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Commit d832245d authored by Stephen Hemminger's avatar Stephen Hemminger Committed by Linus Torvalds
Browse files

[PATCH] x86: fls() in asm 



There is a single instruction on i386 to find largest set bit; so it makes
sense to use it (like we use bfs for ffs()).

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e31b88ba

include/asm-i386/bitops.h

+17 −5
Original line number Diff line number Diff line
@@ -367,11 +367,6 @@ static inline unsigned long ffz(unsigned long word) 
	return word;

}



/*

 * fls: find last bit set.

 */



#define fls(x) generic_fls(x)

#define fls64(x)   generic_fls64(x)



#ifdef __KERNEL__
@@ -414,6 +409,23 @@ static inline int ffs(int x) 
	return r+1;

}



/**

 * fls - find last bit set

 * @x: the word to search

 *

 * This is defined the same way as ffs.

 */

static inline int fls(int x)

{

	int r;



	__asm__("bsrl %1,%0\n\t"

		"jnz 1f\n\t"

		"movl $-1,%0\n"

		"1:" : "=r" (r) : "rm" (x));

	return r+1;

}



/**

 * hweightN - returns the hamming weight of a N-bit word

 * @x: the word to weigh