1/* mpn_add_n -- add (or subtract) bignums.
2 Copyright (C) 2013-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20#include <arm-features.h>
21
22 .syntax unified
23 .text
24
25#ifdef USE_AS_SUB_N
26# define INITC cmp r0, r0
27# define OPC sbcs
28# define RETC sbc r0, r0, r0; neg r0, r0
29# define FUNC __mpn_sub_n
30#else
31# define INITC cmn r0, #0
32# define OPC adcs
33# define RETC mov r0, #0; adc r0, r0, r0
34# define FUNC __mpn_add_n
35#endif
36
37/* mp_limb_t mpn_add_n(res_ptr, src1_ptr, src2_ptr, size) */
38
39ENTRY (FUNC)
40 push { r4, r5, r6, r7, r8, r10, lr }
41 cfi_adjust_cfa_offset (28)
42 cfi_rel_offset (r4, 0)
43 cfi_rel_offset (r5, 4)
44 cfi_rel_offset (r6, 8)
45 cfi_rel_offset (r7, 12)
46 cfi_rel_offset (r8, 16)
47 cfi_rel_offset (r10, 20)
48 cfi_rel_offset (lr, 24)
49
50 INITC /* initialize carry flag */
51 tst r3, #1 /* count & 1 == 1? */
52 add lr, r1, r3, lsl #2 /* compute end src1 */
53 beq 1f
54
55 ldr r4, [r1], #4 /* do one to make count even */
56 ldr r5, [r2], #4
57 OPC r4, r4, r5
58 teq r1, lr /* end of count? (preserve carry) */
59 str r4, [r0], #4
60 beq 9f
611:
62 tst r3, #2 /* count & 2 == 2? */
63 beq 2f
64 ldm r1!, { r4, r5 } /* do two to make count 0 mod 4 */
65 ldm r2!, { r6, r7 }
66 OPC r4, r4, r6
67 OPC r5, r5, r7
68 teq r1, lr /* end of count? */
69 stm r0!, { r4, r5 }
70 beq 9f
712:
72 ldm r1!, { r3, r5, r7, r10 } /* do four each loop */
73 ldm r2!, { r4, r6, r8, ip }
74 OPC r3, r3, r4
75 OPC r5, r5, r6
76 OPC r7, r7, r8
77 OPC r10, r10, ip
78 teq r1, lr
79 stm r0!, { r3, r5, r7, r10 }
80 bne 2b
81
829:
83 RETC /* copy carry out */
84#ifndef ARM_ALWAYS_BX
85 pop { r4, r5, r6, r7, r8, r10, pc }
86#else
87 pop { r4, r5, r6, r7, r8, r10, lr }
88 bx lr
89#endif
90END (FUNC)
91

source code of glibc/sysdeps/arm/add_n.S