glibc/sysdeps/i386/rshift.S

/* i80386 __mpn_rshift --
   Copyright (C) 1992, 1994, 1997, 1998, 1999, 2000 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. */

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

#define PARMS	LINKAGE+12		/* space for 3 saved regs */
#define RES	PARMS
#define S	RES+PTR_SIZE
#define SIZE	S+PTR_SIZE
#define CNT	SIZE+4

	.text
ENTRY(__mpn_rshift)
	ENTER

	pushl	%edi
	pushl	%esi
	pushl	%ebx

	movl	RES(%esp),%edi
	movl	S(%esp),%esi
	movl	SIZE(%esp),%edx
	movl	CNT(%esp),%ecx

	leal	-4(%edi,%edx,4),%edi
	leal	(%esi,%edx,4),%esi
	negl	%edx

	movl	(%esi,%edx,4),%ebx	/* read least significant limb */
	xorl	%eax,%eax
	shrdl	%cl,%ebx,%eax		/* compute carry limb */
	incl	%edx
	jz	L(end)
	pushl	%eax			/* push carry limb onto stack */
	testb	$1,%dl
	jnz	L(1)			/* enter loop in the middle */
	movl	%ebx,%eax

	ALIGN (3)
L(oop):	movl	(%esi,%edx,4),%ebx	/* load next higher limb */
	shrdl	%cl,%ebx,%eax		/* compute result limb */
	movl	%eax,(%edi,%edx,4)	/* store it */
	incl	%edx
L(1):	movl	(%esi,%edx,4),%eax
	shrdl	%cl,%eax,%ebx
	movl	%ebx,(%edi,%edx,4)
	incl	%edx
	jnz	L(oop)

	shrl	%cl,%eax		/* compute most significant limb */
	movl	%eax,(%edi)		/* store it */

	popl	%eax			/* pop carry limb */

	popl	%ebx
	popl	%esi
	popl	%edi

	LEAVE
	ret

L(end):	shrl	%cl,%ebx		/* compute most significant limb */
	movl	%ebx,(%edi)		/* store it */

	popl	%ebx
	popl	%esi
	popl	%edi

	LEAVE
	ret
END(__mpn_rshift)