1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/alpha/lib/memcpy.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 */
7
8 /*
9 * This is a reasonably optimized memcpy() routine.
10 */
11
12 /*
13 * Note that the C code is written to be optimized into good assembly. However,
14 * at this point gcc is unable to sanely compile "if (n >= 0)", resulting in a
15 * explicit compare against 0 (instead of just using the proper "blt reg, xx" or
16 * "bge reg, xx"). I hope alpha-gcc will be fixed to notice this eventually..
17 */
18
19 #include <linux/types.h>
20 #include <linux/export.h>
21
22 /*
23 * This should be done in one go with ldq_u*2/mask/stq_u. Do it
24 * with a macro so that we can fix it up later..
25 */
26 #define ALIGN_DEST_TO8_UP(d,s,n) \
27 while (d & 7) { \
28 if (n <= 0) return; \
29 n--; \
30 *(char *) d = *(char *) s; \
31 d++; s++; \
32 }
33 #define ALIGN_DEST_TO8_DN(d,s,n) \
34 while (d & 7) { \
35 if (n <= 0) return; \
36 n--; \
37 d--; s--; \
38 *(char *) d = *(char *) s; \
39 }
40
41 /*
42 * This should similarly be done with ldq_u*2/mask/stq. The destination
43 * is aligned, but we don't fill in a full quad-word
44 */
45 #define DO_REST_UP(d,s,n) \
46 while (n > 0) { \
47 n--; \
48 *(char *) d = *(char *) s; \
49 d++; s++; \
50 }
51 #define DO_REST_DN(d,s,n) \
52 while (n > 0) { \
53 n--; \
54 d--; s--; \
55 *(char *) d = *(char *) s; \
56 }
57
58 /*
59 * This should be done with ldq/mask/stq. The source and destination are
60 * aligned, but we don't fill in a full quad-word
61 */
62 #define DO_REST_ALIGNED_UP(d,s,n) DO_REST_UP(d,s,n)
63 #define DO_REST_ALIGNED_DN(d,s,n) DO_REST_DN(d,s,n)
64
65 /*
66 * This does unaligned memory copies. We want to avoid storing to
67 * an unaligned address, as that would do a read-modify-write cycle.
68 * We also want to avoid double-reading the unaligned reads.
69 *
70 * Note the ordering to try to avoid load (and address generation) latencies.
71 */
72 static inline void __memcpy_unaligned_up (unsigned long d, unsigned long s,
73 long n)
74 {
75 ALIGN_DEST_TO8_UP(d,s,n);
76 n -= 8; /* to avoid compare against 8 in the loop */
77 if (n >= 0) {
78 unsigned long low_word, high_word;
79 __asm__("ldq_u %0,%1":"=r" (low_word):"m" (*(unsigned long *) s));
80 do {
81 unsigned long tmp;
82 __asm__("ldq_u %0,%1":"=r" (high_word):"m" (*(unsigned long *)(s+8)));
83 n -= 8;
84 __asm__("extql %1,%2,%0"
85 :"=r" (low_word)
86 :"r" (low_word), "r" (s));
87 __asm__("extqh %1,%2,%0"
88 :"=r" (tmp)
89 :"r" (high_word), "r" (s));
90 s += 8;
91 *(unsigned long *) d = low_word | tmp;
92 d += 8;
93 low_word = high_word;
94 } while (n >= 0);
95 }
96 n += 8;
97 DO_REST_UP(d,s,n);
98 }
99
100 static inline void __memcpy_unaligned_dn (unsigned long d, unsigned long s,
101 long n)
102 {
103 /* I don't understand AXP assembler well enough for this. -Tim */
104 s += n;
105 d += n;
106 while (n--)
107 * (char *) --d = * (char *) --s;
108 }
109
110 /*
111 * Hmm.. Strange. The __asm__ here is there to make gcc use an integer register
112 * for the load-store. I don't know why, but it would seem that using a floating
113 * point register for the move seems to slow things down (very small difference,
114 * though).
115 *
116 * Note the ordering to try to avoid load (and address generation) latencies.
117 */
118 static inline void __memcpy_aligned_up (unsigned long d, unsigned long s,
119 long n)
120 {
121 ALIGN_DEST_TO8_UP(d,s,n);
122 n -= 8;
123 while (n >= 0) {
124 unsigned long tmp;
125 __asm__("ldq %0,%1":"=r" (tmp):"m" (*(unsigned long *) s));
126 n -= 8;
127 s += 8;
128 *(unsigned long *) d = tmp;
129 d += 8;
130 }
131 n += 8;
132 DO_REST_ALIGNED_UP(d,s,n);
133 }
134 static inline void __memcpy_aligned_dn (unsigned long d, unsigned long s,
135 long n)
136 {
137 s += n;
138 d += n;
139 ALIGN_DEST_TO8_DN(d,s,n);
140 n -= 8;
141 while (n >= 0) {
142 unsigned long tmp;
143 s -= 8;
144 __asm__("ldq %0,%1":"=r" (tmp):"m" (*(unsigned long *) s));
145 n -= 8;
146 d -= 8;
147 *(unsigned long *) d = tmp;
148 }
149 n += 8;
150 DO_REST_ALIGNED_DN(d,s,n);
151 }
152
153 void * memcpy(void * dest, const void *src, size_t n)
154 {
155 if (!(((unsigned long) dest ^ (unsigned long) src) & 7)) {
156 __memcpy_aligned_up ((unsigned long) dest, (unsigned long) src,
157 n);
158 return dest;
159 }
160 __memcpy_unaligned_up ((unsigned long) dest, (unsigned long) src, n);
161 return dest;
162 }
163 EXPORT_SYMBOL(memcpy);