1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/src/core/SkUtilsArm.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,199 @@
1.4 +
1.5 +/*
1.6 + * Copyright 2012 The Android Open Source Project
1.7 + *
1.8 + * Use of this source code is governed by a BSD-style license that can be
1.9 + * found in the LICENSE file.
1.10 + */
1.11 +
1.12 +#include "SkUtilsArm.h"
1.13 +
1.14 +#if SK_ARM_NEON_IS_DYNAMIC
1.15 +
1.16 +#include <unistd.h>
1.17 +#include <fcntl.h>
1.18 +#include <errno.h>
1.19 +#include <string.h>
1.20 +#include <pthread.h>
1.21 +
1.22 +// Set USE_ANDROID_NDK_CPU_FEATURES to use the Android NDK's
1.23 +// cpu-features helper library to detect NEON at runtime. See
1.24 +// http://crbug.com/164154 to see why this is needed in Chromium
1.25 +// for Android.
1.26 +#if !defined(USE_ANDROID_NDK_CPU_FEATURES)
1.27 +# if defined(SK_BUILD_FOR_ANDROID)
1.28 +# define USE_ANDROID_NDK_CPU_FEATURES 1
1.29 +# else
1.30 +# define USE_ANDROID_NDK_CPU_FEATURES 0
1.31 +# endif
1.32 +#endif
1.33 +
1.34 +#if USE_ANDROID_NDK_CPU_FEATURES
1.35 +# include <cpu-features.h>
1.36 +#endif
1.37 +
1.38 +// Set NEON_DEBUG to 1 to allow debugging of the CPU features probing.
1.39 +// For now, we always set it for SK_DEBUG builds.
1.40 +#ifdef SK_DEBUG
1.41 +# define NEON_DEBUG 1
1.42 +#else
1.43 +# define NEON_DEBUG 0
1.44 +#endif
1.45 +
1.46 +#if NEON_DEBUG
1.47 +# ifdef SK_BUILD_FOR_ANDROID
1.48 + // used to declare PROP_VALUE_MAX and __system_property_get()
1.49 +# include <sys/system_properties.h>
1.50 +# endif
1.51 +#endif
1.52 +
1.53 +// A function used to determine at runtime if the target CPU supports
1.54 +// the ARM NEON instruction set. This implementation is Linux-specific.
1.55 +static bool sk_cpu_arm_check_neon(void) {
1.56 + bool result = false;
1.57 +
1.58 +#if NEON_DEBUG
1.59 + // Allow forcing the mode through the environment during debugging.
1.60 +# ifdef SK_BUILD_FOR_ANDROID
1.61 + // On Android, we use a system property
1.62 +# define PROP_NAME "debug.skia.arm_neon_mode"
1.63 + char prop[PROP_VALUE_MAX];
1.64 + if (__system_property_get(PROP_NAME, prop) > 0) {
1.65 +# else
1.66 +# define PROP_NAME "SKIA_ARM_NEON_MODE"
1.67 + // On ARM Linux, we use an environment variable
1.68 + const char* prop = getenv(PROP_NAME);
1.69 + if (prop != NULL) {
1.70 +# endif
1.71 + SkDebugf("%s: %s", PROP_NAME, prop);
1.72 + if (!strcmp(prop, "1")) {
1.73 + SkDebugf("Forcing ARM Neon mode to full!\n");
1.74 + return true;
1.75 + }
1.76 + if (!strcmp(prop, "0")) {
1.77 + SkDebugf("Disabling ARM NEON mode\n");
1.78 + return false;
1.79 + }
1.80 + }
1.81 + SkDebugf("Running dynamic CPU feature detection\n");
1.82 +#endif
1.83 +
1.84 +#if USE_ANDROID_NDK_CPU_FEATURES
1.85 +
1.86 + result = (android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
1.87 +
1.88 +#else // USE_ANDROID_NDK_CPU_FEATURES
1.89 +
1.90 + // There is no user-accessible CPUID instruction on ARM that we can use.
1.91 + // Instead, we must parse /proc/cpuinfo and look for the 'neon' feature.
1.92 + // For example, here's a typical output (Nexus S running ICS 4.0.3):
1.93 + /*
1.94 + Processor : ARMv7 Processor rev 2 (v7l)
1.95 + BogoMIPS : 994.65
1.96 + Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3
1.97 + CPU implementer : 0x41
1.98 + CPU architecture: 7
1.99 + CPU variant : 0x2
1.100 + CPU part : 0xc08
1.101 + CPU revision : 2
1.102 +
1.103 + Hardware : herring
1.104 + Revision : 000b
1.105 + Serial : 3833c77d6dc000ec
1.106 + */
1.107 + char buffer[4096];
1.108 +
1.109 + // If we fail any of the following, assume we don't have NEON instructions
1.110 + // This allows us to return immediately in case of error.
1.111 + result = false;
1.112 +
1.113 + do {
1.114 + // open /proc/cpuinfo
1.115 + int fd = TEMP_FAILURE_RETRY(open("/proc/cpuinfo", O_RDONLY));
1.116 + if (fd < 0) {
1.117 + SkDebugf("Could not open /proc/cpuinfo: %s\n", strerror(errno));
1.118 + break;
1.119 + }
1.120 +
1.121 + // Read the file. To simplify our search, we're going to place two
1.122 + // sentinel '\n' characters: one at the start of the buffer, and one at
1.123 + // the end. This means we reserve the first and last buffer bytes.
1.124 + buffer[0] = '\n';
1.125 + int size = TEMP_FAILURE_RETRY(read(fd, buffer+1, sizeof(buffer)-2));
1.126 + close(fd);
1.127 +
1.128 + if (size < 0) { // should not happen
1.129 + SkDebugf("Could not read /proc/cpuinfo: %s\n", strerror(errno));
1.130 + break;
1.131 + }
1.132 +
1.133 + SkDebugf("START /proc/cpuinfo:\n%.*s\nEND /proc/cpuinfo\n",
1.134 + size, buffer+1);
1.135 +
1.136 + // Compute buffer limit, and place final sentinel
1.137 + char* buffer_end = buffer + 1 + size;
1.138 + buffer_end[0] = '\n';
1.139 +
1.140 + // Now, find a line that starts with "Features", i.e. look for
1.141 + // '\nFeatures ' in our buffer.
1.142 + const char features[] = "\nFeatures\t";
1.143 + const size_t features_len = sizeof(features)-1;
1.144 +
1.145 + char* line = (char*) memmem(buffer, buffer_end - buffer,
1.146 + features, features_len);
1.147 + if (line == NULL) { // Weird, no Features line, bad kernel?
1.148 + SkDebugf("Could not find a line starting with 'Features'"
1.149 + "in /proc/cpuinfo ?\n");
1.150 + break;
1.151 + }
1.152 +
1.153 + line += features_len; // Skip the "\nFeatures\t" prefix
1.154 +
1.155 + // Find the end of the current line
1.156 + char* line_end = (char*) memchr(line, '\n', buffer_end - line);
1.157 + if (line_end == NULL)
1.158 + line_end = buffer_end;
1.159 +
1.160 + // Now find an instance of 'neon' in the flags list. We want to
1.161 + // ensure it's only 'neon' and not something fancy like 'noneon'
1.162 + // so check that it follows a space.
1.163 + const char neon[] = " neon";
1.164 + const size_t neon_len = sizeof(neon)-1;
1.165 + const char* flag = (const char*) memmem(line, line_end - line,
1.166 + neon, neon_len);
1.167 + if (flag == NULL)
1.168 + break;
1.169 +
1.170 + // Ensure it is followed by a space or a newline.
1.171 + if (flag[neon_len] != ' ' && flag[neon_len] != '\n')
1.172 + break;
1.173 +
1.174 + // Fine, we support Arm NEON !
1.175 + result = true;
1.176 +
1.177 + } while (0);
1.178 +
1.179 +#endif // USE_ANDROID_NDK_CPU_FEATURES
1.180 +
1.181 + if (result) {
1.182 + SkDebugf("Device supports ARM NEON instructions!\n");
1.183 + } else {
1.184 + SkDebugf("Device does NOT support ARM NEON instructions!\n");
1.185 + }
1.186 + return result;
1.187 +}
1.188 +
1.189 +static pthread_once_t sOnce;
1.190 +static bool sHasArmNeon;
1.191 +
1.192 +// called through pthread_once()
1.193 +void sk_cpu_arm_probe_features(void) {
1.194 + sHasArmNeon = sk_cpu_arm_check_neon();
1.195 +}
1.196 +
1.197 +bool sk_cpu_arm_has_neon(void) {
1.198 + pthread_once(&sOnce, sk_cpu_arm_probe_features);
1.199 + return sHasArmNeon;
1.200 +}
1.201 +
1.202 +#endif // SK_ARM_NEON_IS_DYNAMIC
