[wasm] Int64Lowering: changing to DFS.

src/compiler/int64-lowering.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_INT64_LOWERING_H_
 #define V8_COMPILER_INT64_LOWERING_H_
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-marker.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 class Int64Lowering {
  public:
   Int64Lowering(Graph* graph, MachineOperatorBuilder* machine,
                 CommonOperatorBuilder* common, Zone* zone,
                 Signature<MachineRepresentation>* signature);
 
   void LowerGraph();
 
  private:
-  enum class State : uint8_t { kUnvisited, kOnStack, kInputsPushed, kVisited };
+  enum class State : uint8_t { kUnvisited, kOnStack, kVisited };
 
   struct Replacement {
     Node* low;
     Node* high;
   };
 
   Zone* zone() const { return zone_; }
   Graph* graph() const { return graph_; }
   MachineOperatorBuilder* machine() const { return machine_; }
   CommonOperatorBuilder* common() const { return common_; }
   Signature<MachineRepresentation>* signature() const { return signature_; }
 
   void LowerNode(Node* node);
   bool DefaultLowering(Node* node);
   void LowerComparison(Node* node, const Operator* signed_op,
                        const Operator* unsigned_op);
 
   void ReplaceNode(Node* old, Node* new_low, Node* new_high);
   bool HasReplacementLow(Node* node);
   Node* GetReplacementLow(Node* node);
   bool HasReplacementHigh(Node* node);
   Node* GetReplacementHigh(Node* node);
 
+  struct NodeState {
+    Node* node;
+    int input_index;
+  };
+
   Zone* zone_;
   Graph* const graph_;
   MachineOperatorBuilder* machine_;
   CommonOperatorBuilder* common_;
   NodeMarker<State> state_;
-  ZoneStack<Node*> stack_;
+  ZoneStack<NodeState> stack_;
   Replacement* replacements_;
   Signature<MachineRepresentation>* signature_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INT64_LOWERING_H_