[turbofan] Simply context specialization and fix for OSR.

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 135 matching lines @@
     ControlReducer::ReduceGraph(main_zone(), &jsgraph, &common);
   }
 
   // Checks one-step reduction of a phi.
   void ReducePhi(Node* expect, Node* phi) {
     Node* result = ControlReducer::ReducePhiForTesting(&jsgraph, &common, phi);
     CHECK_EQ(expect, result);
     ReducePhiIterative(expect, phi);  // iterative should give the same result.
   }
 
+  // Checks one-step reduction of a phi.
+  void ReducePhiNonIterative(Node* expect, Node* phi) {
+    Node* result = ControlReducer::ReducePhiForTesting(&jsgraph, &common, phi);
+    CHECK_EQ(expect, result);
+  }
+
   void ReducePhiIterative(Node* expect, Node* phi) {
     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);
   }
 
@@ skipping 311 matching lines @@
     Node* a = R.leaf[i];
     R.ReducePhi(a, R.Phi(R.self, a));
     R.ReducePhi(a, R.Phi(a, R.self));
     R.ReducePhi(a, R.Phi(R.self, a, R.dead));
     R.ReducePhi(a, R.Phi(a, R.self, R.dead));
   }
 
   for (size_t i = 1; i < kNumLeafs; i++) {
     Node* a = R.leaf[i], *b = R.leaf[0];
     Node* phi1 = R.Phi(b, a, R.dead);
-    R.ReducePhi(phi1, phi1);
+    R.ReducePhiNonIterative(phi1, phi1);
 
     Node* phi2 = R.Phi(a, b, R.dead);
-    R.ReducePhi(phi2, phi2);
+    R.ReducePhiNonIterative(phi2, phi2);
   }
 }
 
 
 TEST(CReducePhi3) {
   ControlReducerTester R;
 
   for (size_t i = 0; i < kNumLeafs; i++) {
     Node* a = R.leaf[i];
     R.ReducePhi(a, R.Phi(a, a, a));
@@ skipping 1003 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);
 }