[turbofan] Do not reduce Return nodes with multiple value inputs.

test/unittests/compiler/common-operator-reducer-unittest.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/common-operator.h"
 #include "src/compiler/common-operator-reducer.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/operator.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/machine-type.h"
@@ skipping 356 matching lines @@
   graph()->SetEnd(graph()->NewNode(common()->End(1), ret));
   StrictMock<MockAdvancedReducerEditor> editor;
   EXPECT_CALL(editor, Replace(merge, IsDead()));
   Reduction const r = Reduce(&editor, ret);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsDead());
   EXPECT_THAT(graph()->end(), IsEnd(ret, IsReturn(vtrue, etrue, if_true),
                                     IsReturn(vfalse, efalse, if_false)));
 }
 
+TEST_F(CommonOperatorReducerTest, MultiReturnWithPhiAndEffectPhiAndMerge) {
+  Node* cond = Parameter(2);
+  Node* branch = graph()->NewNode(common()->Branch(), cond, graph()->start());
+  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
+  Node* etrue = graph()->start();
+  Node* vtrue1 = Parameter(0);
+  Node* vtrue2 = Parameter(1);
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* efalse = graph()->start();
+  Node* vfalse1 = Parameter(1);
+  Node* vfalse2 = Parameter(0);
+  Node* merge = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  Node* ephi = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, merge);
+  Node* phi1 = graph()->NewNode(
+      common()->Phi(MachineRepresentation::kTagged, 2), vtrue1, vfalse1, merge);
+  Node* phi2 = graph()->NewNode(
+      common()->Phi(MachineRepresentation::kTagged, 2), vtrue2, vfalse2, merge);
+
+  Node* zero = graph()->NewNode(common()->Int32Constant(0));
+  Node* ret =
+      graph()->NewNode(common()->Return(2), zero, phi1, phi2, ephi, merge);
+  graph()->SetEnd(graph()->NewNode(common()->End(1), ret));
+  StrictMock<MockAdvancedReducerEditor> editor;
+  Reduction const r = Reduce(&editor, ret);
+  // For now a return with multiple return values should not be reduced.
+  ASSERT_TRUE(!r.Changed());
+}
 
 // -----------------------------------------------------------------------------
 // Select
 
 
 TEST_F(CommonOperatorReducerTest, SelectWithSameThenAndElse) {
   Node* const input = graph()->NewNode(&kOp0);
   TRACED_FOREACH(BranchHint, hint, kBranchHints) {
     TRACED_FOREACH(MachineRepresentation, rep, kMachineRepresentations) {
       Reduction r = Reduce(
@@ skipping 73 matching lines @@
       graph()->NewNode(common()->Select(MachineRepresentation::kFloat64), check,
                        p0, graph()->NewNode(machine()->Float64Sub(), c0, p0));
   Reduction r = Reduce(select);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsFloat64Abs(p0));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8