diff options
| author | David Howells <dhowells@redhat.com> | 2006-09-25 23:32:09 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-26 08:48:54 -0700 |
| commit | cf134483b2cd657039b305777215c531a1009947 (patch) | |
| tree | 2dad894d6e916bcf785611ded852151bbea5063b | |
| parent | a8ad27d03f17e6154c61e81d4a7028c56ca6390d (diff) | |
| download | linux-3.10-cf134483b2cd657039b305777215c531a1009947.tar.gz linux-3.10-cf134483b2cd657039b305777215c531a1009947.tar.bz2 linux-3.10-cf134483b2cd657039b305777215c531a1009947.zip | |
[PATCH] FRV: Optimise ffs()
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>
| -rw-r--r-- | include/asm-frv/bitops.h | 33 |
1 files changed, 31 insertions, 2 deletions
diff --git a/include/asm-frv/bitops.h b/include/asm-frv/bitops.h index 591eecc1f8c..1f70d47148b 100644 --- a/include/asm-frv/bitops.h +++ b/include/asm-frv/bitops.h @@ -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> |