glibc/sysdeps/i386/sub_n.S

/* i80386 __mpn_sub_n -- Add two limb vectors of the same length > 0 and store
   sum in a third limb vector.

Copyright (C) 1992, 1994, 1995 Free Software Foundation, Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.

The GNU MP 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 Library General Public
License for more details.

You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

/*
  INPUT PARAMETERS
  res_ptr	(sp + 4)
  s1_ptr	(sp + 8)
  s2_ptr	(sp + 12)
  size		(sp + 16)
*/

#include "sysdep.h"
#include "asm-syntax.h"

.text
	ALIGN (3)
	.globl C_SYMBOL_NAME(__mpn_sub_n)
C_SYMBOL_NAME(__mpn_sub_n:)
	pushl %edi
	pushl %esi

	movl 12(%esp),%edi		/* res_ptr */
	movl 16(%esp),%esi		/* s1_ptr */
	movl 20(%esp),%edx		/* s2_ptr */
	movl 24(%esp),%ecx		/* size */

	movl	%ecx,%eax
	shrl	$3,%ecx			/* compute count for unrolled loop */
	negl	%eax
	andl	$7,%eax			/* get index where to start loop */
	jz	Loop			/* necessary special case for 0 */
	incl	%ecx			/* adjust loop count */
	shll	$2,%eax			/* adjustment for pointers... */
	subl	%eax,%edi		/* ... since they are offset ... */
	subl	%eax,%esi		/* ... by a constant when we ... */
	subl	%eax,%edx		/* ... enter the loop */
	shrl	$2,%eax			/* restore previous value */
#ifdef PIC
/* Calculate start address in loop for PIC.  Due to limitations in some
   assemblers, Loop-L0-3 cannot be put into the leal */
	call	L0
L0:	leal	(%eax,%eax,8),%eax
	addl	(%esp),%eax
	addl	$(Loop-L0-3),%eax 
	addl	$4,%esp
#else
/* Calculate start address in loop for non-PIC.  */
 	leal	(Loop - 3)(%eax,%eax,8),%eax
#endif
	jmp	*%eax			/* jump into loop */
	ALIGN (3)
Loop:	movl	(%esi),%eax
	sbbl	(%edx),%eax
	movl	%eax,(%edi)
	movl	4(%esi),%eax
	sbbl	4(%edx),%eax
	movl	%eax,4(%edi)
	movl	8(%esi),%eax
	sbbl	8(%edx),%eax
	movl	%eax,8(%edi)
	movl	12(%esi),%eax
	sbbl	12(%edx),%eax
	movl	%eax,12(%edi)
	movl	16(%esi),%eax
	sbbl	16(%edx),%eax
	movl	%eax,16(%edi)
	movl	20(%esi),%eax
	sbbl	20(%edx),%eax
	movl	%eax,20(%edi)
	movl	24(%esi),%eax
	sbbl	24(%edx),%eax
	movl	%eax,24(%edi)
	movl	28(%esi),%eax
	sbbl	28(%edx),%eax
	movl	%eax,28(%edi)
	leal	32(%edi),%edi
	leal	32(%esi),%esi
	leal	32(%edx),%edx
	decl	%ecx
	jnz	Loop

	sbbl	%eax,%eax
	negl	%eax

	popl %esi
	popl %edi
	ret