From: Vincent Pit <perl@profvince.com>
Date: Thu, 27 Aug 2009 09:13:09 +0000 (+0200)
Subject: Speed up repeatcpy() by at least 40% for 1-char or numerous repeats
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=16fa5c119c4bda5c0396a5f81296bd1ccc128a9c;p=p5sagit%2Fp5-mst-13.2.git

Speed up repeatcpy() by at least 40% for 1-char or numerous repeats

And don't make it receive the interpreter anymore.

For 1-char repeats, use memset(). Otherwise, use the old implementation up
to some (small) length, and then use memcpy() in a binary manner, based on
what we previously copied.

Note that we use memcpy() so both strings shouldn't overlap. The previous
implementation didn't allow this as well. This would be a good place to use
the restrict keyword from C99. I'm not sure if Configure has a probe for it.
---

diff --git a/embed.fnc b/embed.fnc
index f2c7050..74cc604 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -860,7 +860,7 @@ EXp	|SV*|reg_qr_package|NN REGEXP * const rx
 
 : FIXME - why the E?
 Ep	|void	|regprop	|NULLOK const regexp *prog|NN SV* sv|NN const regnode* o
-Ap	|void	|repeatcpy	|NN char* to|NN const char* from|I32 len|I32 count
+Anp	|void	|repeatcpy	|NN char* to|NN const char* from|I32 len|I32 count
 AnpP	|char*	|rninstr	|NN const char* big|NN const char* bigend \
 				|NN const char* little|NN const char* lend
 Ap	|Sighandler_t|rsignal	|int i|Sighandler_t t
diff --git a/embed.h b/embed.h
index 921c63d..fa2561f 100644
--- a/embed.h
+++ b/embed.h
@@ -3076,7 +3076,7 @@
 #if defined(PERL_CORE) || defined(PERL_EXT)
 #define regprop(a,b,c)		Perl_regprop(aTHX_ a,b,c)
 #endif
-#define repeatcpy(a,b,c,d)	Perl_repeatcpy(aTHX_ a,b,c,d)
+#define repeatcpy		Perl_repeatcpy
 #define rninstr			Perl_rninstr
 #define rsignal(a,b)		Perl_rsignal(aTHX_ a,b)
 #ifdef PERL_CORE
diff --git a/proto.h b/proto.h
index cb04ab8..9734b14 100644
--- a/proto.h
+++ b/proto.h
@@ -2665,9 +2665,9 @@ PERL_CALLCONV void	Perl_regprop(pTHX_ const regexp *prog, SV* sv, const regnode*
 #define PERL_ARGS_ASSERT_REGPROP	\
 	assert(sv); assert(o)
 
-PERL_CALLCONV void	Perl_repeatcpy(pTHX_ char* to, const char* from, I32 len, I32 count)
-			__attribute__nonnull__(pTHX_1)
-			__attribute__nonnull__(pTHX_2);
+PERL_CALLCONV void	Perl_repeatcpy(char* to, const char* from, I32 len, I32 count)
+			__attribute__nonnull__(1)
+			__attribute__nonnull__(2);
 #define PERL_ARGS_ASSERT_REPEATCPY	\
 	assert(to); assert(from)
 
diff --git a/util.c b/util.c
index 3f43393..ae8c688 100644
--- a/util.c
+++ b/util.c
@@ -3026,26 +3026,36 @@ Perl_my_pclose(pTHX_ PerlIO *ptr)
 }
 #endif
 
+#define PERL_REPEATCPY_LINEAR 4
 void
-Perl_repeatcpy(pTHX_ register char *to, register const char *from, I32 len, register I32 count)
+Perl_repeatcpy(register char *to, register const char *from, I32 len, register I32 count)
 {
-    register I32 todo;
-    register const char * const frombase = from;
-    PERL_UNUSED_CONTEXT;
-
     PERL_ARGS_ASSERT_REPEATCPY;
 
-    if (len == 1) {
-	register const char c = *from;
-	while (count-- > 0)
-	    *to++ = c;
-	return;
-    }
-    while (count-- > 0) {
-	for (todo = len; todo > 0; todo--) {
-	    *to++ = *from++;
+    if (len == 1)
+	memset(to, *from, count);
+    else if (count) {
+	register char *p = to;
+	I32 items, linear, half;
+
+	linear = count < PERL_REPEATCPY_LINEAR ? count : PERL_REPEATCPY_LINEAR;
+	for (items = 0; items < linear; ++items) {
+	    register const char *q = from;
+	    I32 todo;
+	    for (todo = len; todo > 0; todo--)
+		*p++ = *q++;
+        }
+
+	half = count / 2;
+	while (items <= half) {
+	    I32 size = items * len;
+	    memcpy(p, to, size);
+	    p     += size;
+	    items *= 2;
 	}
-	from = frombase;
+
+	if (count > items)
+	    memcpy(p, to, (count - items) * len);
     }
 }