[turbofan] Use appropriate type for NodeId.

src/compiler/graph-reducer.h

 // Copyright 2014 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_REDUCER_H_
 #define V8_COMPILER_GRAPH_REDUCER_H_
 
 #include "src/compiler/node-marker.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Forward declarations.
 class Graph;
 class Node;
 
 
 // NodeIds are identifying numbers for nodes that can be used to index auxiliary
 // out-of-line data associated with each node.
-typedef int32_t NodeId;
+typedef uint32_t NodeId;
 
 
 // Represents the result of trying to reduce a node in the graph.
 class Reduction final {
  public:
   explicit Reduction(Node* replacement = nullptr) : replacement_(replacement) {}
 
   Node* replacement() const { return replacement_; }
   bool Changed() const { return replacement() != nullptr; }
 
@@ skipping 146 matching lines @@
   ZoneStack<NodeState> stack_;
 
   DISALLOW_COPY_AND_ASSIGN(GraphReducer);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_GRAPH_REDUCER_H_