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mpih-lshift.S
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/* i80586 lshift
*
* Copyright (C) 1992, 1994, 1998,
* 2001, 2002 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt 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.
*
* Libgcrypt 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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.
*/
#include "sysdep.h"
#include "asm-syntax.h"
/*******************
* mpi_limb_t
* _gcry_mpih_lshift( 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(_gcry_mpih_lshift)
C_SYMBOL_NAME(_gcry_mpih_lshift:)
pushl %edi
pushl %esi
pushl %ebx
pushl %ebp
movl 20(%esp),%edi /* res_ptr */
movl 24(%esp),%esi /* s_ptr */
movl 28(%esp),%ebp /* size */
movl 32(%esp),%ecx /* cnt */
/* We can use faster code for shift-by-1 under certain conditions. */
cmp $1,%ecx
jne Lnormal
leal 4(%esi),%eax
cmpl %edi,%eax
jnc Lspecial /* jump if s_ptr + 1 >= res_ptr */
leal (%esi,%ebp,4),%eax
cmpl %eax,%edi
jnc Lspecial /* jump if res_ptr >= s_ptr + size */
Lnormal:
leal -4(%edi,%ebp,4),%edi
leal -4(%esi,%ebp,4),%esi
movl (%esi),%edx
subl $4,%esi
xorl %eax,%eax
shldl %cl,%edx,%eax /* compute carry limb */
pushl %eax /* push carry limb onto stack */
decl %ebp
pushl %ebp
shrl $3,%ebp
jz Lend
movl (%edi),%eax /* fetch destination cache line */
ALIGN (2)
Loop: movl -28(%edi),%eax /* fetch destination cache line */
movl %edx,%ebx
movl (%esi),%eax
movl -4(%esi),%edx
shldl %cl,%eax,%ebx
shldl %cl,%edx,%eax
movl %ebx,(%edi)
movl %eax,-4(%edi)
movl -8(%esi),%ebx
movl -12(%esi),%eax
shldl %cl,%ebx,%edx
shldl %cl,%eax,%ebx
movl %edx,-8(%edi)
movl %ebx,-12(%edi)
movl -16(%esi),%edx
movl -20(%esi),%ebx
shldl %cl,%edx,%eax
shldl %cl,%ebx,%edx
movl %eax,-16(%edi)
movl %edx,-20(%edi)
movl -24(%esi),%eax
movl -28(%esi),%edx
shldl %cl,%eax,%ebx
shldl %cl,%edx,%eax
movl %ebx,-24(%edi)
movl %eax,-28(%edi)
subl $32,%esi
subl $32,%edi
decl %ebp
jnz Loop
Lend: popl %ebp
andl $7,%ebp
jz Lend2
Loop2: movl (%esi),%eax
shldl %cl,%eax,%edx
movl %edx,(%edi)
movl %eax,%edx
subl $4,%esi
subl $4,%edi
decl %ebp
jnz Loop2
Lend2: shll %cl,%edx /* compute least significant limb */
movl %edx,(%edi) /* store it */
popl %eax /* pop carry limb */
popl %ebp
popl %ebx
popl %esi
popl %edi
ret
/* We loop from least significant end of the arrays, which is only
permissable if the source and destination don't overlap, since the
function is documented to work for overlapping source and destination.
*/
Lspecial:
movl (%esi),%edx
addl $4,%esi
decl %ebp
pushl %ebp
shrl $3,%ebp
addl %edx,%edx
incl %ebp
decl %ebp
jz LLend
movl (%edi),%eax /* fetch destination cache line */
ALIGN (2)
LLoop: movl 28(%edi),%eax /* fetch destination cache line */
movl %edx,%ebx
movl (%esi),%eax
movl 4(%esi),%edx
adcl %eax,%eax
movl %ebx,(%edi)
adcl %edx,%edx
movl %eax,4(%edi)
movl 8(%esi),%ebx
movl 12(%esi),%eax
adcl %ebx,%ebx
movl %edx,8(%edi)
adcl %eax,%eax
movl %ebx,12(%edi)
movl 16(%esi),%edx
movl 20(%esi),%ebx
adcl %edx,%edx
movl %eax,16(%edi)
adcl %ebx,%ebx
movl %edx,20(%edi)
movl 24(%esi),%eax
movl 28(%esi),%edx
adcl %eax,%eax
movl %ebx,24(%edi)
adcl %edx,%edx
movl %eax,28(%edi)
leal 32(%esi),%esi /* use leal not to clobber carry */
leal 32(%edi),%edi
decl %ebp
jnz LLoop
LLend: popl %ebp
sbbl %eax,%eax /* save carry in %eax */
andl $7,%ebp
jz LLend2
addl %eax,%eax /* restore carry from eax */
LLoop2: movl %edx,%ebx
movl (%esi),%edx
adcl %edx,%edx
movl %ebx,(%edi)
leal 4(%esi),%esi /* use leal not to clobber carry */
leal 4(%edi),%edi
decl %ebp
jnz LLoop2
jmp LL1
LLend2: addl %eax,%eax /* restore carry from eax */
LL1: movl %edx,(%edi) /* store last limb */
sbbl %eax,%eax
negl %eax
popl %ebp
popl %ebx
popl %esi
popl %edi
ret

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