[turbofan] Introduce dedicated StringIndexOf operator.

src/compiler/simplified-operator.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_SIMPLIFIED_OPERATOR_H_
 #define V8_COMPILER_SIMPLIFIED_OPERATOR_H_
 
 #include <iosfwd>
 
 #include "src/base/compiler-specific.h"
@@ skipping 338 matching lines @@
 
   const Operator* ReferenceEqual();
 
   const Operator* StringEqual();
   const Operator* StringLessThan();
   const Operator* StringLessThanOrEqual();
   const Operator* StringCharAt();
   const Operator* StringCharCodeAt();
   const Operator* StringFromCharCode();
   const Operator* StringFromCodePoint(UnicodeEncoding encoding);
+  const Operator* StringIndexOf();
 
   const Operator* PlainPrimitiveToNumber();
   const Operator* PlainPrimitiveToWord32();
   const Operator* PlainPrimitiveToFloat64();
 
   const Operator* ChangeTaggedSignedToInt32();
   const Operator* ChangeTaggedToInt32();
   const Operator* ChangeTaggedToUint32();
   const Operator* ChangeTaggedToFloat64();
   const Operator* ChangeInt31ToTaggedSigned();
@@ skipping 96 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(SimplifiedOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_SIMPLIFIED_OPERATOR_H_