[wasm] Unittest for Int64Lowering.

src/compiler/int64-lowering.cc

 // 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.
 
 #include "src/compiler/int64-lowering.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-properties.h"
@@ skipping 191 matching lines @@
     case IrOpcode::kParameter: {
       DCHECK(node->InputCount() == 1);
       // Only exchange the node if the parameter count actually changed. We do
       // not even have to do the default lowering because the the start node,
       // the only input of a parameter node, only changes if the parameter count
       // changes.
       if (GetParameterCountAfterLowering(signature()) !=
           signature()->parameter_count()) {
         int old_index = ParameterIndexOf(node->op());
         int new_index = GetParameterIndexAfterLowering(signature(), old_index);
+        // TODO(ahaas): Use NodeProperties::ChangeOp here instead of allocating
+        // a new node.
         Node* low_node =
             graph()->NewNode(common()->Parameter(new_index), graph()->start());
 
         Node* high_node = nullptr;
         if (signature()->GetParam(old_index) ==
             MachineRepresentation::kWord64) {
           high_node = graph()->NewNode(common()->Parameter(new_index + 1),
                                        graph()->start());
         }
         ReplaceNode(node, low_node, high_node);
@@ skipping 69 matching lines @@
 }
 
 Node* Int64Lowering::GetReplacementHigh(Node* node) {
   Node* result = replacements_[node->id()].high;
   DCHECK(result);
   return result;
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8