Environment bookkeping has linear time complexity now, not a quadratic one.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 0aa063bb628b3b1cbb8fbd28eaeadff91e1cc913..f286dacbe8d43366828c5dfad4651c6056cff07c 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -152,8 +152,11 @@ HSimulate* HBasicBlock::CreateSimulate(BailoutId ast_id,
   for (int i = 0; i < push_count; ++i) {
     instr->AddPushedValue(environment->ExpressionStackAt(i));
   }
-  for (int i = 0; i < environment->assigned_variables()->length(); ++i) {
-    int index = environment->assigned_variables()->at(i);
+  for (GrowableBitVector::Iterator it(environment->assigned_variables(),
+                                      zone());
+       !it.Done();
+       it.Advance()) {
+    int index = it.Current();
     instr->AddAssignedValue(index, environment->Lookup(index));
   }
   environment->ClearHistory();
@@ -9570,7 +9573,6 @@ HEnvironment::HEnvironment(HEnvironment* outer,
                            Zone* zone)
     : closure_(closure),
       values_(0, zone),
-      assigned_variables_(4, zone),
       frame_type_(JS_FUNCTION),
       parameter_count_(0),
       specials_count_(1),
@@ -9587,7 +9589,6 @@ HEnvironment::HEnvironment(HEnvironment* outer,
 
 HEnvironment::HEnvironment(Zone* zone)
     : values_(0, zone),
-      assigned_variables_(0, zone),
       frame_type_(STUB),
       parameter_count_(0),
       specials_count_(0),
@@ -9604,7 +9605,6 @@ HEnvironment::HEnvironment(Zone* zone)
 
 HEnvironment::HEnvironment(const HEnvironment* other, Zone* zone)
     : values_(0, zone),
-      assigned_variables_(0, zone),
       frame_type_(JS_FUNCTION),
       parameter_count_(0),
       specials_count_(1),
@@ -9626,7 +9626,6 @@ HEnvironment::HEnvironment(HEnvironment* outer,
                            Zone* zone)
     : closure_(closure),
       values_(arguments, zone),
-      assigned_variables_(0, zone),
       frame_type_(frame_type),
       parameter_count_(arguments),
       local_count_(0),
@@ -9655,7 +9654,7 @@ void HEnvironment::Initialize(int parameter_count,
 void HEnvironment::Initialize(const HEnvironment* other) {
   closure_ = other->closure();
   values_.AddAll(other->values_, zone());
-  assigned_variables_.AddAll(other->assigned_variables_, zone());
+  assigned_variables_.Union(other->assigned_variables_, zone());
   frame_type_ = other->frame_type_;
   parameter_count_ = other->parameter_count_;
   local_count_ = other->local_count_;
@@ -9699,9 +9698,7 @@ void HEnvironment::AddIncomingEdge(HBasicBlock* block, HEnvironment* other) {
 
 void HEnvironment::Bind(int index, HValue* value) {
   ASSERT(value != NULL);
-  if (!assigned_variables_.Contains(index)) {
-    assigned_variables_.Add(index, zone());
-  }
+  assigned_variables_.Add(index, zone());
   values_[index] = value;
 }