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| author | Will Deacon <will.deacon@arm.com> | 2013-12-12 21:40:22 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-12-12 22:39:01 +0400 |
| commit | 11ec50caedb56e3a87715edeff6a1852e6ae5416 (patch) | |
| tree | a94b6a3d2456800197d67effa2677d426d00d31d /include | |
| parent | a5c21dcefa1c3d759457a604b3cfc4af29c8713f (diff) | |
| download | linux-11ec50caedb56e3a87715edeff6a1852e6ae5416.tar.xz | |
word-at-a-time: provide generic big-endian zero_bytemask implementation
Whilst architectures may be able to do better than this (which they can,
by simply defining their own macro), this is a generic stab at a
zero_bytemask implementation for the asm-generic, big-endian
word-at-a-time implementation.
On arm64, a clz instruction is used to implement the fls efficiently.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-generic/word-at-a-time.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/asm-generic/word-at-a-time.h b/include/asm-generic/word-at-a-time.h index 3f21f1b72e45..d3909effd725 100644 --- a/include/asm-generic/word-at-a-time.h +++ b/include/asm-generic/word-at-a-time.h @@ -49,4 +49,12 @@ static inline bool has_zero(unsigned long val, unsigned long *data, const struct return (val + c->high_bits) & ~rhs; } +#ifndef zero_bytemask +#ifdef CONFIG_64BIT +#define zero_bytemask(mask) (~0ul << fls64(mask)) +#else +#define zero_bytemask(mask) (~0ul << fls(mask)) +#endif /* CONFIG_64BIT */ +#endif /* zero_bytemask */ + #endif /* _ASM_WORD_AT_A_TIME_H */ |