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/* i80386 rshift
*
* Copyright (C) 1992, 1994, 1998,
* 2001, 2002 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* GnuPG is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* GnuPG 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* Note: This code is heavily based on the GNU MP Library.
* Actually it's the same code with only minor changes in the
* way the data is stored; this is to support the abstraction
* of an optional secure memory allocation which may be used
* to avoid revealing of sensitive data due to paging etc.
* The GNU MP Library itself is published under the LGPL;
* however I decided to publish this code under the plain GPL.
*/
#include "sysdep.h"
#include "asm-syntax.h"
/*******************
* mpi_limb_t
* mpihelp_rshift( mpi_ptr_t wp, (sp + 4)
* mpi_ptr_t up, (sp + 8)
* mpi_size_t usize, (sp + 12)
* unsigned cnt) (sp + 16)
*/
.text
ALIGN (3)
.globl C_SYMBOL_NAME(mpihelp_rshift)
C_SYMBOL_NAME(mpihelp_rshift:)
pushl %edi
pushl %esi
pushl %ebx
movl 16(%esp),%edi /* wp */
movl 20(%esp),%esi /* up */
movl 24(%esp),%edx /* usize */
movl 28(%esp),%ecx /* cnt */
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 %ebx,%eax /* compute carry limb */
incl %edx
jz Lend2
pushl %eax /* push carry limb onto stack */
testb $1,%dl
jnz L2 /* enter loop in the middle */
movl %ebx,%eax
ALIGN (3)
Loop2: movl (%esi,%edx,4),%ebx /* load next higher limb */
shrdl %ebx,%eax /* compute result limb */
movl %eax,(%edi,%edx,4) /* store it */
incl %edx
L2: movl (%esi,%edx,4),%eax
shrdl %eax,%ebx
movl %ebx,(%edi,%edx,4)
incl %edx
jnz Loop2
shrl %cl,%eax /* compute most significant limb */
movl %eax,(%edi) /* store it */
popl %eax /* pop carry limb */
popl %ebx
popl %esi
popl %edi
ret
Lend2: shrl %cl,%ebx /* compute most significant limb */
movl %ebx,(%edi) /* store it */
popl %ebx
popl %esi
popl %edi
ret
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