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1/* Copyright (C) 1996 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by David Mosberger (davidm@cs.arizona.edu).
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If not,
17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA. */
19
20/* Finds characters in a memory area. Optimized for the Alpha:
21
22 - memory accessed as aligned quadwords only
23 - uses cmpbge to compare 8 bytes in parallel
24 - does binary search to find 0 byte in last
25 quadword (HAKMEM needed 12 instructions to
26 do this instead of the 9 instructions that
27 binary search needs).
28
29For correctness consider that:
30
31 - only minimum number of quadwords may be accessed
32 - the third argument is an unsigned long
33*/
34
35 .set noreorder
36 .set noat
37
38 .globl memchr
39 .ent memchr
40memchr:
41 .frame $30,0,$26,0
42 .prologue 0
43
44 # Hack -- if someone passes in (size_t)-1, hoping to just
45 # search til the end of the address space, we will overflow
46 # below when we find the address of the last byte. Given
47 # that we will never have a 56-bit address space, cropping
48 # the length is the easiest way to avoid trouble.
49 zap $18, 0x80, $5 #-e0 :
50
51 beq $18, $not_found # .. e1 :
52 ldq_u $1, 0($16) # e1 : load first quadword
53 insbl $17, 1, $2 # .. e0 : $2 = 000000000000ch00
54 and $17, 0xff, $17 #-e0 : $17 = 00000000000000ch
55 cmpult $18, 9, $4 # .. e1 :
56 or $2, $17, $17 # e0 : $17 = 000000000000chch
57 lda $3, -1($31) # .. e1 :
58 sll $17, 16, $2 #-e0 : $2 = 00000000chch0000
59 addq $16, $5, $5 # .. e1 :
60 or $2, $17, $17 # e1 : $17 = 00000000chchchch
61 unop # :
62 sll $17, 32, $2 #-e0 : $2 = chchchch00000000
63 or $2, $17, $17 # e1 : $17 = chchchchchchchch
64 extql $1, $16, $7 # e0 :
65 beq $4, $first_quad # .. e1 :
66
67 ldq_u $6, -1($5) #-e1 : eight or less bytes to search
68 extqh $6, $16, $6 # .. e0 :
69 mov $16, $0 # e0 :
70 or $7, $6, $1 # .. e1 : $1 = quadword starting at $16
71
72 # Deal with the case where at most 8 bytes remain to be searched
73 # in $1. E.g.:
74 # $18 = 6
75 # $1 = ????c6c5c4c3c2c1
76$last_quad:
77 negq $18, $6 #-e0 :
78 xor $17, $1, $1 # .. e1 :
79 srl $3, $6, $6 # e0 : $6 = mask of $18 bits set
80 cmpbge $31, $1, $2 # .. e1 :
81 and $2, $6, $2 #-e0 :
82 beq $2, $not_found # .. e1 :
83
84$found_it:
85 # Now, determine which byte matched:
86 negq $2, $3 # e0 :
87 and $2, $3, $2 # e1 :
88
89 and $2, 0x0f, $1 #-e0 :
90 addq $0, 4, $3 # .. e1 :
91 cmoveq $1, $3, $0 # e0 :
92
93 addq $0, 2, $3 # .. e1 :
94 and $2, 0x33, $1 #-e0 :
95 cmoveq $1, $3, $0 # .. e1 :
96
97 and $2, 0x55, $1 # e0 :
98 addq $0, 1, $3 # .. e1 :
99 cmoveq $1, $3, $0 #-e0 :
100
101$done: ret # .. e1 :
102
103 # Deal with the case where $18 > 8 bytes remain to be
104 # searched. $16 may not be aligned.
105 .align 4
106$first_quad:
107 andnot $16, 0x7, $0 #-e1 :
108 insqh $3, $16, $2 # .. e0 : $2 = 0000ffffffffffff ($16<0:2> ff)
109 xor $1, $17, $1 # e0 :
110 or $1, $2, $1 # e1 : $1 = ====ffffffffffff
111 cmpbge $31, $1, $2 #-e0 :
112 bne $2, $found_it # .. e1 :
113
114 # At least one byte left to process.
115
116 ldq $1, 8($0) # e0 :
117 subq $5, 1, $18 # .. e1 :
118 addq $0, 8, $0 #-e0 :
119
120 # Make $18 point to last quad to be accessed (the
121 # last quad may or may not be partial).
122
123 andnot $18, 0x7, $18 # .. e1 :
124 cmpult $0, $18, $2 # e0 :
125 beq $2, $final # .. e1 :
126
127 # At least two quads remain to be accessed.
128
129 subq $18, $0, $4 #-e0 : $4 <- nr quads to be processed
130 and $4, 8, $4 # e1 : odd number of quads?
131 bne $4, $odd_quad_count # e1 :
132
133 # At least three quads remain to be accessed
134
135 mov $1, $4 # e0 : move prefetched value to correct reg
136
137 .align 4
138$unrolled_loop:
139 ldq $1, 8($0) #-e0 : prefetch $1
140 xor $17, $4, $2 # .. e1 :
141 cmpbge $31, $2, $2 # e0 :
142 bne $2, $found_it # .. e1 :
143
144 addq $0, 8, $0 #-e0 :
145$odd_quad_count:
146 xor $17, $1, $2 # .. e1 :
147 ldq $4, 8($0) # e0 : prefetch $4
148 cmpbge $31, $2, $2 # .. e1 :
149 addq $0, 8, $6 #-e0 :
150 bne $2, $found_it # .. e1 :
151
152 cmpult $6, $18, $6 # e0 :
153 addq $0, 8, $0 # .. e1 :
154 bne $6, $unrolled_loop #-e1 :
155
156 mov $4, $1 # e0 : move prefetched value into $1
157$final: subq $5, $0, $18 # .. e1 : $18 <- number of bytes left to do
158 bne $18, $last_quad # e1 :
159
160$not_found:
161 mov $31, $0 #-e0 :
162 ret # .. e1 :
163
164 .end memchr
1/* Copyright (C) 1996 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by David Mosberger (davidm@cs.arizona.edu).
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB. If not,
17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA. */
19
20/* Finds characters in a memory area. Optimized for the Alpha:
21
22 - memory accessed as aligned quadwords only
23 - uses cmpbge to compare 8 bytes in parallel
24 - does binary search to find 0 byte in last
25 quadword (HAKMEM needed 12 instructions to
26 do this instead of the 9 instructions that
27 binary search needs).
28
29For correctness consider that:
30
31 - only minimum number of quadwords may be accessed
32 - the third argument is an unsigned long
33*/
34#include <linux/export.h>
35 .set noreorder
36 .set noat
37
38 .globl memchr
39 .ent memchr
40memchr:
41 .frame $30,0,$26,0
42 .prologue 0
43
44 # Hack -- if someone passes in (size_t)-1, hoping to just
45 # search til the end of the address space, we will overflow
46 # below when we find the address of the last byte. Given
47 # that we will never have a 56-bit address space, cropping
48 # the length is the easiest way to avoid trouble.
49 zap $18, 0x80, $5 #-e0 :
50
51 beq $18, $not_found # .. e1 :
52 ldq_u $1, 0($16) # e1 : load first quadword
53 insbl $17, 1, $2 # .. e0 : $2 = 000000000000ch00
54 and $17, 0xff, $17 #-e0 : $17 = 00000000000000ch
55 cmpult $18, 9, $4 # .. e1 :
56 or $2, $17, $17 # e0 : $17 = 000000000000chch
57 lda $3, -1($31) # .. e1 :
58 sll $17, 16, $2 #-e0 : $2 = 00000000chch0000
59 addq $16, $5, $5 # .. e1 :
60 or $2, $17, $17 # e1 : $17 = 00000000chchchch
61 unop # :
62 sll $17, 32, $2 #-e0 : $2 = chchchch00000000
63 or $2, $17, $17 # e1 : $17 = chchchchchchchch
64 extql $1, $16, $7 # e0 :
65 beq $4, $first_quad # .. e1 :
66
67 ldq_u $6, -1($5) #-e1 : eight or less bytes to search
68 extqh $6, $16, $6 # .. e0 :
69 mov $16, $0 # e0 :
70 or $7, $6, $1 # .. e1 : $1 = quadword starting at $16
71
72 # Deal with the case where at most 8 bytes remain to be searched
73 # in $1. E.g.:
74 # $18 = 6
75 # $1 = ????c6c5c4c3c2c1
76$last_quad:
77 negq $18, $6 #-e0 :
78 xor $17, $1, $1 # .. e1 :
79 srl $3, $6, $6 # e0 : $6 = mask of $18 bits set
80 cmpbge $31, $1, $2 # .. e1 :
81 and $2, $6, $2 #-e0 :
82 beq $2, $not_found # .. e1 :
83
84$found_it:
85 # Now, determine which byte matched:
86 negq $2, $3 # e0 :
87 and $2, $3, $2 # e1 :
88
89 and $2, 0x0f, $1 #-e0 :
90 addq $0, 4, $3 # .. e1 :
91 cmoveq $1, $3, $0 # e0 :
92
93 addq $0, 2, $3 # .. e1 :
94 and $2, 0x33, $1 #-e0 :
95 cmoveq $1, $3, $0 # .. e1 :
96
97 and $2, 0x55, $1 # e0 :
98 addq $0, 1, $3 # .. e1 :
99 cmoveq $1, $3, $0 #-e0 :
100
101$done: ret # .. e1 :
102
103 # Deal with the case where $18 > 8 bytes remain to be
104 # searched. $16 may not be aligned.
105 .align 4
106$first_quad:
107 andnot $16, 0x7, $0 #-e1 :
108 insqh $3, $16, $2 # .. e0 : $2 = 0000ffffffffffff ($16<0:2> ff)
109 xor $1, $17, $1 # e0 :
110 or $1, $2, $1 # e1 : $1 = ====ffffffffffff
111 cmpbge $31, $1, $2 #-e0 :
112 bne $2, $found_it # .. e1 :
113
114 # At least one byte left to process.
115
116 ldq $1, 8($0) # e0 :
117 subq $5, 1, $18 # .. e1 :
118 addq $0, 8, $0 #-e0 :
119
120 # Make $18 point to last quad to be accessed (the
121 # last quad may or may not be partial).
122
123 andnot $18, 0x7, $18 # .. e1 :
124 cmpult $0, $18, $2 # e0 :
125 beq $2, $final # .. e1 :
126
127 # At least two quads remain to be accessed.
128
129 subq $18, $0, $4 #-e0 : $4 <- nr quads to be processed
130 and $4, 8, $4 # e1 : odd number of quads?
131 bne $4, $odd_quad_count # e1 :
132
133 # At least three quads remain to be accessed
134
135 mov $1, $4 # e0 : move prefetched value to correct reg
136
137 .align 4
138$unrolled_loop:
139 ldq $1, 8($0) #-e0 : prefetch $1
140 xor $17, $4, $2 # .. e1 :
141 cmpbge $31, $2, $2 # e0 :
142 bne $2, $found_it # .. e1 :
143
144 addq $0, 8, $0 #-e0 :
145$odd_quad_count:
146 xor $17, $1, $2 # .. e1 :
147 ldq $4, 8($0) # e0 : prefetch $4
148 cmpbge $31, $2, $2 # .. e1 :
149 addq $0, 8, $6 #-e0 :
150 bne $2, $found_it # .. e1 :
151
152 cmpult $6, $18, $6 # e0 :
153 addq $0, 8, $0 # .. e1 :
154 bne $6, $unrolled_loop #-e1 :
155
156 mov $4, $1 # e0 : move prefetched value into $1
157$final: subq $5, $0, $18 # .. e1 : $18 <- number of bytes left to do
158 bne $18, $last_quad # e1 :
159
160$not_found:
161 mov $31, $0 #-e0 :
162 ret # .. e1 :
163
164 .end memchr
165 EXPORT_SYMBOL(memchr)