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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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9
arch/x86/include/asm/alternative.h
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@@ -39,9 +39,6 @@
#define LOCK_PREFIX ""
#endif
/* This must be included *after* the definition of LOCK_PREFIX */
#include <asm/cpufeature.h>
struct alt_instr {
u8 *instr; /* original instruction */
u8 *replacement;
@@ -95,6 +92,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
"663:\n\t" newinstr "\n664:\n" /* replacement */ \
".previous"
/*
* This must be included *after* the definition of ALTERNATIVE due to
* <asm/arch_hweight.h>
*/
#include <asm/cpufeature.h>
/*
* Alternative instructions for different CPU types or capabilities.
*