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
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
|
/* Copyright (C) 2001, 2003 Free Software Foundation, Inc.
Copyright (C) 1999, 2000 Axis Communications AB.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/*#************************************************************************#*/
/*#-------------------------------------------------------------------------*/
/*# */
/*# 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. */
/*# */
/*#-------------------------------------------------------------------------*/
/* 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 *, int, unsigned long);
/* Experimentally off - libc_hidden_proto(memset) */
void *memset(void *pdst,
int c,
unsigned long 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 long 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 $r13,%0"
: "=r" (lc) : "0" (lc) : "r13");
{
register char *dst __asm__ ("r13") = pdst;
if (((unsigned long) pdst & 3) != 0
/* Oops! n=0 must be a legal call, regardless of alignment. */
&& n >= 3)
{
if ((unsigned long)dst & 1)
{
*dst = (char) lc;
n--;
dst++;
}
if ((unsigned long)dst & 2)
{
*(short *)dst = lc;
n -= 2;
dst += 2;
}
}
/* Now the fun part. For the threshold value of this, check the equation
above. */
/* Decide which copying method to use. */
if (n >= ZERO_BLOCK_SIZE)
{
/* For large copies we use 'movem' */
/* It is not optimal to tell the compiler about clobbering any
registers; that will move the saving/restoring of those registers
to the function prologue/epilogue, and make non-movem sizes
suboptimal.
This method is not foolproof; it assumes that the "asm reg"
declarations at the beginning of the function really are used
here (beware: they may be moved to temporary registers).
This way, we do not have to save/move the registers around into
temporaries; we can safely use them straight away. */
__asm__ __volatile__ (" \n\
.syntax no_register_prefix \n\
\n\
;; Check that the register asm declaration got right. \n\
;; The GCC manual explicitly says there's no warranty for that (too). \n\
.ifnc %0-%1-%4,$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() */
libc_hidden_def(memset)
|
