Begins work on ARM64, first assembler test.

runtime/vm/cpu_arm64.h

Index: runtime/vm/cpu_arm64.h
===================================================================
--- runtime/vm/cpu_arm64.h	(revision 0)
+++ runtime/vm/cpu_arm64.h	(revision 0)
@@ -0,0 +1,55 @@
+// Copyright (c) 2014, 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_ARM64_H_
+#define VM_CPU_ARM64_H_
+
+#include "vm/allocation.h"
+#include "vm/simulator.h"
+
+namespace dart {
+
+// TargetCPUFeatures gives CPU features for the architecture that we are
+// generating code for. HostCPUFeatures gives the CPU features for the
+// architecture that we are actually running on. When the architectures
+// are the same, TargetCPUFeatures will query HostCPUFeatures. When they are
+// different (i.e. we are running in a simulator), HostCPUFeatures will
+// additionally mock the options needed for the target architecture so that
+// they may be altered for testing.
+
+class HostCPUFeatures: public AllStatic {
+ public:
+  static void InitOnce();
+  static void Cleanup();
+  static const char* hardware() {
+    DEBUG_ASSERT(initialized_);
+    return hardware_;
+  }
+
+ private:
+  static const char* hardware_;
+#if defined(DEBUG)
+  static bool initialized_;
+#endif
+};
+
+class TargetCPUFeatures : public AllStatic {
+ public:
+  static void InitOnce() {
+    HostCPUFeatures::InitOnce();
+  }
+  static void Cleanup() {
+    HostCPUFeatures::Cleanup();
+  }
+  static const char* hardware() {
+    return HostCPUFeatures::hardware();
+  }
+  static bool double_truncate_round_supported() {
+    return false;
+  }
+};
+
+}  // namespace dart
+
+#endif  // VM_CPU_ARM64_H_