[turbofan] Introduce ObjectIsString operator.

src/compiler/simplified-operator.cc

 // Copyright 2012 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.
 
 #include "src/compiler/simplified-operator.h"
 
 #include "src/base/lazy-instance.h"
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 #include "src/types.h"
@@ skipping 175 matching lines @@
   V(ChangeTaggedToUint32, Operator::kNoProperties, 1)    \
   V(ChangeTaggedToFloat64, Operator::kNoProperties, 1)   \
   V(ChangeInt32ToTagged, Operator::kNoProperties, 1)     \
   V(ChangeUint32ToTagged, Operator::kNoProperties, 1)    \
   V(ChangeFloat64ToTagged, Operator::kNoProperties, 1)   \
   V(ChangeBoolToBit, Operator::kNoProperties, 1)         \
   V(ChangeBitToBool, Operator::kNoProperties, 1)         \
   V(ObjectIsNumber, Operator::kNoProperties, 1)          \
   V(ObjectIsReceiver, Operator::kNoProperties, 1)        \
   V(ObjectIsSmi, Operator::kNoProperties, 1)             \
+  V(ObjectIsString, Operator::kNoProperties, 1)          \
   V(ObjectIsUndetectable, Operator::kNoProperties, 1)
 
 #define NO_THROW_OP_LIST(V)                 \
   V(StringEqual, Operator::kCommutative, 2) \
   V(StringLessThan, Operator::kNoThrow, 2)  \
   V(StringLessThanOrEqual, Operator::kNoThrow, 2)
 
 struct SimplifiedOperatorGlobalCache final {
 #define PURE(Name, properties, input_count)                                \
   struct Name##Operator final : public Operator {                          \
@@ skipping 106 matching lines @@
         Operator1<Type>(IrOpcode::k##Name, Operator::kNoThrow | properties,    \
                         #Name, value_input_count, 1, control_input_count,      \
                         output_count, 1, 0, access);                           \
   }
 ACCESS_OP_LIST(ACCESS)
 #undef ACCESS
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8