[turbofan] Fix control reducer for dead loops.

test/cctest/compiler/test-control-reducer.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/v8.h"
 #include "test/cctest/cctest.h"
 
 #include "src/base/bits.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/control-reducer.h"
@@ skipping 146 matching lines @@
     p0->ReplaceInput(0, start);  // hack: parameters may be trimmed.
     Node* ret = graph.NewNode(common.Return(), phi, start, start);
     Node* end = graph.NewNode(common.End(), ret);
     graph.SetEnd(end);
     ControlReducer::ReduceGraph(main_zone(), &jsgraph, &common);
     CheckInputs(end, ret);
     CheckInputs(ret, expect, start, start);
   }
 
   void ReduceMerge(Node* expect, Node* merge) {
-    Node* result =
-        ControlReducer::ReduceMergeForTesting(&jsgraph, &common, merge);
+    Node* result = ControlReducer::ReduceMerge(&jsgraph, &common, merge);
     CHECK_EQ(expect, result);
   }
 
   void ReduceMergeIterative(Node* expect, Node* merge) {
     p0->ReplaceInput(0, start);  // hack: parameters may be trimmed.
     Node* end = graph.NewNode(common.End(), merge);
     graph.SetEnd(end);
     ReduceGraph();
     CheckInputs(end, expect);
   }
@@ skipping 688 matching lines @@
     Node* phi_use =
         R.graph.NewNode(R.common.Phi(kMachAnyTagged, 1), phi, R.start);
     Node* ephi_use = R.graph.NewNode(R.common.EffectPhi(1), ephi, R.start);
 
     Selector selector(mask);
 
     for (int i = 0; i < kSelectorSize; i++) {  // set up dead merge inputs.
       if (!selector.is_selected(i)) merge->ReplaceInput(i, R.dead);
     }
 
-    Node* result =
-        ControlReducer::ReduceMergeForTesting(&R.jsgraph, &R.common, merge);
+    Node* result = ControlReducer::ReduceMerge(&R.jsgraph, &R.common, merge);
 
     int count = selector.count;
     if (count == 0) {
       // result should be dead.
       CHECK_EQ(IrOpcode::kDead, result->opcode());
     } else if (count == 1) {
       // merge should be replaced with one of the controls.
       CHECK_EQ(controls[selector.single_index()], result);
       // Phis should have been directly replaced.
       CHECK_EQ(values[selector.single_index()], phi_use->InputAt(0));
@@ skipping 617 matching lines @@
 
   Node* ret = R.Return(d1.phi, R.start, d1.merge);
 
   R.ReduceGraph();  // d1 gets folded true.
 
   CheckInputs(ret, y2, R.start, R.start);
   CheckDeadDiamond(d1);
   CheckDeadDiamond(d2);
   CheckDeadDiamond(d3);
 }