Commit be5f3c77 authored Jul 10, 2017 by Alexey Dobriyan Committed by Linus Torvalds Jul 10, 2017

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@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 512750ef

lib/kstrtox.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -52,12 +52,14 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
		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;

Admin message