/* 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