include/asm-generic/bitops/fls64.h

Source file repositories/reference/linux-study-clean/include/asm-generic/bitops/fls64.h

File Facts

System
Linux kernel
Corpus path
include/asm-generic/bitops/fls64.h
Extension
.h
Size
900 bytes
Lines
38
Domain
Repository Root And Misc
Bucket
include
Inferred role
Repository Root And Misc: implementation source
Status
source implementation candidate

Why This File Exists

Top-level or miscellaneous repository surface. Use this as map coverage unless a later manual pass promotes the file into a deeper subsystem dossier.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _ASM_GENERIC_BITOPS_FLS64_H_
#define _ASM_GENERIC_BITOPS_FLS64_H_

#include <asm/types.h>

/**
 * fls64 - find last set bit in a 64-bit word
 * @x: the word to search
 *
 * This is defined in a similar way as the libc and compiler builtin
 * ffsll, but returns the position of the most significant set bit.
 *
 * fls64(value) returns 0 if value is 0 or the position of the last
 * set bit if value is nonzero. The last (most significant) bit is
 * at position 64.
 */
#if BITS_PER_LONG == 32
static __always_inline __attribute_const__ int fls64(__u64 x)
{
	__u32 h = x >> 32;
	if (h)
		return fls(h) + 32;
	return fls(x);
}
#elif BITS_PER_LONG == 64
static __always_inline __attribute_const__ int fls64(__u64 x)
{
	if (x == 0)
		return 0;
	return __fls(x) + 1;
}
#else
#error BITS_PER_LONG not 32 or 64
#endif

#endif /* _ASM_GENERIC_BITOPS_FLS64_H_ */

Annotation

Implementation Notes