Avoid creating duplicate entries for a value when merging HSimulates

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/15660003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14766 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/code-stubs-hydrogen.cc

@@ -148,7 +148,7 @@ bool CodeStubGraphBuilderBase::BuildGraph() {
                                                  HParameter::REGISTER_PARAMETER,
                                                  Representation::Integer32());
     stack_parameter_count->set_type(HType::Smi());
-    // it's essential to bind this value to the environment in case of deopt
+    // It's essential to bind this value to the environment in case of deopt.
     AddInstruction(stack_parameter_count);
     start_environment->Bind(param_count, stack_parameter_count);
     arguments_length_ = stack_parameter_count;
@@ -169,7 +169,7 @@ bool CodeStubGraphBuilderBase::BuildGraph() {
   HValue* return_value = BuildCodeStub();
 
   // We might have extra expressions to pop from the stack in addition to the
-  // arguments above
+  // arguments above.
   HInstruction* stack_pop_count = stack_parameter_count;
   if (descriptor_->function_mode_ == JS_FUNCTION_STUB_MODE) {
     if (!stack_parameter_count->IsConstant() &&

src/hydrogen-instructions.cc

@@ -2016,8 +2016,9 @@ void HSimulate::MergeWith(ZoneList<HSimulate*>* list) {
     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_--;
@@ -2038,13 +2039,13 @@ void HSimulate::PrintDataTo(StringStream* stream) {
   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(",");
     }
   }
 }

src/hydrogen-instructions.h

@@ -1858,6 +1858,12 @@ class HSimulate: public HInstruction {
     // use lists are correctly updated.
     SetOperandAt(values_.length() - 1, value);
   }
+  bool HasValueForIndex(int index) {
+    for (int i = 0; i < assigned_indexes_.length(); ++i) {
+      if (assigned_indexes_[i] == index) return true;
+    }
+    return false;
+  }
   BailoutId ast_id_;
   int pop_count_;
   ZoneList<HValue*> values_;

src/hydrogen.cc

@@ -157,7 +157,7 @@ HSimulate* HBasicBlock::CreateSimulate(BailoutId ast_id,
   HSimulate* instr =
       new(zone()) HSimulate(ast_id, pop_count, zone(), removable);
   // Order of pushed values: newest (top of stack) first. This allows
-  // HSimulate::MergeInto() to easily append additional pushed values
+  // HSimulate::MergeWith() to easily append additional pushed values
   // that are older (from further down the stack).
   for (int i = 0; i < push_count; ++i) {
     instr->AddPushedValue(environment->ExpressionStackAt(i));