[turbofan] Connect loops to end via Terminate during graph building.

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/all-nodes.h"
 #include "src/compiler/common-operator.h"
@@ skipping 1243 matching lines @@
   Node* if_true = R.graph.NewNode(R.common.IfTrue(), branch);
   Node* if_false = R.graph.NewNode(R.common.IfFalse(), branch);
   Node* merge = R.graph.NewNode(R.common.Merge(2), if_false, if_true);
   R.ReduceMergeIterative(R.start, merge);
 }
 
 
 TEST(CDeadLoop1) {
   ControlReducerTester R;
 
-  Node* loop = R.graph.NewNode(R.common.Loop(1), R.start);
-  Branch b(R, R.p0, loop);
-  loop->ReplaceInput(0, b.if_true);  // loop is not connected to start.
-  Node* merge = R.graph.NewNode(R.common.Merge(2), R.start, b.if_false);
-  R.ReduceMergeIterative(R.start, merge);
-
-  DeadChecker dead(&R.graph);
-  dead.Check(b.if_true);
-  dead.Check(b.if_false);
-  dead.Check(b.branch);
-  dead.Check(loop);
-}
-
-
-TEST(CDeadLoop2) {
-  ControlReducerTester R;
-
   While w(R, R.p0);
   Diamond d(R, R.zero);
   // if (0) { while (p0) ; } else { }
   w.branch->ReplaceInput(1, d.if_true);
   d.merge->ReplaceInput(0, w.exit);
 
   R.ReduceMergeIterative(R.start, d.merge);
 
   DeadChecker dead(&R.graph);
   dead.Check(d);
@@ skipping 341 matching lines @@
 
   R.ReduceGraph();  // d1 gets folded true.
 
   CheckInputs(ret, y2, R.start, R.start);
 
   DeadChecker dead(&R.graph);
   dead.Check(d1);
   dead.Check(d2);
   dead.Check(d3);
 }