Make visualizer robust to graphs with NULL inputs.

test/cctest/compiler/test-graph-visualizer.cc

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/v8.h"
+#include "test/cctest/cctest.h"
+
+#include "src/compiler/common-operator.h"
+#include "src/compiler/generic-node-inl.h"
+#include "src/compiler/generic-node.h"
+#include "src/compiler/graph.h"
+#include "src/compiler/graph-visualizer.h"
+#include "src/compiler/js-operator.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node.h"
+#include "src/compiler/operator.h"
+#include "src/compiler/schedule.h"
+#include "src/compiler/scheduler.h"
+#include "src/compiler/verifier.h"
+
+using namespace v8::internal;
+using namespace v8::internal::compiler;
+
+TEST(NodeWithNullInputReachableFromEnd) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+
+  Node* start = graph.NewNode(common.Start(0));
+  graph.SetStart(start);
+  Node* k = graph.NewNode(common.Int32Constant(0));
+  Node* phi = graph.NewNode(common.Phi(kMachAnyTagged, 1), k, start);
+  phi->ReplaceInput(0, NULL);
+  graph.SetEnd(phi);
+
+  OFStream os(stdout);
+  os << AsDOT(graph);
+  os << AsJSON(graph);
+}
+
+
+TEST(NodeWithNullControlReachableFromEnd) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+
+  Node* start = graph.NewNode(common.Start(0));
+  graph.SetStart(start);
+  Node* k = graph.NewNode(common.Int32Constant(0));
+  Node* phi = graph.NewNode(common.Phi(kMachAnyTagged, 1), k, start);
+  phi->ReplaceInput(1, NULL);
+  graph.SetEnd(phi);
+
+  OFStream os(stdout);
+  os << AsDOT(graph);
+  os << AsJSON(graph);
+}
+
+
+TEST(NodeWithNullInputReachableFromStart) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+
+  Node* start = graph.NewNode(common.Start(0));
+  graph.SetStart(start);
+  Node* k = graph.NewNode(common.Int32Constant(0));
+  Node* phi = graph.NewNode(common.Phi(kMachAnyTagged, 1), k, start);
+  phi->ReplaceInput(0, NULL);
+  graph.SetEnd(start);
+
+  OFStream os(stdout);
+  os << AsDOT(graph);
+  os << AsJSON(graph);
+}
+
+
+TEST(NodeWithNullControlReachableFromStart) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+
+  Node* start = graph.NewNode(common.Start(0));
+  graph.SetStart(start);
+  Node* k = graph.NewNode(common.Int32Constant(0));
+  Node* phi = graph.NewNode(common.Phi(kMachAnyTagged, 1), k, start);
+  phi->ReplaceInput(1, NULL);

[Michael Starzinger, 2014/11/03 17:16:43]

nit: It doesn't seem like this phi is reachable from start. Maybe use a Merge
instead if a Phi here.

+  graph.SetEnd(start);
+
+  OFStream os(stdout);
+  os << AsDOT(graph);
+  os << AsJSON(graph);
+}