1/* mpn_submul_1 -- multiply and subtract bignums.
2 Copyright (C) 2013-2022 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
21 .syntax unified
22 .text
23
24@ cycles/limb
25@ StrongArm ?
26@ Cortex-A8 ?
27@ Cortex-A9 ?
28@ Cortex-A15 4
29
30/* mp_limb_t mpn_submul_1(res_ptr, src1_ptr, size, s2_limb) */
31
32ENTRY (__mpn_submul_1)
33 push { r4, r5, r6, r7 }
34 cfi_adjust_cfa_offset (16)
35 cfi_rel_offset (r4, 0)
36 cfi_rel_offset (r5, 4)
37 cfi_rel_offset (r6, 8)
38 cfi_rel_offset (r7, 12)
39
40 ldr r6, [r1], #4
41 ldr r7, [r0]
42 mov r4, #0 /* init carry in */
43 b 1f
440:
45 ldr r6, [r1], #4 /* load next ul */
46 adds r5, r5, r4 /* (lpl, c) = lpl + cl */
47 adc r4, ip, #0 /* cl = hpl + c */
48 subs r5, r7, r5 /* (lpl, !c) = rl - lpl */
49 ldr r7, [r0, #4] /* load next rl */
50 it cc
51 addcc r4, r4, #1 /* cl += !c */
52 str r5, [r0], #4
531:
54 umull r5, ip, r6, r3 /* (hpl, lpl) = ul * vl */
55 subs r2, r2, #1
56 bne 0b
57
58 adds r5, r5, r4 /* (lpl, c) = lpl + cl */
59 adc r4, ip, #0 /* cl = hpl + c */
60 subs r5, r7, r5 /* (lpl, !c) = rl - lpl */
61 str r5, [r0], #4
62 it cc
63 addcc r4, r4, #1 /* cl += !c */
64 mov r0, r4 /* return carry */
65
66 pop { r4, r5, r6, r7 }
67 DO_RET (lr)
68END (__mpn_submul_1)
69

source code of glibc/sysdeps/arm/submul_1.S