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
|
/*
* Copyright 2012 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkUtilsArm.h"
#if SK_ARM_NEON_IS_DYNAMIC
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
// Set USE_ANDROID_NDK_CPU_FEATURES to use the Android NDK's
// cpu-features helper library to detect NEON at runtime. See
// http://crbug.com/164154 to see why this is needed in Chromium
// for Android.
#if defined(SK_BUILD_FOR_ANDROID) && defined(SK_BUILD_FOR_CHROMIUM)
# define USE_ANDROID_NDK_CPU_FEATURES 1
#else
# define USE_ANDROID_NDK_CPU_FEATURES 0
#endif
#if USE_ANDROID_NDK_CPU_FEATURES
# include <cpu-features.h>
#endif
// Set NEON_DEBUG to 1 to allow debugging of the CPU features probing.
// For now, we always set it for SK_DEBUG builds.
#ifdef SK_DEBUG
# define NEON_DEBUG 1
#else
# define NEON_DEBUG 0
#endif
#if NEON_DEBUG
# ifdef SK_BUILD_FOR_ANDROID
// used to declare PROP_VALUE_MAX and __system_property_get()
# include <sys/system_properties.h>
# endif
#endif
// A function used to determine at runtime if the target CPU supports
// the ARM NEON instruction set. This implementation is Linux-specific.
static bool sk_cpu_arm_check_neon(void) {
bool result = false;
#if NEON_DEBUG
// Allow forcing the mode through the environment during debugging.
# ifdef SK_BUILD_FOR_ANDROID
// On Android, we use a system property
# define PROP_NAME "debug.skia.arm_neon_mode"
char prop[PROP_VALUE_MAX];
if (__system_property_get(PROP_NAME, prop) > 0) {
# else
# define PROP_NAME "SKIA_ARM_NEON_MODE"
// On ARM Linux, we use an environment variable
const char* prop = getenv(PROP_NAME);
if (prop != NULL) {
# endif
SkDebugf("%s: %s", PROP_NAME, prop);
if (!strcmp(prop, "1")) {
SkDebugf("Forcing ARM Neon mode to full!\n");
return true;
}
if (!strcmp(prop, "0")) {
SkDebugf("Disabling ARM NEON mode\n");
return false;
}
}
SkDebugf("Running dynamic CPU feature detection\n");
#endif
#if USE_ANDROID_NDK_CPU_FEATURES
result = (android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
#else // USE_ANDROID_NDK_CPU_FEATURES
// There is no user-accessible CPUID instruction on ARM that we can use.
// Instead, we must parse /proc/cpuinfo and look for the 'neon' feature.
// For example, here's a typical output (Nexus S running ICS 4.0.3):
/*
Processor : ARMv7 Processor rev 2 (v7l)
BogoMIPS : 994.65
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x2
CPU part : 0xc08
CPU revision : 2
Hardware : herring
Revision : 000b
Serial : 3833c77d6dc000ec
*/
char buffer[4096];
// If we fail any of the following, assume we don't have NEON instructions
// This allows us to return immediately in case of error.
result = false;
do {
// open /proc/cpuinfo
int fd = TEMP_FAILURE_RETRY(open("/proc/cpuinfo", O_RDONLY));
if (fd < 0) {
SkDebugf("Could not open /proc/cpuinfo: %s\n", strerror(errno));
break;
}
// Read the file. To simplify our search, we're going to place two
// sentinel '\n' characters: one at the start of the buffer, and one at
// the end. This means we reserve the first and last buffer bytes.
buffer[0] = '\n';
int size = TEMP_FAILURE_RETRY(read(fd, buffer+1, sizeof(buffer)-2));
close(fd);
if (size < 0) { // should not happen
SkDebugf("Could not read /proc/cpuinfo: %s\n", strerror(errno));
break;
}
SkDebugf("START /proc/cpuinfo:\n%.*s\nEND /proc/cpuinfo\n",
size, buffer+1);
// Compute buffer limit, and place final sentinel
char* buffer_end = buffer + 1 + size;
buffer_end[0] = '\n';
// Now, find a line that starts with "Features", i.e. look for
// '\nFeatures ' in our buffer.
const char features[] = "\nFeatures\t";
const size_t features_len = sizeof(features)-1;
char* line = (char*) memmem(buffer, buffer_end - buffer,
features, features_len);
if (line == NULL) { // Weird, no Features line, bad kernel?
SkDebugf("Could not find a line starting with 'Features'"
"in /proc/cpuinfo ?\n");
break;
}
line += features_len; // Skip the "\nFeatures\t" prefix
// Find the end of the current line
char* line_end = (char*) memchr(line, '\n', buffer_end - line);
if (line_end == NULL)
line_end = buffer_end;
// Now find an instance of 'neon' in the flags list. We want to
// ensure it's only 'neon' and not something fancy like 'noneon'
// so check that it follows a space.
const char neon[] = " neon";
const size_t neon_len = sizeof(neon)-1;
const char* flag = (const char*) memmem(line, line_end - line,
neon, neon_len);
if (flag == NULL)
break;
// Ensure it is followed by a space or a newline.
if (flag[neon_len] != ' ' && flag[neon_len] != '\n')
break;
// Fine, we support Arm NEON !
result = true;
} while (0);
#endif // USE_ANDROID_NDK_CPU_FEATURES
if (result) {
SkDebugf("Device supports ARM NEON instructions!\n");
} else {
SkDebugf("Device does NOT support ARM NEON instructions!\n");
}
return result;
}
static pthread_once_t sOnce;
static bool sHasArmNeon;
// called through pthread_once()
void sk_cpu_arm_probe_features(void) {
sHasArmNeon = sk_cpu_arm_check_neon();
}
bool sk_cpu_arm_has_neon(void) {
pthread_once(&sOnce, sk_cpu_arm_probe_features);
return sHasArmNeon;
}
#endif // SK_ARM_NEON_IS_DYNAMIC
|
