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
|
/* Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by David Mosberger (davidm@cs.arizona.edu).
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. */
/* Finds characters in a memory area. Optimized for the Alpha:
- memory accessed as aligned quadwords only
- uses cmpbge to compare 8 bytes in parallel
- does binary search to find 0 byte in last
quadword (HAKMEM needed 12 instructions to
do this instead of the 9 instructions that
binary search needs).
For correctness consider that:
- only minimum number of quadwords may be accessed
- the third argument is an unsigned long
*/
#include <sysdep.h>
.set noreorder
.set noat
ENTRY(memchr)
#ifdef PROF
ldgp gp, 0(pv)
lda AT, _mcount
jsr AT, (AT), _mcount
.prologue 1
#else
.prologue 0
#endif
# Hack -- if someone passes in (size_t)-1, hoping to just
# search til the end of the address space, we will overflow
# below when we find the address of the last byte. Given
# that we will never have a 56-bit address space, cropping
# the length is the easiest way to avoid trouble.
zap a2, 0x80, t4 #-e0 :
beq a2, $not_found # .. e1 :
ldq_u t0, 0(a0) # e1 : load first quadword
insbl a1, 1, t1 # .. e0 : t1 = 000000000000ch00
and a1, 0xff, a1 #-e0 : a1 = 00000000000000ch
cmpult a2, 9, t3 # .. e1 :
or t1, a1, a1 # e0 : a1 = 000000000000chch
lda t2, -1(zero) # .. e1 :
sll a1, 16, t1 #-e0 : t1 = 00000000chch0000
addq a0, t4, t4 # .. e1 :
or t1, a1, a1 # e1 : a1 = 00000000chchchch
unop # :
sll a1, 32, t1 #-e0 : t1 = chchchch00000000
or t1, a1, a1 # e1 : a1 = chchchchchchchch
extql t0, a0, t6 # e0 :
beq t3, $first_quad # .. e1 :
ldq_u t5, -1(t4) #-e1 : eight or less bytes to search
extqh t5, a0, t5 # .. e0 :
mov a0, v0 # e0 :
or t6, t5, t0 # .. e1 : t0 = quadword starting at a0
# Deal with the case where at most 8 bytes remain to be searched
# in t0. E.g.:
# a2 = 6
# t0 = ????c6c5c4c3c2c1
$last_quad:
negq a2, t5 #-e0 :
xor a1, t0, t0 # .. e1 :
srl t2, t5, t5 # e0 : t5 = mask of a2 bits set
cmpbge zero, t0, t1 # .. e1 :
and t1, t5, t1 #-e0 :
beq t1, $not_found # .. e1 :
$found_it:
# Now, determine which byte matched:
negq t1, t2 # e0 :
and t1, t2, t1 # e1 :
and t1, 0x0f, t0 #-e0 :
addq v0, 4, t2 # .. e1 :
cmoveq t0, t2, v0 # e0 :
addq v0, 2, t2 # .. e1 :
and t1, 0x33, t0 #-e0 :
cmoveq t0, t2, v0 # .. e1 :
and t1, 0x55, t0 # e0 :
addq v0, 1, t2 # .. e1 :
cmoveq t0, t2, v0 #-e0 :
$done: ret # .. e1 :
# Deal with the case where a2 > 8 bytes remain to be
# searched. a0 may not be aligned.
.align 4
$first_quad:
andnot a0, 0x7, v0 #-e1 :
insqh t2, a0, t1 # .. e0 : t1 = 0000ffffffffffff (a0<0:2> ff)
xor t0, a1, t0 # e0 :
or t0, t1, t0 # e1 : t0 = ====ffffffffffff
cmpbge zero, t0, t1 #-e0 :
bne t1, $found_it # .. e1 :
# At least one byte left to process.
ldq t0, 8(v0) # e0 :
subq t4, 1, a2 # .. e1 :
addq v0, 8, v0 #-e0 :
# Make a2 point to last quad to be accessed (the
# last quad may or may not be partial).
andnot a2, 0x7, a2 # .. e1 :
cmpult v0, a2, t1 # e0 :
beq t1, $final # .. e1 :
# At least two quads remain to be accessed.
subq a2, v0, t3 #-e0 : t3 <- nr quads to be processed
and t3, 8, t3 # e1 : odd number of quads?
bne t3, $odd_quad_count # e1 :
# At least three quads remain to be accessed
mov t0, t3 # e0 : move prefetched value to correct reg
.align 4
$unrolled_loop:
ldq t0, 8(v0) #-e0 : prefetch t0
xor a1, t3, t1 # .. e1 :
cmpbge zero, t1, t1 # e0 :
bne t1, $found_it # .. e1 :
addq v0, 8, v0 #-e0 :
$odd_quad_count:
xor a1, t0, t1 # .. e1 :
ldq t3, 8(v0) # e0 : prefetch t3
cmpbge zero, t1, t1 # .. e1 :
addq v0, 8, t5 #-e0 :
bne t1, $found_it # .. e1 :
cmpult t5, a2, t5 # e0 :
addq v0, 8, v0 # .. e1 :
bne t5, $unrolled_loop #-e1 :
mov t3, t0 # e0 : move prefetched value into t0
$final: subq t4, v0, a2 # .. e1 : a2 <- number of bytes left to do
bne a2, $last_quad # e1 :
$not_found:
mov zero, v0 #-e0 :
ret # .. e1 :
END(memchr)
|
