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authorH. Peter Anvin <hpa@linux.intel.com>2010-05-17 15:13:23 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2010-05-17 15:17:16 -0700
commitc59bd5688299cddb71183e156e7a3c1409b90df2 (patch)
treed7b99407367b30aa7766219083ad0262c8edbab8 /include/asm-generic/bitops/const_hweight.h
parent4677d4a53e0d565742277e8913e91c821453e63e (diff)
downloadlinux-2.6.34-ux500-c59bd5688299cddb71183e156e7a3c1409b90df2.tar.gz
x86, hweight: Use a 32-bit popcnt for __arch_hweight32()
Use a 32-bit popcnt instruction for __arch_hweight32(), even on x86-64. Even though the input register will *usually* be zero-extended due to the standard operation of the hardware, it isn't necessarily so if the input value was the result of truncating a 64-bit operation. Note: the POPCNT32 variant used on x86-64 has a technically unnecessary REX prefix to make it five bytes long, the same as a CALL instruction, therefore avoiding an unnecessary NOP. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: Borislav Petkov <borislav.petkov@amd.com> LKML-Reference: <alpine.LFD.2.00.1005171443060.4195@i5.linux-foundation.org>
Diffstat (limited to 'include/asm-generic/bitops/const_hweight.h')
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