Optimize redundant HCompareMap instructions with known successors.

src/hydrogen-instructions.h

 // Copyright 2012 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 1511 matching lines @@
   ToBooleanStub::Types expected_input_types_;
 };
 
 
 class HCompareMap V8_FINAL : public HUnaryControlInstruction {
  public:
   DECLARE_INSTRUCTION_FACTORY_P2(HCompareMap, HValue*, Handle<Map>);
   DECLARE_INSTRUCTION_FACTORY_P4(HCompareMap, HValue*, Handle<Map>,
                                  HBasicBlock*, HBasicBlock*);
 
+  virtual bool KnownSuccessorBlock(HBasicBlock** block) V8_OVERRIDE {
+    if (known_successor_index() != kNoKnownSuccessorIndex) {
+      *block = SuccessorAt(known_successor_index());
+      return true;
+    }
+    *block = NULL;
+    return false;
+  }
+
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
+  static const int kNoKnownSuccessorIndex = -1;
+  int known_successor_index() const { return known_successor_index_; }
+  void set_known_successor_index(int known_successor_index) {
+    known_successor_index_ = known_successor_index;
+  }
+
   Unique<Map> map() const { return map_; }
 
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     return Representation::Tagged();
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CompareMap)
 
  protected:
   virtual int RedefinedOperandIndex() { return 0; }
 
  private:
   HCompareMap(HValue* value,
               Handle<Map> map,
               HBasicBlock* true_target = NULL,
               HBasicBlock* false_target = NULL)
       : HUnaryControlInstruction(value, true_target, false_target),
-        map_(Unique<Map>(map)) {
+        known_successor_index_(kNoKnownSuccessorIndex), map_(Unique<Map>(map)) {
     ASSERT(!map.is_null());
   }
 
+  int known_successor_index_;
   Unique<Map> map_;
 };
 
 
 class HContext V8_FINAL : public HTemplateInstruction<0> {
  public:
   static HContext* New(Zone* zone) {
     return new(zone) HContext();
   }
 
@@ skipping 5839 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_