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bitops: Ensure the compile time HWEIGHT is only used for such

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Avoid accidental misuse by failing to compile things

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-01-29 13:25:12 +01:00 • committed by Ingo Molnar
parent 8c48e44419
commit fce877e3a4
2 changed files with 29 additions and 14 deletions
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33
include/linux/bitops.h
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@ -45,19 +45,30 @@ static inline unsigned long hweight_long(unsigned long w)
return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
}
#define HWEIGHT8(w) \
( (!!((w) & (1ULL << 0))) + \
(!!((w) & (1ULL << 1))) + \
(!!((w) & (1ULL << 2))) + \
(!!((w) & (1ULL << 3))) + \
(!!((w) & (1ULL << 4))) + \
(!!((w) & (1ULL << 5))) + \
(!!((w) & (1ULL << 6))) + \
/*
* Clearly slow versions of the hweightN() functions, their benefit is
* of course compile time evaluation of constant arguments.
*/
#define HWEIGHT8(w) \
( BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) + \
(!!((w) & (1ULL << 0))) + \
(!!((w) & (1ULL << 1))) + \
(!!((w) & (1ULL << 2))) + \
(!!((w) & (1ULL << 3))) + \
(!!((w) & (1ULL << 4))) + \
(!!((w) & (1ULL << 5))) + \
(!!((w) & (1ULL << 6))) + \
(!!((w) & (1ULL << 7))) )
#define HWEIGHT16(w) (HWEIGHT8(w) + HWEIGHT8(w >> 8))
#define HWEIGHT32(w) (HWEIGHT16(w) + HWEIGHT16(w >> 16))
#define HWEIGHT64(w) (HWEIGHT32(w) + HWEIGHT32(w >> 32))
#define HWEIGHT16(w) (HWEIGHT8(w) + HWEIGHT8((w) >> 8))
#define HWEIGHT32(w) (HWEIGHT16(w) + HWEIGHT16((w) >> 16))
#define HWEIGHT64(w) (HWEIGHT32(w) + HWEIGHT32((w) >> 32))
/*
* Type invariant version that simply casts things to the
* largest type.
*/
#define HWEIGHT(w) HWEIGHT64((u64)(w))
/**
* rol32 - rotate a 32-bit value left