Avoid creating duplicate entries for a value when merging HSimulates

src/hydrogen-instructions.cc

 // 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 1998 matching lines @@
   }
 }
 
 
 void HSimulate::MergeWith(ZoneList<HSimulate*>* list) {
   while (!list->is_empty()) {
     HSimulate* from = list->RemoveLast();
     ZoneList<HValue*>* from_values = &from->values_;
     for (int i = 0; i < from_values->length(); ++i) {
       if (from->HasAssignedIndexAt(i)) {
-        AddAssignedValue(from->GetAssignedIndexAt(i),
-                         from_values->at(i));
+        int index = from->GetAssignedIndexAt(i);
+        if (HasValueForIndex(index)) continue;
+        AddAssignedValue(index, from_values->at(i));
       } else {
         if (pop_count_ > 0) {
           pop_count_--;
         } else {
           AddPushedValue(from_values->at(i));
         }
       }
     }
     pop_count_ += from->pop_count_;
     from->DeleteAndReplaceWith(NULL);
   }
 }
 
 
 void HSimulate::PrintDataTo(StringStream* stream) {
   stream->Add("id=%d", ast_id().ToInt());
   if (pop_count_ > 0) stream->Add(" pop %d", pop_count_);
   if (values_.length() > 0) {
     if (pop_count_ > 0) stream->Add(" /");
     for (int i = values_.length() - 1; i >= 0; --i) {
-      if (i > 0) stream->Add(",");
       if (HasAssignedIndexAt(i)) {
         stream->Add(" var[%d] = ", GetAssignedIndexAt(i));
       } else {
         stream->Add(" push ");
       }
       values_[i]->PrintNameTo(stream);
+      if (i > 0) stream->Add(",");
     }
   }
 }
 
 
 void HDeoptimize::PrintDataTo(StringStream* stream) {
   if (OperandCount() == 0) return;
   OperandAt(0)->PrintNameTo(stream);
   for (int i = 1; i < OperandCount(); ++i) {
     stream->Add(" ");
@@ skipping 1604 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal