1 /* SPDX-License-Identifier: GPL-2.0-or-later *
2 /*
3 * OpenRISC memset.S
4 *
5 * Hand-optimized assembler version of memset
6 * Algorithm inspired by several other arch-sp
7 * in the kernel tree
8 *
9 * Copyright (C) 2015 Olof Kindgren <olof.kindg
10 */
11
12 .global memset
13 .type memset, @function
14 memset:
15 /* arguments:
16 * r3 = *s
17 * r4 = c
18 * r5 = n
19 * r13, r15, r17, r19 used as temp reg
20 */
21
22 /* Exit if n == 0 */
23 l.sfeqi r5, 0
24 l.bf 4f
25
26 /* Truncate c to char */
27 l.andi r13, r4, 0xff
28
29 /* Skip word extension if c is 0 */
30 l.sfeqi r13, 0
31 l.bf 1f
32 /* Check for at least two whole words
33 l.sfleui r5, 7
34
35 /* Extend char c to 32-bit word cccc i
36 l.slli r15, r13, 16 // r13 =
37 l.or r13, r13, r15 // r13 =
38 l.slli r15, r13, 8 // r13 =
39 l.or r13, r13, r15 // r13 =
40
41 1: l.addi r19, r3, 0 // Set r19
42 /* Jump to byte copy loop if less than
43 l.bf 3f
44 l.or r17, r5, r0 // Set r17
45
46 /* Mask out two LSBs to check alignmen
47 l.andi r15, r3, 0x3
48
49 /* lsb == 00, jump to word copy loop *
50 l.sfeqi r15, 0
51 l.bf 2f
52 l.addi r19, r3, 0 // Set r19
53
54 /* lsb == 01,10 or 11 */
55 l.sb 0(r3), r13 // *src =
56 l.addi r17, r17, -1 // Decrea
57
58 l.sfeqi r15, 3
59 l.bf 2f
60 l.addi r19, r3, 1 // src +=
61
62 /* lsb == 01 or 10 */
63 l.sb 1(r3), r13 // *(src+
64 l.addi r17, r17, -1 // Decrea
65
66 l.sfeqi r15, 2
67 l.bf 2f
68 l.addi r19, r3, 2 // src +=
69
70 /* lsb == 01 */
71 l.sb 2(r3), r13 // *(src+
72 l.addi r17, r17, -1 // Decrea
73 l.addi r19, r3, 3 // src +=
74
75 /* Word copy loop */
76 2: l.sw 0(r19), r13 // *src =
77 l.addi r17, r17, -4 // Decrea
78 l.sfgeui r17, 4
79 l.bf 2b
80 l.addi r19, r19, 4 // Increa
81
82 /* When n > 0, copy the remaining byte
83 l.sfeqi r17, 0
84 l.bf 4f
85
86 /* Byte copy loop */
87 3: l.addi r17, r17, -1 // Decrea
88 l.sb 0(r19), r13 // *src =
89 l.sfnei r17, 0
90 l.bf 3b
91 l.addi r19, r19, 1 // Increa
92
93 4: l.jr r9
94 l.ori r11, r3, 0
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