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x86: Add optimized popcnt variants

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Add support for the hardware version of the Hamming weight function,
popcnt, present in CPUs which advertize it under CPUID, Function
0x0000_0001_ECX[23]. On CPUs which don't support it, we fallback to the
default lib/hweight.c sw versions.

A synthetic benchmark comparing popcnt with __sw_hweight64 showed almost
a 3x speedup on a F10h machine.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <20100318112015.GC11152@aftab>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Borislav Petkov
2010-03-05 17:34:46 +01:00
committed by H. Peter Anvin
parent 1527bc8b92
commit d61931d89b
8 changed files with 108 additions and 18 deletions
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4
arch/x86/include/asm/bitops.h
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@ -444,7 +444,9 @@ static inline int fls(int x)
#define ARCH_HAS_FAST_MULTIPLIER 1
#include <asm-generic/bitops/hweight.h>
#include <asm/arch_hweight.h>
#include <asm-generic/bitops/const_hweight.h>
#endif /* __KERNEL__ */