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| author | Alexander van Heukelum <heukelum@mailshack.com> | 2008-03-15 18:30:57 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-04-26 19:21:16 +0200 |
| commit | 7d9dff22e8ad06ad330968c9e3d3a2fb55a5f9c3 (patch) | |
| tree | 1c65cd4cdf14f42d59e72514991c4b04278db8d5 /include | |
| parent | x86: merge the simple bitops and move them to bitops.h (diff) | |
| download | linux-7d9dff22e8ad06ad330968c9e3d3a2fb55a5f9c3.tar.xz linux-7d9dff22e8ad06ad330968c9e3d3a2fb55a5f9c3.zip | |
generic: introduce a generic __fls implementation
Add a generic __fls implementation in the same spirit as
the generic __ffs one. It finds the last (most significant)
set bit in the given long value.
Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-generic/bitops/__fls.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/__fls.h b/include/asm-generic/bitops/__fls.h new file mode 100644 index 000000000000..be24465403d6 --- /dev/null +++ b/include/asm-generic/bitops/__fls.h @@ -0,0 +1,43 @@ +#ifndef _ASM_GENERIC_BITOPS___FLS_H_ +#define _ASM_GENERIC_BITOPS___FLS_H_ + +#include <asm/types.h> + +/** + * __fls - find last (most-significant) set bit in a long word + * @word: the word to search + * + * Undefined if no set bit exists, so code should check against 0 first. + */ +static inline unsigned long __fls(unsigned long word) +{ + int num = BITS_PER_LONG - 1; + +#if BITS_PER_LONG == 64 + if (!(word & (~0ul << 32))) { + num -= 32; + word <<= 32; + } +#endif + if (!(word & (~0ul << (BITS_PER_LONG-16)))) { + num -= 16; + word <<= 16; + } + if (!(word & (~0ul << (BITS_PER_LONG-8)))) { + num -= 8; + word <<= 8; + } + if (!(word & (~0ul << (BITS_PER_LONG-4)))) { + num -= 4; + word <<= 4; + } + if (!(word & (~0ul << (BITS_PER_LONG-2)))) { + num -= 2; + word <<= 2; + } + if (!(word & (~0ul << (BITS_PER_LONG-1)))) + num -= 1; + return num; +} + +#endif /* _ASM_GENERIC_BITOPS___FLS_H_ */ |