[turbofan] Add support for pushing returns into merges.

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/machine-type.h"
 #include "src/compiler/operator.h"
 #include "src/compiler/simplified-operator.h"
@@ skipping 407 matching lines @@
   Node* phi = graph()->NewNode(common()->Phi(kMachFloat64, 2), p0, p1, merge);
   StrictMock<MockAdvancedReducerEditor> editor;
   EXPECT_CALL(editor, Revisit(merge));
   Reduction r = Reduce(&editor, phi, MachineOperatorBuilder::kFloat64Min);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsFloat64Min(p0, p1));
 }
 
 
 // -----------------------------------------------------------------------------
+// Return
+
+
+TEST_F(CommonOperatorReducerTest, ReturnWithPhiAndEffectPhiAndMerge) {
+  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* vtrue = Parameter(0);
+  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
+  Node* efalse = graph()->start();
+  Node* vfalse = Parameter(1);
+  Node* merge = graph()->NewNode(common()->Merge(2), if_true, if_false);
+  Node* ephi = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, merge);
+  Node* phi =
+      graph()->NewNode(common()->Phi(kMachAnyTagged, 2), vtrue, vfalse, merge);
+  Node* ret = graph()->NewNode(common()->Return(), phi, ephi, merge);
+  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)));
+}
+
+
+// -----------------------------------------------------------------------------
 // Select
 
 
 TEST_F(CommonOperatorReducerTest, SelectWithSameThenAndElse) {
   Node* const input = graph()->NewNode(&kOp0);
   TRACED_FOREACH(BranchHint, hint, kBranchHints) {
     TRACED_FOREACH(MachineType, type, kMachineTypes) {
       Reduction r = Reduce(
           graph()->NewNode(common()->Select(type, hint), input, input, input));
       ASSERT_TRUE(r.Changed());
@@ skipping 138 matching lines @@
   Node* select =
       graph()->NewNode(common()->Select(kMachFloat64), check, p0, p1);
   Reduction r = Reduce(select, MachineOperatorBuilder::kFloat64Min);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsFloat64Min(p0, p1));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8