[PATCH] drivers/video/fbdev/sis/sis_main.c: avoid repeated strlen() calls

[PATCH] drivers/video/fbdev/sis/sis_main.c: avoid repeated strlen() calls

[Rasmus Villemoes]

gcc is not smart enough to realize that strlen(strbuf1) cannot be
changed by the loop body, so it is forced to recompute it, at least in
the branch containing the assignment. Avoid this by using an
equivalent stopping condition.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/video/fbdev/sis/sis_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/sis/sis_main.c b/drivers/video/fbdev/sis/sis_main.c
index fcf610edf217..ea95f8bf3922 100644
--- a/drivers/video/fbdev/sis/sis_main.c
+++ b/drivers/video/fbdev/sis/sis_main.c
@@ -172,7 +172,7 @@ static void sisfb_search_mode(char *name, bool quiet)
 
 	if(strlen(name) <= 19) {
 		strcpy(strbuf1, name);
-		for(i = 0; i < strlen(strbuf1); i++) {
+		for(i = 0; strbuf1[i]; i++) {
 			if(strbuf1[i] < '0' || strbuf1[i] > '9') strbuf1[i] = ' ';
 		}
 
-- 
2.1.3

[PATCH] drivers/video/fbdev/sis/sis_main.c: avoid repeated strlen() calls

[Rasmus Villemoes]

gcc is not smart enough to realize that strlen(strbuf1) cannot be
changed by the loop body, so it is forced to recompute it, at least in
the branch containing the assignment. Avoid this by using an
equivalent stopping condition.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/video/fbdev/sis/sis_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/sis/sis_main.c b/drivers/video/fbdev/sis/sis_main.c
index fcf610edf217..ea95f8bf3922 100644
--- a/drivers/video/fbdev/sis/sis_main.c
+++ b/drivers/video/fbdev/sis/sis_main.c
@@ -172,7 +172,7 @@ static void sisfb_search_mode(char *name, bool quiet)
 
 	if(strlen(name) <= 19) {
 		strcpy(strbuf1, name);
-		for(i = 0; i < strlen(strbuf1); i++) {
+		for(i = 0; strbuf1[i]; i++) {
 			if(strbuf1[i] < '0' || strbuf1[i] > '9') strbuf1[i] = ' ';
 		}
 
-- 
2.1.3

Re: [PATCH] drivers/video/fbdev/sis/sis_main.c: avoid repeated strlen() calls

[Tomi Valkeinen]

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On 09/06/15 16:04, Rasmus Villemoes wrote:
> gcc is not smart enough to realize that strlen(strbuf1) cannot be
> changed by the loop body, so it is forced to recompute it, at least in
> the branch containing the assignment. Avoid this by using an
> equivalent stopping condition.

Does it matter? Is sisfb calling sisfb_search_mode thousands of times?

 Tomi


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Re: [PATCH] drivers/video/fbdev/sis/sis_main.c: avoid repeated strlen() calls

[Tomi Valkeinen]

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On 09/06/15 16:04, Rasmus Villemoes wrote:
> gcc is not smart enough to realize that strlen(strbuf1) cannot be
> changed by the loop body, so it is forced to recompute it, at least in
> the branch containing the assignment. Avoid this by using an
> equivalent stopping condition.

Does it matter? Is sisfb calling sisfb_search_mode thousands of times?

 Tomi


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