From d61931d89be506372d01a90d1755f6d0a9fafe2d Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Fri, 5 Mar 2010 17:34:46 +0100 Subject: x86: Add optimized popcnt variants 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 LKML-Reference: <20100318112015.GC11152@aftab> Signed-off-by: H. Peter Anvin --- lib/hweight.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'lib/hweight.c') diff --git a/lib/hweight.c b/lib/hweight.c index a6927e7..3c79d50 100644 --- a/lib/hweight.c +++ b/lib/hweight.c @@ -9,7 +9,7 @@ * The Hamming Weight of a number is the total number of bits set in it. */ -unsigned int __arch_hweight32(unsigned int w) +unsigned int __sw_hweight32(unsigned int w) { #ifdef ARCH_HAS_FAST_MULTIPLIER w -= (w >> 1) & 0x55555555; @@ -24,30 +24,30 @@ unsigned int __arch_hweight32(unsigned int w) return (res + (res >> 16)) & 0x000000FF; #endif } -EXPORT_SYMBOL(__arch_hweight32); +EXPORT_SYMBOL(__sw_hweight32); -unsigned int __arch_hweight16(unsigned int w) +unsigned int __sw_hweight16(unsigned int w) { unsigned int res = w - ((w >> 1) & 0x5555); res = (res & 0x3333) + ((res >> 2) & 0x3333); res = (res + (res >> 4)) & 0x0F0F; return (res + (res >> 8)) & 0x00FF; } -EXPORT_SYMBOL(__arch_hweight16); +EXPORT_SYMBOL(__sw_hweight16); -unsigned int __arch_hweight8(unsigned int w) +unsigned int __sw_hweight8(unsigned int w) { unsigned int res = w - ((w >> 1) & 0x55); res = (res & 0x33) + ((res >> 2) & 0x33); return (res + (res >> 4)) & 0x0F; } -EXPORT_SYMBOL(__arch_hweight8); +EXPORT_SYMBOL(__sw_hweight8); -unsigned long __arch_hweight64(__u64 w) +unsigned long __sw_hweight64(__u64 w) { #if BITS_PER_LONG == 32 - return __arch_hweight32((unsigned int)(w >> 32)) + - __arch_hweight32((unsigned int)w); + return __sw_hweight32((unsigned int)(w >> 32)) + + __sw_hweight32((unsigned int)w); #elif BITS_PER_LONG == 64 #ifdef ARCH_HAS_FAST_MULTIPLIER w -= (w >> 1) & 0x5555555555555555ul; @@ -64,4 +64,4 @@ unsigned long __arch_hweight64(__u64 w) #endif #endif } -EXPORT_SYMBOL(__arch_hweight64); +EXPORT_SYMBOL(__sw_hweight64); -- cgit v1.1