[turbofan] Optimize certain chains of Branch into a Switch.

test/unittests/compiler/control-flow-optimizer-unittest.cc

+// Copyright 2015 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/control-flow-optimizer.h"
+#include "src/compiler/js-graph.h"
+#include "src/compiler/js-operator.h"
+#include "src/compiler/machine-operator.h"
+#include "test/unittests/compiler/graph-unittest.h"
+#include "test/unittests/compiler/node-test-utils.h"
+#include "testing/gmock-support.h"
+
+using testing::AllOf;
+using testing::Capture;
+using testing::CaptureEq;
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class ControlFlowOptimizerTest : public GraphTest {
+ public:
+  explicit ControlFlowOptimizerTest(int num_parameters = 3)
+      : GraphTest(num_parameters), machine_(zone()) {}
+  ~ControlFlowOptimizerTest() OVERRIDE {}
+
+ protected:
+  void Optimize() {
+    JSOperatorBuilder javascript(zone());
+    JSGraph jsgraph(isolate(), graph(), common(), &javascript, machine());
+    ControlFlowOptimizer optimizer(&jsgraph, zone());
+    optimizer.Optimize();
+  }
+
+  MachineOperatorBuilder* machine() { return &machine_; }
+
+ private:
+  MachineOperatorBuilder machine_;
+};
+
+
+TEST_F(ControlFlowOptimizerTest, Switch) {
+  Node* index = Parameter(0);
+  Node* branch0 = graph()->NewNode(
+      common()->Branch(),
+      graph()->NewNode(machine()->Word32Equal(), index, Int32Constant(0)),
+      start());
+  Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
+  Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
+  Node* branch1 = graph()->NewNode(
+      common()->Branch(),
+      graph()->NewNode(machine()->Word32Equal(), index, Int32Constant(1)),
+      if_false0);
+  Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
+  Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
+  Node* merge =
+      graph()->NewNode(common()->Merge(3), if_true0, if_true1, if_false1);
+  graph()->SetEnd(graph()->NewNode(common()->End(), merge));
+  Optimize();
+  Capture<Node*> switch_capture;
+  EXPECT_THAT(end(),
+              IsEnd(IsMerge(IsIfValue(0, CaptureEq(&switch_capture)),
+                            IsIfValue(1, CaptureEq(&switch_capture)),
+                            IsIfDefault(AllOf(CaptureEq(&switch_capture),
+                                              IsSwitch(index, start()))))));
+}
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8