A64: Move the dispatching logic of the decoder to a separate class.

src/a64/decoder-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 79 matching lines @@
 class DecoderVisitor {
  public:
   virtual ~DecoderVisitor() {}
 
   #define DECLARE(A) virtual void Visit##A(Instruction* instr) = 0;
   VISITOR_LIST(DECLARE)
   #undef DECLARE
 };
 
 
-class Decoder {
+// A visitor that dispatches to a list of visitors.
+class DispatchingDecoderVisitor : public DecoderVisitor {
  public:
-  Decoder() {}
-
-  // Top-level instruction decoder function. Decodes an instruction and calls
-  // the visitor functions registered with the Decoder class.
-  void Decode(Instruction *instr);
+  DispatchingDecoderVisitor() {}
+  virtual ~DispatchingDecoderVisitor() {}
 
   // Register a new visitor class with the decoder.
   // Decode() will call the corresponding visitor method from all registered
   // visitor classes when decoding reaches the leaf node of the instruction
   // decode tree.
   // Visitors are called in the order.
   // A visitor can only be registered once.
   // Registering an already registered visitor will update its position.
   //
   //   d.AppendVisitor(V1);
@@ skipping 15 matching lines @@
 
   // Remove a previously registered visitor class from the list of visitors
   // stored by the decoder.
   void RemoveVisitor(DecoderVisitor* visitor);
 
   #define DECLARE(A) void Visit##A(Instruction* instr);
   VISITOR_LIST(DECLARE)
   #undef DECLARE
 
  private:
+  // Visitors are registered in a list.
+  std::list<DecoderVisitor*> visitors_;
+};
+
+
+class Decoder : public DispatchingDecoderVisitor {
+ public:
+  Decoder() {}
+
+  // Top-level instruction decoder function. Decodes an instruction and calls
+  // the visitor functions registered with the Decoder class.
+  void Decode(Instruction *instr);
+
+ private:
   // Decode the PC relative addressing instruction, and call the corresponding
   // visitors.
   // On entry, instruction bits 27:24 = 0x0.
   void DecodePCRelAddressing(Instruction* instr);
 
   // Decode the add/subtract immediate instruction, and call the corresponding
   // visitors.
   // On entry, instruction bits 27:24 = 0x1.
   void DecodeAddSubImmediate(Instruction* instr);
 
@@ skipping 29 matching lines @@
 
   // Decode the Advanced SIMD (NEON) load/store part of the instruction tree,
   // and call the corresponding visitors.
   // On entry, instruction bits 29:25 = 0x6.
   void DecodeAdvSIMDLoadStore(Instruction* instr);
 
   // Decode the Advanced SIMD (NEON) data processing part of the instruction
   // tree, and call the corresponding visitors.
   // On entry, instruction bits 27:25 = 0x7.
   void DecodeAdvSIMDDataProcessing(Instruction* instr);
-
-  // Visitors are registered in a list.
-  std::list<DecoderVisitor*> visitors_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_A64_DECODER_A64_H_