From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: lib/kstrtox.c: use "unsigned int" more gcc does generates stupid code sign extending data back and forth. Help by using "unsigned int". add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-61 (-61) function old new delta _parse_integer 128 123 -5 It _still_ does generate useless MOVSX but I don't know how to delete it: 0000000000000070 <_parse_integer>: ... a0: 89 c2 mov edx,eax a2: 83 e8 30 sub eax,0x30 a5: 83 f8 09 cmp eax,0x9 a8: 76 11 jbe bb <_parse_integer+0x4b> aa: 83 ca 20 or edx,0x20 ad: 0f be c2 ===> movsx eax,dl <=== useless b0: 8d 50 9f lea edx,[rax-0x61] b3: 83 fa 05 cmp edx,0x5 Patch also helps on embedded archs which generally only like "int". On arm "and 0xff" is generated which is waste because all values used in comparisons are positive. Link: http://lkml.kernel.org/r/20170514194720.GB32563@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/kstrtox.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff -puN lib/kstrtox.c~kstrtox-use-unsigned-int-more lib/kstrtox.c --- a/lib/kstrtox.c~kstrtox-use-unsigned-int-more +++ a/lib/kstrtox.c @@ -52,12 +52,14 @@ unsigned int _parse_integer(const char * res = 0; rv = 0; while (1) { + unsigned int c = *s; + unsigned int lc = c | 0x20; /* don't tolower() this line */ unsigned int val; - if ('0' <= *s && *s <= '9') - val = *s - '0'; - else if ('a' <= _tolower(*s) && _tolower(*s) <= 'f') - val = _tolower(*s) - 'a' + 10; + if ('0' <= c && c <= '9') + val = c - '0'; + else if ('a' <= lc && lc <= 'f') + val = lc - 'a' + 10; else break; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
