add intuit-only match to s///

pp_match() has an intuit-only match mode: if intuit_start() succeeds and
the regex is marked as only needing intuit (RXf_CHECK_ALL), then calling
regexec() is skipped, and just $& set and then returns.

The commit which originally added that feature to pp_match() also added a
comment to pp_subst() suggesting that the same thing could be done there.

This commit finally achieves that. It builds on the previous commit (which
moved this mechanism from pp_match() directly into regexec()), skipping
calling intuit_start() and directly calling regexec() with the
REXEC_CHECKED flag not set.

This appears to reduce the execution time of a simple substitution
like s/abc/def/ by a fifth.

1 files changed, 2 insertions, 15 deletions

diff --git a/pp_hot.c b/pp_hot.c
index ddb0acd2f8..e0a543c8ef 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2132,28 +2132,15 @@ PP(pp_subst)
 #endif
 
     orig = m = s;
-    if (RX_EXTFLAGS(rx) & RXf_USE_INTUIT) {
-	s = CALLREG_INTUIT_START(rx, TARG, orig, s, strend, r_flags, NULL);
-
-	if (!s)
-	    goto ret_no;
-	/* How to do it in subst? */
-/*	if ( (RX_EXTFLAGS(rx) & RXf_CHECK_ALL)
-	     && !PL_sawampersand
-	     && !(RX_EXTFLAGS(rx) & RXf_KEEPCOPY))
-	    goto yup;
-*/
-    }
 
-    if (!CALLREGEXEC(rx, s, strend, orig, 0, TARG, NULL,
-			 r_flags | REXEC_CHECKED))
+    if (!CALLREGEXEC(rx, s, strend, orig, 0, TARG, NULL, r_flags))
     {
-      ret_no:
 	SPAGAIN;
 	PUSHs(rpm->op_pmflags & PMf_NONDESTRUCT ? TARG : &PL_sv_no);
 	LEAVE_SCOPE(oldsave);
 	RETURN;
     }
+    s = RX_OFFS(rx)[0].start + orig;
 
     PL_curpm = pm;