pp_unshift: av_store is often unnecessary

1 files changed, 24 insertions, 3 deletions

diff --git a/pp.c b/pp.c
index 4908cb5892..168b96d4f4 100644
--- a/pp.c
+++ b/pp.c
@@ -5859,10 +5859,31 @@ PP(pp_unshift)
 
         av_unshift(ary, SP - MARK);
         PL_delaymagic = DM_DELAY;
-        while (MARK < SP) {
-            SV * const sv = newSVsv(*++MARK);
-            (void)av_store(ary, i++, sv);
+
+        if (!SvMAGICAL(ary)) {
+            /* The av_unshift above means that many of the checks inside
+             * av_store are unnecessary. If ary does not have magic attached
+             * then a simple direct assignment is possible here. */
+            while (MARK < SP) {
+                SV * const sv = newSVsv(*++MARK);
+                assert( !SvTIED_mg((const SV *)ary, PERL_MAGIC_tied) );
+                assert( i >= 0 );
+                assert( !SvREADONLY(ary) );
+                assert( AvREAL(ary) || !AvREIFY(ary) );
+                assert( i <= AvMAX(ary) );
+                assert( i <= AvFILLp(ary) );
+                if (AvREAL(ary))
+                    SvREFCNT_dec(AvARRAY(ary)[i]);
+                AvARRAY(ary)[i] = sv;
+                i++;
+            }
+        } else {
+            while (MARK < SP) {
+                SV * const sv = newSVsv(*++MARK);
+                (void)av_store(ary, i++, sv);
+            }
         }
+
         if (PL_delaymagic & DM_ARRAY_ISA)
             mg_set(MUTABLE_SV(ary));
         PL_delaymagic = old_delaymagic;