Implement representation selection as part of SimplifiedLowering. Representation selection also req…

test/cctest/compiler/test-simplified-lowering.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 <limits>
 
 #include "src/compiler/control-builders.h"
 #include "src/compiler/generic-node-inl.h"
+#include "src/compiler/graph-visualizer.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/compiler/pipeline.h"
+#include "src/compiler/representation-change.h"
 #include "src/compiler/simplified-lowering.h"
 #include "src/compiler/simplified-node-factory.h"
 #include "src/compiler/typer.h"
 #include "src/compiler/verifier.h"
 #include "src/execution.h"
 #include "src/parser.h"
 #include "src/rewriter.h"
 #include "src/scopes.h"
 #include "test/cctest/cctest.h"
 #include "test/cctest/compiler/codegen-tester.h"
@@ skipping 16 matching lines @@
         typer(this->zone()),
         source_positions(this->graph()),
         jsgraph(this->graph(), this->common(), &typer),
         lowering(&jsgraph, &source_positions) {}
 
   Typer typer;
   SourcePositionTable source_positions;
   JSGraph jsgraph;
   SimplifiedLowering lowering;
 
-  // Close graph and lower one node.
-  void Lower(Node* node) {
+  void LowerAllNodes() {
     this->End();
-    if (node == NULL) {
-      lowering.LowerAllNodes();
-    } else {
-      lowering.Lower(node);
-    }
-  }
-
-  // Close graph and lower all nodes.
-  void LowerAllNodes() { Lower(NULL); }
-
-  void StoreFloat64(Node* node, double* ptr) {
-    Node* ptr_node = this->PointerConstant(ptr);
-    this->Store(kMachineFloat64, ptr_node, node);
-  }
-
-  Node* LoadInt32(int32_t* ptr) {
-    Node* ptr_node = this->PointerConstant(ptr);
-    return this->Load(kMachineWord32, ptr_node);
-  }
-
-  Node* LoadUint32(uint32_t* ptr) {
-    Node* ptr_node = this->PointerConstant(ptr);
-    return this->Load(kMachineWord32, ptr_node);
-  }
-
-  Node* LoadFloat64(double* ptr) {
-    Node* ptr_node = this->PointerConstant(ptr);
-    return this->Load(kMachineFloat64, ptr_node);
+    lowering.LowerAllNodes();
   }
 
   Factory* factory() { return this->isolate()->factory(); }
   Heap* heap() { return this->isolate()->heap(); }
 };
 
 
 // TODO(dcarney): find a home for these functions.
 namespace {
 
@@ skipping 47 matching lines @@
 
 
 TEST(RunLoadMap) {
   SimplifiedGraphBuilderTester<Object*> t(kMachineTagged);
   FieldAccess access = ForJSObjectMap();
   Node* load = t.LoadField(access, t.Parameter(0));
   t.Return(load);
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<JSObject> src = TestObject();
-  Handle<Map> src_map(src->map());
-  Object* result = t.Call(*src);
-  CHECK_EQ(*src_map, result);
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<JSObject> src = TestObject();
+    Handle<Map> src_map(src->map());
+    Object* result = t.Call(*src);  // TODO(titzer): raw pointers in call
+    CHECK_EQ(*src_map, result);
+  }
 }
 
 
 TEST(RunStoreMap) {
   SimplifiedGraphBuilderTester<int32_t> t(kMachineTagged, kMachineTagged);
   FieldAccess access = ForJSObjectMap();
   t.StoreField(access, t.Parameter(1), t.Parameter(0));
-  t.Return(t.Int32Constant(0));
+  t.Return(t.jsgraph.TrueConstant());
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<JSObject> src = TestObject();
-  Handle<Map> src_map(src->map());
-  Handle<JSObject> dst = TestObject();
-  CHECK(src->map() != dst->map());
-  t.Call(*src_map, *dst);
-  CHECK(*src_map == dst->map());
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<JSObject> src = TestObject();
+    Handle<Map> src_map(src->map());
+    Handle<JSObject> dst = TestObject();
+    CHECK(src->map() != dst->map());
+    t.Call(*src_map, *dst);  // TODO(titzer): raw pointers in call
+    CHECK(*src_map == dst->map());
+  }
 }
 
 
 TEST(RunLoadProperties) {
   SimplifiedGraphBuilderTester<Object*> t(kMachineTagged);
   FieldAccess access = ForJSObjectProperties();
   Node* load = t.LoadField(access, t.Parameter(0));
   t.Return(load);
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<JSObject> src = TestObject();
-  Handle<FixedArray> src_props(src->properties());
-  Object* result = t.Call(*src);
-  CHECK_EQ(*src_props, result);
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<JSObject> src = TestObject();
+    Handle<FixedArray> src_props(src->properties());
+    Object* result = t.Call(*src);  // TODO(titzer): raw pointers in call
+    CHECK_EQ(*src_props, result);
+  }
 }
 
 
 TEST(RunLoadStoreMap) {
   SimplifiedGraphBuilderTester<Object*> t(kMachineTagged, kMachineTagged);
   FieldAccess access = ForJSObjectMap();
   Node* load = t.LoadField(access, t.Parameter(0));
   t.StoreField(access, t.Parameter(1), load);
   t.Return(load);
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<JSObject> src = TestObject();
-  Handle<Map> src_map(src->map());
-  Handle<JSObject> dst = TestObject();
-  CHECK(src->map() != dst->map());
-  Object* result = t.Call(*src, *dst);
-  CHECK(result->IsMap());
-  CHECK_EQ(*src_map, result);
-  CHECK(*src_map == dst->map());
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<JSObject> src = TestObject();
+    Handle<Map> src_map(src->map());
+    Handle<JSObject> dst = TestObject();
+    CHECK(src->map() != dst->map());
+    Object* result = t.Call(*src, *dst);  // TODO(titzer): raw pointers in call
+    CHECK(result->IsMap());
+    CHECK_EQ(*src_map, result);
+    CHECK(*src_map == dst->map());
+  }
 }
 
 
 TEST(RunLoadStoreFixedArrayIndex) {
   SimplifiedGraphBuilderTester<Object*> t(kMachineTagged);
   ElementAccess access = ForFixedArrayElement();
   Node* load = t.LoadElement(access, t.Parameter(0), t.Int32Constant(0));
   t.StoreElement(access, t.Parameter(0), t.Int32Constant(1), load);
   t.Return(load);
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<FixedArray> array = t.factory()->NewFixedArray(2);
-  Handle<JSObject> src = TestObject();
-  Handle<JSObject> dst = TestObject();
-  array->set(0, *src);
-  array->set(1, *dst);
-  Object* result = t.Call(*array);
-  CHECK_EQ(*src, result);
-  CHECK_EQ(*src, array->get(0));
-  CHECK_EQ(*src, array->get(1));
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<FixedArray> array = t.factory()->NewFixedArray(2);
+    Handle<JSObject> src = TestObject();
+    Handle<JSObject> dst = TestObject();
+    array->set(0, *src);
+    array->set(1, *dst);
+    Object* result = t.Call(*array);
+    CHECK_EQ(*src, result);
+    CHECK_EQ(*src, array->get(0));
+    CHECK_EQ(*src, array->get(1));
+  }
 }
 
 
 TEST(RunLoadStoreArrayBuffer) {
-  SimplifiedGraphBuilderTester<int32_t> t(kMachineTagged);
+  SimplifiedGraphBuilderTester<Object*> t(kMachineTagged);
   const int index = 12;
-  FieldAccess access = ForArrayBufferBackingStore();
-  Node* backing_store = t.LoadField(access, t.Parameter(0));
   ElementAccess buffer_access = ForBackingStoreElement(kMachineWord8);
+  Node* backing_store =
+      t.LoadField(ForArrayBufferBackingStore(), t.Parameter(0));
   Node* load =
       t.LoadElement(buffer_access, backing_store, t.Int32Constant(index));
   t.StoreElement(buffer_access, backing_store, t.Int32Constant(index + 1),
                  load);
-  t.Return(load);
+  t.Return(t.jsgraph.TrueConstant());
 
   t.LowerAllNodes();
 
-  if (!Pipeline::SupportedTarget()) return;
+  if (Pipeline::SupportedTarget()) {
+    t.GenerateCode();
+    Handle<JSArrayBuffer> array = t.factory()->NewJSArrayBuffer();
+    const int array_length = 2 * index;
+    Runtime::SetupArrayBufferAllocatingData(t.isolate(), array, array_length);
+    uint8_t* data = reinterpret_cast<uint8_t*>(array->backing_store());
+    for (int i = 0; i < array_length; i++) {
+      data[i] = i;
+    }
 
-  Handle<JSArrayBuffer> array = t.factory()->NewJSArrayBuffer();
-  const int array_length = 2 * index;
-  Runtime::SetupArrayBufferAllocatingData(t.isolate(), array, array_length);
-  uint8_t* data = reinterpret_cast<uint8_t*>(array->backing_store());
-  for (int i = 0; i < array_length; i++) {
-    data[i] = i;
-  }
-  int32_t result = t.Call(*array);
-  CHECK_EQ(index, result);
-  for (int i = 0; i < array_length; i++) {
-    uint8_t expected = i;
-    if (i == (index + 1)) expected = result;
-    CHECK_EQ(data[i], expected);
+    // TODO(titzer): raw pointers in call
+    Object* result = t.Call(*array);
+    CHECK_EQ(t.isolate()->heap()->true_value(), result);
+    for (int i = 0; i < array_length; i++) {
+      uint8_t expected = i;
+      if (i == (index + 1)) expected = index;
+      CHECK_EQ(data[i], expected);
+    }
   }
 }
 
-
-TEST(RunCopyFixedArray) {
-  SimplifiedGraphBuilderTester<int32_t> t(kMachineTagged, kMachineTagged);
-
-  const int kArraySize = 15;
-  Node* one = t.Int32Constant(1);
-  Node* index = t.Int32Constant(0);
-  Node* limit = t.Int32Constant(kArraySize);
-  t.environment()->Push(index);
-  {
-    LoopBuilder loop(&t);
-    loop.BeginLoop();
-    // Loop exit condition.
-    index = t.environment()->Top();
-    Node* condition = t.Int32LessThan(index, limit);
-    loop.BreakUnless(condition);
-    // src[index] = dst[index].
-    index = t.environment()->Pop();
-    ElementAccess access = ForFixedArrayElement();
-    Node* src = t.Parameter(0);
-    Node* load = t.LoadElement(access, src, index);
-    Node* dst = t.Parameter(1);
-    t.StoreElement(access, dst, index, load);
-    // index++
-    index = t.Int32Add(index, one);
-    t.environment()->Push(index);
-    // continue.
-    loop.EndBody();
-    loop.EndLoop();
-  }
-  index = t.environment()->Pop();
-  t.Return(index);
-
-  t.LowerAllNodes();
-
-  if (!Pipeline::SupportedTarget()) return;
-
-  Handle<FixedArray> src = t.factory()->NewFixedArray(kArraySize);
-  Handle<FixedArray> src_copy = t.factory()->NewFixedArray(kArraySize);
-  Handle<FixedArray> dst = t.factory()->NewFixedArray(kArraySize);
-  for (int i = 0; i < kArraySize; i++) {
-    src->set(i, *TestObject());
-    src_copy->set(i, src->get(i));
-    dst->set(i, *TestObject());
-    CHECK_NE(src_copy->get(i), dst->get(i));
-  }
-  CHECK_EQ(kArraySize, t.Call(*src, *dst));
-  for (int i = 0; i < kArraySize; i++) {
-    CHECK_EQ(src_copy->get(i), dst->get(i));
-  }
-}
-
 
 TEST(RunLoadFieldFromUntaggedBase) {
   Smi* smis[] = {Smi::FromInt(1), Smi::FromInt(2), Smi::FromInt(3)};
 
   for (size_t i = 0; i < ARRAY_SIZE(smis); i++) {
     int offset = static_cast<int>(i * sizeof(Smi*));
     FieldAccess access = {kUntaggedBase, offset, Handle<Name>(),
                           Type::Integral32(), kMachineTagged};
 
     SimplifiedGraphBuilderTester<Object*> t;
@@ skipping 89 matching lines @@
         Smi* expected = Smi::FromInt(k);
         smis[i + j] = Smi::FromInt(-100);
         CHECK_EQ(expected, t.Call(expected));
         CHECK_EQ(expected, smis[i + j]);
       }
 
       // TODO(titzer): assert the contents of the array.
     }
   }
 }
+
+
+// A helper class for accessing fields and elements of various types, on both
+// tagged and untagged base pointers. Contains both tagged and untagged buffers
+// for testing direct memory access from generated code.
+template <typename E>
+class AccessTester : public HandleAndZoneScope {
+ public:
+  bool tagged;
+  MachineRepresentation rep;
+  E* original_elements;
+  int num_elements;
+  E* untagged_array;
+  Handle<ByteArray> tagged_array;  // TODO(titzer): use FixedArray for tagged.
+
+  AccessTester(bool t, MachineRepresentation r, E* orig, int num)
+      : tagged(t),
+        rep(r),
+        original_elements(orig),
+        num_elements(num),
+        untagged_array(static_cast<E*>(malloc(ByteSize()))),
+        tagged_array(main_isolate()->factory()->NewByteArray(ByteSize())) {
+    Reinitialize();
+  }
+
+  ~AccessTester() { free(untagged_array); }
+
+  size_t ByteSize() { return num_elements * sizeof(E); }
+
+  // Nuke both {untagged_array} and {tagged_array} with {original_elements}.
+  void Reinitialize() {
+    memcpy(untagged_array, original_elements, ByteSize());
+    CHECK_EQ(ByteSize(), tagged_array->length());
+    E* raw = reinterpret_cast<E*>(tagged_array->GetDataStartAddress());
+    memcpy(raw, original_elements, ByteSize());
+  }
+
+  // Create and run code that copies the element in either {untagged_array}
+  // or {tagged_array} at index {from_index} to index {to_index}.
+  void RunCopyElement(int from_index, int to_index) {
+    // TODO(titzer): test element and field accesses where the base is not
+    // a constant in the code.
+    BoundsCheck(from_index);
+    BoundsCheck(to_index);
+    ElementAccess access = GetElementAccess();
+
+    SimplifiedGraphBuilderTester<Object*> t;
+    Node* ptr = GetBaseNode(&t);
+    Node* load = t.LoadElement(access, ptr, t.Int32Constant(from_index));
+    t.StoreElement(access, ptr, t.Int32Constant(to_index), load);
+    t.Return(t.jsgraph.TrueConstant());
+    t.LowerAllNodes();
+    t.GenerateCode();
+
+    if (Pipeline::SupportedTarget()) {
+      Object* result = t.Call();
+      CHECK_EQ(t.isolate()->heap()->true_value(), result);
+    }
+  }
+
+  // Create and run code that copies the field in either {untagged_array}
+  // or {tagged_array} at index {from_index} to index {to_index}.
+  void RunCopyField(int from_index, int to_index) {
+    BoundsCheck(from_index);
+    BoundsCheck(to_index);
+    FieldAccess from_access = GetFieldAccess(from_index);
+    FieldAccess to_access = GetFieldAccess(to_index);
+
+    SimplifiedGraphBuilderTester<Object*> t;
+    Node* ptr = GetBaseNode(&t);
+    Node* load = t.LoadField(from_access, ptr);
+    t.StoreField(to_access, ptr, load);
+    t.Return(t.jsgraph.TrueConstant());
+    t.LowerAllNodes();
+    t.GenerateCode();
+
+    if (Pipeline::SupportedTarget()) {
+      Object* result = t.Call();
+      CHECK_EQ(t.isolate()->heap()->true_value(), result);
+    }
+  }
+
+  // Create and run code that copies the elements from {this} to {that}.
+  void RunCopyElements(AccessTester<E>* that) {
+    SimplifiedGraphBuilderTester<Object*> t;
+
+    Node* one = t.Int32Constant(1);
+    Node* index = t.Int32Constant(0);
+    Node* limit = t.Int32Constant(num_elements);
+    t.environment()->Push(index);
+    Node* src = this->GetBaseNode(&t);
+    Node* dst = that->GetBaseNode(&t);
+    {
+      LoopBuilder loop(&t);
+      loop.BeginLoop();
+      // Loop exit condition
+      index = t.environment()->Top();
+      Node* condition = t.Int32LessThan(index, limit);
+      loop.BreakUnless(condition);
+      // dst[index] = src[index]
+      index = t.environment()->Pop();
+      Node* load = t.LoadElement(this->GetElementAccess(), src, index);
+      t.StoreElement(that->GetElementAccess(), dst, index, load);
+      // index++
+      index = t.Int32Add(index, one);
+      t.environment()->Push(index);
+      // continue
+      loop.EndBody();
+      loop.EndLoop();
+    }
+    index = t.environment()->Pop();
+    t.Return(t.jsgraph.TrueConstant());
+    t.LowerAllNodes();
+    t.GenerateCode();
+
+    if (Pipeline::SupportedTarget()) {
+      Object* result = t.Call();
+      CHECK_EQ(t.isolate()->heap()->true_value(), result);
+    }
+  }
+
+  E GetElement(int index) {
+    BoundsCheck(index);
+    if (tagged) {
+      E* raw = reinterpret_cast<E*>(tagged_array->GetDataStartAddress());
+      return raw[index];
+    } else {
+      return untagged_array[index];
+    }
+  }
+
+ private:
+  ElementAccess GetElementAccess() {
+    ElementAccess access = {tagged ? kTaggedBase : kUntaggedBase,
+                            tagged ? FixedArrayBase::kHeaderSize : 0,
+                            Type::Any(), rep};
+    return access;
+  }
+
+  FieldAccess GetFieldAccess(int field) {
+    int offset = field * sizeof(E);
+    FieldAccess access = {tagged ? kTaggedBase : kUntaggedBase,
+                          offset + (tagged ? FixedArrayBase::kHeaderSize : 0),
+                          Handle<Name>(), Type::Any(), rep};
+    return access;
+  }
+
+  template <typename T>
+  Node* GetBaseNode(SimplifiedGraphBuilderTester<T>* t) {
+    return tagged ? t->HeapConstant(tagged_array)
+                  : t->PointerConstant(untagged_array);
+  }
+
+  void BoundsCheck(int index) {
+    CHECK_GE(index, 0);
+    CHECK_LT(index, num_elements);
+    CHECK_EQ(ByteSize(), tagged_array->length());
+  }
+};
+
+
+template <typename E>
+static void RunAccessTest(MachineRepresentation rep, E* original_elements,
+                          size_t num) {
+  int num_elements = static_cast<int>(num);
+
+  for (int taggedness = 0; taggedness < 2; taggedness++) {
+    AccessTester<E> a(taggedness == 1, rep, original_elements, num_elements);
+    for (int field = 0; field < 2; field++) {
+      for (int i = 0; i < num_elements - 1; i++) {
+        a.Reinitialize();
+        if (field == 0) {
+          a.RunCopyField(i, i + 1);  // Test field read/write.
+        } else {
+          a.RunCopyElement(i, i + 1);  // Test element read/write.
+        }
+        if (Pipeline::SupportedTarget()) {  // verify.
+          for (int j = 0; j < num_elements; j++) {
+            E expect =
+                j == (i + 1) ? original_elements[i] : original_elements[j];
+            CHECK_EQ(expect, a.GetElement(j));
+          }
+        }
+      }
+    }
+  }
+  // Test array copy.
+  for (int tf = 0; tf < 2; tf++) {
+    for (int tt = 0; tt < 2; tt++) {
+      AccessTester<E> a(tf == 1, rep, original_elements, num_elements);
+      AccessTester<E> b(tt == 1, rep, original_elements, num_elements);
+      a.RunCopyElements(&b);
+      if (Pipeline::SupportedTarget()) {  // verify.
+        for (int i = 0; i < num_elements; i++) {
+          CHECK_EQ(a.GetElement(i), b.GetElement(i));
+        }
+      }
+    }
+  }
+}
+
+
+TEST(RunAccessTests_uint8) {
+  uint8_t data[] = {0x07, 0x16, 0x25, 0x34, 0x43, 0x99,
+                    0xab, 0x78, 0x89, 0x19, 0x2b, 0x38};
+  RunAccessTest<uint8_t>(kMachineWord8, data, ARRAY_SIZE(data));
+}
+
+
+TEST(RunAccessTests_uint16) {
+  uint16_t data[] = {0x071a, 0x162b, 0x253c, 0x344d, 0x435e, 0x7777};
+  RunAccessTest<uint16_t>(kMachineWord16, data, ARRAY_SIZE(data));
+}
+
+
+TEST(RunAccessTests_int32) {
+  int32_t data[] = {0xf10733aa, 0xf21644bb, 0xf32555cc,
+                    0xf43466dd, 0xf54377ee, 0x34455667};
+  RunAccessTest<int32_t>(kMachineWord32, data, ARRAY_SIZE(data));
+}
+
+
+TEST(RunAccessTests_int64) {
+  if (kPointerSize != 8) return;
+  int64_t data[] = {0x1011121314151617L, 0x2021222324252627L,
+                    0x3031323334353637L, 0xa0a1a2a3a4a5a6a7L,
+                    0xf0f1f2f3f4f5f6f7L};
+  RunAccessTest<int64_t>(kMachineWord64, data, ARRAY_SIZE(data));
+}
+
+
+TEST(RunAccessTests_float64) {
+  double data[] = {1.25, -1.25, 2.75, 11.0, 11100.8};
+  RunAccessTest<double>(kMachineFloat64, data, ARRAY_SIZE(data));
+}
+
+
+TEST(RunAccessTests_Smi) {
+  Smi* data[] = {Smi::FromInt(-1),    Smi::FromInt(-9),
+                 Smi::FromInt(0),     Smi::FromInt(666),
+                 Smi::FromInt(77777), Smi::FromInt(Smi::kMaxValue)};
+  RunAccessTest<Smi*>(kMachineTagged, data, ARRAY_SIZE(data));
+}
+
+
+// Fills in most of the nodes of the graph in order to make tests shorter.
+class TestingGraph : public HandleAndZoneScope, public GraphAndBuilders {
+ public:
+  Typer typer;
+  JSGraph jsgraph;
+  Node* p0;
+  Node* p1;
+  Node* start;
+  Node* end;
+  Node* ret;
+
+  TestingGraph(Type* p0_type, Type* p1_type = Type::None())
+      : GraphAndBuilders(main_zone()),
+        typer(main_zone()),
+        jsgraph(graph(), common(), &typer) {
+    start = graph()->NewNode(common()->Start(2));
+    graph()->SetStart(start);
+    ret =
+        graph()->NewNode(common()->Return(), jsgraph.Constant(0), start, start);
+    end = graph()->NewNode(common()->End(), ret);
+    graph()->SetEnd(end);
+    p0 = graph()->NewNode(common()->Parameter(0), start);
+    p1 = graph()->NewNode(common()->Parameter(1), start);
+    NodeProperties::SetBounds(p0, Bounds(p0_type));
+    NodeProperties::SetBounds(p1, Bounds(p1_type));
+  }
+
+  void CheckLoweringBinop(IrOpcode::Value expected, Operator* op) {
+    Node* node = Return(graph()->NewNode(op, p0, p1));
+    Lower();
+    CHECK_EQ(expected, node->opcode());
+  }
+
+  void CheckLoweringTruncatedBinop(IrOpcode::Value expected, Operator* op,
+                                   Operator* trunc) {
+    Node* node = graph()->NewNode(op, p0, p1);
+    Return(graph()->NewNode(trunc, node));
+    Lower();
+    CHECK_EQ(expected, node->opcode());
+  }
+
+  void Lower() {
+    SimplifiedLowering lowering(&jsgraph, NULL);
+    lowering.LowerAllNodes();
+  }
+
+  // Inserts the node as the return value of the graph.
+  Node* Return(Node* node) {
+    ret->ReplaceInput(0, node);
+    return node;
+  }
+
+  Node* ExampleWithOutput(RepType type) {
+    // TODO(titzer): use parameters with guaranteed representations.
+    if (type & tInt32) {
+      return graph()->NewNode(machine()->Int32Add(), jsgraph.Int32Constant(1),
+                              jsgraph.Int32Constant(1));
+    } else if (type & tUint32) {
+      return graph()->NewNode(machine()->Word32Sar(), jsgraph.Int32Constant(1),
+                              jsgraph.Int32Constant(1));
+    } else if (type & rFloat64) {
+      return graph()->NewNode(machine()->Float64Add(),
+                              jsgraph.Float64Constant(1),
+                              jsgraph.Float64Constant(1));
+    } else if (type & rBit) {
+      return graph()->NewNode(machine()->Word32Equal(),
+                              jsgraph.Int32Constant(1),
+                              jsgraph.Int32Constant(1));
+    } else {
+      CHECK_EQ(rTagged, type);
+      return p0;
+    }
+  }
+
+  Node* Use(Node* node, RepType type) {
+    if (type & tInt32) {
+      return graph()->NewNode(machine()->Int32LessThan(), node,
+                              jsgraph.Int32Constant(1));
+    } else if (type & tUint32) {
+      return graph()->NewNode(machine()->Uint32LessThan(), node,
+                              jsgraph.Int32Constant(1));
+    } else if (type & rFloat64) {
+      return graph()->NewNode(machine()->Float64Add(), node,
+                              jsgraph.Float64Constant(1));
+    } else {
+      return graph()->NewNode(simplified()->ReferenceEqual(Type::Any()), node,
+                              jsgraph.TrueConstant());
+    }
+  }
+
+  Node* Branch(Node* cond) {
+    Node* br = graph()->NewNode(common()->Branch(), cond, start);
+    Node* tb = graph()->NewNode(common()->IfTrue(), br);
+    Node* fb = graph()->NewNode(common()->IfFalse(), br);
+    Node* m = graph()->NewNode(common()->Merge(2), tb, fb);
+    ret->ReplaceInput(NodeProperties::FirstControlIndex(ret), m);
+    return br;
+  }
+
+  SimplifiedOperatorBuilder* simplified() { return &main_simplified_; }
+  MachineOperatorBuilder* machine() { return &main_machine_; }
+  CommonOperatorBuilder* common() { return &main_common_; }
+  Graph* graph() { return main_graph_; }
+};
+
+
+#define TODO_TITZER
+
+TEST(LowerBooleanNot_bit_bit) {
+  // BooleanNot(x: rBit) used as rBit
+  TestingGraph t(Type::Boolean());
+  Node* b = t.ExampleWithOutput(rBit);
+  Node* inv = t.graph()->NewNode(t.simplified()->BooleanNot(), b);
+  Node* use = t.Branch(inv);
+  t.Lower();
+  Node* cmp = use->InputAt(0);
+  CHECK_EQ(t.machine()->WordEqual()->opcode(), cmp->opcode());
+  CHECK(b == cmp->InputAt(0) || b == cmp->InputAt(1));
+  Node* f = t.jsgraph.Int32Constant(0);
+  CHECK(f == cmp->InputAt(0) || f == cmp->InputAt(1));
+}
+
+
+TEST(LowerBooleanNot_bit_tagged) {
+  // BooleanNot(x: rBit) used as rTagged
+  TestingGraph t(Type::Boolean());
+  Node* b = t.ExampleWithOutput(rBit);
+  Node* inv = t.graph()->NewNode(t.simplified()->BooleanNot(), b);
+  Node* use = t.Use(inv, rTagged);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeBitToBool, use->InputAt(0)->opcode());
+  Node* cmp = use->InputAt(0)->InputAt(0);
+  CHECK_EQ(t.machine()->WordEqual()->opcode(), cmp->opcode());
+  CHECK(b == cmp->InputAt(0) || b == cmp->InputAt(1));
+  Node* f = t.jsgraph.Int32Constant(0);
+  CHECK(f == cmp->InputAt(0) || f == cmp->InputAt(1));
+}
+
+
+TEST(LowerBooleanNot_tagged_bit) {
+  // BooleanNot(x: rTagged) used as rBit
+  TestingGraph t(Type::Boolean());
+  Node* b = t.p0;
+  Node* inv = t.graph()->NewNode(t.simplified()->BooleanNot(), b);
+  Node* use = t.Branch(inv);
+  t.Lower();
+  Node* cmp = use->InputAt(0);
+  CHECK_EQ(t.machine()->WordEqual()->opcode(), cmp->opcode());
+  CHECK(b == cmp->InputAt(0) || b == cmp->InputAt(1));
+  Node* f = t.jsgraph.FalseConstant();
+  CHECK(f == cmp->InputAt(0) || f == cmp->InputAt(1));
+}
+
+
+TEST(LowerBooleanNot_tagged_tagged) {
+  // BooleanNot(x: rTagged) used as rTagged
+  TestingGraph t(Type::Boolean());
+  Node* b = t.p0;
+  Node* inv = t.graph()->NewNode(t.simplified()->BooleanNot(), b);
+  Node* use = t.Use(inv, rTagged);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeBitToBool, use->InputAt(0)->opcode());
+  Node* cmp = use->InputAt(0)->InputAt(0);
+  CHECK_EQ(t.machine()->WordEqual()->opcode(), cmp->opcode());
+  CHECK(b == cmp->InputAt(0) || b == cmp->InputAt(1));
+  Node* f = t.jsgraph.FalseConstant();
+  CHECK(f == cmp->InputAt(0) || f == cmp->InputAt(1));
+}
+
+
+static Type* test_types[] = {Type::Signed32(), Type::Unsigned32(),
+                             Type::Number(), Type::Any()};
+
+
+TEST(LowerNumberCmp_to_int32) {
+  TestingGraph t(Type::Signed32(), Type::Signed32());
+
+  t.CheckLoweringBinop(IrOpcode::kWord32Equal, t.simplified()->NumberEqual());
+  t.CheckLoweringBinop(IrOpcode::kInt32LessThan,
+                       t.simplified()->NumberLessThan());
+  t.CheckLoweringBinop(IrOpcode::kInt32LessThanOrEqual,
+                       t.simplified()->NumberLessThanOrEqual());
+}
+
+
+TEST(LowerNumberCmp_to_uint32) {
+  TestingGraph t(Type::Unsigned32(), Type::Unsigned32());
+
+  t.CheckLoweringBinop(IrOpcode::kWord32Equal, t.simplified()->NumberEqual());
+  t.CheckLoweringBinop(IrOpcode::kUint32LessThan,
+                       t.simplified()->NumberLessThan());
+  t.CheckLoweringBinop(IrOpcode::kUint32LessThanOrEqual,
+                       t.simplified()->NumberLessThanOrEqual());
+}
+
+
+TEST(LowerNumberCmp_to_float64) {
+  static Type* types[] = {Type::Number(), Type::Any()};
+
+  for (size_t i = 0; i < ARRAY_SIZE(types); i++) {
+    TestingGraph t(types[i], types[i]);
+
+    t.CheckLoweringBinop(IrOpcode::kFloat64Equal,
+                         t.simplified()->NumberEqual());
+    t.CheckLoweringBinop(IrOpcode::kFloat64LessThan,
+                         t.simplified()->NumberLessThan());
+    t.CheckLoweringBinop(IrOpcode::kFloat64LessThanOrEqual,
+                         t.simplified()->NumberLessThanOrEqual());
+  }
+}
+
+
+TEST(LowerNumberAddSub_to_int32) {
+  TestingGraph t(Type::Signed32(), Type::Signed32());
+  t.CheckLoweringTruncatedBinop(IrOpcode::kInt32Add,
+                                t.simplified()->NumberAdd(),
+                                t.simplified()->NumberToInt32());
+  t.CheckLoweringTruncatedBinop(IrOpcode::kInt32Sub,
+                                t.simplified()->NumberSubtract(),
+                                t.simplified()->NumberToInt32());
+}
+
+
+TEST(LowerNumberAddSub_to_uint32) {
+  TestingGraph t(Type::Unsigned32(), Type::Unsigned32());
+  t.CheckLoweringTruncatedBinop(IrOpcode::kInt32Add,
+                                t.simplified()->NumberAdd(),
+                                t.simplified()->NumberToUint32());
+  t.CheckLoweringTruncatedBinop(IrOpcode::kInt32Sub,
+                                t.simplified()->NumberSubtract(),
+                                t.simplified()->NumberToUint32());
+}
+
+
+TEST(LowerNumberAddSub_to_float64) {
+  for (size_t i = 0; i < ARRAY_SIZE(test_types); i++) {
+    TestingGraph t(test_types[i], test_types[i]);
+
+    t.CheckLoweringBinop(IrOpcode::kFloat64Add, t.simplified()->NumberAdd());
+    t.CheckLoweringBinop(IrOpcode::kFloat64Sub,
+                         t.simplified()->NumberSubtract());
+  }
+}
+
+
+TEST(LowerNumberDivMod_to_float64) {
+  for (size_t i = 0; i < ARRAY_SIZE(test_types); i++) {
+    TestingGraph t(test_types[i], test_types[i]);
+
+    t.CheckLoweringBinop(IrOpcode::kFloat64Div, t.simplified()->NumberDivide());
+    t.CheckLoweringBinop(IrOpcode::kFloat64Mod,
+                         t.simplified()->NumberModulus());
+  }
+}
+
+
+TEST(LowerNumberToInt32_to_nop) {
+  // NumberToInt32(x: rTagged | tInt32) used as rTagged
+  TestingGraph t(Type::Signed32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToInt32(), t.p0);
+  Node* use = t.Use(trunc, rTagged);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(t.p0, use->InputAt(0));
+}
+
+
+TEST(LowerNumberToInt32_to_ChangeTaggedToFloat64) {
+  // NumberToInt32(x: rTagged | tInt32) used as rFloat64
+  TestingGraph t(Type::Signed32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToInt32(), t.p0);
+  Node* use = t.Use(trunc, rFloat64);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeTaggedToFloat64, use->InputAt(0)->opcode());
+  CHECK_EQ(t.p0, use->InputAt(0)->InputAt(0));
+}
+
+
+TEST(LowerNumberToInt32_to_ChangeTaggedToInt32) {
+  // NumberToInt32(x: rTagged | tInt32) used as rWord32
+  TestingGraph t(Type::Signed32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToInt32(), t.p0);
+  Node* use = t.Use(trunc, tInt32);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeTaggedToInt32, use->InputAt(0)->opcode());
+  CHECK_EQ(t.p0, use->InputAt(0)->InputAt(0));
+}
+
+
+TEST(LowerNumberToInt32_to_ChangeFloat64ToTagged) {
+  // NumberToInt32(x: rFloat64 | tInt32) used as rTagged
+  TODO_TITZER;
+}
+
+
+TEST(LowerNumberToInt32_to_ChangeFloat64ToInt32) {
+  // NumberToInt32(x: rFloat64 | tInt32) used as rWord32 | tInt32
+  TODO_TITZER;
+}
+
+
+TEST(LowerNumberToInt32_to_TruncateFloat64ToInt32) {
+  // NumberToInt32(x: rFloat64) used as rWord32 | tUint32
+  TODO_TITZER;
+}
+
+
+TEST(LowerNumberToUint32_to_nop) {
+  // NumberToUint32(x: rTagged | tUint32) used as rTagged
+  TestingGraph t(Type::Unsigned32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToUint32(), t.p0);
+  Node* use = t.Use(trunc, rTagged);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(t.p0, use->InputAt(0));
+}
+
+
+TEST(LowerNumberToUint32_to_ChangeTaggedToFloat64) {
+  // NumberToUint32(x: rTagged | tUint32) used as rWord32
+  TestingGraph t(Type::Unsigned32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToUint32(), t.p0);
+  Node* use = t.Use(trunc, rFloat64);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeTaggedToFloat64, use->InputAt(0)->opcode());
+  CHECK_EQ(t.p0, use->InputAt(0)->InputAt(0));
+}
+
+
+TEST(LowerNumberToUint32_to_ChangeTaggedToUint32) {
+  // NumberToUint32(x: rTagged | tUint32) used as rWord32
+  TestingGraph t(Type::Unsigned32());
+  Node* trunc = t.graph()->NewNode(t.simplified()->NumberToUint32(), t.p0);
+  Node* use = t.Use(trunc, tUint32);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(IrOpcode::kChangeTaggedToUint32, use->InputAt(0)->opcode());
+  CHECK_EQ(t.p0, use->InputAt(0)->InputAt(0));
+}
+
+
+TEST(LowerNumberToUint32_to_ChangeFloat64ToTagged) {
+  // NumberToUint32(x: rFloat64 | tUint32) used as rTagged
+  TODO_TITZER;
+}
+
+
+TEST(LowerNumberToUint32_to_ChangeFloat64ToUint32) {
+  // NumberToUint32(x: rFloat64 | tUint32) used as rWord32
+  TODO_TITZER;
+}
+
+
+TEST(LowerNumberToUint32_to_TruncateFloat64ToUint32) {
+  // NumberToUint32(x: rFloat64) used as rWord32
+  TODO_TITZER;
+}
+
+
+TEST(LowerReferenceEqual_to_wordeq) {
+  TestingGraph t(Type::Any(), Type::Any());
+  IrOpcode::Value opcode =
+      static_cast<IrOpcode::Value>(t.machine()->WordEqual()->opcode());
+  t.CheckLoweringBinop(opcode, t.simplified()->ReferenceEqual(Type::Any()));
+}
+
+
+TEST(LowerStringOps_to_rtcalls) {
+  if (false) {  // TODO(titzer): lower StringOps to runtime calls
+    TestingGraph t(Type::String(), Type::String());
+    t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringEqual());
+    t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringLessThan());
+    t.CheckLoweringBinop(IrOpcode::kCall,
+                         t.simplified()->StringLessThanOrEqual());
+    t.CheckLoweringBinop(IrOpcode::kCall, t.simplified()->StringAdd());
+  }
+}
+
+
+TEST(LowerLoadField_to_load) { TODO_TITZER; }
+
+
+TEST(LowerStoreField_to_store) { TODO_TITZER; }
+
+
+TEST(LowerStoreField_to_store_wb) { TODO_TITZER; }
+
+
+TEST(LowerLoadElement_to_load) { TODO_TITZER; }
+
+
+TEST(LowerStoreElement_to_store) { TODO_TITZER; }
+
+
+TEST(LowerStoreElement_to_store_wb) { TODO_TITZER; }
+
+
+void CheckChangeInsertion(IrOpcode::Value expected, RepType from, RepType to) {
+  TestingGraph t(Type::Any());
+  Node* in = t.ExampleWithOutput(from);
+  Node* use = t.Use(in, to);
+  t.Return(use);
+  t.Lower();
+  CHECK_EQ(expected, use->InputAt(0)->opcode());
+  CHECK_EQ(in, use->InputAt(0)->InputAt(0));
+}
+
+
+TEST(InsertBasicChanges) {
+  CheckChangeInsertion(IrOpcode::kChangeFloat64ToInt32, rFloat64, tInt32);
+  CheckChangeInsertion(IrOpcode::kChangeFloat64ToUint32, rFloat64, tUint32);
+  CheckChangeInsertion(IrOpcode::kChangeFloat64ToTagged, rFloat64, rTagged);
+
+  CheckChangeInsertion(IrOpcode::kChangeTaggedToInt32, rTagged, tInt32);
+  CheckChangeInsertion(IrOpcode::kChangeTaggedToUint32, rTagged, tUint32);
+  CheckChangeInsertion(IrOpcode::kChangeTaggedToFloat64, rTagged, rFloat64);
+
+  CheckChangeInsertion(IrOpcode::kChangeInt32ToFloat64, tInt32, rFloat64);
+  CheckChangeInsertion(IrOpcode::kChangeInt32ToTagged, tInt32, rTagged);
+
+  CheckChangeInsertion(IrOpcode::kChangeUint32ToFloat64, tUint32, rFloat64);
+  CheckChangeInsertion(IrOpcode::kChangeUint32ToTagged, tUint32, rTagged);
+}
+
+
+static void CheckChangesAroundBinop(TestingGraph* t, Operator* op,
+                                    IrOpcode::Value input_change,
+                                    IrOpcode::Value output_change) {
+  Node* binop = t->graph()->NewNode(op, t->p0, t->p1);
+  t->Return(binop);
+  t->Lower();
+  CHECK_EQ(input_change, binop->InputAt(0)->opcode());
+  CHECK_EQ(input_change, binop->InputAt(1)->opcode());
+  CHECK_EQ(t->p0, binop->InputAt(0)->InputAt(0));
+  CHECK_EQ(t->p1, binop->InputAt(1)->InputAt(0));
+  CHECK_EQ(output_change, t->ret->InputAt(0)->opcode());
+  CHECK_EQ(binop, t->ret->InputAt(0)->InputAt(0));
+}
+
+
+TEST(InsertChangesAroundInt32Binops) {
+  TestingGraph t(Type::Signed32(), Type::Signed32());
+
+  Operator* ops[] = {t.machine()->Int32Add(),  t.machine()->Int32Sub(),
+                     t.machine()->Int32Mul(),  t.machine()->Int32Div(),
+                     t.machine()->Int32Mod(),  t.machine()->Word32And(),
+                     t.machine()->Word32Or(),  t.machine()->Word32Xor(),
+                     t.machine()->Word32Shl(), t.machine()->Word32Sar()};
+
+  for (size_t i = 0; i < ARRAY_SIZE(ops); i++) {
+    CheckChangesAroundBinop(&t, ops[i], IrOpcode::kChangeTaggedToInt32,
+                            IrOpcode::kChangeInt32ToTagged);
+  }
+}
+
+
+TEST(InsertChangesAroundInt32Cmp) {
+  TestingGraph t(Type::Signed32(), Type::Signed32());
+
+  Operator* ops[] = {t.machine()->Int32LessThan(),
+                     t.machine()->Int32LessThanOrEqual()};
+
+  for (size_t i = 0; i < ARRAY_SIZE(ops); i++) {
+    CheckChangesAroundBinop(&t, ops[i], IrOpcode::kChangeTaggedToInt32,
+                            IrOpcode::kChangeBitToBool);
+  }
+}
+
+
+TEST(InsertChangesAroundUint32Cmp) {
+  TestingGraph t(Type::Unsigned32(), Type::Unsigned32());
+
+  Operator* ops[] = {t.machine()->Uint32LessThan(),
+                     t.machine()->Uint32LessThanOrEqual()};
+
+  for (size_t i = 0; i < ARRAY_SIZE(ops); i++) {
+    CheckChangesAroundBinop(&t, ops[i], IrOpcode::kChangeTaggedToUint32,
+                            IrOpcode::kChangeBitToBool);
+  }
+}
+
+
+TEST(InsertChangesAroundFloat64Binops) {
+  TestingGraph t(Type::Number(), Type::Number());
+
+  Operator* ops[] = {
+      t.machine()->Float64Add(), t.machine()->Float64Sub(),
+      t.machine()->Float64Mul(), t.machine()->Float64Div(),
+      t.machine()->Float64Mod(),
+  };
+
+  for (size_t i = 0; i < ARRAY_SIZE(ops); i++) {
+    CheckChangesAroundBinop(&t, ops[i], IrOpcode::kChangeTaggedToFloat64,
+                            IrOpcode::kChangeFloat64ToTagged);
+  }
+}
+
+
+TEST(InsertChangesAroundFloat64Cmp) {
+  TestingGraph t(Type::Number(), Type::Number());
+
+  Operator* ops[] = {t.machine()->Float64Equal(),
+                     t.machine()->Float64LessThan(),
+                     t.machine()->Float64LessThanOrEqual()};
+
+  for (size_t i = 0; i < ARRAY_SIZE(ops); i++) {
+    CheckChangesAroundBinop(&t, ops[i], IrOpcode::kChangeTaggedToFloat64,
+                            IrOpcode::kChangeBitToBool);
+  }
+}
+
+
+TEST(InsertChangesForElementAccessIndex) { TODO_TITZER; }