Messages in this thread Patch in this message | | | Date | Thu, 26 Jan 2006 12:32:36 +0900 | Subject | [PATCH 4/12] generic fls() and fls64() | From | (Akinobu Mita) |
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This patch introduces the C-language equivalent of the function: int fls(int x); int fls64(__u64 x);
HAVE_ARCH_FLS_BITOPS is defined when the architecture has its own fls(). HAVE_ARCH_FLS64_BITOPS is defined when the architecture has its own fls64()
This code largely copied from: include/linux/bitops.h
Index: 2.6-git/include/asm-generic/bitops.h =================================================================== --- 2.6-git.orig/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900 +++ 2.6-git/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900 @@ -237,12 +237,54 @@ #endif /* HAVE_ARCH_FFZ_BITOPS */ +#ifndef HAVE_ARCH_FLS_BITOPS + /* * fls: find last bit set. */ -#define fls(x) generic_fls(x) -#define fls64(x) generic_fls64(x) +static __inline__ int fls(int x) +{ + int r = 32; + + if (!x) + return 0; + if (!(x & 0xffff0000u)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xff000000u)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xf0000000u)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xc0000000u)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x80000000u)) { + x <<= 1; + r -= 1; + } + return r; +} + +#endif /* HAVE_ARCH_FLS_BITOPS */ + +#ifndef HAVE_ARCH_FLS64_BITOPS + +static inline int fls64(__u64 x) +{ + __u32 h = x >> 32; + if (h) + return fls(x) + 32; + return fls(x); +} + +#endif /* HAVE_ARCH_FLS64_BITOPS */ #ifdef __KERNEL__ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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