diff options
| author | Maciej W. Rozycki | 2015-04-03 23:25:00 +0100 |
|---|---|---|
| committer | Ralf Baechle | 2015-04-08 01:09:12 +0200 |
| commit | cb5d4aad6844cdbe2f3b9f5d581ae1c9ec342009 (patch) | |
| tree | 2a20f707e1c7711f773e05746e5d8342bc576137 /arch/mips | |
| parent | 2cfcf8a8313bd9bdb54d62ca4ea581f130869aca (diff) | |
MIPS: bitops.h: Avoid inline asm for constant FLS
GCC is smart enough to substitute the final result for FLS calculations
as implemented in the fallback C code we have in `__fls' and `fls'
applied to constant values. The presence of inline asm defeats the
compiler though, forcing it to emit extraneous CLZ/DCLZ calculation for
processors that support these instructions.
Use `__builtin_constant_p' then to avoid inline asm altogether for
constants.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9681/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/include/asm/bitops.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h index 9f935f6aa996..0cf29bd5dc5c 100644 --- a/arch/mips/include/asm/bitops.h +++ b/arch/mips/include/asm/bitops.h @@ -481,7 +481,7 @@ static inline unsigned long __fls(unsigned long word) { int num; - if (BITS_PER_LONG == 32 && + if (BITS_PER_LONG == 32 && !__builtin_constant_p(word) && __builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) { __asm__( " .set push \n" @@ -494,7 +494,7 @@ static inline unsigned long __fls(unsigned long word) return 31 - num; } - if (BITS_PER_LONG == 64 && + if (BITS_PER_LONG == 64 && !__builtin_constant_p(word) && __builtin_constant_p(cpu_has_mips64) && cpu_has_mips64) { __asm__( " .set push \n" @@ -559,7 +559,8 @@ static inline int fls(int x) { int r; - if (__builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) { + if (!__builtin_constant_p(x) && + __builtin_constant_p(cpu_has_clo_clz) && cpu_has_clo_clz) { __asm__( " .set push \n" " .set "MIPS_ISA_LEVEL" \n" |