lib_generic memcpy: copy one word at a time if possible

If source and destination are aligned, this copies ulong values until possible, trailing part is copied by byte. Thanks for the details to Wolfgang Denk, Mike Frysinger, Peter Tyser, Chris Moore. Signed-off-by: Alessandro Rubini <rubini@unipv.it> Acked-by: Andrea Gallo <andrea.gallo@stericsson.com> Acked-by: Mike Frysinger <vapier@gentoo.org>

lib_generic memcpy: copy one word at a time if possible
If source and destination are aligned, this copies ulong values until possible, trailing part is copied by byte. Thanks for the details to Wolfgang Denk, Mike Frysinger, Peter Tyser, Chris Moore. Signed-off-by: Alessandro Rubini <rubini@unipv.it> Acked-by: Andrea Gallo <andrea.gallo@stericsson.com> Acked-by: Mike Frysinger <vapier@gentoo.org>
Alessandro Rubini · Wolfgang Denk
1 parent 9c5586aa19
Showing 1 changed file with 15 additions and 4 deletions Side-by-side Diff
lib_generic/string.c
@@ -446,12 +446,23 @@
  * You should not use this function to access IO space, use memcpy_toio()
  * or memcpy_fromio() instead.
  */
-void * memcpy(void * dest,const void *src,size_t count)
+void * memcpy(void *dest, const void *src, size_t count)
 {
-	char *tmp = (char *) dest, *s = (char *) src;
+	unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src;
+	char *d8, *s8;
  
+	/* while all data is aligned (common case), copy a word at a time */
+	if ( (((ulong)dest | (ulong)src) & (sizeof(*dl) - 1)) == 0) {
+		while (count >= sizeof(*dl)) {
+			*dl++ = *sl++;
+			count -= sizeof(*dl);
+		}
+	}
+	/* copy the reset one byte at a time */
+	d8 = (char *)dl;
+	s8 = (char *)sl;
 	while (count--)
-		*tmp++ = *s++;
+		*d8++ = *s8++;
  
 	return dest;
 }
...	...	@@ -446,12 +446,23 @@
446	446	* You should not use this function to access IO space, use memcpy_toio()
447	447	* or memcpy_fromio() instead.
448	448	*/
449		-void * memcpy(void * dest,const void *src,size_t count)
	449	+void * memcpy(void dest, const void src, size_t count)
450	450	{
451		- char tmp = (char ) dest, s = (char ) src;
	451	+ unsigned long dl = (unsigned long )dest, sl = (unsigned long )src;
	452	+ char d8, s8;
452	453
	454	+ /* while all data is aligned (common case), copy a word at a time */
	455	+ if ( (((ulong)dest \| (ulong)src) & (sizeof(*dl) - 1)) == 0) {
	456	+ while (count >= sizeof(*dl)) {
	457	+ dl++ = sl++;
	458	+ count -= sizeof(*dl);
	459	+ }
	460	+ }
	461	+ /* copy the reset one byte at a time */
	462	+ d8 = (char *)dl;
	463	+ s8 = (char *)sl;
453	464	while (count--)
454		- tmp++ = s++;
	465	+ d8++ = s8++;
455	466
456	467	return dest;
457	468	}