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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-02-28 10:35:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-02-28 10:35:09 -0800 |
| commit | a7f16d10b510f9ee3500af7831f2e3094fab3dca (patch) | |
| tree | bd2bff5e13083e1103205ff926342d6674f8e5c5 /lib | |
| parent | f66ffdedbf0fc059a92219bb08c1dbcac88f074b (diff) | |
| parent | 17c0e7107bed3d578864e6519f7f4e4c324c8f58 (diff) | |
| download | lwn-a7f16d10b510f9ee3500af7831f2e3094fab3dca.tar.gz lwn-a7f16d10b510f9ee3500af7831f2e3094fab3dca.zip | |
Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86: Mark atomic irq ops raw for 32bit legacy
x86: Merge show_regs()
x86: Macroise x86 cache descriptors
x86-32: clean up rwsem inline asm statements
x86: Merge asm/atomic_{32,64}.h
x86: Sync asm/atomic_32.h and asm/atomic_64.h
x86: Split atomic64_t functions into seperate headers
x86-64: Modify memcpy()/memset() alternatives mechanism
x86-64: Modify copy_user_generic() alternatives mechanism
x86: Lift restriction on the location of FIX_BTMAP_*
x86, core: Optimize hweight32()
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/hweight.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/hweight.c b/lib/hweight.c index 389424ecb129..63ee4eb1228d 100644 --- a/lib/hweight.c +++ b/lib/hweight.c @@ -11,11 +11,18 @@ unsigned int hweight32(unsigned int w) { +#ifdef ARCH_HAS_FAST_MULTIPLIER + w -= (w >> 1) & 0x55555555; + w = (w & 0x33333333) + ((w >> 2) & 0x33333333); + w = (w + (w >> 4)) & 0x0f0f0f0f; + return (w * 0x01010101) >> 24; +#else unsigned int res = w - ((w >> 1) & 0x55555555); res = (res & 0x33333333) + ((res >> 2) & 0x33333333); res = (res + (res >> 4)) & 0x0F0F0F0F; res = res + (res >> 8); return (res + (res >> 16)) & 0x000000FF; +#endif } EXPORT_SYMBOL(hweight32); |