Pepper: Refactor cpu feature attributes.

components/nacl/renderer/platform_info.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/cpu.h"
+#include "base/logging.h"
+#include "base/strings/string_util.h"
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+#endif
+
+namespace nacl {
+
+const char* GetSandboxArch() {
+#if defined(ARCH_CPU_ARM_FAMILY)
+  return "arm";
+#elif defined(ARCH_CPU_MIPS_FAMILY)
+  return "mips32";
+#elif defined(ARCH_CPU_X86_FAMILY)
+
+#if defined(OS_WIN)
+  // We have to check the host architecture on Windows.
+  // See sandbox_isa.h for an explanation why.
+  if (base::win::OSInfo::GetInstance()->architecture() ==
+      base::win::OSInfo::X64_ARCHITECTURE)
+    return "x86-64";
+  else
+    return "x86-32";
+#elif ARCH_CPU_64_BITS
+  return "x86-64";
+#else
+  return "x86-32";
+#endif  // defined(OS_WIN)
+
+#else
+#error Architecture not supported.
+#endif
+}
+
+std::string GetCpuFeatures() {
+  // PNaCl's translator from pexe to nexe can be told exactly what
+  // capabilities the user's machine has because the pexe to nexe
+  // translation is specific to the machine, and CPU information goes
+  // into the translation cache. This allows the translator to generate
+  // faster code.
+  //
+  // Care must be taken to avoid instructions which aren't supported by
+  // the NaCl sandbox. Ideally the translator would do this, but there's
+  // no point in not doing the whitelist here.
+  //
+  // TODO(jfb) Some features are missing, either because the NaCl
+  //           sandbox doesn't support them, because base::CPU doesn't
+  //           detect them, or because they don't help vector shuffles
+  //           (and we omit them because it simplifies testing). Add the
+  //           other features.
+  //
+  // TODO(jfb) The following is x86-specific. The base::CPU class
+  //           doesn't handle other architectures very well, and we
+  //           should at least detect the presence of ARM's integer
+  //           divide.
+  std::vector<std::string> features;
+  base::CPU cpu;
+
+  // On x86, SSE features are ordered: the most recent one implies the
+  // others. Care is taken here to only specify the latest SSE version,
+  // whereas non-SSE features don't follow this model: POPCNT is
+  // effectively always implied by SSE4.2 but has to be specified
+  // separately.
+  //
+  // TODO: AVX2, AVX, SSE 4.2.
+  if (cpu.has_sse41()) features.push_back("+sse4.1");
+  // TODO: SSE 4A, SSE 4.
+  else if (cpu.has_ssse3()) features.push_back("+ssse3");
+  // TODO: SSE 3
+  else if (cpu.has_sse2()) features.push_back("+sse2");
+
+  // TODO: AES, POPCNT, LZCNT, ...
+  return JoinString(features, ',');
+}
+
+}  // namespace nacl