[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..af4ebfb442fe29b0fd8bfdd32b6d2f816cd19b45 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -540,6 +540,10 @@ class AstGraphBuilder::Environment : public ZoneObject {
                                          OutputFrameStateCombine::Ignore(),
                    bool node_has_exception = false);
 
+  // Inserts a loop exit control node and renames the environment.
+  // This is useful for loop peeling to insert phis at loop exits.
+  void PrepareForLoopExit(Node* loop, BitVector* assigned_variables);
+
   // Control dependency tracked by this environment.
   Node* GetControlDependency() { return control_dependency_; }
   void UpdateControlDependency(Node* dependency) {