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

test/cctest/compiler/test-control-reducer.cc

Index: test/cctest/compiler/test-control-reducer.cc
diff --git a/test/cctest/compiler/test-control-reducer.cc b/test/cctest/compiler/test-control-reducer.cc
index 0e8dc177e234c1de6a2fb58ef8882cb4b6e03c57..dc80cc383f77c6c0eee9543db0f662cb5d0641c1 100644
--- a/test/cctest/compiler/test-control-reducer.cc
+++ b/test/cctest/compiler/test-control-reducer.cc
@@ -5,27 +5,82 @@
 #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;
+
+// TODO(titzer): convert this whole file into unit tests.
+
+static int CheckInputs(Node* node, Node* i0 = NULL, Node* i1 = NULL,
+                       Node* i2 = NULL) {
+  int count = 3;
+  if (i2 == NULL) count = 2;
+  if (i1 == NULL) count = 1;
+  if (i0 == NULL) count = 0;
+  CHECK_EQ(count, node->InputCount());
+  if (i0 != NULL) CHECK_EQ(i0, node->InputAt(0));
+  if (i1 != NULL) CHECK_EQ(i1, node->InputAt(1));
+  if (i2 != NULL) CHECK_EQ(i2, node->InputAt(2));
+  return count;
+}
+
+
+static int CheckMerge(Node* node, Node* i0 = NULL, Node* i1 = NULL,
+                      Node* i2 = NULL) {
+  CHECK_EQ(IrOpcode::kMerge, node->opcode());
+  int count = CheckInputs(node, i0, i1, i2);
+  CHECK_EQ(count, OperatorProperties::GetControlInputCount(node->op()));
+  return count;
+}
+
+
+static int CheckLoop(Node* node, Node* i0 = NULL, Node* i1 = NULL,
+                     Node* i2 = NULL) {
+  CHECK_EQ(IrOpcode::kLoop, node->opcode());
+  int count = CheckInputs(node, i0, i1, i2);
+  CHECK_EQ(count, OperatorProperties::GetControlInputCount(node->op()));
+  return count;
+}
+
+
+bool IsUsedBy(Node* a, Node* b) {
+  for (UseIter i = a->uses().begin(); i != a->uses().end(); ++i) {
+    if (b == *i) return true;
+  }
+  return false;
+}
+
+
+// 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;
@@ -33,34 +88,124 @@ class CTrimTester : HandleAndZoneScope {
   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); }
-};
 
+  void ReduceGraph() {
+    ControlReducer::ReduceGraph(main_zone(), &jsgraph, &common);
+  }
 
-bool IsUsedBy(Node* a, Node* b) {
-  for (UseIter i = a->uses().begin(); i != a->uses().end(); ++i) {
-    if (b == *i) return true;
+  // 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, 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);
+    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);
   }
-  return false;
-}
+
+  void ReduceBranch(Node* expect, Node* branch) {
+    Node* result =
+        ControlReducer::ReduceBranchForTesting(&jsgraph, &common, branch);
+    CHECK_EQ(expect, result);
+  }
+
+  Node* Return(Node* val, Node* effect, Node* control) {
+    Node* ret = graph.NewNode(common.Return(), val, effect, control);
+    end->ReplaceInput(0, ret);
+    return ret;
+  }
+};
 
 
 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));
+  CheckInputs(T.p0, T.start);
 }
 
 
 TEST(Trim1_dead) {
-  CTrimTester T;
+  ControlReducerTester T;
   CHECK(IsUsedBy(T.start, T.p0));
   T.Trim();
   CHECK(!IsUsedBy(T.start, T.p0));
@@ -69,7 +214,7 @@ TEST(Trim1_dead) {
 
 
 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));
@@ -80,14 +225,12 @@ TEST(Trim2_live) {
   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));
+  CheckInputs(phi, T.one, T.half, T.start);
 }
 
 
 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));
@@ -104,7 +247,7 @@ TEST(Trim2_dead) {
 
 
 TEST(Trim_chain1) {
-  CTrimTester T;
+  ControlReducerTester T;
   const int kDepth = 15;
   Node* live[kDepth];
   Node* dead[kDepth];
@@ -126,7 +269,7 @@ TEST(Trim_chain1) {
 
 
 TEST(Trim_chain2) {
-  CTrimTester T;
+  ControlReducerTester T;
   const int kDepth = 15;
   Node* live[kDepth];
   Node* dead[kDepth];
@@ -149,7 +292,7 @@ TEST(Trim_chain2) {
 
 
 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);
@@ -165,14 +308,13 @@ TEST(Trim_cycle1) {
   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));
+  CheckInputs(loop, T.start, loop);
+  CheckInputs(end, loop);
 }
 
 
 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);
@@ -193,9 +335,8 @@ TEST(Trim_cycle2) {
   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));
+  CheckInputs(loop, T.start, loop);
+  CheckInputs(end, loop);
 
   // phi should have been trimmed away.
   CHECK(!IsUsedBy(loop, phi));
@@ -207,7 +348,7 @@ TEST(Trim_cycle2) {
 }
 
 
-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();
@@ -218,7 +359,7 @@ void CheckTrimConstant(CTrimTester* T, Node* k) {
 
 
 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};
@@ -240,3 +381,1300 @@ TEST(Trim_constants) {
     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);
+    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);
+  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);
+    }
+  }
+}
+
+
+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);
+    CheckLoop(loop, R.start, R.start);
+  }
+}
+
+
+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));
+  }
+}
+
+
+static const int kSelectorSize = 4;
+
+// Helper to select K of N nodes according to a mask, useful for the test below.
+struct Selector {
+  int mask;
+  int count;
+  explicit Selector(int m) {
+    mask = m;
+    count = v8::base::bits::CountPopulation32(m);
+  }
+  bool is_selected(int i) { return (mask & (1 << i)) != 0; }
+  void CheckNode(Node* node, IrOpcode::Value opcode, Node** inputs,
+                 Node* control) {
+    CHECK_EQ(opcode, node->opcode());
+    CHECK_EQ(count + (control != NULL ? 1 : 0), node->InputCount());
+    int index = 0;
+    for (int i = 0; i < kSelectorSize; i++) {
+      if (mask & (1 << i)) {
+        CHECK_EQ(inputs[i], node->InputAt(index++));
+      }
+    }
+    CHECK_EQ(count, index);
+    if (control != NULL) CHECK_EQ(control, node->InputAt(index++));
+  }
+  int single_index() {
+    CHECK_EQ(1, count);
+    return WhichPowerOf2(mask);
+  }
+};
+
+
+TEST(CMergeReduce_exhaustive_4) {
+  ControlReducerTester R;
+  Node* controls[] = {
+      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.jsgraph.Float64Constant(123.4), R.jsgraph.Float64Constant(223.4),
+      R.jsgraph.Float64Constant(323.4), R.jsgraph.Float64Constant(423.4)};
+
+  for (int mask = 0; mask < (1 << (kSelectorSize - 1)); mask++) {
+    // Reduce a single merge with a given mask.
+    Node* merge = R.graph.NewNode(R.common.Merge(4), controls[0], controls[1],
+                                  controls[2], controls[3]);
+    Node* phi = R.graph.NewNode(R.common.Phi(kMachAnyTagged, 4), values[0],
+                                values[1], values[2], values[3], merge);
+    Node* ephi = R.graph.NewNode(R.common.EffectPhi(4), effects[0], effects[1],
+                                 effects[2], effects[3], merge);
+
+    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);
+
+    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));
+      CHECK_EQ(effects[selector.single_index()], ephi_use->InputAt(0));
+    } else {
+      // Otherwise, nodes should be edited in place.
+      CHECK_EQ(merge, result);
+      selector.CheckNode(merge, IrOpcode::kMerge, controls, NULL);
+      selector.CheckNode(phi, IrOpcode::kPhi, values, merge);
+      selector.CheckNode(ephi, IrOpcode::kEffectPhi, effects, merge);
+      CHECK_EQ(phi, phi_use->InputAt(0));
+      CHECK_EQ(ephi, ephi_use->InputAt(0));
+      CHECK_EQ(count, phi->op()->InputCount());
+      CHECK_EQ(count + 1, phi->InputCount());
+      CHECK_EQ(count, OperatorProperties::GetEffectInputCount(ephi->op()));
+      CHECK_EQ(count + 1, ephi->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);
+    }
+    Node* end = R.graph.NewNode(R.common.End(), merge);
+    R.graph.SetEnd(end);
+    R.ReduceGraph();
+    CHECK(merge->IsDead());
+    CHECK_EQ(NULL, end->InputAt(0));  // end dies.
+  }
+}
+
+
+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 Branch {
+  Node* branch;
+  Node* if_true;
+  Node* if_false;
+
+  Branch(ControlReducerTester& R, Node* cond, Node* control = NULL) {
+    if (control == NULL) control = R.start;
+    branch = R.graph.NewNode(R.common.Branch(), cond, control);
+    if_true = R.graph.NewNode(R.common.IfTrue(), branch);
+    if_false = R.graph.NewNode(R.common.IfFalse(), branch);
+  }
+};
+
+
+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); }
+
+  // Nest {this} into either the if_true or if_false branch of {that}.
+  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);
+  CheckInputs(d2.branch, R.p0, R.start);
+}
+
+
+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);
+  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());
+}
+
+
+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(d.if_true->IsDead());
+  CHECK(d.if_false->IsDead());
+}
+
+
+TEST(CNonTermLoop1) {
+  ControlReducerTester R;
+  Node* loop =
+      R.SetSelfReferences(R.graph.NewNode(R.common.Loop(2), R.start, R.self));
+  R.ReduceGraph();
+  Node* end = R.graph.end();
+  CheckLoop(loop, R.start, loop);
+  Node* merge = end->InputAt(0);
+  CheckMerge(merge, R.start, loop);
+}
+
+
+TEST(CNonTermLoop2) {
+  ControlReducerTester R;
+  Diamond d(R, R.p0);
+  Node* loop = R.SetSelfReferences(
+      R.graph.NewNode(R.common.Loop(2), d.if_false, R.self));
+  d.merge->ReplaceInput(1, R.dead);
+  Node* end = R.graph.end();
+  end->ReplaceInput(0, d.merge);
+  R.ReduceGraph();
+  CHECK_EQ(end, R.graph.end());
+  CheckLoop(loop, d.if_false, loop);
+  Node* merge = end->InputAt(0);
+  CheckMerge(merge, d.if_true, loop);
+}
+
+
+TEST(NonTermLoop3) {
+  ControlReducerTester R;
+  Node* loop = R.graph.NewNode(R.common.Loop(2), R.start, R.start);
+  Branch b(R, R.one, loop);
+  loop->ReplaceInput(1, b.if_true);
+  Node* end = R.graph.end();
+  end->ReplaceInput(0, b.if_false);
+
+  R.ReduceGraph();
+
+  CHECK_EQ(end, R.graph.end());
+  CheckInputs(end, loop);
+  CheckInputs(loop, R.start, loop);
+}
+
+
+TEST(CNonTermLoop_terminate1) {
+  ControlReducerTester R;
+  Node* loop = R.graph.NewNode(R.common.Loop(2), R.start, R.start);
+  Node* effect = R.SetSelfReferences(
+      R.graph.NewNode(R.common.EffectPhi(2), R.start, R.self, loop));
+  Branch b(R, R.one, loop);
+  loop->ReplaceInput(1, b.if_true);
+  Node* end = R.graph.end();
+  end->ReplaceInput(0, b.if_false);
+
+  R.ReduceGraph();
+
+  CHECK_EQ(end, R.graph.end());
+  CheckLoop(loop, R.start, loop);
+  Node* terminate = end->InputAt(0);
+  CHECK_EQ(IrOpcode::kTerminate, terminate->opcode());
+  CHECK_EQ(2, terminate->InputCount());
+  CHECK_EQ(1, OperatorProperties::GetEffectInputCount(terminate->op()));
+  CHECK_EQ(1, OperatorProperties::GetControlInputCount(terminate->op()));
+  CheckInputs(terminate, effect, loop);
+}
+
+
+TEST(CNonTermLoop_terminate2) {
+  ControlReducerTester R;
+  Node* loop = R.graph.NewNode(R.common.Loop(2), R.start, R.start);
+  Node* effect1 = R.SetSelfReferences(
+      R.graph.NewNode(R.common.EffectPhi(2), R.start, R.self, loop));
+  Node* effect2 = R.SetSelfReferences(
+      R.graph.NewNode(R.common.EffectPhi(2), R.start, R.self, loop));
+  Branch b(R, R.one, loop);
+  loop->ReplaceInput(1, b.if_true);
+  Node* end = R.graph.end();
+  end->ReplaceInput(0, b.if_false);
+
+  R.ReduceGraph();
+
+  CheckLoop(loop, R.start, loop);
+  CHECK_EQ(end, R.graph.end());
+  Node* terminate = end->InputAt(0);
+  CHECK_EQ(IrOpcode::kTerminate, terminate->opcode());
+  CHECK_EQ(3, terminate->InputCount());
+  CHECK_EQ(2, OperatorProperties::GetEffectInputCount(terminate->op()));
+  CHECK_EQ(1, OperatorProperties::GetControlInputCount(terminate->op()));
+  Node* e0 = terminate->InputAt(0);
+  Node* e1 = terminate->InputAt(1);
+  CHECK(e0 == effect1 || e1 == effect1);
+  CHECK(e0 == effect2 || e1 == effect2);
+  CHECK_EQ(loop, terminate->InputAt(2));
+}
+
+
+TEST(CNonTermLoop_terminate_m1) {
+  ControlReducerTester R;
+  Node* loop =
+      R.SetSelfReferences(R.graph.NewNode(R.common.Loop(2), R.start, R.self));
+  Node* effect = R.SetSelfReferences(
+      R.graph.NewNode(R.common.EffectPhi(2), R.start, R.self, loop));
+  R.ReduceGraph();
+  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));
+
+  Node* terminate = merge->InputAt(1);
+  CHECK_EQ(IrOpcode::kTerminate, terminate->opcode());
+  CHECK_EQ(2, terminate->InputCount());
+  CHECK_EQ(1, OperatorProperties::GetEffectInputCount(terminate->op()));
+  CHECK_EQ(1, OperatorProperties::GetControlInputCount(terminate->op()));
+  CHECK_EQ(effect, terminate->InputAt(0));
+  CHECK_EQ(loop, terminate->InputAt(1));
+}
+
+
+TEST(CNonTermLoop_big1) {
+  ControlReducerTester R;
+  Branch b1(R, R.p0);
+  Node* rt = R.graph.NewNode(R.common.Return(), R.one, R.start, b1.if_true);
+
+  Branch b2(R, R.p0, b1.if_false);
+  Node* rf = R.graph.NewNode(R.common.Return(), R.zero, R.start, b2.if_true);
+  Node* loop = R.SetSelfReferences(
+      R.graph.NewNode(R.common.Loop(2), b2.if_false, R.self));
+  Node* merge = R.graph.NewNode(R.common.Merge(2), rt, rf);
+  R.end->ReplaceInput(0, merge);
+
+  R.ReduceGraph();
+
+  CheckInputs(R.end, merge);
+  CheckInputs(merge, rt, rf, loop);
+  CheckInputs(loop, b2.if_false, loop);
+}
+
+
+TEST(CNonTermLoop_big2) {
+  ControlReducerTester R;
+  Branch b1(R, R.p0);
+  Node* rt = R.graph.NewNode(R.common.Return(), R.one, R.start, b1.if_true);
+
+  Branch b2(R, R.zero, b1.if_false);
+  Node* rf = R.graph.NewNode(R.common.Return(), R.zero, R.start, b2.if_true);
+  Node* loop = R.SetSelfReferences(
+      R.graph.NewNode(R.common.Loop(2), b2.if_false, R.self));
+  Node* merge = R.graph.NewNode(R.common.Merge(2), rt, rf);
+  R.end->ReplaceInput(0, merge);
+
+  R.ReduceGraph();
+
+  Node* new_merge = R.end->InputAt(0);  // old merge was reduced.
+  CHECK_NE(merge, new_merge);
+  CheckInputs(new_merge, rt, loop);
+  CheckInputs(loop, b1.if_false, loop);
+  CHECK(merge->IsDead());
+  CHECK(rf->IsDead());
+  CHECK(b2.if_true->IsDead());
+}
+
+
+TEST(Return1) {
+  ControlReducerTester R;
+  Node* ret = R.Return(R.one, R.start, R.start);
+  R.ReduceGraph();
+  CheckInputs(R.graph.end(), ret);
+  CheckInputs(ret, R.one, R.start, R.start);
+}
+
+
+TEST(Return2) {
+  ControlReducerTester R;
+  Diamond d(R, R.one);
+  Node* ret = R.Return(R.half, R.start, d.merge);
+  R.ReduceGraph();
+  CHECK(d.branch->IsDead());
+  CHECK(d.if_true->IsDead());
+  CHECK(d.if_false->IsDead());
+  CHECK(d.merge->IsDead());
+
+  CheckInputs(R.graph.end(), ret);
+  CheckInputs(ret, R.half, R.start, R.start);
+}
+
+
+TEST(Return_true1) {
+  ControlReducerTester R;
+  Diamond d(R, R.one, R.half, R.zero);
+  Node* ret = R.Return(d.phi, R.start, d.merge);
+  R.ReduceGraph();
+  CHECK(d.branch->IsDead());
+  CHECK(d.if_true->IsDead());
+  CHECK(d.if_false->IsDead());
+  CHECK(d.merge->IsDead());
+  CHECK(d.phi->IsDead());
+
+  CheckInputs(R.graph.end(), ret);
+  CheckInputs(ret, R.half, R.start, R.start);
+}
+
+
+TEST(Return_false1) {
+  ControlReducerTester R;
+  Diamond d(R, R.zero, R.one, R.half);
+  Node* ret = R.Return(d.phi, R.start, d.merge);
+  R.ReduceGraph();
+  CHECK(d.branch->IsDead());
+  CHECK(d.if_true->IsDead());
+  CHECK(d.if_false->IsDead());
+  CHECK(d.merge->IsDead());
+  CHECK(d.phi->IsDead());
+
+  CheckInputs(R.graph.end(), ret);
+  CheckInputs(ret, R.half, R.start, R.start);
+}
+
+
+void CheckDeadDiamond(Diamond& d) {
+  CHECK(d.branch->IsDead());
+  CHECK(d.if_true->IsDead());
+  CHECK(d.if_false->IsDead());
+  CHECK(d.merge->IsDead());
+  if (d.phi != NULL) CHECK(d.phi->IsDead());
+}
+
+
+void CheckLiveDiamond(Diamond& d, bool live_phi = true) {
+  CheckInputs(d.merge, d.if_true, d.if_false);
+  CheckInputs(d.if_true, d.branch);
+  CheckInputs(d.if_false, d.branch);
+  if (d.phi != NULL) {
+    if (live_phi) {
+      CHECK_EQ(3, d.phi->InputCount());
+      CHECK_EQ(d.merge, d.phi->InputAt(2));
+    } else {
+      CHECK(d.phi->IsDead());
+    }
+  }
+}
+
+
+TEST(Return_effect1) {
+  ControlReducerTester R;
+  Diamond d(R, R.one);
+  Node* e1 = R.jsgraph.Float64Constant(-100.1);
+  Node* e2 = R.jsgraph.Float64Constant(+100.1);
+  Node* effect = R.graph.NewNode(R.common.EffectPhi(2), e1, e2, d.merge);
+  Node* ret = R.Return(R.p0, effect, d.merge);
+  R.ReduceGraph();
+  CheckDeadDiamond(d);
+  CHECK(effect->IsDead());
+
+  CheckInputs(R.graph.end(), ret);
+  CheckInputs(ret, R.p0, e1, R.start);
+}
+
+
+TEST(Return_nested_diamonds1) {
+  ControlReducerTester R;
+  Diamond d1(R, R.p0, 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();  // 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);
+}
+
+
+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);
+}
+
+
+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);
+}
+
+
+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);
+  d3.nest(d1, false);
+
+  Node* ret = R.Return(d1.phi, R.start, d1.merge);
+
+  R.ReduceGraph();  // d1 and d2 both get folded true.
+
+  CheckInputs(ret, R.one, R.start, R.start);
+  CheckDeadDiamond(d1);
+  CheckDeadDiamond(d2);
+  CheckDeadDiamond(d3);
+}
+
+
+TEST(Return_nested_diamonds_true_false1) {
+  ControlReducerTester R;
+  Diamond d1(R, R.one, R.one, R.zero);
+  Diamond d2(R, R.zero);
+  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 and d2 gets folded false.
+
+  CheckInputs(ret, R.one, R.start, R.start);
+  CheckDeadDiamond(d1);
+  CheckDeadDiamond(d2);
+  CheckDeadDiamond(d3);
+}
+
+
+TEST(Return_nested_diamonds2) {
+  ControlReducerTester R;
+  Node* x2 = R.jsgraph.Float64Constant(11.1);
+  Node* y2 = R.jsgraph.Float64Constant(22.2);
+  Node* x3 = R.jsgraph.Float64Constant(33.3);
+  Node* y3 = R.jsgraph.Float64Constant(44.4);
+
+  Diamond d2(R, R.p0, x2, y2);
+  Diamond d3(R, R.p0, x3, y3);
+  Diamond d1(R, R.p0, d2.phi, d3.phi);
+
+  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, d2.phi, d3.phi, d1.merge);
+  CheckInputs(d1.merge, d2.merge, d3.merge);
+  CheckLiveDiamond(d2);
+  CheckLiveDiamond(d3);
+}
+
+
+TEST(Return_nested_diamonds_true2) {
+  ControlReducerTester R;
+  Node* x2 = R.jsgraph.Float64Constant(11.1);
+  Node* y2 = R.jsgraph.Float64Constant(22.2);
+  Node* x3 = R.jsgraph.Float64Constant(33.3);
+  Node* y3 = R.jsgraph.Float64Constant(44.4);
+
+  Diamond d2(R, R.p0, x2, y2);
+  Diamond d3(R, R.p0, x3, y3);
+  Diamond d1(R, R.one, d2.phi, d3.phi);
+
+  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, d2.phi, R.start, d2.merge);
+  CheckInputs(d2.branch, R.p0, R.start);
+  CheckDeadDiamond(d1);
+  CheckLiveDiamond(d2);
+  CheckDeadDiamond(d3);
+}
+
+
+TEST(Return_nested_diamonds_true_true2) {
+  ControlReducerTester R;
+  Node* x2 = R.jsgraph.Float64Constant(11.1);
+  Node* y2 = R.jsgraph.Float64Constant(22.2);
+  Node* x3 = R.jsgraph.Float64Constant(33.3);
+  Node* y3 = R.jsgraph.Float64Constant(44.4);
+
+  Diamond d2(R, R.one, x2, y2);
+  Diamond d3(R, R.p0, x3, y3);
+  Diamond d1(R, R.one, d2.phi, d3.phi);
+
+  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, x2, R.start, R.start);
+  CheckDeadDiamond(d1);
+  CheckDeadDiamond(d2);
+  CheckDeadDiamond(d3);
+}
+
+
+TEST(Return_nested_diamonds_true_false2) {
+  ControlReducerTester R;
+  Node* x2 = R.jsgraph.Float64Constant(11.1);
+  Node* y2 = R.jsgraph.Float64Constant(22.2);
+  Node* x3 = R.jsgraph.Float64Constant(33.3);
+  Node* y3 = R.jsgraph.Float64Constant(44.4);
+
+  Diamond d2(R, R.zero, x2, y2);
+  Diamond d3(R, R.p0, x3, y3);
+  Diamond d1(R, R.one, d2.phi, d3.phi);
+
+  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, y2, R.start, R.start);
+  CheckDeadDiamond(d1);
+  CheckDeadDiamond(d2);
+  CheckDeadDiamond(d3);
+}