From 1204c77f9b6ab8ba8cc6cfe00342f5e64a740cdf Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 11 Oct 2016 13:51:30 -0700 Subject: [PATCH] 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@p183.telecom.by Signed-off-by: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/ctype.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/ctype.h b/include/linux/ctype.h index 653589e3e30e..f13e4ff6835a 100644 --- a/include/linux/ctype.h +++ b/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) -- 2.39.5