Move DeadControl into the JSGraph so that it can be reused.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/929123002

Cr-Commit-Position: refs/heads/master@{#26672}

src/compiler/ast-graph-builder.cc

@@ -2970,9 +2970,9 @@ Node* AstGraphBuilder::MakeNode(const Operator* op, int value_input_count,
     }
     if (has_framestate) {
       // The frame state will be inserted later. Here we misuse
-      // the dead_control node as a sentinel to be later overwritten
+      // the {DeadControl} node as a sentinel to be later overwritten
       // with the real frame state.
-      *current_input++ = dead_control();
+      *current_input++ = jsgraph()->DeadControl();
     }
     if (has_effect) {
       *current_input++ = environment_->GetEffectDependency();
@@ -3157,16 +3157,6 @@ Node* AstGraphBuilder::MergeValue(Node* value, Node* other, Node* control) {
   return value;
 }
 
-
-Node* AstGraphBuilder::dead_control() {
-  if (!dead_control_.is_set()) {
-    Node* dead_node = graph()->NewNode(common()->Dead());
-    dead_control_.set(dead_node);
-    return dead_node;
-  }
-  return dead_control_.get();
-}
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

src/compiler/ast-graph-builder.h

@@ -94,9 +94,6 @@ class AstGraphBuilder : public AstVisitor {
   int input_buffer_size_;
   Node** input_buffer_;
 
-  // Node representing the control dependency for dead code.
-  SetOncePointer<Node> dead_control_;
-
   // Merge of all control nodes that exit the function body.
   Node* exit_control_;
 
@@ -122,7 +119,6 @@ class AstGraphBuilder : public AstVisitor {
   ZoneVector<Handle<Object>>* globals() { return &globals_; }
   Scope* current_scope() const;
   Node* current_context() const;
-  Node* dead_control();
   Node* exit_control() const { return exit_control_; }
 
   void set_environment(Environment* env) { environment_ = env; }
@@ -411,7 +407,7 @@ class AstGraphBuilder::Environment : public ZoneObject {
 
   // Mark this environment as being unreachable.
   void MarkAsUnreachable() {
-    UpdateControlDependency(builder()->dead_control());
+    UpdateControlDependency(builder()->jsgraph()->DeadControl());
   }
   bool IsMarkedAsUnreachable() {
     return GetControlDependency()->opcode() == IrOpcode::kDead;

src/compiler/control-reducer.cc

@@ -54,8 +54,7 @@ class ControlReducerImpl {
         common_(common),
         state_(jsgraph->graph()->NodeCount(), kUnvisited, zone_),
         stack_(zone_),
-        revisit_(zone_),
-        dead_(NULL) {}
+        revisit_(zone_) {}
 
   Zone* zone_;
   JSGraph* jsgraph_;
@@ -63,7 +62,6 @@ class ControlReducerImpl {
   ZoneVector<VisitState> state_;
   ZoneDeque<Node*> stack_;
   ZoneDeque<Node*> revisit_;
-  Node* dead_;
 
   void Reduce() {
     Push(graph()->end());
@@ -380,10 +378,7 @@ class ControlReducerImpl {
     state_[id] = kVisited;
   }
 
-  Node* dead() {
-    if (dead_ == NULL) dead_ = graph()->NewNode(common_->Dead());
-    return dead_;
-  }
+  Node* dead() { return jsgraph_->DeadControl(); }
 
   //===========================================================================
   // Reducer implementation: perform reductions on a node.

src/compiler/js-graph.cc

@@ -191,6 +191,15 @@ Node* JSGraph::Float64Constant(double value) {
 }
 
 
+Node* JSGraph::ExternalConstant(ExternalReference reference) {
+  Node** loc = cache_.FindExternalConstant(reference);
+  if (*loc == NULL) {
+    *loc = graph()->NewNode(common()->ExternalConstant(reference));
+  }
+  return *loc;
+}
+
+
 Node* JSGraph::EmptyFrameState() {
   if (!empty_frame_state_.is_set()) {
     Node* values = graph()->NewNode(common()->StateValues(0));
@@ -204,12 +213,12 @@ Node* JSGraph::EmptyFrameState() {
 }
 
 
-Node* JSGraph::ExternalConstant(ExternalReference reference) {
-  Node** loc = cache_.FindExternalConstant(reference);
-  if (*loc == NULL) {
-    *loc = graph()->NewNode(common()->ExternalConstant(reference));
+Node* JSGraph::DeadControl() {
+  if (!dead_control_.is_set()) {
+    Node* dead_node = graph()->NewNode(common()->Dead());
+    dead_control_.set(dead_node);
   }
-  return *loc;
+  return dead_control_.get();
 }
 
 

src/compiler/js-graph.h

@@ -114,6 +114,9 @@ class JSGraph : public ZoneObject {
   // cannot deopt.
   Node* EmptyFrameState();
 
+  // Create a control node that serves as control dependency for dead nodes.
+  Node* DeadControl();
+
   JSOperatorBuilder* javascript() const { return javascript_; }
   CommonOperatorBuilder* common() const { return common_; }
   MachineOperatorBuilder* machine() const { return machine_; }
@@ -142,6 +145,7 @@ class JSGraph : public ZoneObject {
   SetOncePointer<Node> one_constant_;
   SetOncePointer<Node> nan_constant_;
   SetOncePointer<Node> empty_frame_state_;
+  SetOncePointer<Node> dead_control_;
 
   CommonNodeCache cache_;
 

src/compiler/osr.cc

@@ -207,7 +207,7 @@ bool OsrHelper::Deconstruct(JSGraph* jsgraph, CommonOperatorBuilder* common,
   // Analyze the graph to determine how deeply nested the OSR loop is.
   LoopTree* loop_tree = LoopFinder::BuildLoopTree(graph, tmp_zone);
 
-  Node* dead = graph->NewNode(common->Dead());
+  Node* dead = jsgraph->DeadControl();
   LoopTree::Loop* loop = loop_tree->ContainingLoop(osr_loop);
   if (loop->depth() > 0) {
     PeelOuterLoopsForOsr(graph, common, tmp_zone, dead, loop_tree, loop,