[turbofan] Avoid unnecessary copying of nodes during inlining.

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 1d0fc9015e55b3dbdbe141573c6d79d004531d57..96fc2fae03a611c624abd9edd4164cdccebfeadd 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -106,6 +106,9 @@ class AstGraphBuilder : public AstVisitor {
   // Optimization to cache loaded feedback vector.
   SetOncePointer<Node> feedback_vector_;
 
+  // Optimization to cache empty frame state.
+  SetOncePointer<Node> empty_frame_state_;
+
   // Control nodes that exit the function body.
   ZoneVector<Node*> exit_controls_;
 
@@ -167,6 +170,9 @@ class AstGraphBuilder : public AstVisitor {
   // Get or create the node that represents the incoming new target value.
   Node* GetNewTarget();
 
+  // Get or create the node that represents the empty frame state.
+  Node* GetEmptyFrameState();
+
   // Node creation helpers.
   Node* NewNode(const Operator* op, bool incomplete = false) {
     return MakeNode(op, 0, static_cast<Node**>(nullptr), incomplete);