[turbofan] Address a couple of Type-related TODOs.

src/compiler/type-cache.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_TYPE_CACHE_H_
 #define V8_COMPILER_TYPE_CACHE_H_
 
 #include "src/compiler/types.h"
 #include "src/date.h"
 
@@ skipping 17 matching lines @@
   Type* const kUint8Clamped = kUint8;
   Type* const kUint8OrMinusZeroOrNaN =
       Type::Union(kUint8, Type::MinusZeroOrNaN(), zone());
   Type* const kInt16 = CreateRange<int16_t>();
   Type* const kUint16 = CreateRange<uint16_t>();
   Type* const kInt32 = Type::Signed32();
   Type* const kUint32 = Type::Unsigned32();
   Type* const kFloat32 = Type::Number();
   Type* const kFloat64 = Type::Number();
 
-  Type* const kSmi = Type::SignedSmall();
-  Type* const kHoleySmi = Type::Union(kSmi, Type::Hole(), zone());
-  Type* const kHeapNumber = Type::Number();
+  Type* const kHoleySmi =
+      Type::Union(Type::SignedSmall(), Type::Hole(), zone());
 
   Type* const kSingletonZero = CreateRange(0.0, 0.0);
   Type* const kSingletonOne = CreateRange(1.0, 1.0);
   Type* const kSingletonTen = CreateRange(10.0, 10.0);
   Type* const kSingletonMinusOne = CreateRange(-1.0, -1.0);
   Type* const kZeroOrUndefined =
       Type::Union(kSingletonZero, Type::Undefined(), zone());
   Type* const kTenOrUndefined =
       Type::Union(kSingletonTen, Type::Undefined(), zone());
   Type* const kMinusOneOrZero = CreateRange(-1.0, 0.0);
@@ skipping 99 matching lines @@
   }
 
   Zone* zone() { return &zone_; }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_TYPE_CACHE_H_