[patch 010/102] include/linux/ctype.h: make isdigit() table lookupless

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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)
_
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