[wasm] Break a cycle with a loop node in the int64-lowering.

test/unittests/compiler/int64-lowering-unittest.cc

 // Copyright 2016 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/linkage.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node.h"
 
@@ skipping 857 matching lines @@
   Node* store =
       graph()->NewNode(machine()->Store(store_rep), Int64Constant(value(0)),
                        Int64Constant(value(1)), load, load, graph()->start());
 
   eff_phi->InsertInput(zone(), 1, store);
   NodeProperties::ChangeOp(eff_phi,
                            common()->ResizeMergeOrPhi(eff_phi->op(), 2));
 
   LowerGraph(load, MachineRepresentation::kWord64);
 }
+
+TEST_F(Int64LoweringTest, LoopCycle) {
+  // New node with two placeholders.
+  Node* compare = graph()->NewNode(machine()->Word64Equal(), Int64Constant(0),
+                                   Int64Constant(value(0)));
+
+  Node* load = graph()->NewNode(
+      machine()->Load(MachineType::Int64()), Int64Constant(value(1)),
+      Int64Constant(value(2)), graph()->start(),
+      graph()->NewNode(
+          common()->Loop(2), graph()->start(),
+          graph()->NewNode(common()->IfFalse(),
+                           graph()->NewNode(common()->Branch(), compare,
+                                            graph()->start()))));
+
+  NodeProperties::ReplaceValueInput(compare, load, 0);
+
+  LowerGraph(load, MachineRepresentation::kWord64);
+}
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8