Implement loop variable assignment analysis.

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index 15f9230fa018d7a19e567779aa6a1bba62c33394..7cff07ce3eaf05cb8bbc82144a37cd060c0f59a2 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -16,8 +16,9 @@ namespace internal {
 namespace compiler {
 
 class ControlBuilder;
-class LoopBuilder;
 class Graph;
+class LoopAssignmentAnalysis;
+class LoopBuilder;
 
 // The AstGraphBuilder produces a high-level IR graph, based on an
 // underlying AST. The produced graph can either be compiled into a
@@ -135,6 +136,8 @@ class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
   SetOncePointer<Node> function_closure_;
   SetOncePointer<Node> function_context_;
 
+  LoopAssignmentAnalysis* loop_assignment_analysis_;
+
   CompilationInfo* info() const { return info_; }
   inline StrictMode strict_mode() const;
   JSGraph* jsgraph() { return jsgraph_; }
@@ -188,6 +191,8 @@ class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
 
   OutputFrameStateCombine StateCombineFromAstContext();
 
+  BitVector* GetVariablesAssignedInLoop(IterationStatement* stmt);
+
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
   DISALLOW_COPY_AND_ASSIGN(AstGraphBuilder);
 };