redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

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 <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Alexey Dobriyan 2016-10-11 13:51:30 -07:00 committed by Linus Torvalds
parent bf90e56e46
commit 1204c77f9b
1 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/ctype.h
View File

@ -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)