[turbofan] Properly recognize and optimize comparisons with the_hole.

src/compiler/typer.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_TYPER_H_
 #define V8_COMPILER_TYPER_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/graph.h"
 #include "src/types.h"
@@ skipping 40 matching lines @@
   Isolate* const isolate_;
   Graph* const graph_;
   Flags const flags_;
   CompilationDependencies* const dependencies_;
   Type::FunctionType* function_type_;
   Decorator* decorator_;
   TypeCache const& cache_;
 
   Type* singleton_false_;
   Type* singleton_true_;
+  Type* singleton_the_hole_;
   Type* signed32ish_;
   Type* unsigned32ish_;
   Type* falsish_;
   Type* truish_;
 
   DISALLOW_COPY_AND_ASSIGN(Typer);
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(Typer::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_TYPER_H_