Move CPU feature detection to its own file.

src/core/SkUtilsArm.cpp

 /*
  * 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>
-
-#if defined(SK_BUILD_FOR_ANDROID)
-#  include <cpu-features.h>
-#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) {
-    // If we fail any of the following, assume we don't have NEON instructions
-    // This allows us to return immediately in case of error.
-    bool result = false;
-
-// 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.
-#ifdef SK_BUILD_FOR_ANDROID
-
-  result = (android_getCpuFeatures() & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
-
-#else  // SK_BUILD_FOR_ANDROID
-
-    // 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];
-
-    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 == nullptr) {  // 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 == nullptr)
-            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 == nullptr)
-            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  // SK_BUILD_FOR_ANDROID
-
-    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
+// This file no longer needs to exist, but it's still referenced by Chrome's GYP / GN builds.