Use sv_catpvn instead of sv_catsv in doop.c:do_join

Bunchmarking shows that SvPV+sv_catpvn is faster that sv_catsv.  Why
exactly I don’t know, but perhaps fewer functions and flag checks
are the cause.

1 files changed, 11 insertions, 2 deletions

diff --git a/doop.c b/doop.c
index 3b6f1e752a..007ff5e2e3 100644
--- a/doop.c
+++ b/doop.c
@@ -709,13 +709,22 @@ Perl_do_join(pTHX_ SV *sv, SV *delim, SV **mark, SV **sp)
 
     if (delimlen) {
 	for (; items > 0; items--,mark++) {
+	    STRLEN len;
+	    const char *s;
 	    sv_catsv_nomg(sv,delim);
-	    sv_catsv(sv,*mark);
+	    s = SvPV_const(*mark,len);
+	    sv_catpvn_flags(sv,s,len,
+			    DO_UTF8(*mark) ? SV_CATUTF8 : SV_CATBYTES);
 	}
     }
     else {
 	for (; items > 0; items--,mark++)
-	    sv_catsv(sv,*mark);
+	{
+	    STRLEN len;
+	    const char *s = SvPV_const(*mark,len);
+	    sv_catpvn_flags(sv,s,len,
+			    DO_UTF8(*mark) ? SV_CATUTF8 : SV_CATBYTES);
+	}
     }
     SvSETMAGIC(sv);
 }