/* Compare two memory blocks for differences in the first COUNT bytes.

   Copyright (C) 1995-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include "asm-syntax.h"

#define PARMS	4+4	/* space for 1 saved reg */

#define BLK1	PARMS

#define BLK2	BLK1+4

#define LEN	BLK2+4

	.text

ENTRY (memcmp)

	pushl %esi		/* Save callee-safe registers.  */

	cfi_adjust_cfa_offset (4)

	movl %edi, %edx		/* Note that %edx is not used and can

				   so be used to save %edi.  It's faster.  */

	cfi_register (edi, edx)

	movl BLK1(%esp), %esi

	cfi_rel_offset (esi, 0)

	movl BLK2(%esp), %edi

	movl LEN(%esp), %ecx

	cld			/* Set direction of comparison.  */

	xorl %eax, %eax		/* Default result.  */

	repe			/* Compare at most %ecx bytes.  */

	cmpsb

	jz L(1)			/* If even last byte was equal we return 0.  */

	/* The memory blocks are not equal.  So result of the last

	   subtraction is present in the carry flag.  It is set when

	   the byte in block #2 is bigger.  In this case we have to

	   return -1 (=0xffffffff), else 1.  */

	sbbl %eax, %eax		/* This is tricky.  %eax == 0 and carry is set

				   or not depending on last subtraction.  */

	/* At this point %eax == 0, if the byte of block #1 was bigger, and

	   0xffffffff if the last byte of block #2 was bigger.  The latter

	   case is already correct but the former needs a little adjustment.

	   Note that the following operation does not change 0xffffffff.  */

	orb $1, %al		/* Change 0 to 1.  */

L(1):	popl %esi		/* Restore registers.  */

	cfi_adjust_cfa_offset (-4)

	cfi_restore (esi)

	movl %edx, %edi

	cfi_restore (edi)

	ret

END (memcmp)

#undef bcmp

weak_alias (memcmp, bcmp)

libc_hidden_builtin_def (memcmp)