VM: Small generated code size improvements on x64.

runtime/vm/assembler_x64.h

 // Copyright (c) 2013, 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 334 matching lines @@
   static const bool kFarJump = false;
 
   /*
    * Emit Machine Instructions.
    */
   void call(Register reg);
   void call(const Address& address);
   void call(Label* label);
   void call(const ExternalLabel* label);
 
-  static const intptr_t kCallExternalLabelSize = 10;
+  static const intptr_t kCallExternalLabelSize = 7;
+  static const intptr_t kJmpExternalLabelSize = 10;
 
   void pushq(Register reg);
   void pushq(const Address& address);
   void pushq(const Immediate& imm);
   void PushImmediate(const Immediate& imm, Register pp);
 
   void popq(Register reg);
   void popq(const Address& address);
 
   void setcc(Condition condition, ByteRegister dst);
@@ skipping 353 matching lines @@
   // Macros accepting a pp Register argument may attempt to load values from
   // the object pool when possible. Unless you are sure that the untagged object
   // pool pointer is in another register, or that it is not available at all,
   // PP should be passed for pp.
   // TODO(koda): Assert that these are not used for heap objects.
   void AddImmediate(Register reg, const Immediate& imm, Register pp);
   void AddImmediate(const Address& address, const Immediate& imm, Register pp);
   void SubImmediate(Register reg, const Immediate& imm, Register pp);
   void SubImmediate(const Address& address, const Immediate& imm, Register pp);
 
-  void Drop(intptr_t stack_elements);
+  void Drop(intptr_t stack_elements, Register tmp = TMP);
 
   enum Patchability {
     kPatchable,
     kNotPatchable,
   };
 
   bool allow_constant_pool() const {
     return allow_constant_pool_;
   }
   void set_allow_constant_pool(bool b) {
@@ skipping 457 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_