| /* i80586 rshift |
| * |
| * 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_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(_gcry_mpih_rshift) |
| C_SYMBOL_NAME(_gcry_mpih_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 Rnormal |
| leal 4(%edi),%eax |
| cmpl %esi,%eax |
| jnc Rspecial /* jump if res_ptr + 1 >= s_ptr */ |
| leal (%edi,%ebp,4),%eax |
| cmpl %eax,%esi |
| jnc Rspecial /* jump if s_ptr >= res_ptr + size */ |
| |
| Rnormal: |
| 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 Rend |
| |
| movl (%edi),%eax /* fetch destination cache line */ |
| |
| ALIGN (2) |
| Roop: 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 Roop |
| |
| Rend: popl %ebp |
| andl $7,%ebp |
| jz Rend2 |
| Roop2: 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 Roop2 |
| |
| Rend2: 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. |
| */ |
| |
| Rspecial: |
| 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 RLend |
| |
| movl (%edi),%eax /* fetch destination cache line */ |
| |
| ALIGN (2) |
| RLoop: 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 RLoop |
| |
| RLend: popl %ebp |
| sbbl %eax,%eax /* save carry in %eax */ |
| andl $7,%ebp |
| jz RLend2 |
| addl %eax,%eax /* restore carry from eax */ |
| RLoop2: 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 RLoop2 |
| |
| jmp RL1 |
| RLend2: addl %eax,%eax /* restore carry from eax */ |
| RL1: movl %edx,(%edi) /* store last limb */ |
| |
| movl $0,%eax |
| rcrl $1,%eax |
| |
| popl %ebp |
| popl %ebx |
| popl %esi |
| popl %edi |
| ret |
| |
