1/* i80386 rshift 2 * 3 * Copyright (C) 1992, 1994, 1998, 4 * 2001, 2002 Free Software Foundation, Inc. 5 * 6 * This file is part of Libgcrypt. 7 * 8 * Libgcrypt is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU Lesser General Public License as 10 * published by the Free Software Foundation; either version 2.1 of 11 * the License, or (at your option) any later version. 12 * 13 * Libgcrypt is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU Lesser General Public License for more details. 17 * 18 * You should have received a copy of the GNU Lesser General Public 19 * License along with this program; if not, write to the Free Software 20 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA 21 * 22 * Note: This code is heavily based on the GNU MP Library. 23 * Actually it's the same code with only minor changes in the 24 * way the data is stored; this is to support the abstraction 25 * of an optional secure memory allocation which may be used 26 * to avoid revealing of sensitive data due to paging etc. 27 */ 28 29 30#include "sysdep.h" 31#include "asm-syntax.h" 32 33 34/******************* 35 * mpi_limb_t 36 * _gcry_mpih_rshift( mpi_ptr_t wp, (sp + 4) 37 * mpi_ptr_t up, (sp + 8) 38 * mpi_size_t usize, (sp + 12) 39 * unsigned cnt) (sp + 16) 40 */ 41 42.text 43 ALIGN (2) 44 .globl C_SYMBOL_NAME(_gcry_mpih_rshift) 45C_SYMBOL_NAME(_gcry_mpih_rshift:) 46 CFI_STARTPROC() 47 pushl %edi 48 CFI_PUSH(%edi) 49 pushl %esi 50 CFI_PUSH(%esi) 51 pushl %ebx 52 CFI_PUSH(%ebx) 53 54 movl 16(%esp),%edi /* wp */ 55 movl 20(%esp),%esi /* up */ 56 movl 24(%esp),%edx /* usize */ 57 movl 28(%esp),%ecx /* cnt */ 58 59 leal -4(%edi,%edx,4),%edi 60 leal (%esi,%edx,4),%esi 61 negl %edx 62 63 movl (%esi,%edx,4),%ebx /* read least significant limb */ 64 xorl %eax,%eax 65 shrdl %cl,%ebx,%eax /* compute carry limb */ 66 incl %edx 67 jz Lend2 68 pushl %eax /* push carry limb onto stack */ 69 testb $1,%dl 70 jnz L2 /* enter loop in the middle */ 71 movl %ebx,%eax 72 73 ALIGN (2) 74Loop2: movl (%esi,%edx,4),%ebx /* load next higher limb */ 75 shrdl %cl,%ebx,%eax /* compute result limb */ 76 movl %eax,(%edi,%edx,4) /* store it */ 77 incl %edx 78L2: movl (%esi,%edx,4),%eax 79 shrdl %cl,%eax,%ebx 80 movl %ebx,(%edi,%edx,4) 81 incl %edx 82 jnz Loop2 83 84 shrl %cl,%eax /* compute most significant limb */ 85 movl %eax,(%edi) /* store it */ 86 87 popl %eax /* pop carry limb */ 88 89 popl %ebx 90 popl %esi 91 popl %edi 92 ret 93 94Lend2: shrl %cl,%ebx /* compute most significant limb */ 95 movl %ebx,(%edi) /* store it */ 96 97 popl %ebx 98 CFI_POP(%ebx) 99 popl %esi 100 CFI_POP(%esi) 101 popl %edi 102 CFI_POP(%edi) 103 ret 104 CFI_ENDPROC() 105 106