summaryrefslogtreecommitdiff
path: root/arch/cris/arch-v32/lib/memset.c
blob: ffca1214674edabaa71f205e45c0044ce67ec3db (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
/*#************************************************************************#*/
/*#-------------------------------------------------------------------------*/
/*#                                                                         */
/*# FUNCTION NAME: memset()                                                 */
/*#                                                                         */
/*# PARAMETERS:  void* dst;   Destination address.                          */
/*#              int     c;   Value of byte to write.                       */
/*#              int   len;   Number of bytes to write.                     */
/*#                                                                         */
/*# RETURNS:     dst.                                                       */
/*#                                                                         */
/*# DESCRIPTION: Sets the memory dst of length len bytes to c, as standard. */
/*#              Framework taken from memcpy.  This routine is              */
/*#              very sensitive to compiler changes in register allocation. */
/*#              Should really be rewritten to avoid this problem.          */
/*#                                                                         */
/*#-------------------------------------------------------------------------*/
/*#                                                                         */
/*# HISTORY                                                                 */
/*#                                                                         */
/*# DATE      NAME            CHANGES                                       */
/*# ----      ----            -------                                       */
/*# 990713    HP              Tired of watching this function (or           */
/*#                           really, the nonoptimized generic              */
/*#                           implementation) take up 90% of simulator      */
/*#                           output.  Measurements needed.                 */
/*#                                                                         */
/*#-------------------------------------------------------------------------*/

#include <linux/types.h>

/* No, there's no macro saying 12*4, since it is "hard" to get it into
   the asm in a good way.  Thus better to expose the problem everywhere.
   */

/* Assuming 1 cycle per dword written or read (ok, not really true), and
   one per instruction, then 43+3*(n/48-1) <= 24+24*(n/48-1)
   so n >= 45.7; n >= 0.9; we win on the first full 48-byte block to set. */

#define ZERO_BLOCK_SIZE (1*12*4)

void *memset(void *pdst,
             int c,
             size_t plen)
{
  /* Ok.  Now we want the parameters put in special registers.
     Make sure the compiler is able to make something useful of this. */

  register char *return_dst __asm__ ("r10") = pdst;
  register int n __asm__ ("r12") = plen;
  register int lc __asm__ ("r11") = c;

  /* Most apps use memset sanely.  Only those memsetting about 3..4
     bytes or less get penalized compared to the generic implementation
     - and that's not really sane use. */

  /* Ugh.  This is fragile at best.  Check with newer GCC releases, if
     they compile cascaded "x |= x << 8" sanely! */
  __asm__("movu.b %0,$r13	\n\
           lslq 8,$r13		\n\
	   move.b %0,$r13	\n\
	   move.d $r13,%0	\n\
	   lslq 16,$r13		\n\
	   or.d $r13,%0"
          : "=r" (lc) : "0" (lc) : "r13");

  {
    register char *dst __asm__ ("r13") = pdst;

  /* This is NONPORTABLE, but since this whole routine is     */
  /* grossly nonportable that doesn't matter.                 */

  if (((unsigned long) pdst & 3) != 0
     /* Oops! n=0 must be a legal call, regardless of alignment. */
      && n >= 3)
  {
    if ((unsigned long)dst & 1)
    {
      *dst = (char) lc;
      n--;
      dst++;
    }

    if ((unsigned long)dst & 2)
    {
      *(short *)dst = lc;
      n -= 2;
      dst += 2;
    }
  }

  /* Now the fun part.  For the threshold value of this, check the equation
     above. */
  /* Decide which copying method to use. */
  if (n >= ZERO_BLOCK_SIZE)
  {
    /* For large copies we use 'movem' */

  /* It is not optimal to tell the compiler about clobbering any
     registers; that will move the saving/restoring of those registers
     to the function prologue/epilogue, and make non-movem sizes
     suboptimal.

      This method is not foolproof; it assumes that the "asm reg"
     declarations at the beginning of the function really are used
     here (beware: they may be moved to temporary registers).
      This way, we do not have to save/move the registers around into
     temporaries; we can safely use them straight away.

      If you want to check that the allocation was right; then
      check the equalities in the first comment.  It should say
      "r13=r13, r12=r12, r11=r11" */
    __asm__ volatile ("							\n\
        ;; Check that the register asm declaration got right.		\n\
        ;; The GCC manual says it will work, but there *has* been bugs.	\n\
	.ifnc %0-%1-%4,$r13-$r12-$r11					\n\
	.err								\n\
	.endif								\n\
									\n\
	;; Save the registers we'll clobber in the movem process	\n\
	;; on the stack.  Don't mention them to gcc, it will only be	\n\
	;; upset.							\n\
	subq 	11*4,$sp						\n\
        movem   $r10,[$sp]						\n\
									\n\
        move.d  $r11,$r0						\n\
        move.d  $r11,$r1						\n\
        move.d  $r11,$r2						\n\
        move.d  $r11,$r3						\n\
        move.d  $r11,$r4						\n\
        move.d  $r11,$r5						\n\
        move.d  $r11,$r6						\n\
        move.d  $r11,$r7						\n\
        move.d  $r11,$r8						\n\
        move.d  $r11,$r9						\n\
        move.d  $r11,$r10						\n\
									\n\
        ;; Now we've got this:						\n\
	;; r13 - dst							\n\
	;; r12 - n							\n\
									\n\
        ;; Update n for the first loop					\n\
        subq    12*4,$r12						\n\
0:									\n\
        subq   12*4,$r12						\n\
        bge     0b							\n\
	movem	$r11,[$r13+]						\n\
									\n\
        addq   12*4,$r12  ;; compensate for last loop underflowing n	\n\
									\n\
	;; Restore registers from stack					\n\
        movem [$sp+],$r10"

     /* Outputs */ : "=r" (dst), "=r" (n)
     /* Inputs */ : "0" (dst), "1" (n), "r" (lc));
  }

    /* Either we directly starts copying, using dword copying
       in a loop, or we copy as much as possible with 'movem'
       and then the last block (<44 bytes) is copied here.
       This will work since 'movem' will have updated src,dst,n. */

    while ( n >= 16 )
    {
      *((long*)dst)++ = lc;
      *((long*)dst)++ = lc;
      *((long*)dst)++ = lc;
      *((long*)dst)++ = lc;
      n -= 16;
    }

    /* A switch() is definitely the fastest although it takes a LOT of code.
     * Particularly if you inline code this.
     */
    switch (n)
    {
      case 0:
        break;
      case 1:
        *(char*)dst = (char) lc;
        break;
      case 2:
        *(short*)dst = (short) lc;
        break;
      case 3:
        *((short*)dst)++ = (short) lc;
        *(char*)dst = (char) lc;
        break;
      case 4:
        *((long*)dst)++ = lc;
        break;
      case 5:
        *((long*)dst)++ = lc;
        *(char*)dst = (char) lc;
        break;
      case 6:
        *((long*)dst)++ = lc;
        *(short*)dst = (short) lc;
        break;
      case 7:
        *((long*)dst)++ = lc;
        *((short*)dst)++ = (short) lc;
        *(char*)dst = (char) lc;
        break;
      case 8:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        break;
      case 9:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *(char*)dst = (char) lc;
        break;
      case 10:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *(short*)dst = (short) lc;
        break;
      case 11:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((short*)dst)++ = (short) lc;
        *(char*)dst = (char) lc;
        break;
      case 12:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        break;
      case 13:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *(char*)dst = (char) lc;
        break;
      case 14:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *(short*)dst = (short) lc;
        break;
      case 15:
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((long*)dst)++ = lc;
        *((short*)dst)++ = (short) lc;
        *(char*)dst = (char) lc;
        break;
    }
  }

  return return_dst; /* destination pointer. */
} /* memset() */