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

src/hydrogen.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 134 matching lines @@
   int pop_count = environment->pop_count();
 
   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
   // that are older (from further down the stack).
   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();
   return instr;
 }
 
 
 void HBasicBlock::Finish(HControlInstruction* end) {
   ASSERT(!IsFinished());
   AddInstruction(end);
@@ skipping 9396 matching lines @@
 #undef CHECK_BAILOUT
 #undef CHECK_ALIVE
 
 
 HEnvironment::HEnvironment(HEnvironment* outer,
                            Scope* scope,
                            Handle<JSFunction> closure,
                            Zone* zone)
     : closure_(closure),
       values_(0, zone),
-      assigned_variables_(4, zone),
       frame_type_(JS_FUNCTION),
       parameter_count_(0),
       specials_count_(1),
       local_count_(0),
       outer_(outer),
       entry_(NULL),
       pop_count_(0),
       push_count_(0),
       ast_id_(BailoutId::None()),
       zone_(zone) {
   Initialize(scope->num_parameters() + 1, scope->num_stack_slots(), 0);
 }
 
 
 HEnvironment::HEnvironment(Zone* zone)
     : values_(0, zone),
-      assigned_variables_(0, zone),
       frame_type_(STUB),
       parameter_count_(0),
       specials_count_(0),
       local_count_(0),
       outer_(NULL),
       entry_(NULL),
       pop_count_(0),
       push_count_(0),
       ast_id_(BailoutId::None()),
       zone_(zone) {
   Initialize(0, 0, 0);
 }
 
 
 HEnvironment::HEnvironment(const HEnvironment* other, Zone* zone)
     : values_(0, zone),
-      assigned_variables_(0, zone),
       frame_type_(JS_FUNCTION),
       parameter_count_(0),
       specials_count_(1),
       local_count_(0),
       outer_(NULL),
       entry_(NULL),
       pop_count_(0),
       push_count_(0),
       ast_id_(other->ast_id()),
       zone_(zone) {
   Initialize(other);
 }
 
 
 HEnvironment::HEnvironment(HEnvironment* outer,
                            Handle<JSFunction> closure,
                            FrameType frame_type,
                            int arguments,
                            Zone* zone)
     : closure_(closure),
       values_(arguments, zone),
-      assigned_variables_(0, zone),
       frame_type_(frame_type),
       parameter_count_(arguments),
       local_count_(0),
       outer_(outer),
       entry_(NULL),
       pop_count_(0),
       push_count_(0),
       ast_id_(BailoutId::None()),
       zone_(zone) {
 }
 
 
 void HEnvironment::Initialize(int parameter_count,
                               int local_count,
                               int stack_height) {
   parameter_count_ = parameter_count;
   local_count_ = local_count;
 
   // Avoid reallocating the temporaries' backing store on the first Push.
   int total = parameter_count + specials_count_ + local_count + stack_height;
   values_.Initialize(total + 4, zone());
   for (int i = 0; i < total; ++i) values_.Add(NULL, zone());
 }
 
 
 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_;
   if (other->outer_ != NULL) outer_ = other->outer_->Copy();  // Deep copy.
   entry_ = other->entry_;
   pop_count_ = other->pop_count_;
   push_count_ = other->push_count_;
   ast_id_ = other->ast_id_;
 }
 
@@ skipping 23 matching lines @@
       phi->AddInput(other->values_[i]);
       this->values_[i] = phi;
       block->AddPhi(phi);
     }
   }
 }
 
 
 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;
 }
 
 
 bool HEnvironment::HasExpressionAt(int index) const {
   return index >= parameter_count_ + specials_count_ + local_count_;
 }
 
 
 bool HEnvironment::ExpressionStackIsEmpty() const {
@@ skipping 486 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal