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Commit 048fa2df authored Sep 12, 2012 by Catalin Marinas

generic: Implement generic ffs/fls using __builtin_* functions



This patch implements ffs, __ffs, fls, __fls using __builtin_* gcc
functions. These header files can be used by other architectures that
rely on the gcc builtins.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

parent 0753f70f

include/asm-generic/bitops/builtin-__ffs.h

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		#ifndef _ASM_GENERIC_BITOPS_BUILTIN___FFS_H_
		#define _ASM_GENERIC_BITOPS_BUILTIN___FFS_H_

		/**
		* __ffs - find first bit in word.
		* @word: The word to search
		*
		* Undefined if no bit exists, so code should check against 0 first.
		*/
		static __always_inline unsigned long __ffs(unsigned long word)
		{
		return __builtin_ctzl(word);
		}

		#endif

include/asm-generic/bitops/builtin-__fls.h

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Original line number	Diff line number	Diff line
		#ifndef _ASM_GENERIC_BITOPS_BUILTIN___FLS_H_
		#define _ASM_GENERIC_BITOPS_BUILTIN___FLS_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 __always_inline unsigned long __fls(unsigned long word)
		{
		return (sizeof(word) * 8) - 1 - __builtin_clzl(word);
		}

		#endif

include/asm-generic/bitops/builtin-ffs.h

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Original line number	Diff line number	Diff line
		#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_
		#define _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_

		/**
		* ffs - find first bit set
		* @x: the word to search
		*
		* This is defined the same way as
		* the libc and compiler builtin ffs routines, therefore
		* differs in spirit from the above ffz (man ffs).
		*/
		static __always_inline int ffs(int x)
		{
		return __builtin_ffs(x);
		}

		#endif

include/asm-generic/bitops/builtin-fls.h

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Original line number	Diff line number	Diff line
		#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FLS_H_
		#define _ASM_GENERIC_BITOPS_BUILTIN_FLS_H_

		/**
		* fls - find last (most-significant) bit set
		* @x: the word to search
		*
		* This is defined the same way as ffs.
		* Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
		*/
		static __always_inline int fls(int x)
		{
		return x ? sizeof(x) * 8 - __builtin_clz(x) : 0;
		}

		#endif