Using PL_sv_no in place of any !SvOK() maximum removes a little bit of

hot code in pp_iter.

p4raw-id: //depot/perl@33068

2 files changed, 11 insertions, 3 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index 67f450c252..1e4b1e9bf1 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -1922,7 +1922,15 @@ PP(pp_enteriter)
 	    else {
 		cx->blk_loop.lval_max_u.iterlval = newSVsv(sv);
 		(void) SvPV_force_nolen(cx->blk_loop.lval_max_u.iterlval);
+		/* This will do the upgrade to SVt_PV, and warn if the value
+		   is uninitialised.  */
 		(void) SvPV_nolen_const(right);
+		/* Doing this avoids a check every time in pp_iter in pp_hot.c
+		   to replace !SvOK() with a pointer to "".  */
+		if (!SvOK(right)) {
+		    SvREFCNT_dec(right);
+		    cx->blk_loop.ary_min_u.iterary = (AV*) &PL_sv_no;
+		}
 	    }
 	}
 	else if (PL_op->op_private & OPpITER_REVERSED) {
diff --git a/pp_hot.c b/pp_hot.c
index 4e55f2678b..4e28a12487 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1918,10 +1918,10 @@ PP(pp_iter)
 	if (CxTYPE(cx) != CXt_LOOP_LAZYIV) {
 	    /* string increment */
 	    register SV* cur = cx->blk_loop.lval_max_u.iterlval;
+	    /* If the maximum is !SvOK(), pp_enteriter substitutes PL_sv_no.
+	       It has SvPVX of "" and SvCUR of 0, which is what we want.  */
 	    STRLEN maxlen = 0;
-	    const char *max =
-	      SvOK((SV*)av) ?
-	      SvPV_const((SV*)av, maxlen) : (const char *)"";
+	    const char *max = SvPV_const((SV*)av, maxlen);
 	    if (!SvNIOK(cur) && SvCUR(cur) <= maxlen) {
 		if (SvREFCNT(*itersvp) == 1 && !SvMAGICAL(*itersvp)) {
 		    /* safe to reuse old SV */