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/* mc68020 __mpn_sub_n -- Subtract two limb vectors of the same length > 0 and
* store difference in a third limb vector.
*
* Copyright (C) 1992, 1994, 1996, 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_sub_n( mpi_ptr_t res_ptr, (sp + 4)
* mpi_ptr_t s1_ptr, (sp + 8)
* mpi_ptr_t s2_ptr, (sp + 16)
* mpi_size_t size) (sp + 12)
*/
TEXT
ALIGN
GLOBL C_SYMBOL_NAME(_gcry_mpih_sub_n)
C_SYMBOL_NAME(_gcry_mpih_sub_n:)
PROLOG(_gcry_mpih_sub_n)
/* Save used registers on the stack. */
movel R(d2),MEM_PREDEC(sp)
movel R(a2),MEM_PREDEC(sp)
/* Copy the arguments to registers. Better use movem? */
movel MEM_DISP(sp,12),R(a2)
movel MEM_DISP(sp,16),R(a0)
movel MEM_DISP(sp,20),R(a1)
movel MEM_DISP(sp,24),R(d2)
eorw #1,R(d2)
lsrl #1,R(d2)
bcc L(L1)
subql #1,R(d2) /* clears cy as side effect */
L(Loop:)
movel MEM_POSTINC(a0),R(d0)
movel MEM_POSTINC(a1),R(d1)
subxl R(d1),R(d0)
movel R(d0),MEM_POSTINC(a2)
L(L1:) movel MEM_POSTINC(a0),R(d0)
movel MEM_POSTINC(a1),R(d1)
subxl R(d1),R(d0)
movel R(d0),MEM_POSTINC(a2)
dbf R(d2),L(Loop) /* loop until 16 lsb of %4 == -1 */
subxl R(d0),R(d0) /* d0 <= -cy; save cy as 0 or -1 in d0 */
subl #0x10000,R(d2)
bcs L(L2)
addl R(d0),R(d0) /* restore cy */
bra L(Loop)
L(L2:)
negl R(d0)
/* Restore used registers from stack frame. */
movel MEM_POSTINC(sp),R(a2)
movel MEM_POSTINC(sp),R(d2)
rts
EPILOG(_gcry_mpih_sub_n)
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