Refactors CPU feature detection.

runtime/vm/cpu_x64.h

Index: runtime/vm/cpu_x64.h
===================================================================
--- runtime/vm/cpu_x64.h	(revision 0)
+++ runtime/vm/cpu_x64.h	(revision 0)
@@ -0,0 +1,36 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_CPU_X64_H_
+#define VM_CPU_X64_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+class CPUFeatures : public AllStatic {
+ public:
+  static void InitOnce();
+  static bool sse2_supported() { return true; }
+  static bool sse4_1_supported();
+  static bool double_truncate_round_supported() { return false; }
+  static char* hardware();
+
+ private:
+  static const uint64_t kSSE4_1BitMask = static_cast<uint64_t>(1) << 51;
+
+  static bool sse2_supported_;
+  static bool sse4_1_supported_;
+
+#define HARDWARE_LEN 64
+  static char hardware_[HARDWARE_LEN];
+
+#if defined(DEBUG)
+  static bool initialized_;
+#endif
+};
+
+}  // namespace dart
+
+#endif  // VM_CPU_X64_H_