[turbofan] Remove unused diamonds during control reduction.

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 676 matching lines @@
   ControlReducerTester R;
 
   Node* merge = R.graph.NewNode(R.common.Merge(2), R.start, R.start);
   R.ReduceMerge(merge, merge);
 }
 
 
 TEST(CMergeReduce_none2) {
   ControlReducerTester R;
 
-  Node* t = R.graph.NewNode(R.common.IfTrue(), R.start);
-  Node* f = R.graph.NewNode(R.common.IfFalse(), R.start);
-  Node* merge = R.graph.NewNode(R.common.Merge(2), t, f);
+  Node* t1 = R.graph.NewNode(R.common.IfTrue(), R.start);
+  Node* t2 = R.graph.NewNode(R.common.IfTrue(), R.start);
+  Node* merge = R.graph.NewNode(R.common.Merge(2), t1, t2);
   R.ReduceMerge(merge, merge);
 }
 
 
 TEST(CMergeReduce_self3) {
   ControlReducerTester R;
 
   Node* merge =
       R.SetSelfReferences(R.graph.NewNode(R.common.Merge(2), R.start, R.self));
   R.ReduceMerge(merge, merge);
@@ skipping 27 matching lines @@
     R.ReduceMerge(merge, merge);
     CheckMerge(merge, R.start, R.start);
   }
 }
 
 
 TEST(CMergeReduce_dead_rm1b) {
   ControlReducerTester R;
 
   Node* t = R.graph.NewNode(R.common.IfTrue(), R.start);
-  Node* f = R.graph.NewNode(R.common.IfFalse(), R.start);
+  Node* f = R.graph.NewNode(R.common.IfTrue(), R.start);
   for (int i = 0; i < 2; i++) {
     Node* merge = R.graph.NewNode(R.common.Merge(3), R.dead, R.dead, R.dead);
     for (int j = i + 1; j < 3; j++) {
       merge->ReplaceInput(i, t);
       merge->ReplaceInput(j, f);
       R.ReduceMerge(merge, merge);
       CheckMerge(merge, t, f);
     }
   }
 }
@@ skipping 353 matching lines @@
   R.ReduceMergeIterative(R.start, d2.merge);
 }
 
 
 TEST(CChainedDiamondsReduce_x_false) {
   ControlReducerTester R;
   Diamond d1(R, R.p0);
   Diamond d2(R, R.zero);
   d2.chain(d1);
 
-  R.ReduceMergeIterative(d1.merge, d2.merge);
+  R.ReduceMergeIterative(R.start, d2.merge);
 }
 
 
 TEST(CChainedDiamondsReduce_false_x) {
   ControlReducerTester R;
   Diamond d1(R, R.zero);
   Diamond d2(R, R.p0);
   d2.chain(d1);
 
-  R.ReduceMergeIterative(d2.merge, d2.merge);
-  CheckInputs(d2.branch, R.p0, R.start);
+  R.ReduceMergeIterative(R.start, d2.merge);
 }
 
 
 TEST(CChainedDiamondsReduce_phi1) {
   ControlReducerTester R;
   Diamond d1(R, R.zero, R.one, R.zero);  // foldable branch, phi.
   Diamond d2(R, d1.phi);
   d2.chain(d1);
 
   R.ReduceMergeIterative(R.start, d2.merge);
@@ skipping 40 matching lines @@
         Diamond d2(R, R.jsgraph.Int32Constant(b));
         d2.nest(d1, c);
 
         R.ReduceMergeIterative(R.start, d1.merge);
       }
     }
   }
 }
 
 
+TEST(CDeadDiamond) {
+  ControlReducerTester R;
+  // if (p0) { } else { }
+  Diamond d(R, R.p0);
+  R.ReduceMergeIterative(R.start, d.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);
   CHECK(b.if_true->IsDead());
   CHECK(b.if_false->IsDead());
@@ skipping 119 matching lines @@
 
   d2.nest(d1, true);
   d3.nest(d1, false);
 
   Node* ret = R.Return(d1.phi, R.start, d1.merge);
 
   R.ReduceGraph();  // nothing should happen.
 
   CheckInputs(ret, d1.phi, R.start, d1.merge);
   CheckInputs(d1.phi, R.one, R.zero, d1.merge);
-  CheckInputs(d1.merge, d2.merge, d3.merge);
-  CheckLiveDiamond(d2);
-  CheckLiveDiamond(d3);
+  CheckInputs(d1.merge, d1.if_true, d1.if_false);
 }
 
 
 TEST(Return_nested_diamonds_true1) {
   ControlReducerTester R;
   Diamond d1(R, R.one, R.one, R.zero);
   Diamond d2(R, R.p0);
   Diamond d3(R, R.p0);
 
   d2.nest(d1, true);
   d3.nest(d1, false);
 
   Node* ret = R.Return(d1.phi, R.start, d1.merge);
 
   R.ReduceGraph();  // d1 gets folded true.
 
-  CheckInputs(ret, R.one, R.start, d2.merge);
-  CheckInputs(d2.branch, R.p0, R.start);
-  CheckDeadDiamond(d1);
-  CheckLiveDiamond(d2);
-  CheckDeadDiamond(d3);
+  CheckInputs(ret, R.one, R.start, R.start);
 }
 
 
 TEST(Return_nested_diamonds_false1) {
   ControlReducerTester R;
   Diamond d1(R, R.zero, R.one, R.zero);
   Diamond d2(R, R.p0);
   Diamond d3(R, R.p0);
 
   d2.nest(d1, true);
   d3.nest(d1, false);
 
   Node* ret = R.Return(d1.phi, R.start, d1.merge);
 
   R.ReduceGraph();  // d1 gets folded false.
 
-  CheckInputs(ret, R.zero, R.start, d3.merge);
-  CheckInputs(d3.branch, R.p0, R.start);
-  CheckDeadDiamond(d1);
-  CheckDeadDiamond(d2);
-  CheckLiveDiamond(d3);
+  CheckInputs(ret, R.zero, R.start, R.start);
 }
 
 
 TEST(Return_nested_diamonds_true_true1) {
   ControlReducerTester R;
   Diamond d1(R, R.one, R.one, R.zero);
   Diamond d2(R, R.one);
   Diamond d3(R, R.p0);
 
   d2.nest(d1, true);
@@ skipping 123 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);
 }