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[PATCH] FRV: Optimise ffs()

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

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
David Howells 2006-09-25 23:32:09 -07:00 committed by Linus Torvalds
parent a8ad27d03f
commit cf134483b2
1 changed files with 31 additions and 2 deletions
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33
include/asm-frv/bitops.h
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@ -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>