diff options
Diffstat (limited to 'arch/x86/include/asm/bitops.h')
| -rw-r--r-- | arch/x86/include/asm/bitops.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index 2edf68475fec..50e5ebf9d0a0 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -293,6 +293,9 @@ static __always_inline unsigned long variable_ffz(unsigned long word) */ static __always_inline unsigned long __fls(unsigned long word) { + if (__builtin_constant_p(word)) + return BITS_PER_LONG - 1 - __builtin_clzl(word); + asm("bsr %1,%0" : "=r" (word) : "rm" (word)); @@ -360,6 +363,9 @@ static __always_inline int fls(unsigned int x) { int r; + if (__builtin_constant_p(x)) + return x ? 32 - __builtin_clz(x) : 0; + #ifdef CONFIG_X86_64 /* * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the @@ -401,6 +407,9 @@ static __always_inline int fls(unsigned int x) static __always_inline int fls64(__u64 x) { int bitpos = -1; + + if (__builtin_constant_p(x)) + return x ? 64 - __builtin_clzll(x) : 0; /* * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the * dest reg is undefined if x==0, but their CPU architect says its |