[wasm] Break effect cycles in the Int64Lowering.

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

Index: test/unittests/compiler/int64-lowering-unittest.cc
diff --git a/test/unittests/compiler/int64-lowering-unittest.cc b/test/unittests/compiler/int64-lowering-unittest.cc
index 06ac524111aea85251f7f68505e26fa719bee4a5..fb6c76b1ea1814e3949bb79a8fd92757ba2b6c1a 100644
--- a/test/unittests/compiler/int64-lowering-unittest.cc
+++ b/test/unittests/compiler/int64-lowering-unittest.cc
@@ -849,6 +849,30 @@ TEST_F(Int64LoweringTest, I64ReverseBytes) {
                 IsWord32ReverseBytes(IsInt32Constant(low_word_value(0))),
                 start(), start()));
 }
+
+TEST_F(Int64LoweringTest, EffectPhiLoop) {
+  // Construct a cycle consisting of an EffectPhi, a Store, and a Load.
+  Node* eff_phi = graph()->NewNode(common()->EffectPhi(1), graph()->start(),
+                                   graph()->start());
+
+  StoreRepresentation store_rep(MachineRepresentation::kWord64,
+                                WriteBarrierKind::kNoWriteBarrier);
+  LoadRepresentation load_rep(MachineType::Int64());
+
+  Node* load =
+      graph()->NewNode(machine()->Load(load_rep), Int64Constant(value(0)),
+                       Int64Constant(value(1)), eff_phi, graph()->start());
+
+  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);
+}
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8