[turbofan] Revive the useful parts of the SimplifiedOperatorReducer.

This partially reverts https://codereview.chromium.org/1162563002
because we might actually be able to optimize certain combinations
now due to dead code elimination.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/1202263006

Cr-Commit-Position: refs/heads/master@{#29277}

BUILD.gn

@@ -732,6 +732,8 @@ source_set("v8_base") {
     "src/compiler/select-lowering.h",
     "src/compiler/simplified-lowering.cc",
     "src/compiler/simplified-lowering.h",
+    "src/compiler/simplified-operator-reducer.cc",
+    "src/compiler/simplified-operator-reducer.h",
     "src/compiler/simplified-operator.cc",
     "src/compiler/simplified-operator.h",
     "src/compiler/source-position.cc",

src/compiler/pipeline.cc

@@ -45,6 +45,7 @@
 #include "src/compiler/scheduler.h"
 #include "src/compiler/select-lowering.h"
 #include "src/compiler/simplified-lowering.h"
+#include "src/compiler/simplified-operator-reducer.h"
 #include "src/compiler/tail-call-optimization.h"
 #include "src/compiler/typer.h"
 #include "src/compiler/value-numbering-reducer.h"
@@ -597,12 +598,14 @@ struct SimplifiedLoweringPhase {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
-    ValueNumberingReducer vn_reducer(temp_zone);
+    SimplifiedOperatorReducer simple_reducer(data->jsgraph());
+    ValueNumberingReducer value_numbering(temp_zone);
     MachineOperatorReducer machine_reducer(data->jsgraph());
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
     AddReducer(data, &graph_reducer, &dead_code_elimination);
-    AddReducer(data, &graph_reducer, &vn_reducer);
+    AddReducer(data, &graph_reducer, &simple_reducer);
+    AddReducer(data, &graph_reducer, &value_numbering);
     AddReducer(data, &graph_reducer, &machine_reducer);
     AddReducer(data, &graph_reducer, &common_reducer);
     graph_reducer.ReduceGraph();
@@ -628,13 +631,15 @@ struct ChangeLoweringPhase {
     JSGraphReducer graph_reducer(data->jsgraph(), temp_zone);
     DeadCodeElimination dead_code_elimination(&graph_reducer, data->graph(),
                                               data->common());
-    ValueNumberingReducer vn_reducer(temp_zone);
+    SimplifiedOperatorReducer simple_reducer(data->jsgraph());
+    ValueNumberingReducer value_numbering(temp_zone);
     ChangeLowering lowering(data->jsgraph());
     MachineOperatorReducer machine_reducer(data->jsgraph());
     CommonOperatorReducer common_reducer(&graph_reducer, data->graph(),
                                          data->common(), data->machine());
     AddReducer(data, &graph_reducer, &dead_code_elimination);
-    AddReducer(data, &graph_reducer, &vn_reducer);
+    AddReducer(data, &graph_reducer, &simple_reducer);
+    AddReducer(data, &graph_reducer, &value_numbering);
     AddReducer(data, &graph_reducer, &lowering);
     AddReducer(data, &graph_reducer, &machine_reducer);
     AddReducer(data, &graph_reducer, &common_reducer);

src/compiler/simplified-operator-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/compiler/simplified-operator-reducer.h"
+
+#include "src/compiler/js-graph.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node-matchers.h"
+#include "src/compiler/operator-properties.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+SimplifiedOperatorReducer::SimplifiedOperatorReducer(JSGraph* jsgraph)
+    : jsgraph_(jsgraph), simplified_(jsgraph->zone()) {}
+
+
+SimplifiedOperatorReducer::~SimplifiedOperatorReducer() {}
+
+
+Reduction SimplifiedOperatorReducer::Reduce(Node* node) {
+  switch (node->opcode()) {
+    case IrOpcode::kBooleanNot: {
+      HeapObjectMatcher m(node->InputAt(0));
+      if (m.HasValue()) {
+        return Replace(
+            jsgraph()->BooleanConstant(!m.Value().handle()->BooleanValue()));
+      }
+      if (m.IsBooleanNot()) return Replace(m.InputAt(0));
+      break;
+    }
+    case IrOpcode::kChangeBitToBool: {
+      Int32Matcher m(node->InputAt(0));
+      if (m.Is(0)) return Replace(jsgraph()->FalseConstant());
+      if (m.Is(1)) return Replace(jsgraph()->TrueConstant());
+      if (m.IsChangeBoolToBit()) return Replace(m.InputAt(0));
+      break;
+    }
+    case IrOpcode::kChangeBoolToBit: {
+      HeapObjectMatcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceInt32(m.Value().handle()->BooleanValue());
+      if (m.IsChangeBitToBool()) return Replace(m.InputAt(0));
+      break;
+    }
+    case IrOpcode::kChangeFloat64ToTagged: {
+      Float64Matcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceNumber(m.Value());
+      break;
+    }
+    case IrOpcode::kChangeInt32ToTagged: {
+      Int32Matcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceNumber(m.Value());
+      break;
+    }
+    case IrOpcode::kChangeTaggedToFloat64: {
+      NumberMatcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceFloat64(m.Value());
+      if (m.IsChangeFloat64ToTagged()) return Replace(m.node()->InputAt(0));
+      if (m.IsChangeInt32ToTagged()) {
+        return Change(node, machine()->ChangeInt32ToFloat64(), m.InputAt(0));
+      }
+      if (m.IsChangeUint32ToTagged()) {
+        return Change(node, machine()->ChangeUint32ToFloat64(), m.InputAt(0));
+      }
+      break;
+    }
+    case IrOpcode::kChangeTaggedToInt32: {
+      NumberMatcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceInt32(DoubleToInt32(m.Value()));
+      if (m.IsChangeFloat64ToTagged()) {
+        return Change(node, machine()->ChangeFloat64ToInt32(), m.InputAt(0));
+      }
+      if (m.IsChangeInt32ToTagged()) return Replace(m.InputAt(0));
+      break;
+    }
+    case IrOpcode::kChangeTaggedToUint32: {
+      NumberMatcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceUint32(DoubleToUint32(m.Value()));
+      if (m.IsChangeFloat64ToTagged()) {
+        return Change(node, machine()->ChangeFloat64ToUint32(), m.InputAt(0));
+      }
+      if (m.IsChangeUint32ToTagged()) return Replace(m.InputAt(0));
+      break;
+    }
+    case IrOpcode::kChangeUint32ToTagged: {
+      Uint32Matcher m(node->InputAt(0));
+      if (m.HasValue()) return ReplaceNumber(FastUI2D(m.Value()));
+      break;
+    }
+    default:
+      break;
+  }
+  return NoChange();
+}
+
+
+Reduction SimplifiedOperatorReducer::Change(Node* node, const Operator* op,
+                                            Node* a) {
+  DCHECK_EQ(node->InputCount(), OperatorProperties::GetTotalInputCount(op));
+  DCHECK_LE(1, node->InputCount());
+  node->set_op(op);
+  node->ReplaceInput(0, a);
+  return Changed(node);
+}
+
+
+Reduction SimplifiedOperatorReducer::ReplaceFloat64(double value) {
+  return Replace(jsgraph()->Float64Constant(value));
+}
+
+
+Reduction SimplifiedOperatorReducer::ReplaceInt32(int32_t value) {
+  return Replace(jsgraph()->Int32Constant(value));
+}
+
+
+Reduction SimplifiedOperatorReducer::ReplaceNumber(double value) {
+  return Replace(jsgraph()->Constant(value));
+}
+
+
+Reduction SimplifiedOperatorReducer::ReplaceNumber(int32_t value) {
+  return Replace(jsgraph()->Constant(value));
+}
+
+
+Graph* SimplifiedOperatorReducer::graph() const { return jsgraph()->graph(); }
+
+
+MachineOperatorBuilder* SimplifiedOperatorReducer::machine() const {
+  return jsgraph()->machine();
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8

src/compiler/simplified-operator-reducer.h

+// 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.
+
+#ifndef V8_COMPILER_SIMPLIFIED_OPERATOR_REDUCER_H_
+#define V8_COMPILER_SIMPLIFIED_OPERATOR_REDUCER_H_
+
+#include "src/compiler/graph-reducer.h"
+#include "src/compiler/simplified-operator.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// Forward declarations.
+class JSGraph;
+class MachineOperatorBuilder;
+
+
+class SimplifiedOperatorReducer final : public Reducer {
+ public:
+  explicit SimplifiedOperatorReducer(JSGraph* jsgraph);
+  ~SimplifiedOperatorReducer() final;
+
+  Reduction Reduce(Node* node) final;
+
+ private:
+  Reduction Change(Node* node, const Operator* op, Node* a);
+  Reduction ReplaceFloat64(double value);
+  Reduction ReplaceInt32(int32_t value);
+  Reduction ReplaceUint32(uint32_t value) {
+    return ReplaceInt32(bit_cast<int32_t>(value));
+  }
+  Reduction ReplaceNumber(double value);
+  Reduction ReplaceNumber(int32_t value);
+
+  Graph* graph() const;
+  JSGraph* jsgraph() const { return jsgraph_; }
+  MachineOperatorBuilder* machine() const;
+  SimplifiedOperatorBuilder* simplified() { return &simplified_; }
+
+  JSGraph* const jsgraph_;
+  SimplifiedOperatorBuilder simplified_;
+
+  DISALLOW_COPY_AND_ASSIGN(SimplifiedOperatorReducer);
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_SIMPLIFIED_OPERATOR_REDUCER_H_

test/unittests/compiler/simplified-operator-reducer-unittest.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/compiler/access-builder.h"
+#include "src/compiler/js-graph.h"
+#include "src/compiler/node-properties.h"
+#include "src/compiler/simplified-operator.h"
+#include "src/compiler/simplified-operator-reducer.h"
+#include "src/conversions.h"
+#include "src/types.h"
+#include "test/unittests/compiler/graph-unittest.h"
+#include "test/unittests/compiler/node-test-utils.h"
+#include "testing/gmock-support.h"
+
+using testing::BitEq;
+
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class SimplifiedOperatorReducerTest : public TypedGraphTest {
+ public:
+  explicit SimplifiedOperatorReducerTest(int num_parameters = 1)
+      : TypedGraphTest(num_parameters), simplified_(zone()) {}
+  ~SimplifiedOperatorReducerTest() override {}
+
+ protected:
+  Reduction Reduce(Node* node) {
+    MachineOperatorBuilder machine(zone());
+    JSOperatorBuilder javascript(zone());
+    JSGraph jsgraph(isolate(), graph(), common(), &javascript, &machine);
+    SimplifiedOperatorReducer reducer(&jsgraph);
+    return reducer.Reduce(node);
+  }
+
+  SimplifiedOperatorBuilder* simplified() { return &simplified_; }
+
+ private:
+  SimplifiedOperatorBuilder simplified_;
+};
+
+
+template <typename T>
+class SimplifiedOperatorReducerTestWithParam
+    : public SimplifiedOperatorReducerTest,
+      public ::testing::WithParamInterface<T> {
+ public:
+  explicit SimplifiedOperatorReducerTestWithParam(int num_parameters = 1)
+      : SimplifiedOperatorReducerTest(num_parameters) {}
+  ~SimplifiedOperatorReducerTestWithParam() override {}
+};
+
+
+namespace {
+
+const double kFloat64Values[] = {
+    -V8_INFINITY, -6.52696e+290, -1.05768e+290, -5.34203e+268, -1.01997e+268,
+    -8.22758e+266, -1.58402e+261, -5.15246e+241, -5.92107e+226, -1.21477e+226,
+    -1.67913e+188, -1.6257e+184, -2.60043e+170, -2.52941e+168, -3.06033e+116,
+    -4.56201e+52, -3.56788e+50, -9.9066e+38, -3.07261e+31, -2.1271e+09,
+    -1.91489e+09, -1.73053e+09, -9.30675e+08, -26030, -20453, -15790, -11699,
+    -111, -97, -78, -63, -58, -1.53858e-06, -2.98914e-12, -1.14741e-39,
+    -8.20347e-57, -1.48932e-59, -3.17692e-66, -8.93103e-81, -3.91337e-83,
+    -6.0489e-92, -8.83291e-113, -4.28266e-117, -1.92058e-178, -2.0567e-192,
+    -1.68167e-194, -1.51841e-214, -3.98738e-234, -7.31851e-242, -2.21875e-253,
+    -1.11612e-293, -0.0, 0.0, 2.22507e-308, 1.06526e-307, 4.16643e-227,
+    6.76624e-223, 2.0432e-197, 3.16254e-184, 1.37315e-173, 2.88603e-172,
+    1.54155e-99, 4.42923e-81, 1.40539e-73, 5.4462e-73, 1.24064e-58, 3.11167e-58,
+    2.75826e-39, 0.143815, 58, 67, 601, 7941, 11644, 13697, 25680, 29882,
+    1.32165e+08, 1.62439e+08, 4.16837e+08, 9.59097e+08, 1.32491e+09, 1.8728e+09,
+    1.0672e+17, 2.69606e+46, 1.98285e+79, 1.0098e+82, 7.93064e+88, 3.67444e+121,
+    9.36506e+123, 7.27954e+162, 3.05316e+168, 1.16171e+175, 1.64771e+189,
+    1.1622e+202, 2.00748e+239, 2.51778e+244, 3.90282e+306, 1.79769e+308,
+    V8_INFINITY};
+
+
+const int32_t kInt32Values[] = {
+    -2147483647 - 1, -2104508227, -2103151830, -1435284490, -1378926425,
+    -1318814539, -1289388009, -1287537572, -1279026536, -1241605942,
+    -1226046939, -941837148, -779818051, -413830641, -245798087, -184657557,
+    -127145950, -105483328, -32325, -26653, -23858, -23834, -22363, -19858,
+    -19044, -18744, -15528, -5309, -3372, -2093, -104, -98, -97, -93, -84, -80,
+    -78, -76, -72, -58, -57, -56, -55, -45, -40, -34, -32, -25, -24, -5, -2, 0,
+    3, 10, 24, 34, 42, 46, 47, 48, 52, 56, 64, 65, 71, 76, 79, 81, 82, 97, 102,
+    103, 104, 106, 107, 109, 116, 122, 3653, 4485, 12405, 16504, 26262, 28704,
+    29755, 30554, 16476817, 605431957, 832401070, 873617242, 914205764,
+    1062628108, 1087581664, 1488498068, 1534668023, 1661587028, 1696896187,
+    1866841746, 2032089723, 2147483647};
+
+
+const uint32_t kUint32Values[] = {
+    0x0,        0x5,        0x8,        0xc,        0xd,        0x26,
+    0x28,       0x29,       0x30,       0x34,       0x3e,       0x42,
+    0x50,       0x5b,       0x63,       0x71,       0x77,       0x7c,
+    0x83,       0x88,       0x96,       0x9c,       0xa3,       0xfa,
+    0x7a7,      0x165d,     0x234d,     0x3acb,     0x43a5,     0x4573,
+    0x5b4f,     0x5f14,     0x6996,     0x6c6e,     0x7289,     0x7b9a,
+    0x7bc9,     0x86bb,     0xa839,     0xaa41,     0xb03b,     0xc942,
+    0xce68,     0xcf4c,     0xd3ad,     0xdea3,     0xe90c,     0xed86,
+    0xfba5,     0x172dcc6,  0x114d8fc1, 0x182d6c9d, 0x1b1e3fad, 0x1db033bf,
+    0x1e1de755, 0x1f625c80, 0x28f6cf00, 0x2acb6a94, 0x2c20240e, 0x2f0fe54e,
+    0x31863a7c, 0x33325474, 0x3532fae3, 0x3bab82ea, 0x4c4b83a2, 0x4cd93d1e,
+    0x4f7331d4, 0x5491b09b, 0x57cc6ff9, 0x60d3b4dc, 0x653f5904, 0x690ae256,
+    0x69fe3276, 0x6bebf0ba, 0x6e2c69a3, 0x73b84ff7, 0x7b3a1924, 0x7ed032d9,
+    0x84dd734b, 0x8552ea53, 0x8680754f, 0x8e9660eb, 0x94fe2b9c, 0x972d30cf,
+    0x9b98c482, 0xb158667e, 0xb432932c, 0xb5b70989, 0xb669971a, 0xb7c359d1,
+    0xbeb15c0d, 0xc171c53d, 0xc743dd38, 0xc8e2af50, 0xc98e2df0, 0xd9d1cdf9,
+    0xdcc91049, 0xe46f396d, 0xee991950, 0xef64e521, 0xf7aeefc9, 0xffffffff};
+
+
+const double kNaNs[] = {-std::numeric_limits<double>::quiet_NaN(),
+                        std::numeric_limits<double>::quiet_NaN(),
+                        bit_cast<double>(V8_UINT64_C(0x7FFFFFFFFFFFFFFF)),
+                        bit_cast<double>(V8_UINT64_C(0xFFFFFFFFFFFFFFFF))};
+
+}  // namespace
+
+
+// -----------------------------------------------------------------------------
+// BooleanNot
+
+
+TEST_F(SimplifiedOperatorReducerTest, BooleanNotWithBooleanNot) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(
+      graph()->NewNode(simplified()->BooleanNot(),
+                       graph()->NewNode(simplified()->BooleanNot(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, BooleanNotWithFalseConstant) {
+  Reduction reduction0 =
+      Reduce(graph()->NewNode(simplified()->BooleanNot(), FalseConstant()));
+  ASSERT_TRUE(reduction0.Changed());
+  EXPECT_THAT(reduction0.replacement(), IsTrueConstant());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, BooleanNotWithTrueConstant) {
+  Reduction reduction1 =
+      Reduce(graph()->NewNode(simplified()->BooleanNot(), TrueConstant()));
+  ASSERT_TRUE(reduction1.Changed());
+  EXPECT_THAT(reduction1.replacement(), IsFalseConstant());
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeBoolToBit
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBitToBoolWithChangeBoolToBit) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeBitToBool(),
+      graph()->NewNode(simplified()->ChangeBoolToBit(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBitToBoolWithZeroConstant) {
+  Reduction reduction = Reduce(
+      graph()->NewNode(simplified()->ChangeBitToBool(), Int32Constant(0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsFalseConstant());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBitToBoolWithOneConstant) {
+  Reduction reduction = Reduce(
+      graph()->NewNode(simplified()->ChangeBitToBool(), Int32Constant(1)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsTrueConstant());
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeBoolToBit
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBoolToBitWithFalseConstant) {
+  Reduction reduction = Reduce(
+      graph()->NewNode(simplified()->ChangeBoolToBit(), FalseConstant()));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsInt32Constant(0));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBoolToBitWithTrueConstant) {
+  Reduction reduction =
+      Reduce(graph()->NewNode(simplified()->ChangeBoolToBit(), TrueConstant()));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsInt32Constant(1));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeBoolToBitWithChangeBitToBool) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeBoolToBit(),
+      graph()->NewNode(simplified()->ChangeBitToBool(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeFloat64ToTagged
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeFloat64ToTaggedWithConstant) {
+  TRACED_FOREACH(double, n, kFloat64Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeFloat64ToTagged(), Float64Constant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsNumberConstant(BitEq(n)));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeInt32ToTagged
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeInt32ToTaggedWithConstant) {
+  TRACED_FOREACH(int32_t, n, kInt32Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeInt32ToTagged(), Int32Constant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsNumberConstant(BitEq(FastI2D(n))));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeTaggedToFloat64
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToFloat64WithChangeFloat64ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToFloat64(),
+      graph()->NewNode(simplified()->ChangeFloat64ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToFloat64WithChangeInt32ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToFloat64(),
+      graph()->NewNode(simplified()->ChangeInt32ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsChangeInt32ToFloat64(param0));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToFloat64WithChangeUint32ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToFloat64(),
+      graph()->NewNode(simplified()->ChangeUint32ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsChangeUint32ToFloat64(param0));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToFloat64WithConstant) {
+  TRACED_FOREACH(double, n, kFloat64Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToFloat64(), NumberConstant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsFloat64Constant(BitEq(n)));
+  }
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToFloat64WithNaNConstant) {
+  TRACED_FOREACH(double, nan, kNaNs) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToFloat64(), NumberConstant(nan)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsFloat64Constant(BitEq(nan)));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeTaggedToInt32
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToInt32WithChangeFloat64ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToInt32(),
+      graph()->NewNode(simplified()->ChangeFloat64ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsChangeFloat64ToInt32(param0));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToInt32WithChangeInt32ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToInt32(),
+      graph()->NewNode(simplified()->ChangeInt32ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToInt32WithConstant) {
+  TRACED_FOREACH(double, n, kFloat64Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToInt32(), NumberConstant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsInt32Constant(DoubleToInt32(n)));
+  }
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToInt32WithNaNConstant) {
+  TRACED_FOREACH(double, nan, kNaNs) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToInt32(), NumberConstant(nan)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsInt32Constant(0));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeTaggedToUint32
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToUint32WithChangeFloat64ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToUint32(),
+      graph()->NewNode(simplified()->ChangeFloat64ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsChangeFloat64ToUint32(param0));
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest,
+       ChangeTaggedToUint32WithChangeUint32ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->ChangeTaggedToUint32(),
+      graph()->NewNode(simplified()->ChangeUint32ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(param0, reduction.replacement());
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToUint32WithConstant) {
+  TRACED_FOREACH(double, n, kFloat64Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToUint32(), NumberConstant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(),
+                IsInt32Constant(bit_cast<int32_t>(DoubleToUint32(n))));
+  }
+}
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeTaggedToUint32WithNaNConstant) {
+  TRACED_FOREACH(double, nan, kNaNs) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->ChangeTaggedToUint32(), NumberConstant(nan)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsInt32Constant(0));
+  }
+}
+
+
+// -----------------------------------------------------------------------------
+// ChangeUint32ToTagged
+
+
+TEST_F(SimplifiedOperatorReducerTest, ChangeUint32ToTagged) {
+  TRACED_FOREACH(uint32_t, n, kUint32Values) {
+    Reduction reduction =
+        Reduce(graph()->NewNode(simplified()->ChangeUint32ToTagged(),
+                                Int32Constant(bit_cast<int32_t>(n))));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsNumberConstant(BitEq(FastUI2D(n))));
+  }
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8

test/unittests/unittests.gyp

@@ -79,6 +79,7 @@
         'compiler/schedule-unittest.cc',
         'compiler/select-lowering-unittest.cc',
         'compiler/scheduler-unittest.cc',
+        'compiler/simplified-operator-reducer-unittest.cc',
         'compiler/simplified-operator-unittest.cc',
         'compiler/state-values-utils-unittest.cc',
         'compiler/tail-call-optimization-unittest.cc',

tools/gyp/v8.gyp

@@ -566,6 +566,8 @@
         '../../src/compiler/select-lowering.h',
         '../../src/compiler/simplified-lowering.cc',
         '../../src/compiler/simplified-lowering.h',
+        '../../src/compiler/simplified-operator-reducer.cc',
+        '../../src/compiler/simplified-operator-reducer.h',
         '../../src/compiler/simplified-operator.cc',
         '../../src/compiler/simplified-operator.h',
         '../../src/compiler/source-position.cc',