[stubs] Add String and JSReceiver instance type predicates

src/code-stub-assembler.h

 // Copyright 2016 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_CODE_STUB_ASSEMBLER_H_
 #define V8_CODE_STUB_ASSEMBLER_H_
 
 #include <functional>
 
 #include "src/compiler/code-assembler.h"
@@ skipping 469 matching lines @@
                               PrimitiveType primitive_type,
                               char const* method_name);
 
   // Throws a TypeError for {method_name} if {value} is not of the given
   // instance type. Returns {value}'s map.
   compiler::Node* ThrowIfNotInstanceType(compiler::Node* context,
                                          compiler::Node* value,
                                          InstanceType instance_type,
                                          char const* method_name);
 
+  // Type checks.
+  compiler::Node* IsStringInstanceType(compiler::Node* instance_type);
+  compiler::Node* IsJSReceiverInstanceType(compiler::Node* instance_type);
+
   // String helpers.
   // Load a character from a String (might flatten a ConsString).
   compiler::Node* StringCharCodeAt(compiler::Node* string,
                                    compiler::Node* smi_index);
   // Return the single character string with only {code}.
   compiler::Node* StringFromCharCode(compiler::Node* code);
   // Return a new string object which holds a substring containing the range
   // [from,to[ of string.  |from| and |to| are expected to be tagged.
   compiler::Node* SubString(compiler::Node* context, compiler::Node* string,
                             compiler::Node* from, compiler::Node* to);
@@ skipping 383 matching lines @@
                                            Label* bailout);
 
   static const int kElementLoopUnrollThreshold = 8;
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(CodeStubAssembler::AllocationFlags);
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_CODE_STUB_ASSEMBLER_H_