[turbofan] Avoid unnecessary copying of nodes during inlining.

src/compiler/graph.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_GRAPH_H_
 #define V8_COMPILER_GRAPH_H_
 
 #include "src/zone.h"
 #include "src/zone-containers.h"
 
@@ skipping 10 matching lines @@
 // Marks are used during traversal of the graph to distinguish states of nodes.
 // Each node has a mark which is a monotonically increasing integer, and a
 // {NodeMarker} has a range of values that indicate states of a node.
 typedef uint32_t Mark;
 
 
 // NodeIds are identifying numbers for nodes that can be used to index auxiliary
 // out-of-line data associated with each node.
 typedef uint32_t NodeId;
 
-
-class Graph : public ZoneObject {
+class Graph final : public ZoneObject {
  public:
   explicit Graph(Zone* zone);
 
+  // Scope used when creating a subgraph for inlining. Automatically preserves
+  // the original start and end nodes of the graph, and resets them when you
+  // leave the scope.
+  class SubgraphScope final {
+   public:
+    explicit SubgraphScope(Graph* graph)
+        : graph_(graph), start_(graph->start()), end_(graph->end()) {}
+    ~SubgraphScope() {
+      graph_->SetStart(start_);
+      graph_->SetEnd(end_);
+    }
+
+   private:
+    Graph* const graph_;
+    Node* const start_;
+    Node* const end_;
+
+    DISALLOW_COPY_AND_ASSIGN(SubgraphScope);
+  };
+
   // Base implementation used by all factory methods.
   Node* NewNodeUnchecked(const Operator* op, int input_count,
                          Node* const* inputs, bool incomplete = false);
 
   // Factory that checks the input count.
   Node* NewNode(const Operator* op, int input_count, Node* const* inputs,
                 bool incomplete = false);
 
   // Factories for nodes with static input counts.
   Node* NewNode(const Operator* op) {
@@ skipping 76 matching lines @@
  public:
   virtual ~GraphDecorator() {}
   virtual void Decorate(Node* node) = 0;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_GRAPH_H_