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Tip revision: 92d21ac74a9e3c09b0b01c764e530657e4c85c49 authored by Linus Torvalds on 11 July 2016, 03:24:59 UTC
Linux 4.7-rc7
Tip revision: 92d21ac
__ffs.h
#ifndef _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_
#define _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_

#include <asm/types.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)
{
	int num = 0;

#if __BITS_PER_LONG == 64
	if ((word & 0xffffffff) == 0) {
		num += 32;
		word >>= 32;
	}
#endif
	if ((word & 0xffff) == 0) {
		num += 16;
		word >>= 16;
	}
	if ((word & 0xff) == 0) {
		num += 8;
		word >>= 8;
	}
	if ((word & 0xf) == 0) {
		num += 4;
		word >>= 4;
	}
	if ((word & 0x3) == 0) {
		num += 2;
		word >>= 2;
	}
	if ((word & 0x1) == 0)
		num += 1;
	return num;
}

#endif /* _TOOLS_LINUX_ASM_GENERIC_BITOPS___FFS_H_ */
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