Implement a simple register allocator that tries to keep instruction results in registers.

runtime/vm/assembler_x64.h

 // 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_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 483 matching lines @@
   }
 
   /*
    * Macros for High-level operations and implemented on all architectures.
    */
 
   void CompareRegisters(Register a, Register b);
 
   // Issues a move instruction if 'to' is not the same as 'from'.
   void MoveRegister(Register to, Register from);
+  void PushRegister(Register r);
+  void PopRegister(Register r);
 
   void AddImmediate(Register reg, const Immediate& imm);
 
   void Drop(intptr_t stack_elements);
 
   void LoadObject(Register dst, const Object& object);
   void PushObject(const Object& object);
   void CompareObject(Register reg, const Object& object);
   void LoadDoubleConstant(XmmRegister dst, double value);
 
@@ skipping 145 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_