Make visualizer robust to graphs with NULL inputs.

R=mstarzinger@chromium.org, jarin@chromium.org
BUG=

Review URL: https://codereview.chromium.org/652263002

Cr-Commit-Position: refs/heads/master@{#25084}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25084 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/generic-graph.h

@@ -34,8 +34,8 @@ class GenericGraph : public GenericGraphBase {
   explicit GenericGraph(Zone* zone)
       : GenericGraphBase(zone), start_(NULL), end_(NULL) {}
 
-  V* start() { return start_; }
-  V* end() { return end_; }
+  V* start() const { return start_; }
+  V* end() const { return end_; }
 
   void SetStart(V* start) { start_ = start; }
   void SetEnd(V* end) { end_ = end; }

test/cctest/cctest.gyp

@@ -60,6 +60,7 @@
         'compiler/test-control-reducer.cc',
         'compiler/test-gap-resolver.cc',
         'compiler/test-graph-reducer.cc',
+        'compiler/test-graph-visualizer.cc',
         'compiler/test-instruction.cc',
         'compiler/test-js-context-specialization.cc',
         'compiler/test-js-constant-cache.cc',

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* merge = graph.NewNode(common.Merge(2), start, start);
+  merge->ReplaceInput(1, NULL);
+  graph.SetEnd(merge);
+
+  OFStream os(stdout);
+  os << AsDOT(graph);
+  os << AsJSON(graph);
+}