Better handling of Phi nodes with constant inputs

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 3125 matching lines @@
           HValue* input = OperandAt(i);
           PrintF("#%d %s: Input #%d %s at %d is NCTI\n",
                  id(), Mnemonic(), input->id(), input->Mnemonic(), i);
         }
         return false;
       }
     }
     return true;
   }
 
+  void SimplifyConstantInputs();
+
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {
     inputs_[index] = value;
   }
 
   virtual bool IsRelationTrueInternal(NumericRelation relation,
                                       HValue* other,
                                       int offset = 0,
                                       int scale = 0);
@@ skipping 281 matching lines @@
   HValue* LeastConstantOperand() {
     if (IsCommutative() && left()->IsConstant()) return right();
     return left();
   }
 
   HValue* MostConstantOperand() {
     if (IsCommutative() && left()->IsConstant()) return left();
     return right();
   }
 
-  void set_observed_input_representation(Representation left,
-                                         Representation right) {
-    observed_input_representation_[0] = left;
-    observed_input_representation_[1] = right;
+  void set_observed_input_representation(int index, Representation rep) {
+    ASSERT(index >= 1 && index <= 2);
+    observed_input_representation_[index - 1] = rep;
   }
 
   virtual void initialize_output_representation(Representation observed) {
     observed_output_representation_ = observed;
   }
 
   virtual Representation observed_input_representation(int index) {
     if (index == 0) return Representation::Tagged();
     return observed_input_representation_[index - 1];
   }
@@ skipping 3089 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_