don't copy foreach itervar when no external refs exist

	Message-ID: <m33ec3nbfm.fsf@furu.g.aas.no>
	Subject: Re: Testcase for 1..n closure change

p4raw-id: //depot/perl@1508

diff --git a/pp_hot.c b/pp_hot.c
index c721680..4fe40cc 100644 (file)
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1457,11 +1457,20 @@ PP(pp_iter)
            STRLEN maxlen;
            char *max = SvPV((SV*)av, maxlen);
            if (!SvNIOK(cur) && SvCUR(cur) <= maxlen) {
-               /* we need a fresh SV every time so that loop body sees a
-                * completely new SV for closures/references to work as they
-                * used to */
-               SvREFCNT_dec(*cx->blk_loop.itervar);
-               *cx->blk_loop.itervar = newSVsv(cur);
+#ifndef USE_THREADS                      /* don't risk potential race */
+               if (SvREFCNT(*cx->blk_loop.itervar) == 1) {
+                   /* safe to reuse old SV */
+                   sv_setsv(*cx->blk_loop.itervar, cur);
+               }
+               else 
+#endif
+               {
+                   /* we need a fresh SV every time so that loop body sees a
+                    * completely new SV for closures/references to work as
+                    * they used to */
+                   SvREFCNT_dec(*cx->blk_loop.itervar);
+                   *cx->blk_loop.itervar = newSVsv(cur);
+               }
                if (strEQ(SvPVX(cur), max))
                    sv_setiv(cur, 0); /* terminate next time */
                else
@@ -1474,11 +1483,20 @@ PP(pp_iter)
        if (cx->blk_loop.iterix > cx->blk_loop.itermax)
            RETPUSHNO;
 
-       /* we need a fresh SV every time so that loop body sees a
-        * completely new SV for closures/references to work as they
-        * used to */
-       SvREFCNT_dec(*cx->blk_loop.itervar);
-       *cx->blk_loop.itervar = newSViv(cx->blk_loop.iterix++);
+#ifndef USE_THREADS                      /* don't risk potential race */
+       if (SvREFCNT(*cx->blk_loop.itervar) == 1) {
+           /* safe to reuse old SV */
+           sv_setiv(*cx->blk_loop.itervar, cx->blk_loop.iterix++);
+       }
+       else 
+#endif
+       {
+           /* we need a fresh SV every time so that loop body sees a
+            * completely new SV for closures/references to work as they
+            * used to */
+           SvREFCNT_dec(*cx->blk_loop.itervar);
+           *cx->blk_loop.itervar = newSViv(cx->blk_loop.iterix++);
+       }
        RETPUSHYES;
     }