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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Normally compiler builtins are used, but sometimes the compiler calls out
4 * of line code. Based on asm-i386/string.h.
5 *
6 * This assembly file is re-written from memmove_64.c file.
7 * - Copyright 2011 Fenghua Yu <fenghua.yu@intel.com>
8 */
9#include <linux/linkage.h>
10#include <asm/cpufeatures.h>
11#include <asm/alternative.h>
12#include <asm/export.h>
13
14#undef memmove
15
16/*
17 * Implement memmove(). This can handle overlap between src and dst.
18 *
19 * Input:
20 * rdi: dest
21 * rsi: src
22 * rdx: count
23 *
24 * Output:
25 * rax: dest
26 */
27SYM_FUNC_START(__memmove)
28
29 mov %rdi, %rax
30
31 /* Decide forward/backward copy mode */
32 cmp %rdi, %rsi
33 jge .Lmemmove_begin_forward
34 mov %rsi, %r8
35 add %rdx, %r8
36 cmp %rdi, %r8
37 jg 2f
38
39 /* FSRM implies ERMS => no length checks, do the copy directly */
40.Lmemmove_begin_forward:
41 ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM
42 ALTERNATIVE "", __stringify(movq %rdx, %rcx; rep movsb; RET), X86_FEATURE_ERMS
43
44 /*
45 * movsq instruction have many startup latency
46 * so we handle small size by general register.
47 */
48 cmp $680, %rdx
49 jb 3f
50 /*
51 * movsq instruction is only good for aligned case.
52 */
53
54 cmpb %dil, %sil
55 je 4f
563:
57 sub $0x20, %rdx
58 /*
59 * We gobble 32 bytes forward in each loop.
60 */
615:
62 sub $0x20, %rdx
63 movq 0*8(%rsi), %r11
64 movq 1*8(%rsi), %r10
65 movq 2*8(%rsi), %r9
66 movq 3*8(%rsi), %r8
67 leaq 4*8(%rsi), %rsi
68
69 movq %r11, 0*8(%rdi)
70 movq %r10, 1*8(%rdi)
71 movq %r9, 2*8(%rdi)
72 movq %r8, 3*8(%rdi)
73 leaq 4*8(%rdi), %rdi
74 jae 5b
75 addq $0x20, %rdx
76 jmp 1f
77 /*
78 * Handle data forward by movsq.
79 */
80 .p2align 4
814:
82 movq %rdx, %rcx
83 movq -8(%rsi, %rdx), %r11
84 lea -8(%rdi, %rdx), %r10
85 shrq $3, %rcx
86 rep movsq
87 movq %r11, (%r10)
88 jmp 13f
89.Lmemmove_end_forward:
90
91 /*
92 * Handle data backward by movsq.
93 */
94 .p2align 4
957:
96 movq %rdx, %rcx
97 movq (%rsi), %r11
98 movq %rdi, %r10
99 leaq -8(%rsi, %rdx), %rsi
100 leaq -8(%rdi, %rdx), %rdi
101 shrq $3, %rcx
102 std
103 rep movsq
104 cld
105 movq %r11, (%r10)
106 jmp 13f
107
108 /*
109 * Start to prepare for backward copy.
110 */
111 .p2align 4
1122:
113 cmp $0x20, %rdx
114 jb 1f
115 cmp $680, %rdx
116 jb 6f
117 cmp %dil, %sil
118 je 7b
1196:
120 /*
121 * Calculate copy position to tail.
122 */
123 addq %rdx, %rsi
124 addq %rdx, %rdi
125 subq $0x20, %rdx
126 /*
127 * We gobble 32 bytes backward in each loop.
128 */
1298:
130 subq $0x20, %rdx
131 movq -1*8(%rsi), %r11
132 movq -2*8(%rsi), %r10
133 movq -3*8(%rsi), %r9
134 movq -4*8(%rsi), %r8
135 leaq -4*8(%rsi), %rsi
136
137 movq %r11, -1*8(%rdi)
138 movq %r10, -2*8(%rdi)
139 movq %r9, -3*8(%rdi)
140 movq %r8, -4*8(%rdi)
141 leaq -4*8(%rdi), %rdi
142 jae 8b
143 /*
144 * Calculate copy position to head.
145 */
146 addq $0x20, %rdx
147 subq %rdx, %rsi
148 subq %rdx, %rdi
1491:
150 cmpq $16, %rdx
151 jb 9f
152 /*
153 * Move data from 16 bytes to 31 bytes.
154 */
155 movq 0*8(%rsi), %r11
156 movq 1*8(%rsi), %r10
157 movq -2*8(%rsi, %rdx), %r9
158 movq -1*8(%rsi, %rdx), %r8
159 movq %r11, 0*8(%rdi)
160 movq %r10, 1*8(%rdi)
161 movq %r9, -2*8(%rdi, %rdx)
162 movq %r8, -1*8(%rdi, %rdx)
163 jmp 13f
164 .p2align 4
1659:
166 cmpq $8, %rdx
167 jb 10f
168 /*
169 * Move data from 8 bytes to 15 bytes.
170 */
171 movq 0*8(%rsi), %r11
172 movq -1*8(%rsi, %rdx), %r10
173 movq %r11, 0*8(%rdi)
174 movq %r10, -1*8(%rdi, %rdx)
175 jmp 13f
17610:
177 cmpq $4, %rdx
178 jb 11f
179 /*
180 * Move data from 4 bytes to 7 bytes.
181 */
182 movl (%rsi), %r11d
183 movl -4(%rsi, %rdx), %r10d
184 movl %r11d, (%rdi)
185 movl %r10d, -4(%rdi, %rdx)
186 jmp 13f
18711:
188 cmp $2, %rdx
189 jb 12f
190 /*
191 * Move data from 2 bytes to 3 bytes.
192 */
193 movw (%rsi), %r11w
194 movw -2(%rsi, %rdx), %r10w
195 movw %r11w, (%rdi)
196 movw %r10w, -2(%rdi, %rdx)
197 jmp 13f
19812:
199 cmp $1, %rdx
200 jb 13f
201 /*
202 * Move data for 1 byte.
203 */
204 movb (%rsi), %r11b
205 movb %r11b, (%rdi)
20613:
207 RET
208SYM_FUNC_END(__memmove)
209EXPORT_SYMBOL(__memmove)
210
211SYM_FUNC_ALIAS_WEAK(memmove, __memmove)
212EXPORT_SYMBOL(memmove)