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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2011-12-11 21:13:19 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-12 18:33:42 +0100 |
| commit | 890890cb8e415e1e7a61bfe3c8e246f710196824 (patch) | |
| tree | a4694f6470484ebac1d82ed317fa5ce5c198006e /arch/x86/lib | |
| parent | 79f1ddd06471b094ae30eb17b33beb9f1234ca93 (diff) | |
| download | linux-890890cb8e415e1e7a61bfe3c8e246f710196824.tar.gz | |
x86/i386: Use less assembly in strlen(), speed things up a bit
Current i386 strlen() hardcodes NOT/DEC sequence. DEC is mentioned to be suboptimal on Core2. So, put only REPNE SCASB sequence in assembly, compiler can do the rest. The difference in generated code is like below (MCORE2=y): <strlen>: push %edi mov $0xffffffff,%ecx mov %eax,%edi xor %eax,%eax repnz scas %es:(%edi),%al not %ecx - dec %ecx - mov %ecx,%eax + lea -0x1(%ecx),%eax pop %edi ret Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jan Beulich <JBeulich@suse.com> Link: http://lkml.kernel.org/r/20111211181319.GA17097@p183.telecom.by Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/string_32.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/arch/x86/lib/string_32.c b/arch/x86/lib/string_32.c index 82004d2bf05e..bd59090825db 100644 --- a/arch/x86/lib/string_32.c +++ b/arch/x86/lib/string_32.c @@ -164,15 +164,13 @@ EXPORT_SYMBOL(strchr); size_t strlen(const char *s) { int d0; - int res; + size_t res; asm volatile("repne\n\t" - "scasb\n\t" - "notl %0\n\t" - "decl %0" + "scasb" : "=c" (res), "=&D" (d0) : "1" (s), "a" (0), "0" (0xffffffffu) : "memory"); - return res; + return ~res - 1; } EXPORT_SYMBOL(strlen); #endif |