VM: Emit compacter code for x64 branches to external labels.

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 335 matching lines @@
 
   /*
    * 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 = 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 295 matching lines @@
   // 'size' indicates size in bytes and must be in the range 1..8.
   void nop(int size = 1);
   void int3();
   void hlt();
 
   // Note: verified_mem mode forces far jumps.
   void j(Condition condition, Label* label, bool near = kFarJump);
   void j(Condition condition, const ExternalLabel* label);
 
   void jmp(Register reg);
+  void jmp(const Address& address);
   // Note: verified_mem mode forces far jumps.
   void jmp(Label* label, bool near = kFarJump);
   void jmp(const ExternalLabel* label);
 
   void lock();
   void cmpxchgl(const Address& address, Register reg);
   void lock_cmpxchgl(const Address& address, Register reg) {
     lock();
     cmpxchgl(address, reg);
   }
@@ skipping 506 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_