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linux
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>
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include/asm-generic/bitops/builtin-__ffs.h
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include/asm-generic/bitops/builtin-__ffs.h
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#ifndef _ASM_GENERIC_BITOPS_BUILTIN___FFS_H_
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#define _ASM_GENERIC_BITOPS_BUILTIN___FFS_H_
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/**
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* __ffs - find first bit in word.
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* @word: The word to search
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*
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* Undefined if no bit exists, so code should check against 0 first.
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*/
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static __always_inline unsigned long __ffs(unsigned long word)
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{
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return __builtin_ctzl(word);
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}
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#endif
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include/asm-generic/bitops/builtin-__fls.h
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include/asm-generic/bitops/builtin-__fls.h
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#ifndef _ASM_GENERIC_BITOPS_BUILTIN___FLS_H_
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#define _ASM_GENERIC_BITOPS_BUILTIN___FLS_H_
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/**
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* __fls - find last (most-significant) set bit in a long word
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* @word: the word to search
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*
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* Undefined if no set bit exists, so code should check against 0 first.
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*/
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static __always_inline unsigned long __fls(unsigned long word)
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{
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return (sizeof(word) * 8) - 1 - __builtin_clzl(word);
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}
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#endif
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include/asm-generic/bitops/builtin-ffs.h
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include/asm-generic/bitops/builtin-ffs.h
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#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_
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#define _ASM_GENERIC_BITOPS_BUILTIN_FFS_H_
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/**
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* ffs - find first bit set
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* @x: the word to search
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*
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* This is defined the same way as
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* the libc and compiler builtin ffs routines, therefore
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* differs in spirit from the above ffz (man ffs).
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*/
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static __always_inline int ffs(int x)
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{
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return __builtin_ffs(x);
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}
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#endif
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include/asm-generic/bitops/builtin-fls.h
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include/asm-generic/bitops/builtin-fls.h
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#ifndef _ASM_GENERIC_BITOPS_BUILTIN_FLS_H_
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#define _ASM_GENERIC_BITOPS_BUILTIN_FLS_H_
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/**
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* fls - find last (most-significant) bit set
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* @x: the word to search
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*
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* This is defined the same way as ffs.
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* Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
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*/
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static __always_inline int fls(int x)
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{
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return x ? sizeof(x) * 8 - __builtin_clz(x) : 0;
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}
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#endif