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| author |   Peter Zijlstra <peterz@infradead.org> | 2013-11-18 18:27:06 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2013-12-11 15:52:34 +0100 |
| commit | be5e610c0fd6ef772cafb9e0bd4128134804aef3 (patch) | |
| tree | 4cc4da2eea52c51ce868944aba28edf171a2d871 /include/linux | |
| parent | sched: Remove PREEMPT_NEED_RESCHED from generic code (diff) | |
| download | linux-dev-be5e610c0fd6ef772cafb9e0bd4128134804aef3.tar.xz linux-dev-be5e610c0fd6ef772cafb9e0bd4128134804aef3.zip | |
math64: Add mul_u64_u32_shr()
Introduce mul_u64_u32_shr() as proposed by Andy a while back; it
allows using 64x64->128 muls on 64bit archs and recent GCC
which defines __SIZEOF_INT128__ and __int128.
(This new method will be used by the scheduler.)
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: fweisbec@gmail.com
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-hxjoeuzmrcaumR0uZwjpe2pv@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/math64.h | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/include/linux/math64.h b/include/linux/math64.h index 69ed5f5e9f6e..c45c089bfdac 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -133,4 +133,34 @@ __iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) return ret; } +#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__) + +#ifndef mul_u64_u32_shr +static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) +{ + return (u64)(((unsigned __int128)a * mul) >> shift); +} +#endif /* mul_u64_u32_shr */ + +#else + +#ifndef mul_u64_u32_shr +static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift) +{ + u32 ah, al; + u64 ret; + + al = a; + ah = a >> 32; + + ret = ((u64)al * mul) >> shift; + if (ah) + ret += ((u64)ah * mul) << (32 - shift); + + return ret; +} +#endif /* mul_u64_u32_shr */ + +#endif + #endif /* _LINUX_MATH64_H */ |