[turbofan] Utilize the fact that empty string is canonicalized.

src/compiler/types.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_TYPES_H_
 #define V8_COMPILER_TYPES_H_
 
 #include "src/base/compiler-specific.h"
 #include "src/conversions.h"
 #include "src/globals.h"
@@ skipping 134 matching lines @@
   V(OrderedNumber,                kPlainNumber | kMinusZero) \
   V(MinusZeroOrNaN,               kMinusZero | kNaN) \
   V(Number,                       kOrderedNumber | kNaN) \
   V(String,                       kInternalizedString | kOtherString) \
   V(UniqueName,                   kSymbol | kInternalizedString) \
   V(Name,                         kSymbol | kString) \
   V(InternalizedStringOrNull,     kInternalizedString | kNull) \
   V(BooleanOrNumber,              kBoolean | kNumber) \
   V(BooleanOrNullOrNumber,        kBooleanOrNumber | kNull) \
   V(BooleanOrNullOrUndefined,     kBoolean | kNull | kUndefined) \
+  V(Oddball,                      kBooleanOrNullOrUndefined | kHole) \
   V(NullOrNumber,                 kNull | kNumber) \
   V(NullOrUndefined,              kNull | kUndefined) \
   V(Undetectable,                 kNullOrUndefined | kOtherUndetectable) \
   V(NumberOrOddball,              kNumber | kNullOrUndefined | kBoolean | \
                                   kHole) \
   V(NumberOrSimdOrString,         kNumber | kSimd | kString) \
   V(NumberOrString,               kNumber | kString) \
   V(NumberOrUndefined,            kNumber | kUndefined) \
   V(PlainPrimitive,               kNumberOrString | kBoolean | \
                                   kNullOrUndefined) \
   V(Primitive,                    kSymbol | kSimd | kPlainPrimitive) \
   V(OtherUndetectableOrUndefined, kOtherUndetectable | kUndefined) \
   V(Proxy,                        kCallableProxy | kOtherProxy) \
   V(Callable,                     kFunction | kBoundFunction | \
                                   kOtherCallable | kCallableProxy | \
                                   kOtherUndetectable) \
   V(NonCallable,                  kOtherObject | kOtherProxy) \
   V(NonCallableOrNull,            kNonCallable | kNull) \
   V(DetectableObject,             kFunction | kBoundFunction | \
                                   kOtherCallable | kOtherObject) \
   V(DetectableReceiver,           kDetectableObject | kProxy) \
   V(DetectableReceiverOrNull,     kDetectableReceiver | kNull) \
   V(Object,                       kDetectableObject | kOtherUndetectable) \
   V(Receiver,                     kObject | kProxy) \
   V(ReceiverOrUndefined,          kReceiver | kUndefined) \
   V(ReceiverOrNullOrUndefined,    kReceiver | kNull | kUndefined) \
+  V(SymbolOrReceiver,             kSymbol | kReceiver) \
   V(StringOrReceiver,             kString | kReceiver) \
   V(Unique,                       kBoolean | kUniqueName | kNull | \
                                   kUndefined | kReceiver) \
-  V(NonStringUniqueOrHole,        kBoolean | kHole | kNull | kReceiver | \
-                                  kSymbol | kUndefined) \
   V(Internal,                     kHole | kExternalPointer | kOtherInternal) \
   V(NonInternal,                  kPrimitive | kReceiver) \
   V(NonNumber,                    kUnique | kString | kInternal) \
   V(Any,                          0xfffffffeu)
 
 // clang-format on
 
 /*
  * The following diagrams show how integers (in the mathematical sense) are
  * divided among the different atomic numerical types.
@@ skipping 468 matching lines @@
                           RangeType::Limits* limits, Zone* zone);
   static Type* NormalizeUnion(Type* unioned, int size, Zone* zone);
   static Type* NormalizeRangeAndBitset(Type* range, bitset* bits, Zone* zone);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_TYPES_H_