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Commit 048fa2df authored by Catalin Marinas's avatar Catalin Marinas
Browse files

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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarArnd 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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#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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#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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#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