Include initial definitions in reaching definitions analysis.

src/data-flow.h

Index: src/data-flow.h
diff --git a/src/data-flow.h b/src/data-flow.h
index 74a370c0da446898e94feb6ac336e9243f4e5973..f380702c77ef32cd0915e9d8daffe1da18d776c8 100644
--- a/src/data-flow.h
+++ b/src/data-flow.h
@@ -485,19 +485,20 @@ class FlowGraph BASE_EMBEDDED {
 // traversal orders as a byproduct.
 class FlowGraphBuilder: public AstVisitor {
  public:
-  FlowGraphBuilder()
+  explicit FlowGraphBuilder(int variable_count)
       : graph_(FlowGraph::Empty()),
         global_exit_(NULL),
         preorder_(4),
         postorder_(4),
-        definitions_(4) {
+        variable_count_(variable_count),
+        body_definitions_(4) {
   }
 
   void Build(FunctionLiteral* lit);
 
   FlowGraph* graph() { return &graph_; }
   ZoneList<Node*>* postorder() { return &postorder_; }
-  ZoneList<Expression*>* definitions() { return &definitions_; }
+  ZoneList<Expression*>* body_definitions() { return &body_definitions_; }
 
  private:
   ExitNode* global_exit() { return global_exit_; }
@@ -512,11 +513,13 @@ class FlowGraphBuilder: public AstVisitor {
   ZoneList<Node*> preorder_;
   ZoneList<Node*> postorder_;
 
-  // The flow graph builder collects a list of definitions (assignments and
-  // count operations) to stack-allocated variables to use for reaching
-  // definitions analysis.  AST node numbers in the AST are used to refer
-  // into this list.
-  ZoneList<Expression*> definitions_;
+  // The flow graph builder collects a list of explicit definitions
+  // (assignments and count operations) to stack-allocated variables to use
+  // for reaching definitions analysis.  It does not count the implicit
+  // definition at function entry.  AST node numbers in the AST are used to
+  // refer into this list.
+  int variable_count_;
+  ZoneList<Expression*> body_definitions_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphBuilder);
 };
@@ -589,15 +592,11 @@ class AssignedVariablesAnalyzer : public AstVisitor {
 class ReachingDefinitions BASE_EMBEDDED {
  public:
   ReachingDefinitions(ZoneList<Node*>* postorder,
-                      ZoneList<Expression*>* definitions,
+                      ZoneList<Expression*>* body_definitions,
                       int variable_count)
       : postorder_(postorder),
-        definitions_(definitions),
-        variables_(variable_count) {
-    int definition_count = definitions->length();
-    for (int i = 0; i < variable_count; i++) {
-      variables_.Add(new BitVector(definition_count));
-    }
+        body_definitions_(body_definitions),
+        variable_count_(variable_count) {
   }
 
   static int IndexFor(Variable* var, int variable_count);
@@ -609,10 +608,9 @@ class ReachingDefinitions BASE_EMBEDDED {
   ZoneList<Node*>* postorder_;
 
   // A list of all the definitions in the body.
-  ZoneList<Expression*>* definitions_;
+  ZoneList<Expression*>* body_definitions_;
 
-  // For each variable, the set of all its definitions.
-  List<BitVector*> variables_;
+  int variable_count_;
 
   DISALLOW_COPY_AND_ASSIGN(ReachingDefinitions);
 };