Linux Kernel  3.7.1
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memcpy_64.c
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1 /*
2  * Copyright 2011 Tilera Corporation. All Rights Reserved.
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU General Public License
6  * as published by the Free Software Foundation, version 2.
7  *
8  * This program is distributed in the hope that it will be useful, but
9  * WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11  * NON INFRINGEMENT. See the GNU General Public License for
12  * more details.
13  */
14 
15 #include <linux/types.h>
16 #include <linux/string.h>
17 #include <linux/module.h>
18 /* EXPORT_SYMBOL() is in arch/tile/lib/exports.c since this should be asm. */
19 
20 /* Must be 8 bytes in size. */
21 #define word_t uint64_t
22 
23 #if CHIP_L2_LINE_SIZE() != 64 && CHIP_L2_LINE_SIZE() != 128
24 #error "Assumes 64 or 128 byte line size"
25 #endif
26 
27 /* How many cache lines ahead should we prefetch? */
28 #define PREFETCH_LINES_AHEAD 3
29 
30 /*
31  * Provide "base versions" of load and store for the normal code path.
32  * The kernel provides other versions for userspace copies.
33  */
34 #define ST(p, v) (*(p) = (v))
35 #define LD(p) (*(p))
36 
37 #ifndef USERCOPY_FUNC
38 #define ST1 ST
39 #define ST2 ST
40 #define ST4 ST
41 #define ST8 ST
42 #define LD1 LD
43 #define LD2 LD
44 #define LD4 LD
45 #define LD8 LD
46 #define RETVAL dstv
47 void *memcpy(void *__restrict dstv, const void *__restrict srcv, size_t n)
48 #else
49 /*
50  * Special kernel version will provide implementation of the LDn/STn
51  * macros to return a count of uncopied bytes due to mm fault.
52  */
53 #define RETVAL 0
54 int USERCOPY_FUNC(void *__restrict dstv, const void *__restrict srcv, size_t n)
55 #endif
56 {
57  char *__restrict dst1 = (char *)dstv;
58  const char *__restrict src1 = (const char *)srcv;
59  const char *__restrict src1_end;
60  const char *__restrict prefetch;
61  word_t *__restrict dst8; /* 8-byte pointer to destination memory. */
62  word_t final; /* Final bytes to write to trailing word, if any */
63  long i;
64 
65  if (n < 16) {
66  for (; n; n--)
67  ST1(dst1++, LD1(src1++));
68  return RETVAL;
69  }
70 
71  /*
72  * Locate the end of source memory we will copy. Don't
73  * prefetch past this.
74  */
75  src1_end = src1 + n - 1;
76 
77  /* Prefetch ahead a few cache lines, but not past the end. */
78  prefetch = src1;
79  for (i = 0; i < PREFETCH_LINES_AHEAD; i++) {
80  __insn_prefetch(prefetch);
81  prefetch += CHIP_L2_LINE_SIZE();
82  prefetch = (prefetch > src1_end) ? prefetch : src1;
83  }
84 
85  /* Copy bytes until dst is word-aligned. */
86  for (; (uintptr_t)dst1 & (sizeof(word_t) - 1); n--)
87  ST1(dst1++, LD1(src1++));
88 
89  /* 8-byte pointer to destination memory. */
90  dst8 = (word_t *)dst1;
91 
92  if (__builtin_expect((uintptr_t)src1 & (sizeof(word_t) - 1), 0)) {
93  /*
94  * Misaligned copy. Copy 8 bytes at a time, but don't
95  * bother with other fanciness.
96  *
97  * TODO: Consider prefetching and using wh64 as well.
98  */
99 
100  /* Create an aligned src8. */
101  const word_t *__restrict src8 =
102  (const word_t *)((uintptr_t)src1 & -sizeof(word_t));
103  word_t b;
104 
105  word_t a = LD8(src8++);
106  for (; n >= sizeof(word_t); n -= sizeof(word_t)) {
107  b = LD8(src8++);
108  a = __insn_dblalign(a, b, src1);
109  ST8(dst8++, a);
110  a = b;
111  }
112 
113  if (n == 0)
114  return RETVAL;
115 
116  b = ((const char *)src8 <= src1_end) ? *src8 : 0;
117 
118  /*
119  * Final source bytes to write to trailing partial
120  * word, if any.
121  */
122  final = __insn_dblalign(a, b, src1);
123  } else {
124  /* Aligned copy. */
125 
126  const word_t* __restrict src8 = (const word_t *)src1;
127 
128  /* src8 and dst8 are both word-aligned. */
129  if (n >= CHIP_L2_LINE_SIZE()) {
130  /* Copy until 'dst' is cache-line-aligned. */
131  for (; (uintptr_t)dst8 & (CHIP_L2_LINE_SIZE() - 1);
132  n -= sizeof(word_t))
133  ST8(dst8++, LD8(src8++));
134 
135  for (; n >= CHIP_L2_LINE_SIZE(); ) {
136  __insn_wh64(dst8);
137 
138  /*
139  * Prefetch and advance to next line
140  * to prefetch, but don't go past the end
141  */
142  __insn_prefetch(prefetch);
143  prefetch += CHIP_L2_LINE_SIZE();
144  prefetch = (prefetch > src1_end) ? prefetch :
145  (const char *)src8;
146 
147  /*
148  * Copy an entire cache line. Manually
149  * unrolled to avoid idiosyncracies of
150  * compiler unrolling.
151  */
152 #define COPY_WORD(offset) ({ ST8(dst8+offset, LD8(src8+offset)); n -= 8; })
153  COPY_WORD(0);
154  COPY_WORD(1);
155  COPY_WORD(2);
156  COPY_WORD(3);
157  COPY_WORD(4);
158  COPY_WORD(5);
159  COPY_WORD(6);
160  COPY_WORD(7);
161 #if CHIP_L2_LINE_SIZE() == 128
162  COPY_WORD(8);
163  COPY_WORD(9);
164  COPY_WORD(10);
165  COPY_WORD(11);
166  COPY_WORD(12);
167  COPY_WORD(13);
168  COPY_WORD(14);
169  COPY_WORD(15);
170 #elif CHIP_L2_LINE_SIZE() != 64
171 # error Fix code that assumes particular L2 cache line sizes
172 #endif
173 
174  dst8 += CHIP_L2_LINE_SIZE() / sizeof(word_t);
175  src8 += CHIP_L2_LINE_SIZE() / sizeof(word_t);
176  }
177  }
178 
179  for (; n >= sizeof(word_t); n -= sizeof(word_t))
180  ST8(dst8++, LD8(src8++));
181 
182  if (__builtin_expect(n == 0, 1))
183  return RETVAL;
184 
185  final = LD8(src8);
186  }
187 
188  /* n != 0 if we get here. Write out any trailing bytes. */
189  dst1 = (char *)dst8;
190 #ifndef __BIG_ENDIAN__
191  if (n & 4) {
192  ST4((uint32_t *)dst1, final);
193  dst1 += 4;
194  final >>= 32;
195  n &= 3;
196  }
197  if (n & 2) {
198  ST2((uint16_t *)dst1, final);
199  dst1 += 2;
200  final >>= 16;
201  n &= 1;
202  }
203  if (n)
204  ST1((uint8_t *)dst1, final);
205 #else
206  if (n & 4) {
207  ST4((uint32_t *)dst1, final >> 32);
208  dst1 += 4;
209  }
210  else
211  {
212  final >>= 32;
213  }
214  if (n & 2) {
215  ST2((uint16_t *)dst1, final >> 16);
216  dst1 += 2;
217  }
218  else
219  {
220  final >>= 16;
221  }
222  if (n & 1)
223  ST1((uint8_t *)dst1, final >> 8);
224 #endif
225 
226  return RETVAL;
227 }
228 
229 #ifdef USERCOPY_FUNC
230 #undef ST1
231 #undef ST2
232 #undef ST4
233 #undef ST8
234 #undef LD1
235 #undef LD2
236 #undef LD4
237 #undef LD8
238 #undef USERCOPY_FUNC
239 #endif