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231 lines
4.8 KiB
ArmAsm
231 lines
4.8 KiB
ArmAsm
/* i80586 rshift
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*
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* Copyright (C) 1992, 1994, 1998,
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* 2001 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*
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* Note: This code is heavily based on the GNU MP Library.
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* Actually it's the same code with only minor changes in the
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* way the data is stored; this is to support the abstraction
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* of an optional secure memory allocation which may be used
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* to avoid revealing of sensitive data due to paging etc.
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* The GNU MP Library itself is published under the LGPL;
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* however I decided to publish this code under the plain GPL.
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*/
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#include "sysdep.h"
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#include "asm-syntax.h"
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/*******************
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* mpi_limb_t
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* mpihelp_rshift( mpi_ptr_t wp, (sp + 4)
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* mpi_ptr_t up, (sp + 8)
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* mpi_size_t usize, (sp + 12)
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* unsigned cnt) (sp + 16)
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*/
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.text
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ALIGN (3)
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.globl C_SYMBOL_NAME(mpihelp_rshift)
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C_SYMBOL_NAME(mpihelp_rshift:)
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pushl %edi
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pushl %esi
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pushl %ebx
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pushl %ebp
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movl 20(%esp),%edi /* res_ptr */
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movl 24(%esp),%esi /* s_ptr */
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movl 28(%esp),%ebp /* size */
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movl 32(%esp),%ecx /* cnt */
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/* We can use faster code for shift-by-1 under certain conditions. */
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cmp $1,%ecx
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jne Rnormal
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leal 4(%edi),%eax
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cmpl %esi,%eax
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jnc Rspecial /* jump if res_ptr + 1 >= s_ptr */
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leal (%edi,%ebp,4),%eax
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cmpl %eax,%esi
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jnc Rspecial /* jump if s_ptr >= res_ptr + size */
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Rnormal:
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movl (%esi),%edx
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addl $4,%esi
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xorl %eax,%eax
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shrdl %cl,%edx,%eax /* compute carry limb */
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pushl %eax /* push carry limb onto stack */
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decl %ebp
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pushl %ebp
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shrl $3,%ebp
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jz Rend
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movl (%edi),%eax /* fetch destination cache line */
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ALIGN (2)
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Roop: movl 28(%edi),%eax /* fetch destination cache line */
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movl %edx,%ebx
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movl (%esi),%eax
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movl 4(%esi),%edx
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shrdl %cl,%eax,%ebx
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shrdl %cl,%edx,%eax
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movl %ebx,(%edi)
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movl %eax,4(%edi)
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movl 8(%esi),%ebx
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movl 12(%esi),%eax
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shrdl %cl,%ebx,%edx
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shrdl %cl,%eax,%ebx
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movl %edx,8(%edi)
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movl %ebx,12(%edi)
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movl 16(%esi),%edx
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movl 20(%esi),%ebx
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shrdl %cl,%edx,%eax
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shrdl %cl,%ebx,%edx
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movl %eax,16(%edi)
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movl %edx,20(%edi)
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movl 24(%esi),%eax
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movl 28(%esi),%edx
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shrdl %cl,%eax,%ebx
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shrdl %cl,%edx,%eax
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movl %ebx,24(%edi)
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movl %eax,28(%edi)
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addl $32,%esi
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addl $32,%edi
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decl %ebp
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jnz Roop
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Rend: popl %ebp
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andl $7,%ebp
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jz Rend2
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Roop2: movl (%esi),%eax
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shrdl %cl,%eax,%edx /* compute result limb */
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movl %edx,(%edi)
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movl %eax,%edx
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addl $4,%esi
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addl $4,%edi
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decl %ebp
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jnz Roop2
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Rend2: shrl %cl,%edx /* compute most significant limb */
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movl %edx,(%edi) /* store it */
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popl %eax /* pop carry limb */
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popl %ebp
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popl %ebx
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popl %esi
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popl %edi
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ret
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/* We loop from least significant end of the arrays, which is only
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permissable if the source and destination don't overlap, since the
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function is documented to work for overlapping source and destination.
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*/
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Rspecial:
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leal -4(%edi,%ebp,4),%edi
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leal -4(%esi,%ebp,4),%esi
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movl (%esi),%edx
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subl $4,%esi
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decl %ebp
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pushl %ebp
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shrl $3,%ebp
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shrl $1,%edx
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incl %ebp
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decl %ebp
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jz RLend
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movl (%edi),%eax /* fetch destination cache line */
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ALIGN (2)
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RLoop: movl -28(%edi),%eax /* fetch destination cache line */
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movl %edx,%ebx
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movl (%esi),%eax
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movl -4(%esi),%edx
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rcrl $1,%eax
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movl %ebx,(%edi)
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rcrl $1,%edx
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movl %eax,-4(%edi)
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movl -8(%esi),%ebx
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movl -12(%esi),%eax
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rcrl $1,%ebx
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movl %edx,-8(%edi)
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rcrl $1,%eax
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movl %ebx,-12(%edi)
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movl -16(%esi),%edx
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movl -20(%esi),%ebx
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rcrl $1,%edx
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movl %eax,-16(%edi)
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rcrl $1,%ebx
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movl %edx,-20(%edi)
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movl -24(%esi),%eax
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movl -28(%esi),%edx
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rcrl $1,%eax
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movl %ebx,-24(%edi)
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rcrl $1,%edx
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movl %eax,-28(%edi)
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leal -32(%esi),%esi /* use leal not to clobber carry */
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leal -32(%edi),%edi
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decl %ebp
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jnz RLoop
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RLend: popl %ebp
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sbbl %eax,%eax /* save carry in %eax */
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andl $7,%ebp
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jz RLend2
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addl %eax,%eax /* restore carry from eax */
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RLoop2: movl %edx,%ebx
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movl (%esi),%edx
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rcrl $1,%edx
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movl %ebx,(%edi)
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leal -4(%esi),%esi /* use leal not to clobber carry */
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leal -4(%edi),%edi
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decl %ebp
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jnz RLoop2
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jmp RL1
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RLend2: addl %eax,%eax /* restore carry from eax */
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RL1: movl %edx,(%edi) /* store last limb */
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movl $0,%eax
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rcrl $1,%eax
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popl %ebp
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popl %ebx
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popl %esi
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popl %edi
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ret
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