {
+        SV **svp = av_fetch(av, key, 1);
+
+        if (svp)
+            targ = *svp;
+        else
+            DIE(aTHX_ PL_no_aelem, (int)key);
+    }
+
+    /* Inlined, simplified pp_sassign from here */
+    assert(TAINTING_get || !TAINT_get);
+    if (UNLIKELY(TAINT_get) && !SvTAINTED(val))
+        TAINT_NOT;
+
+    if (
+      UNLIKELY(SvTEMP(targ)) && !SvSMAGICAL(targ) && SvREFCNT(targ) == 1 &&
+      (!isGV_with_GP(targ) || SvFAKE(targ)) && ckWARN(WARN_MISC)
+    )
+        Perl_warner(aTHX_
+            packWARN(WARN_MISC), "Useless assignment to a temporary"
+        );
+    SvSetMagicSV(targ, val);
+
+    SETs(targ);
+    RETURN;
+}
+
 PP(pp_sassign)
 {
     dSP;