Implement control reducer, which reduces branches and phis together in a single fixpoint.

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"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-graph.h"
+#include "src/compiler/node-properties-inl.h"
 
 using namespace v8::internal;
 using namespace v8::internal::compiler;
 
-class CTrimTester : HandleAndZoneScope {
+static const size_t kNumLeafs = 4;
+
+// A helper for all tests dealing with ControlTester.
+class ControlReducerTester : HandleAndZoneScope {
  public:
-  CTrimTester()
+  ControlReducerTester()
       : isolate(main_isolate()),
         common(main_zone()),
         graph(main_zone()),
         jsgraph(&graph, &common, NULL, NULL),
         start(graph.NewNode(common.Start(1))),
+        end(graph.NewNode(common.End(), start)),
         p0(graph.NewNode(common.Parameter(0), start)),
+        zero(jsgraph.Int32Constant(0)),
         one(jsgraph.OneConstant()),
-        half(jsgraph.Constant(0.5)) {
-    graph.SetEnd(start);
+        half(jsgraph.Constant(0.5)),
+        self(graph.NewNode(common.Int32Constant(0xaabbccdd))),
+        dead(graph.NewNode(common.Dead())) {
+    graph.SetEnd(end);
     graph.SetStart(start);
+    leaf[0] = zero;
+    leaf[1] = one;
+    leaf[2] = half;
+    leaf[3] = p0;
   }
 
   Isolate* isolate;
   CommonOperatorBuilder common;
   Graph graph;
   JSGraph jsgraph;
   Node* start;
+  Node* end;
   Node* p0;
+  Node* zero;
   Node* one;
   Node* half;
+  Node* self;
+  Node* dead;
+  Node* leaf[kNumLeafs];
+
+  Node* Phi(Node* a) {
+    return SetSelfReferences(graph.NewNode(op(1, false), a, start));
+  }
+
+  Node* Phi(Node* a, Node* b) {
+    return SetSelfReferences(graph.NewNode(op(2, false), a, b, start));
+  }
+
+  Node* Phi(Node* a, Node* b, Node* c) {
+    return SetSelfReferences(graph.NewNode(op(3, false), a, b, c, start));
+  }
+
+  Node* Phi(Node* a, Node* b, Node* c, Node* d) {
+    return SetSelfReferences(graph.NewNode(op(4, false), a, b, c, d, start));
+  }
+
+  Node* EffectPhi(Node* a) {
+    return SetSelfReferences(graph.NewNode(op(1, true), a, start));
+  }
+
+  Node* EffectPhi(Node* a, Node* b) {
+    return SetSelfReferences(graph.NewNode(op(2, true), a, b, start));
+  }
+
+  Node* EffectPhi(Node* a, Node* b, Node* c) {
+    return SetSelfReferences(graph.NewNode(op(3, true), a, b, c, start));
+  }
+
+  Node* EffectPhi(Node* a, Node* b, Node* c, Node* d) {
+    return SetSelfReferences(graph.NewNode(op(4, true), a, b, c, d, start));
+  }
+
+  Node* SetSelfReferences(Node* node) {
+    Node::Inputs inputs = node->inputs();
+    for (Node::Inputs::iterator iter(inputs.begin()); iter != inputs.end();
+         ++iter) {
+      Node* input = *iter;
+      if (input == self) node->ReplaceInput(iter.index(), node);
+    }
+    return node;
+  }
+
+  const Operator* op(int count, bool effect) {
+    return effect ? common.EffectPhi(count) : common.Phi(kMachAnyTagged, count);
+  }
 
   void Trim() { ControlReducer::TrimGraph(main_zone(), &jsgraph); }
+
+  // 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.
+  }
+
+  void ReducePhiIterative(Node* expect, Node* phi) {
+    p0->ReplaceInput(0, start);  // hack: parameters may be trimmed.
+    Node* ret = graph.NewNode(common.Return(), phi, start);
+    Node* end = graph.NewNode(common.End(), ret);
+    graph.SetEnd(end);
+    ControlReducer::ReduceGraph(main_zone(), &jsgraph, &common);
+    CHECK_EQ(expect, ret->InputAt(0));
+  }
+
+  void ReduceMerge(Node* expect, Node* merge) {
+    Node* result =
+        ControlReducer::ReduceMergeForTesting(&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);
+    ControlReducer::ReduceGraph(main_zone(), &jsgraph, &common);
+    CHECK_EQ(expect, end->InputAt(0));
+  }
+
+  void ReduceBranch(Node* expect, Node* branch) {
+    Node* result =
+        ControlReducer::ReduceBranchForTesting(&jsgraph, &common, branch);
+    CHECK_EQ(expect, result);
+  }
 };
 
 
 bool IsUsedBy(Node* a, Node* b) {
   for (UseIter i = a->uses().begin(); i != a->uses().end(); ++i) {
     if (b == *i) return true;
   }
   return false;
 }
 
 
 TEST(Trim1_live) {
-  CTrimTester T;
+  ControlReducerTester T;
   CHECK(IsUsedBy(T.start, T.p0));
   T.graph.SetEnd(T.p0);
   T.Trim();
   CHECK(IsUsedBy(T.start, T.p0));
   CHECK_EQ(T.start, T.p0->InputAt(0));
 }
 
 
 TEST(Trim1_dead) {
-  CTrimTester T;
+  ControlReducerTester T;
   CHECK(IsUsedBy(T.start, T.p0));
   T.Trim();
   CHECK(!IsUsedBy(T.start, T.p0));
   CHECK_EQ(NULL, T.p0->InputAt(0));
 }
 
 
 TEST(Trim2_live) {
-  CTrimTester T;
+  ControlReducerTester T;
   Node* phi =
       T.graph.NewNode(T.common.Phi(kMachAnyTagged, 2), T.one, T.half, T.start);
   CHECK(IsUsedBy(T.one, phi));
   CHECK(IsUsedBy(T.half, phi));
   CHECK(IsUsedBy(T.start, phi));
   T.graph.SetEnd(phi);
   T.Trim();
   CHECK(IsUsedBy(T.one, phi));
   CHECK(IsUsedBy(T.half, phi));
   CHECK(IsUsedBy(T.start, phi));
   CHECK_EQ(T.one, phi->InputAt(0));
   CHECK_EQ(T.half, phi->InputAt(1));
   CHECK_EQ(T.start, phi->InputAt(2));
 }
 
 
 TEST(Trim2_dead) {
-  CTrimTester T;
+  ControlReducerTester T;
   Node* phi =
       T.graph.NewNode(T.common.Phi(kMachAnyTagged, 2), T.one, T.half, T.start);
   CHECK(IsUsedBy(T.one, phi));
   CHECK(IsUsedBy(T.half, phi));
   CHECK(IsUsedBy(T.start, phi));
   T.Trim();
   CHECK(!IsUsedBy(T.one, phi));
   CHECK(!IsUsedBy(T.half, phi));
   CHECK(!IsUsedBy(T.start, phi));
   CHECK_EQ(NULL, phi->InputAt(0));
   CHECK_EQ(NULL, phi->InputAt(1));
   CHECK_EQ(NULL, phi->InputAt(2));
 }
 
 
 TEST(Trim_chain1) {
-  CTrimTester T;
+  ControlReducerTester T;
   const int kDepth = 15;
   Node* live[kDepth];
   Node* dead[kDepth];
   Node* end = T.start;
   for (int i = 0; i < kDepth; i++) {
     live[i] = end = T.graph.NewNode(T.common.Merge(1), end);
     dead[i] = T.graph.NewNode(T.common.Merge(1), end);
   }
   // end         -> live[last] ->  live[last-1] -> ... -> start
   //     dead[last] ^ dead[last-1] ^ ...                  ^
   T.graph.SetEnd(end);
   T.Trim();
   for (int i = 0; i < kDepth; i++) {
     CHECK(!IsUsedBy(live[i], dead[i]));
     CHECK_EQ(NULL, dead[i]->InputAt(0));
     CHECK_EQ(i == 0 ? T.start : live[i - 1], live[i]->InputAt(0));
   }
 }
 
 
 TEST(Trim_chain2) {
-  CTrimTester T;
+  ControlReducerTester T;
   const int kDepth = 15;
   Node* live[kDepth];
   Node* dead[kDepth];
   Node* l = T.start;
   Node* d = T.start;
   for (int i = 0; i < kDepth; i++) {
     live[i] = l = T.graph.NewNode(T.common.Merge(1), l);
     dead[i] = d = T.graph.NewNode(T.common.Merge(1), d);
   }
   // end -> live[last] -> live[last-1] -> ... -> start
   //        dead[last] -> dead[last-1] -> ... -> start
   T.graph.SetEnd(l);
   T.Trim();
   CHECK(!IsUsedBy(T.start, dead[0]));
   for (int i = 0; i < kDepth; i++) {
     CHECK_EQ(i == 0 ? NULL : dead[i - 1], dead[i]->InputAt(0));
     CHECK_EQ(i == 0 ? T.start : live[i - 1], live[i]->InputAt(0));
   }
 }
 
 
 TEST(Trim_cycle1) {
-  CTrimTester T;
+  ControlReducerTester T;
   Node* loop = T.graph.NewNode(T.common.Loop(1), T.start, T.start);
   loop->ReplaceInput(1, loop);
   Node* end = T.graph.NewNode(T.common.End(), loop);
   T.graph.SetEnd(end);
 
   CHECK(IsUsedBy(T.start, loop));
   CHECK(IsUsedBy(loop, end));
   CHECK(IsUsedBy(loop, loop));
 
   T.Trim();
 
   // nothing should have happened to the loop itself.
   CHECK(IsUsedBy(T.start, loop));
   CHECK(IsUsedBy(loop, end));
   CHECK(IsUsedBy(loop, loop));
   CHECK_EQ(T.start, loop->InputAt(0));
   CHECK_EQ(loop, loop->InputAt(1));
   CHECK_EQ(loop, end->InputAt(0));
 }
 
 
 TEST(Trim_cycle2) {
-  CTrimTester T;
+  ControlReducerTester T;
   Node* loop = T.graph.NewNode(T.common.Loop(2), T.start, T.start);
   loop->ReplaceInput(1, loop);
   Node* end = T.graph.NewNode(T.common.End(), loop);
   Node* phi =
       T.graph.NewNode(T.common.Phi(kMachAnyTagged, 2), T.one, T.half, loop);
   T.graph.SetEnd(end);
 
   CHECK(IsUsedBy(T.start, loop));
   CHECK(IsUsedBy(loop, end));
   CHECK(IsUsedBy(loop, loop));
@@ skipping 14 matching lines @@
   // phi should have been trimmed away.
   CHECK(!IsUsedBy(loop, phi));
   CHECK(!IsUsedBy(T.one, phi));
   CHECK(!IsUsedBy(T.half, phi));
   CHECK_EQ(NULL, phi->InputAt(0));
   CHECK_EQ(NULL, phi->InputAt(1));
   CHECK_EQ(NULL, phi->InputAt(2));
 }
 
 
-void CheckTrimConstant(CTrimTester* T, Node* k) {
+void CheckTrimConstant(ControlReducerTester* T, Node* k) {
   Node* phi = T->graph.NewNode(T->common.Phi(kMachInt32, 1), k, T->start);
   CHECK(IsUsedBy(k, phi));
   T->Trim();
   CHECK(!IsUsedBy(k, phi));
   CHECK_EQ(NULL, phi->InputAt(0));
   CHECK_EQ(NULL, phi->InputAt(1));
 }
 
 
 TEST(Trim_constants) {
-  CTrimTester T;
+  ControlReducerTester T;
   int32_t int32_constants[] = {
       0, -1,  -2,  2,  2,  3,  3,  4,  4,  5,  5,  4,  5,  6, 6, 7, 8, 7, 8, 9,
       0, -11, -12, 12, 12, 13, 13, 14, 14, 15, 15, 14, 15, 6, 6, 7, 8, 7, 8, 9};
 
   for (size_t i = 0; i < arraysize(int32_constants); i++) {
     CheckTrimConstant(&T, T.jsgraph.Int32Constant(int32_constants[i]));
     CheckTrimConstant(&T, T.jsgraph.Float64Constant(int32_constants[i]));
     CheckTrimConstant(&T, T.jsgraph.Constant(int32_constants[i]));
   }
 
   Node* other_constants[] = {
       T.jsgraph.UndefinedConstant(), T.jsgraph.TheHoleConstant(),
       T.jsgraph.TrueConstant(),      T.jsgraph.FalseConstant(),
       T.jsgraph.NullConstant(),      T.jsgraph.ZeroConstant(),
       T.jsgraph.OneConstant(),       T.jsgraph.NaNConstant(),
       T.jsgraph.Constant(21),        T.jsgraph.Constant(22.2)};
 
   for (size_t i = 0; i < arraysize(other_constants); i++) {
     CheckTrimConstant(&T, other_constants[i]);
   }
 }
+
+
+TEST(CReducePhi1) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.Phi(R.leaf[0]));
+  R.ReducePhi(R.leaf[1], R.Phi(R.leaf[1]));
+  R.ReducePhi(R.leaf[2], R.Phi(R.leaf[2]));
+  R.ReducePhi(R.leaf[3], R.Phi(R.leaf[3]));
+}
+
+
+TEST(CReducePhi1_dead) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.Phi(R.leaf[0], R.dead));
+  R.ReducePhi(R.leaf[1], R.Phi(R.leaf[1], R.dead));
+  R.ReducePhi(R.leaf[2], R.Phi(R.leaf[2], R.dead));
+  R.ReducePhi(R.leaf[3], R.Phi(R.leaf[3], R.dead));
+
+  R.ReducePhi(R.leaf[0], R.Phi(R.dead, R.leaf[0]));
+  R.ReducePhi(R.leaf[1], R.Phi(R.dead, R.leaf[1]));
+  R.ReducePhi(R.leaf[2], R.Phi(R.dead, R.leaf[2]));
+  R.ReducePhi(R.leaf[3], R.Phi(R.dead, R.leaf[3]));
+}
+
+
+TEST(CReducePhi1_dead2) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.Phi(R.leaf[0], R.dead, R.dead));
+  R.ReducePhi(R.leaf[0], R.Phi(R.dead, R.leaf[0], R.dead));
+  R.ReducePhi(R.leaf[0], R.Phi(R.dead, R.dead, R.leaf[0]));
+}
+
+
+TEST(CReducePhi2a) {
+  ControlReducerTester R;
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(a, a));
+  }
+}
+
+
+TEST(CReducePhi2b) {
+  ControlReducerTester R;
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(R.self, a));
+    R.ReducePhi(a, R.Phi(a, R.self));
+  }
+}
+
+
+TEST(CReducePhi2c) {
+  ControlReducerTester R;
+
+  for (size_t i = 1; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i], *b = R.leaf[0];
+    Node* phi1 = R.Phi(b, a);
+    R.ReducePhi(phi1, phi1);
+
+    Node* phi2 = R.Phi(a, b);
+    R.ReducePhi(phi2, phi2);
+  }
+}
+
+
+TEST(CReducePhi2_dead) {
+  ControlReducerTester R;
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(a, a, R.dead));
+    R.ReducePhi(a, R.Phi(a, R.dead, a));
+    R.ReducePhi(a, R.Phi(R.dead, a, a));
+  }
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    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);
+
+    Node* phi2 = R.Phi(a, b, R.dead);
+    R.ReducePhi(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));
+  }
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(R.self, a, a));
+    R.ReducePhi(a, R.Phi(a, R.self, a));
+    R.ReducePhi(a, R.Phi(a, a, R.self));
+  }
+
+  for (size_t i = 1; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i], *b = R.leaf[0];
+    Node* phi1 = R.Phi(b, a, a);
+    R.ReducePhi(phi1, phi1);
+
+    Node* phi2 = R.Phi(a, b, a);
+    R.ReducePhi(phi2, phi2);
+
+    Node* phi3 = R.Phi(a, a, b);
+    R.ReducePhi(phi3, phi3);
+  }
+}
+
+
+TEST(CReducePhi4) {
+  ControlReducerTester R;
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(a, a, a, a));
+  }
+
+  for (size_t i = 0; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i];
+    R.ReducePhi(a, R.Phi(R.self, a, a, a));
+    R.ReducePhi(a, R.Phi(a, R.self, a, a));
+    R.ReducePhi(a, R.Phi(a, a, R.self, a));
+    R.ReducePhi(a, R.Phi(a, a, a, R.self));
+
+    R.ReducePhi(a, R.Phi(R.self, R.self, a, a));
+    R.ReducePhi(a, R.Phi(a, R.self, R.self, a));
+    R.ReducePhi(a, R.Phi(a, a, R.self, R.self));
+    R.ReducePhi(a, R.Phi(R.self, a, a, R.self));
+  }
+
+  for (size_t i = 1; i < kNumLeafs; i++) {
+    Node* a = R.leaf[i], *b = R.leaf[0];
+    Node* phi1 = R.Phi(b, a, a, a);
+    R.ReducePhi(phi1, phi1);
+
+    Node* phi2 = R.Phi(a, b, a, a);
+    R.ReducePhi(phi2, phi2);
+
+    Node* phi3 = R.Phi(a, a, b, a);
+    R.ReducePhi(phi3, phi3);
+
+    Node* phi4 = R.Phi(a, a, a, b);
+    R.ReducePhi(phi4, phi4);
+  }
+}
+
+
+TEST(CReducePhi_iterative1) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.leaf[0], R.Phi(R.leaf[0])));
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.Phi(R.leaf[0]), R.leaf[0]));
+}
+
+
+TEST(CReducePhi_iterative2) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.Phi(R.leaf[0]), R.Phi(R.leaf[0])));
+}
+
+
+TEST(CReducePhi_iterative3) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(R.leaf[0],
+                       R.Phi(R.leaf[0], R.Phi(R.leaf[0], R.leaf[0])));
+  R.ReducePhiIterative(R.leaf[0],
+                       R.Phi(R.Phi(R.leaf[0], R.leaf[0]), R.leaf[0]));
+}
+
+
+TEST(CReducePhi_iterative4) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.Phi(R.leaf[0], R.leaf[0]),
+                                        R.Phi(R.leaf[0], R.leaf[0])));
+
+  Node* p1 = R.Phi(R.leaf[0], R.leaf[0]);
+  R.ReducePhiIterative(R.leaf[0], R.Phi(p1, p1));
+
+  Node* p2 = R.Phi(R.leaf[0], R.leaf[0], R.leaf[0]);
+  R.ReducePhiIterative(R.leaf[0], R.Phi(p2, p2, p2));
+
+  Node* p3 = R.Phi(R.leaf[0], R.leaf[0], R.leaf[0]);
+  R.ReducePhiIterative(R.leaf[0], R.Phi(p3, p3, R.leaf[0]));
+}
+
+
+TEST(CReducePhi_iterative_self1) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.leaf[0], R.Phi(R.leaf[0], R.self)));
+  R.ReducePhiIterative(R.leaf[0], R.Phi(R.Phi(R.leaf[0], R.self), R.leaf[0]));
+}
+
+
+TEST(CReducePhi_iterative_self2) {
+  ControlReducerTester R;
+
+  R.ReducePhiIterative(
+      R.leaf[0], R.Phi(R.Phi(R.leaf[0], R.self), R.Phi(R.leaf[0], R.self)));
+  R.ReducePhiIterative(
+      R.leaf[0], R.Phi(R.Phi(R.self, R.leaf[0]), R.Phi(R.self, R.leaf[0])));
+
+  Node* p1 = R.Phi(R.leaf[0], R.self);
+  R.ReducePhiIterative(R.leaf[0], R.Phi(p1, p1));
+
+  Node* p2 = R.Phi(R.self, R.leaf[0]);
+  R.ReducePhiIterative(R.leaf[0], R.Phi(p2, p2));
+}
+
+
+TEST(EReducePhi1) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.leaf[0]));
+  R.ReducePhi(R.leaf[1], R.EffectPhi(R.leaf[1]));
+  R.ReducePhi(R.leaf[2], R.EffectPhi(R.leaf[2]));
+  R.ReducePhi(R.leaf[3], R.EffectPhi(R.leaf[3]));
+}
+
+
+TEST(EReducePhi1_dead) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.leaf[0], R.dead));
+  R.ReducePhi(R.leaf[1], R.EffectPhi(R.leaf[1], R.dead));
+  R.ReducePhi(R.leaf[2], R.EffectPhi(R.leaf[2], R.dead));
+  R.ReducePhi(R.leaf[3], R.EffectPhi(R.leaf[3], R.dead));
+
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.dead, R.leaf[0]));
+  R.ReducePhi(R.leaf[1], R.EffectPhi(R.dead, R.leaf[1]));
+  R.ReducePhi(R.leaf[2], R.EffectPhi(R.dead, R.leaf[2]));
+  R.ReducePhi(R.leaf[3], R.EffectPhi(R.dead, R.leaf[3]));
+}
+
+
+TEST(EReducePhi1_dead2) {
+  ControlReducerTester R;
+
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.leaf[0], R.dead, R.dead));
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.dead, R.leaf[0], R.dead));
+  R.ReducePhi(R.leaf[0], R.EffectPhi(R.dead, R.dead, R.leaf[0]));
+}
+
+
+TEST(CMergeReduce_simple1) {
+  ControlReducerTester R;
+
+  Node* merge = R.graph.NewNode(R.common.Merge(1), R.start);
+  R.ReduceMerge(R.start, merge);
+}
+
+
+TEST(CMergeReduce_simple2) {
+  ControlReducerTester R;
+
+  Node* merge1 = R.graph.NewNode(R.common.Merge(1), R.start);
+  Node* merge2 = R.graph.NewNode(R.common.Merge(1), merge1);
+  R.ReduceMerge(merge1, merge2);
+  R.ReduceMergeIterative(R.start, merge2);
+}
+
+
+TEST(CMergeReduce_none1) {
+  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);
+  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);
+}
+
+
+TEST(CMergeReduce_dead1) {
+  ControlReducerTester R;
+
+  Node* merge = R.graph.NewNode(R.common.Merge(2), R.start, R.dead);
+  R.ReduceMerge(R.start, merge);
+}
+
+
+TEST(CMergeReduce_dead2) {
+  ControlReducerTester R;
+
+  Node* merge1 = R.graph.NewNode(R.common.Merge(1), R.start);
+  Node* merge2 = R.graph.NewNode(R.common.Merge(2), merge1, R.dead);
+  R.ReduceMerge(merge1, merge2);
+  R.ReduceMergeIterative(R.start, merge2);
+}
+
+
+TEST(CMergeReduce_dead_rm1a) {
+  ControlReducerTester R;
+
+  for (int i = 0; i < 3; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(3), R.start, R.start, R.start);
+    merge->ReplaceInput(i, R.dead);
+    R.ReduceMerge(merge, merge);
+    CHECK_EQ(IrOpcode::kMerge, merge->opcode());
+    CHECK_EQ(2, OpParameter<int32_t>(merge->op()));
+    CHECK_EQ(2, merge->InputCount());
+    CHECK_EQ(R.start, merge->InputAt(0));
+    CHECK_EQ(R.start, merge->InputAt(1));
+  }
+}
+
+
+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);
+  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);
+      CHECK_EQ(IrOpcode::kMerge, merge->opcode());
+      CHECK_EQ(2, OpParameter<int32_t>(merge->op()));
+      CHECK_EQ(2, merge->InputCount());
+      CHECK_EQ(t, merge->InputAt(0));
+      CHECK_EQ(f, merge->InputAt(1));
+    }
+  }
+}
+
+
+TEST(CMergeReduce_dead_rm2) {
+  ControlReducerTester R;
+
+  for (int i = 0; i < 3; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(3), R.dead, R.dead, R.dead);
+    merge->ReplaceInput(i, R.start);
+    R.ReduceMerge(R.start, merge);
+  }
+}
+
+
+TEST(CLoopReduce_dead_rm1) {
+  ControlReducerTester R;
+
+  for (int i = 0; i < 3; i++) {
+    Node* loop = R.graph.NewNode(R.common.Loop(3), R.dead, R.start, R.start);
+    R.ReduceMerge(loop, loop);
+    CHECK_EQ(IrOpcode::kLoop, loop->opcode());
+    CHECK_EQ(2, OpParameter<int32_t>(loop->op()));
+    CHECK_EQ(2, loop->InputCount());
+    CHECK_EQ(R.start, loop->InputAt(0));
+    CHECK_EQ(R.start, loop->InputAt(1));
+  }
+}
+
+
+TEST(CMergeReduce_edit_phi1) {
+  ControlReducerTester R;
+
+  for (int i = 0; i < 3; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(3), R.start, R.start, R.start);
+    merge->ReplaceInput(i, R.dead);
+    Node* phi = R.graph.NewNode(R.common.Phi(kMachAnyTagged, 3), R.leaf[0],
+                                R.leaf[1], R.leaf[2], merge);
+    R.ReduceMerge(merge, merge);
+    CHECK_EQ(IrOpcode::kPhi, phi->opcode());
+    CHECK_EQ(2, phi->op()->InputCount());
+    CHECK_EQ(3, phi->InputCount());
+    CHECK_EQ(R.leaf[i < 1 ? 1 : 0], phi->InputAt(0));
+    CHECK_EQ(R.leaf[i < 2 ? 2 : 1], phi->InputAt(1));
+    CHECK_EQ(merge, phi->InputAt(2));
+  }
+}
+
+
+TEST(CMergeReduce_edit_effect_phi1) {
+  ControlReducerTester R;
+
+  for (int i = 0; i < 3; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(3), R.start, R.start, R.start);
+    merge->ReplaceInput(i, R.dead);
+    Node* phi = R.graph.NewNode(R.common.EffectPhi(3), R.leaf[0], R.leaf[1],
+                                R.leaf[2], merge);
+    R.ReduceMerge(merge, merge);
+    CHECK_EQ(IrOpcode::kEffectPhi, phi->opcode());
+    CHECK_EQ(0, phi->op()->InputCount());
+    CHECK_EQ(2, OperatorProperties::GetEffectInputCount(phi->op()));
+    CHECK_EQ(3, phi->InputCount());
+    CHECK_EQ(R.leaf[i < 1 ? 1 : 0], phi->InputAt(0));
+    CHECK_EQ(R.leaf[i < 2 ? 2 : 1], phi->InputAt(1));
+    CHECK_EQ(merge, phi->InputAt(2));
+  }
+}
+
+
+TEST(CMergeReduce_exhaustive_4) {
+  ControlReducerTester R;
+  Node* control[] = {
+      R.graph.NewNode(R.common.Start(1)), R.graph.NewNode(R.common.Start(2)),
+      R.graph.NewNode(R.common.Start(3)), R.graph.NewNode(R.common.Start(4))};
+  Node* values[] = {R.jsgraph.Int32Constant(11), R.jsgraph.Int32Constant(22),
+                    R.jsgraph.Int32Constant(33), R.jsgraph.Int32Constant(44)};
+  Node* effects[] = {
+      R.graph.NewNode(R.common.Start(5)), R.graph.NewNode(R.common.Start(6)),
+      R.graph.NewNode(R.common.Start(7)), R.graph.NewNode(R.common.Start(8))};
+
+  for (int p = 0; p < 16; p++) {
+    int a = p & 1, b = p & 2, c = p & 4, d = p & 8;
+    Node* merge = R.graph.NewNode(R.common.Merge(4), control[0], control[1],
+                                  control[2], control[3]);
+
+    if (!a) merge->ReplaceInput(0, R.dead);
+    if (!b) merge->ReplaceInput(1, R.dead);
+    if (!c) merge->ReplaceInput(2, R.dead);
+    if (!d) merge->ReplaceInput(3, R.dead);
+    Node* phi = R.graph.NewNode(R.common.Phi(kMachAnyTagged, 4), values[0],
+                                values[1], values[2], values[3], merge);
+    Node* effect = R.graph.NewNode(R.common.EffectPhi(4), effects[0],
+                                   effects[1], effects[2], effects[3], merge);
+
+    int count = v8::base::bits::CountPopulation32(p);
+    if (count == 0) {
+      // result should be dead.
+      Node* r =
+          ControlReducer::ReduceMergeForTesting(&R.jsgraph, &R.common, merge);
+      CHECK_EQ(IrOpcode::kDead, r->opcode());
+    } else if (count == 1) {
+      // result should be one of the controls.
+      Node* expect = control[WhichPowerOf2(p)];
+      R.ReduceMerge(expect, merge);
+    } else {
+      // merge should be edited.
+      R.ReduceMerge(merge, merge);
+      CHECK_EQ(count, merge->InputCount());
+      CHECK_EQ(count, OperatorProperties::GetControlInputCount(merge->op()));
+
+      CHECK_EQ(IrOpcode::kPhi, phi->opcode());
+      CHECK_EQ(count, phi->op()->InputCount());
+      CHECK_EQ(count + 1, phi->InputCount());
+
+      CHECK_EQ(IrOpcode::kEffectPhi, effect->opcode());
+      CHECK_EQ(0, effect->op()->InputCount());
+      CHECK_EQ(count, OperatorProperties::GetEffectInputCount(effect->op()));
+      CHECK_EQ(count + 1, effect->InputCount());
+    }
+  }
+}
+
+
+TEST(CMergeReduce_edit_many_phis1) {
+  ControlReducerTester R;
+
+  const int kPhiCount = 10;
+  Node* phis[kPhiCount];
+
+  for (int i = 0; i < 3; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(3), R.start, R.start, R.start);
+    merge->ReplaceInput(i, R.dead);
+    for (int j = 0; j < kPhiCount; j++) {
+      phis[j] = R.graph.NewNode(R.common.Phi(kMachAnyTagged, 3), R.leaf[0],
+                                R.leaf[1], R.leaf[2], merge);
+    }
+    R.ReduceMerge(merge, merge);
+    for (int j = 0; j < kPhiCount; j++) {
+      Node* phi = phis[j];
+      CHECK_EQ(IrOpcode::kPhi, phi->opcode());
+      CHECK_EQ(2, phi->op()->InputCount());
+      CHECK_EQ(3, phi->InputCount());
+      CHECK_EQ(R.leaf[i < 1 ? 1 : 0], phi->InputAt(0));
+      CHECK_EQ(R.leaf[i < 2 ? 2 : 1], phi->InputAt(1));
+      CHECK_EQ(merge, phi->InputAt(2));
+    }
+  }
+}
+
+
+TEST(CMergeReduce_simple_chain1) {
+  ControlReducerTester R;
+  for (int i = 0; i < 5; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(1), R.start);
+    for (int j = 0; j < i; j++) {
+      merge = R.graph.NewNode(R.common.Merge(1), merge);
+    }
+    R.ReduceMergeIterative(R.start, merge);
+  }
+}
+
+
+TEST(CMergeReduce_dead_chain1) {
+  ControlReducerTester R;
+  for (int i = 0; i < 5; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(1), R.dead);
+    for (int j = 0; j < i; j++) {
+      merge = R.graph.NewNode(R.common.Merge(1), merge);
+    }
+    // TODO(titzer): the NULL is because end gets killed. Check for dead
+    // properly.
+    R.ReduceMergeIterative(NULL, merge);
+  }
+}
+
+
+TEST(CMergeReduce_dead_chain2) {
+  ControlReducerTester R;
+  for (int i = 0; i < 5; i++) {
+    Node* merge = R.graph.NewNode(R.common.Merge(1), R.start);
+    for (int j = 0; j < i; j++) {
+      merge = R.graph.NewNode(R.common.Merge(2), merge, R.dead);
+    }
+    R.ReduceMergeIterative(R.start, merge);
+  }
+}
+
+
+struct Diamond {
+  Node* branch;
+  Node* if_true;
+  Node* if_false;
+  Node* merge;
+  Node* phi;
+
+  Diamond(ControlReducerTester& R, Node* cond) {
+    branch = R.graph.NewNode(R.common.Branch(), cond, R.start);
+    if_true = R.graph.NewNode(R.common.IfTrue(), branch);
+    if_false = R.graph.NewNode(R.common.IfFalse(), branch);
+    merge = R.graph.NewNode(R.common.Merge(2), if_true, if_false);
+    phi = NULL;
+  }
+
+  Diamond(ControlReducerTester& R, Node* cond, Node* tv, Node* fv) {
+    branch = R.graph.NewNode(R.common.Branch(), cond, R.start);
+    if_true = R.graph.NewNode(R.common.IfTrue(), branch);
+    if_false = R.graph.NewNode(R.common.IfFalse(), branch);
+    merge = R.graph.NewNode(R.common.Merge(2), if_true, if_false);
+    phi = R.graph.NewNode(R.common.Phi(kMachAnyTagged, 2), tv, fv, merge);
+  }
+
+  void chain(Diamond& that) { branch->ReplaceInput(1, that.merge); }
+
+  void nest(Diamond& that, bool if_true) {
+    if (if_true) {
+      branch->ReplaceInput(1, that.if_true);
+      that.merge->ReplaceInput(0, merge);
+    } else {
+      branch->ReplaceInput(1, that.if_false);
+      that.merge->ReplaceInput(1, merge);
+    }
+  }
+};
+
+
+struct While {
+  Node* branch;
+  Node* if_true;
+  Node* exit;
+  Node* loop;
+
+  While(ControlReducerTester& R, Node* cond) {
+    loop = R.graph.NewNode(R.common.Loop(2), R.start, R.start);
+    branch = R.graph.NewNode(R.common.Branch(), cond, loop);
+    if_true = R.graph.NewNode(R.common.IfTrue(), branch);
+    exit = R.graph.NewNode(R.common.IfFalse(), branch);
+    loop->ReplaceInput(1, if_true);
+  }
+
+  void chain(Node* control) { loop->ReplaceInput(0, control); }
+};
+
+
+TEST(CBranchReduce_none1) {
+  ControlReducerTester R;
+  Diamond d(R, R.p0);
+  R.ReduceBranch(d.branch, d.branch);
+}
+
+
+TEST(CBranchReduce_none2) {
+  ControlReducerTester R;
+  Diamond d1(R, R.p0);
+  Diamond d2(R, R.p0);
+  d2.chain(d1);
+  R.ReduceBranch(d2.branch, d2.branch);
+}
+
+
+TEST(CBranchReduce_true) {
+  ControlReducerTester R;
+  Node* true_values[] = {
+      R.one,                               R.jsgraph.Int32Constant(2),
+      R.jsgraph.Int32Constant(0x7fffffff), R.jsgraph.Constant(1.0),
+      R.jsgraph.Constant(22.1),            R.jsgraph.TrueConstant()};
+
+  for (size_t i = 0; i < arraysize(true_values); i++) {
+    Diamond d(R, true_values[i]);
+    Node* true_use = R.graph.NewNode(R.common.Merge(1), d.if_true);
+    Node* false_use = R.graph.NewNode(R.common.Merge(1), d.if_false);
+    R.ReduceBranch(R.start, d.branch);
+    CHECK_EQ(R.start, true_use->InputAt(0));
+    CHECK_EQ(IrOpcode::kDead, false_use->InputAt(0)->opcode());
+    CHECK(d.if_true->IsDead());   // replaced
+    CHECK(d.if_false->IsDead());  // replaced
+  }
+}
+
+
+TEST(CBranchReduce_false) {
+  ControlReducerTester R;
+  Node* false_values[] = {R.zero, R.jsgraph.Constant(0.0),
+                          R.jsgraph.Constant(-0.0), R.jsgraph.FalseConstant()};
+
+  for (size_t i = 0; i < arraysize(false_values); i++) {
+    Diamond d(R, false_values[i]);
+    Node* true_use = R.graph.NewNode(R.common.Merge(1), d.if_true);
+    Node* false_use = R.graph.NewNode(R.common.Merge(1), d.if_false);
+    R.ReduceBranch(R.start, d.branch);
+    CHECK_EQ(R.start, false_use->InputAt(0));
+    CHECK_EQ(IrOpcode::kDead, true_use->InputAt(0)->opcode());
+    CHECK(d.if_true->IsDead());   // replaced
+    CHECK(d.if_false->IsDead());  // replaced
+  }
+}
+
+
+TEST(CDiamondReduce_true) {
+  ControlReducerTester R;
+  Diamond d1(R, R.one);
+  R.ReduceMergeIterative(R.start, d1.merge);
+}
+
+
+TEST(CDiamondReduce_false) {
+  ControlReducerTester R;
+  Diamond d2(R, R.zero);
+  R.ReduceMergeIterative(R.start, d2.merge);
+}
+
+
+TEST(CChainedDiamondsReduce_true_false) {
+  ControlReducerTester R;
+  Diamond d1(R, R.one);
+  Diamond d2(R, R.zero);
+  d2.chain(d1);
+
+  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);
+}
+
+
+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);
+  CHECK_EQ(R.start, d2.branch->InputAt(1));
+}
+
+
+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);
+}
+
+
+TEST(CChainedDiamondsReduce_phi2) {
+  ControlReducerTester R;
+  Diamond d1(R, R.p0, R.one, R.one);  // redundant phi.
+  Diamond d2(R, d1.phi);
+  d2.chain(d1);
+
+  R.ReduceMergeIterative(d1.merge, d2.merge);
+}
+
+
+TEST(CNestedDiamondsReduce_true_true_false) {
+  ControlReducerTester R;
+  Diamond d1(R, R.one);
+  Diamond d2(R, R.zero);
+  d2.nest(d1, true);
+
+  R.ReduceMergeIterative(R.start, d1.merge);
+}
+
+
+TEST(CNestedDiamondsReduce_false_true_false) {
+  ControlReducerTester R;
+  Diamond d1(R, R.one);
+  Diamond d2(R, R.zero);
+  d2.nest(d1, false);
+
+  R.ReduceMergeIterative(R.start, d1.merge);
+}
+
+
+TEST(CNestedDiamonds_xyz) {
+  ControlReducerTester R;
+
+  for (int a = 0; a < 2; a++) {
+    for (int b = 0; b < 2; b++) {
+      for (int c = 0; c < 2; c++) {
+        Diamond d1(R, R.jsgraph.Int32Constant(a));
+        Diamond d2(R, R.jsgraph.Int32Constant(b));
+        d2.nest(d1, c);
+
+        R.ReduceMergeIterative(R.start, d1.merge);
+      }
+    }
+  }
+}
+
+
+TEST(CDeadLoop1) {
+  ControlReducerTester R;
+
+  Node* loop = R.graph.NewNode(R.common.Loop(1), R.start);
+  Node* branch = R.graph.NewNode(R.common.Branch(), R.p0, loop);
+  Node* if_true = R.graph.NewNode(R.common.IfTrue(), branch);
+  Node* if_false = R.graph.NewNode(R.common.IfFalse(), branch);
+  loop->ReplaceInput(0, if_true);  // loop is not connected to start (i.e. dead)
+  Node* merge = R.graph.NewNode(R.common.Merge(2), R.start, if_false);
+  R.ReduceMergeIterative(R.start, merge);
+  CHECK_EQ(NULL, if_true->InputAt(0));
+  CHECK_EQ(NULL, if_false->InputAt(0));
+}
+
+
+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);
+  CHECK_EQ(NULL, d.if_true->InputAt(0));
+  CHECK_EQ(NULL, d.if_false->InputAt(0));
+}
+
+
+TEST(CNonTermLoop1) {
+  ControlReducerTester R;
+  Node* loop =
+      R.SetSelfReferences(R.graph.NewNode(R.common.Loop(1), R.start, R.self));
+  ControlReducer::ReduceGraph(R.graph.zone(), &R.jsgraph, &R.common);
+  Node* end = R.graph.end();
+  CHECK_EQ(R.start, loop->InputAt(0));
+  CHECK_EQ(loop, loop->InputAt(1));
+  Node* merge = end->InputAt(0);
+  CHECK_EQ(IrOpcode::kMerge, merge->opcode());
+  CHECK_EQ(2, merge->InputCount());
+  CHECK_EQ(2, OperatorProperties::GetControlInputCount(merge->op()));
+  CHECK_EQ(R.start, merge->InputAt(0));
+  CHECK_EQ(loop, merge->InputAt(1));
+}
+
+
+TEST(CNonTermLoop2) {}