Add 64-bit stubs to call into the runtime and to call native functions.

runtime/vm/constants_x64.h

 // Copyright (c) 2011, 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_CONSTANTS_X64_H_
 #define VM_CONSTANTS_X64_H_
 
 namespace dart {
 
 enum Register {
@@ skipping 38 matching lines @@
   XMM3 = 3,
   XMM4 = 4,
   XMM5 = 5,
   XMM6 = 6,
   XMM7 = 7,
   kNumberOfXmmRegisters = 8,
   kNoXmmRegister = -1  // Signals an illegal register.
 };
 
 
+enum RexBits {
+  REX_NONE   = 0,
+  REX_B      = 1 << 0,
+  REX_X      = 1 << 1,
+  REX_R      = 1 << 2,
+  REX_W      = 1 << 3,
+  REX_PREFIX = 1 << 6
+};
+
+
 // Register aliases.
 const Register TMP = R11;  // Used as scratch register by the assembler.
-const Register CTX = R12;  // Caches current context in generated code.
+const Register CTX = R15;  // Caches current context in generated code.
 
 // Exception object is passed in this register to the catch handlers when an
 // exception is thrown.
 const Register kExceptionObjectReg = RAX;
 
 // Stack trace object is passed in this register to the catch handlers when
 // an exception is thrown.
 const Register kStackTraceObjectReg = RDX;
 
 enum ScaleFactor {
@@ skipping 49 matching lines @@
 
  private:
   DISALLOW_ALLOCATION();
   // We need to prevent the creation of instances of class Instr.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Instr);
 };
 
 }  // namespace dart
 
 #endif  // VM_CONSTANTS_X64_H_