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
|
/* SSE2 version of strlen.
Copyright (C) 2012-2015 Free Software Foundation, Inc.
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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* Long lived register in strlen(s), strnlen(s, n) are:
%xmm3 - zero
%rdi - s
%r10 (s+n) & (~(64-1))
%r11 s+n
*/
.text
ENTRY(strlen)
/* Test 64 bytes from %rax for zero. Save result as bitmask in %rdx. */
#define FIND_ZERO \
pcmpeqb (%rax), %xmm0; \
pcmpeqb 16(%rax), %xmm1; \
pcmpeqb 32(%rax), %xmm2; \
pcmpeqb 48(%rax), %xmm3; \
pmovmskb %xmm0, %esi; \
pmovmskb %xmm1, %edx; \
pmovmskb %xmm2, %r8d; \
pmovmskb %xmm3, %ecx; \
salq $16, %rdx; \
salq $16, %rcx; \
orq %rsi, %rdx; \
orq %r8, %rcx; \
salq $32, %rcx; \
orq %rcx, %rdx;
#ifdef AS_STRNLEN
/* Do not read anything when n==0. */
test %rsi, %rsi
jne L(n_nonzero)
xor %rax, %rax
ret
L(n_nonzero):
/* Initialize long lived registers. */
add %rdi, %rsi
mov %rsi, %r10
and $-64, %r10
mov %rsi, %r11
#endif
pxor %xmm0, %xmm0
pxor %xmm1, %xmm1
pxor %xmm2, %xmm2
pxor %xmm3, %xmm3
movq %rdi, %rax
movq %rdi, %rcx
andq $4095, %rcx
/* Offsets 4032-4047 will be aligned into 4032 thus fit into page. */
cmpq $4047, %rcx
/* We cannot unify this branching as it would be ~6 cycles slower. */
ja L(cross_page)
#ifdef AS_STRNLEN
/* Test if end is among first 64 bytes. */
# define STRNLEN_PROLOG \
mov %r11, %rsi; \
subq %rax, %rsi; \
andq $-64, %rax; \
testq $-64, %rsi; \
je L(strnlen_ret)
#else
# define STRNLEN_PROLOG andq $-64, %rax;
#endif
/* Ignore bits in mask that come before start of string. */
#define PROLOG(lab) \
movq %rdi, %rcx; \
xorq %rax, %rcx; \
STRNLEN_PROLOG; \
sarq %cl, %rdx; \
test %rdx, %rdx; \
je L(lab); \
bsfq %rdx, %rax; \
ret
#ifdef AS_STRNLEN
andq $-16, %rax
FIND_ZERO
#else
/* Test first 16 bytes unaligned. */
movdqu (%rax), %xmm4
pcmpeqb %xmm0, %xmm4
pmovmskb %xmm4, %edx
test %edx, %edx
je L(next48_bytes)
bsf %edx, %eax /* If eax is zeroed 16bit bsf can be used. */
ret
L(next48_bytes):
/* Same as FIND_ZERO except we do not check first 16 bytes. */
andq $-16, %rax
pcmpeqb 16(%rax), %xmm1
pcmpeqb 32(%rax), %xmm2
pcmpeqb 48(%rax), %xmm3
pmovmskb %xmm1, %edx
pmovmskb %xmm2, %r8d
pmovmskb %xmm3, %ecx
salq $16, %rdx
salq $16, %rcx
orq %r8, %rcx
salq $32, %rcx
orq %rcx, %rdx
#endif
/* When no zero byte is found xmm1-3 are zero so we do not have to
zero them. */
PROLOG(loop)
.p2align 4
L(cross_page):
andq $-64, %rax
FIND_ZERO
PROLOG(loop_init)
#ifdef AS_STRNLEN
/* We must do this check to correctly handle strnlen (s, -1). */
L(strnlen_ret):
bts %rsi, %rdx
sarq %cl, %rdx
test %rdx, %rdx
je L(loop_init)
bsfq %rdx, %rax
ret
#endif
.p2align 4
L(loop_init):
pxor %xmm1, %xmm1
pxor %xmm2, %xmm2
pxor %xmm3, %xmm3
#ifdef AS_STRNLEN
.p2align 4
L(loop):
addq $64, %rax
cmpq %rax, %r10
je L(exit_end)
movdqa (%rax), %xmm0
pminub 16(%rax), %xmm0
pminub 32(%rax), %xmm0
pminub 48(%rax), %xmm0
pcmpeqb %xmm3, %xmm0
pmovmskb %xmm0, %edx
testl %edx, %edx
jne L(exit)
jmp L(loop)
.p2align 4
L(exit_end):
cmp %rax, %r11
je L(first) /* Do not read when end is at page boundary. */
pxor %xmm0, %xmm0
FIND_ZERO
L(first):
bts %r11, %rdx
bsfq %rdx, %rdx
addq %rdx, %rax
subq %rdi, %rax
ret
.p2align 4
L(exit):
pxor %xmm0, %xmm0
FIND_ZERO
bsfq %rdx, %rdx
addq %rdx, %rax
subq %rdi, %rax
ret
#else
/* Main loop. Unrolled twice to improve L2 cache performance on core2. */
.p2align 4
L(loop):
movdqa 64(%rax), %xmm0
pminub 80(%rax), %xmm0
pminub 96(%rax), %xmm0
pminub 112(%rax), %xmm0
pcmpeqb %xmm3, %xmm0
pmovmskb %xmm0, %edx
testl %edx, %edx
jne L(exit64)
subq $-128, %rax
movdqa (%rax), %xmm0
pminub 16(%rax), %xmm0
pminub 32(%rax), %xmm0
pminub 48(%rax), %xmm0
pcmpeqb %xmm3, %xmm0
pmovmskb %xmm0, %edx
testl %edx, %edx
jne L(exit0)
jmp L(loop)
.p2align 4
L(exit64):
addq $64, %rax
L(exit0):
pxor %xmm0, %xmm0
FIND_ZERO
bsfq %rdx, %rdx
addq %rdx, %rax
subq %rdi, %rax
ret
#endif
END(strlen)
libc_hidden_builtin_def (strlen)
|
