sys/lib/libkern/arch/amd64/ffs.S


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/*
 * Written by J.T. Conklin <jtc@netbsd.org>.
 * Public domain.
 * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
 */

#include <machine/asm.h>

ENTRY(ffs)
	bsfl	%edi,%eax
	jz	L1	 		/* ZF is set if all bits are 0 */
	incl	%eax			/* bits numbered from 1, not 0 */
	ret

	_ALIGN_TEXT
L1:	xorl	%eax,%eax		/* clear result */
	ret