[turbofan] Introduce DeadValue and DeadEffect operators.

src/compiler/js-graph.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_JS_GRAPH_H_
 #define V8_COMPILER_JS_GRAPH_H_
 
 #include "src/compiler/common-node-cache.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
@@ skipping 99 matching lines @@
   }
 
   // Creates a dummy Constant node, used to satisfy calling conventions of
   // stubs and runtime functions that do not require a context.
   Node* NoContextConstant() { return ZeroConstant(); }
 
   // Creates an empty frame states for cases where we know that a function
   // cannot deopt.
   Node* EmptyFrameState();
 
-  // Create a control node that serves as control dependency for dead nodes.
+  // Creates a value node that servers as value input for dead nodes.
+  Node* DeadValue();
+
+  // Creates 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_; }
   Graph* graph() const { return graph_; }
   Zone* zone() const { return graph()->zone(); }
   Isolate* isolate() const { return isolate_; }
   Factory* factory() const { return isolate()->factory(); }
 
   void GetCachedNodes(NodeVector* nodes);
 
  private:
   enum CachedNode {
     kCEntryStubConstant,
     kUndefinedConstant,
     kTheHoleConstant,
     kTrueConstant,
     kFalseConstant,
     kNullConstant,
     kZeroConstant,
     kOneConstant,
     kNaNConstant,
     kEmptyFrameState,
+    kDeadValue,
     kDeadControl,
     kNumCachedNodes  // Must remain last.
   };
 
   Isolate* isolate_;
   Graph* graph_;
   CommonOperatorBuilder* common_;
   JSOperatorBuilder* javascript_;
   MachineOperatorBuilder* machine_;
   CommonNodeCache cache_;
   Node* cached_nodes_[kNumCachedNodes];
 
   Node* ImmovableHeapConstant(Handle<HeapObject> value);
   Node* NumberConstant(double value);
 
   DISALLOW_COPY_AND_ASSIGN(JSGraph);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif