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

This reduces the time take for mjsunit/limit-locals from 56.8s to 15.1s in debug
mode and from 12.0s to 1.6s in release mode.

Note that GrowableBitVector and BitVector should really be merged, and probably
have their allocation strategy parmeterized. The current state of affairs
involving tons of checks and delegation is extremely ugly, and it is far from
clear if all that special casing is a clear win. STL FTW! :-P

Review URL: https://codereview.chromium.org/11775016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13327 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/data-flow.h

@@ -201,6 +201,19 @@ class BitVector: public ZoneObject {
 
 class GrowableBitVector BASE_EMBEDDED {
  public:
+  class Iterator BASE_EMBEDDED {
+   public:
+    Iterator(const GrowableBitVector* target, Zone* zone)
+        : it_(target->bits_ == NULL
+              ? new(zone) BitVector(1, zone)
+              : target->bits_) { }
+    bool Done() const { return it_.Done(); }
+    void Advance() { it_.Advance(); }
+    int Current() const { return it_.Current(); }
+   private:
+    BitVector::Iterator it_;
+  };
+
   GrowableBitVector() : bits_(NULL) { }
 
   bool Contains(int value) const {
@@ -213,6 +226,14 @@ class GrowableBitVector BASE_EMBEDDED {
     bits_->Add(value);
   }
 
+  void Union(const GrowableBitVector& other, Zone* zone) {
+    for (Iterator it(&other, zone); !it.Done(); it.Advance()) {
+      Add(it.Current(), zone);
+    }
+  }
+
+  void Clear() { if (bits_ != NULL) bits_->Clear(); }
+
  private:
   static const int kInitialLength = 1024;
 

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;
 }
 

src/hydrogen.h

@@ -450,7 +450,7 @@ class HEnvironment: public ZoneObject {
   // Simple accessors.
   Handle<JSFunction> closure() const { return closure_; }
   const ZoneList<HValue*>* values() const { return &values_; }
-  const ZoneList<int>* assigned_variables() const {
+  const GrowableBitVector* assigned_variables() const {
     return &assigned_variables_;
   }
   FrameType frame_type() const { return frame_type_; }
@@ -557,7 +557,7 @@ class HEnvironment: public ZoneObject {
   void ClearHistory() {
     pop_count_ = 0;
     push_count_ = 0;
-    assigned_variables_.Rewind(0);
+    assigned_variables_.Clear();
   }
 
   void SetValueAt(int index, HValue* value) {
@@ -606,7 +606,7 @@ class HEnvironment: public ZoneObject {
   Handle<JSFunction> closure_;
   // Value array [parameters] [specials] [locals] [temporaries].
   ZoneList<HValue*> values_;
-  ZoneList<int> assigned_variables_;
+  GrowableBitVector assigned_variables_;
   FrameType frame_type_;
   int parameter_count_;
   int specials_count_;