[turbofan] Introduce explicit loop exits markers.

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 b0b4041c5348b3163ed806f6d69ed2b3fd0329b9..3e80456a8679dc2a0f876028e91377f6829392aa 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -49,6 +49,8 @@ class AstGraphBuilder : public AstVisitor {
   Node* NewBranch(Node* condition, BranchHint hint = BranchHint::kNone) {
     return NewNode(common()->Branch(hint), condition);
   }
+  void BuildLoopExit(Node* loop, BitVector* assigned_variables,
+                     Node** extra_value_to_rename);
 
  protected:
 #define DECLARE_VISIT(type) void Visit##type(type* node) override;
@@ -539,6 +541,7 @@ class AstGraphBuilder::Environment : public ZoneObject {
   Node* Checkpoint(BailoutId ast_id, OutputFrameStateCombine combine =
                                          OutputFrameStateCombine::Ignore(),
                    bool node_has_exception = false);
+  void RenameForLoopExit(Node* loop, BitVector* assigned_variables);

[Michael Starzinger, 2016/07/14 12:13:36]

nit: Needs a short comment explaining purpose of method. Also, can we call it
"PrepareForLoopExit" instead?

[Jarin, 2016/07/14 12:51:34]

Done.

 
   // Control dependency tracked by this environment.
   Node* GetControlDependency() { return control_dependency_; }