In pp_subst, use a mortal scalar for dstr, instead of SAVEFREESV().

Creation of the mortal can be done with newSVpvn_flags(), saving 1 function
call. Also, the mortal stack uses 1 pointer, whereas the save stack will use 2.
It doesn't matter that dstr is now marked SVs_TEMP, as both code paths already
gut it, stealing its SvPVX(). The SV head will happen to last a bit longer now,
to the next FREETMPS, instead of the the scope pop at the end of pp_subst or
pp_substcont.

1 files changed, 1 insertions, 2 deletions

diff --git a/pp_hot.c b/pp_hot.c
index b2970d88c6..1b1117e05f 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2437,8 +2437,7 @@ PP(pp_subst)
 #endif
 	if (RX_MATCH_TAINTED(rx)) /* run time pattern taint, eg locale */
 	    rxtainted |= SUBST_TAINT_PAT;
-	dstr = newSVpvn_utf8(m, s-m, DO_UTF8(TARG));
-	SAVEFREESV(dstr);
+	dstr = newSVpvn_flags(m, s-m, SVs_TEMP | (DO_UTF8(TARG) ? SVf_UTF8 : 0));
 	PL_curpm = pm;
 	if (!c) {
 	    register PERL_CONTEXT *cx;