1/* mc68020 __mpn_sub_n -- Subtract two limb vectors of the same length > 0 and
2 *                        store difference in a third limb vector.
3 *
4 *      Copyright (C) 1992, 1994, 1996, 1998,
5 *                    2001, 2002 Free Software Foundation, Inc.
6 *
7 * This file is part of Libgcrypt.
8 *
9 * Libgcrypt is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU Lesser General Public License as
11 * published by the Free Software Foundation; either version 2.1 of
12 * the License, or (at your option) any later version.
13 *
14 * Libgcrypt is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17 * GNU Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
22 *
23 * Note: This code is heavily based on the GNU MP Library.
24 *	 Actually it's the same code with only minor changes in the
25 *	 way the data is stored; this is to support the abstraction
26 *	 of an optional secure memory allocation which may be used
27 *	 to avoid revealing of sensitive data due to paging etc.
28 */
29
30#include "sysdep.h"
31#include "asm-syntax.h"
32
33
34/*******************
35 *  mpi_limb_t
36 *  _gcry_mpih_sub_n( mpi_ptr_t res_ptr,	(sp + 4)
37 *		   mpi_ptr_t s1_ptr,	(sp + 8)
38 *		   mpi_ptr_t s2_ptr,	(sp + 16)
39 *		   mpi_size_t size)	(sp + 12)
40 */
41
42
43	TEXT
44	ALIGN
45	GLOBL	C_SYMBOL_NAME(_gcry_mpih_sub_n)
46
47C_SYMBOL_NAME(_gcry_mpih_sub_n:)
48PROLOG(_gcry_mpih_sub_n)
49/* Save used registers on the stack.  */
50	movel	R(d2),MEM_PREDEC(sp)
51	movel	R(a2),MEM_PREDEC(sp)
52
53/* Copy the arguments to registers.  Better use movem?	*/
54	movel	MEM_DISP(sp,12),R(a2)
55	movel	MEM_DISP(sp,16),R(a0)
56	movel	MEM_DISP(sp,20),R(a1)
57	movel	MEM_DISP(sp,24),R(d2)
58
59	eorw	#1,R(d2)
60	lsrl	#1,R(d2)
61	bcc	L(L1)
62	subql	#1,R(d2)	/* clears cy as side effect */
63
64L(Loop:)
65	movel	MEM_POSTINC(a0),R(d0)
66	movel	MEM_POSTINC(a1),R(d1)
67	subxl	R(d1),R(d0)
68	movel	R(d0),MEM_POSTINC(a2)
69L(L1:)	movel	MEM_POSTINC(a0),R(d0)
70	movel	MEM_POSTINC(a1),R(d1)
71	subxl	R(d1),R(d0)
72	movel	R(d0),MEM_POSTINC(a2)
73
74	dbf	R(d2),L(Loop)		/* loop until 16 lsb of %4 == -1 */
75	subxl	R(d0),R(d0)	/* d0 <= -cy; save cy as 0 or -1 in d0 */
76	subl	#0x10000,R(d2)
77	bcs	L(L2)
78	addl	R(d0),R(d0)	/* restore cy */
79	bra	L(Loop)
80
81L(L2:)
82	negl	R(d0)
83
84/* Restore used registers from stack frame.  */
85	movel	MEM_POSTINC(sp),R(a2)
86	movel	MEM_POSTINC(sp),R(d2)
87
88	rts
89EPILOG(_gcry_mpih_sub_n)
90
91
92