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| author | Stephen Hemminger <shemminger@osdl.org> | 2006-01-11 22:43:24 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-11 19:04:50 -0800 |
| commit | 636dd2b7def5c9c72551b51d4d516a65c269de08 (patch) | |
| tree | 8a3c1ec030fc0924a96e54c0ec19d94f17ecc44e | |
| parent | bd9cb64df1d99c07ea9672661ede6ca3ba5c6579 (diff) | |
| download | linux-636dd2b7def5c9c72551b51d4d516a65c269de08.tar.gz | |
[PATCH] x86_64: fls in asm for x86_64
Use single instruction for find largest set bit on x86_64.
[Updated by Jan Beulich to fix wrong asm constraints in original
patch -AK]
Cc: jbeulich@novell.com
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | include/asm-x86_64/bitops.h | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/include/asm-x86_64/bitops.h b/include/asm-x86_64/bitops.h index 3638ffff87fd7a..eb4df23e1e411c 100644 --- a/include/asm-x86_64/bitops.h +++ b/include/asm-x86_64/bitops.h @@ -397,6 +397,22 @@ static __inline__ int fls64(__u64 x) } /** + * 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" + "cmovzl %2,%0" + : "=&r" (r) : "rm" (x), "rm" (-1)); + return r+1; +} + +/** * hweightN - returns the hamming weight of a N-bit word * @x: the word to weigh * @@ -434,9 +450,6 @@ static __inline__ int fls64(__u64 x) #define minix_find_first_zero_bit(addr,size) \ find_first_zero_bit((void*)addr,size) -/* find last set bit */ -#define fls(x) generic_fls(x) - #endif /* __KERNEL__ */ #endif /* _X86_64_BITOPS_H */ |