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