[turbofan] Introduce DeadValue and DeadEffect operators.

src/compiler/ast-graph-builder.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_AST_GRAPH_BUILDER_H_
 #define V8_COMPILER_AST_GRAPH_BUILDER_H_
 
 #include "src/ast.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/liveness-analyzer.h"
@@ skipping 471 matching lines @@
   void UpdateEffectDependency(Node* dependency) {
     effect_dependency_ = dependency;
   }
 
   // Mark this environment as being unreachable.
   void MarkAsUnreachable() {
     UpdateControlDependency(builder()->jsgraph()->DeadControl());
     liveness_block_ = nullptr;
   }
   bool IsMarkedAsUnreachable() {
-    return GetControlDependency()->opcode() == IrOpcode::kDead;
+    return GetControlDependency()->opcode() == IrOpcode::kDeadControl;
   }
 
   // Merge another environment into this one.
   void Merge(Environment* other);
 
   // Copies this environment at a control-flow split point.
   Environment* CopyForConditional();
 
   // Copies this environment to a potentially unreachable control-flow point.
   Environment* CopyAsUnreachable();
@@ skipping 31 matching lines @@
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_GRAPH_BUILDER_H_