From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: include/linux/ctype.h: make isdigit() table lookupless Make isdigit into a simple range checking inline function: return '0' <= c && c <= '9'; This code is 1 branch, not 2 because any reasonable compiler can optimize this code into SUB+CMP, so the code while (isdigit((c = *s++))) ... remains 1 branch per iteration HOWEVER it suddenly doesn't do table lookup priming cacheline nobody cares about. Link: http://lkml.kernel.org/r/20160826190047.GA12536@xxxxxxxxxxxxxxx Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/ctype.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff -puN include/linux/ctype.h~make-isdigit-table-lookupless include/linux/ctype.h --- a/include/linux/ctype.h~make-isdigit-table-lookupless +++ a/include/linux/ctype.h @@ -22,7 +22,10 @@ extern const unsigned char _ctype[]; #define isalnum(c) ((__ismask(c)&(_U|_L|_D)) != 0) #define isalpha(c) ((__ismask(c)&(_U|_L)) != 0) #define iscntrl(c) ((__ismask(c)&(_C)) != 0) -#define isdigit(c) ((__ismask(c)&(_D)) != 0) +static inline int isdigit(int c) +{ + return '0' <= c && c <= '9'; +} #define isgraph(c) ((__ismask(c)&(_P|_U|_L|_D)) != 0) #define islower(c) ((__ismask(c)&(_L)) != 0) #define isprint(c) ((__ismask(c)&(_P|_U|_L|_D|_SP)) != 0) _ -- 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
