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Commit cf134483 authored by David Howells's avatar David Howells Committed by Linus Torvalds
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[PATCH] FRV: Optimise ffs() 



Optimise ffs(x) by using fls(x & x - 1) which we optimise to use the SCAN
instruction.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent a8ad27d0

include/asm-frv/bitops.h

+31 −2
Original line number Diff line number Diff line
@@ -157,8 +157,6 @@ static inline int __test_bit(int nr, const volatile void * addr) 
 __constant_test_bit((nr),(addr)) : \

 __test_bit((nr),(addr)))



#include <asm-generic/bitops/ffs.h>

#include <asm-generic/bitops/__ffs.h>

#include <asm-generic/bitops/find.h>



/**
@@ -227,6 +225,37 @@ int fls64(u64 n) 


}



/**

 * ffs - find first bit set

 * @x: the word to search

 *

 * - return 32..1 to indicate bit 31..0 most least significant bit set

 * - return 0 to indicate no bits set

 */

static inline __attribute__((const))

int ffs(int x)

{

	/* Note: (x & -x) gives us a mask that is the least significant

	 * (rightmost) 1-bit of the value in x.

	 */

	return fls(x & -x);

}



/**

 * __ffs - find first bit set

 * @x: the word to search

 *

 * - return 31..0 to indicate bit 31..0 most least significant bit set

 * - if no bits are set in x, the result is undefined

 */

static inline __attribute__((const))

int __ffs(unsigned long x)

{

	int bit;

	asm("scan %1,gr0,%0" : "=r"(bit) : "r"(x & -x));

	return 31 - bit;

}



#include <asm-generic/bitops/sched.h>

#include <asm-generic/bitops/hweight.h>