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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-09-13 11:14:53 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-09-13 11:14:53 -0700 |
| commit | 72d931046030beb2d13dad6d205be0e228618432 (patch) | |
| tree | 2a1f26ae904f9476b4269ff0d9a677580d0c8c9b /lib/hweight.c | |
| parent | 186cec317e87b85b296713426fa39eaa41ec6056 (diff) | |
| download | lwn-72d931046030beb2d13dad6d205be0e228618432.tar.gz lwn-72d931046030beb2d13dad6d205be0e228618432.zip | |
Make ARCH_HAS_FAST_MULTIPLIER a real config variable
It used to be an ad-hoc hack defined by the x86 version of
<asm/bitops.h> that enabled a couple of library routines to know whether
an integer multiply is faster than repeated shifts and additions.
This just makes it use the real Kconfig system instead, and makes x86
(which was the only architecture that did this) select the option.
NOTE! Even for x86, this really is kind of wrong. If we cared, we would
probably not enable this for builds optimized for netburst (P4), where
shifts-and-adds are generally faster than multiplies. This patch does
*not* change that kind of logic, though, it is purely a syntactic change
with no code changes.
This was triggered by the fact that we have other places that really
want to know "do I want to expand multiples by constants by hand or
not", particularly the hash generation code.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/hweight.c')
| -rw-r--r-- | lib/hweight.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/hweight.c b/lib/hweight.c index b7d81ba143d1..9a5c1f221558 100644 --- a/lib/hweight.c +++ b/lib/hweight.c @@ -11,7 +11,7 @@ unsigned int __sw_hweight32(unsigned int w) { -#ifdef ARCH_HAS_FAST_MULTIPLIER +#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER w -= (w >> 1) & 0x55555555; w = (w & 0x33333333) + ((w >> 2) & 0x33333333); w = (w + (w >> 4)) & 0x0f0f0f0f; @@ -49,7 +49,7 @@ unsigned long __sw_hweight64(__u64 w) return __sw_hweight32((unsigned int)(w >> 32)) + __sw_hweight32((unsigned int)w); #elif BITS_PER_LONG == 64 -#ifdef ARCH_HAS_FAST_MULTIPLIER +#ifdef CONFIG_ARCH_HAS_FAST_MULTIPLIER w -= (w >> 1) & 0x5555555555555555ul; w = (w & 0x3333333333333333ul) + ((w >> 2) & 0x3333333333333333ul); w = (w + (w >> 4)) & 0x0f0f0f0f0f0f0f0ful; |