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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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22
include/asm-generic/bitops/arch_hweight.h
View file

@ -3,9 +3,23 @@
#include <asm/types.h>
extern unsigned int __arch_hweight32(unsigned int w);
extern unsigned int __arch_hweight16(unsigned int w);
extern unsigned int __arch_hweight8(unsigned int w);
extern unsigned long __arch_hweight64(__u64 w);
inline unsigned int __arch_hweight32(unsigned int w)
{
return __sw_hweight32(w);
}
inline unsigned int __arch_hweight16(unsigned int w)
{
return __sw_hweight16(w);
}
inline unsigned int __arch_hweight8(unsigned int w)
{
return __sw_hweight8(w);
}
inline unsigned long __arch_hweight64(__u64 w)
{
return __sw_hweight64(w);
}
#endif /* _ASM_GENERIC_BITOPS_HWEIGHT_H_ */