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/* Pentium optimized __mpn_rshift --
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., 675 Mass Ave, Cambridge, MA 02139, USA. */
/*
INPUT PARAMETERS
res_ptr (sp + 4)
s_ptr (sp + 8)
size (sp + 12)
cnt (sp + 16)
*/
#include "sysdep.h"
#include "asm-syntax.h"
.text
ALIGN (3)
.globl C_SYMBOL_NAME(__mpn_rshift)
C_SYMBOL_NAME(__mpn_rshift:)
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(%edi),%eax
cmpl %esi,%eax
jnc Lspecial /* jump if res_ptr + 1 >= s_ptr */
leal (%edi,%ebp,4),%eax
cmpl %eax,%esi
jnc Lspecial /* jump if s_ptr >= res_ptr + size */
Lnormal:
movl (%esi),%edx
addl $4,%esi
xorl %eax,%eax
shrdl %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
shrdl %cl,%eax,%ebx
shrdl %cl,%edx,%eax
movl %ebx,(%edi)
movl %eax,4(%edi)
movl 8(%esi),%ebx
movl 12(%esi),%eax
shrdl %cl,%ebx,%edx
shrdl %cl,%eax,%ebx
movl %edx,8(%edi)
movl %ebx,12(%edi)
movl 16(%esi),%edx
movl 20(%esi),%ebx
shrdl %cl,%edx,%eax
shrdl %cl,%ebx,%edx
movl %eax,16(%edi)
movl %edx,20(%edi)
movl 24(%esi),%eax
movl 28(%esi),%edx
shrdl %cl,%eax,%ebx
shrdl %cl,%edx,%eax
movl %ebx,24(%edi)
movl %eax,28(%edi)
addl $32,%esi
addl $32,%edi
decl %ebp
jnz Loop
Lend: popl %ebp
andl $7,%ebp
jz Lend2
Loop2: movl (%esi),%eax
shrdl %cl,%eax,%edx /* compute result limb */
movl %edx,(%edi)
movl %eax,%edx
addl $4,%esi
addl $4,%edi
decl %ebp
jnz Loop2
Lend2: shrl %cl,%edx /* compute most 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:
leal -4(%edi,%ebp,4),%edi
leal -4(%esi,%ebp,4),%esi
movl (%esi),%edx
subl $4,%esi
decl %ebp
pushl %ebp
shrl $3,%ebp
shrl $1,%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
rcrl $1,%eax
movl %ebx,(%edi)
rcrl $1,%edx
movl %eax,-4(%edi)
movl -8(%esi),%ebx
movl -12(%esi),%eax
rcrl $1,%ebx
movl %edx,-8(%edi)
rcrl $1,%eax
movl %ebx,-12(%edi)
movl -16(%esi),%edx
movl -20(%esi),%ebx
rcrl $1,%edx
movl %eax,-16(%edi)
rcrl $1,%ebx
movl %edx,-20(%edi)
movl -24(%esi),%eax
movl -28(%esi),%edx
rcrl $1,%eax
movl %ebx,-24(%edi)
rcrl $1,%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
rcrl $1,%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 */
movl $0,%eax
rcrl $1,%eax
popl %ebp
popl %ebx
popl %esi
popl %edi
ret
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