[turbofan] Extend typer support for typeof operator.

src/compiler/typer.cc

 // 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.
 
 #include "src/compiler/typer.h"
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/common-operator.h"
@@ skipping 1084 matching lines @@
   return TypeUnaryOp(node, JSUnaryNotTyper);
 }
 
 
 Type* Typer::Visitor::JSTypeOfTyper(Type* type, Typer* t) {
   Factory* const f = t->isolate()->factory();
   if (type->Is(Type::Boolean())) {
     return Type::Constant(f->boolean_string(), t->zone());
   } else if (type->Is(Type::Number())) {
     return Type::Constant(f->number_string(), t->zone());
+  } else if (type->Is(Type::String())) {
+    return Type::Constant(f->string_string(), t->zone());
   } else if (type->Is(Type::Symbol())) {
     return Type::Constant(f->symbol_string(), t->zone());
   } else if (type->Is(Type::Union(Type::Undefined(), Type::Undetectable(),
                                   t->zone()))) {
     return Type::Constant(f->undefined_string(), t->zone());
   } else if (type->Is(Type::Null())) {
     return Type::Constant(f->object_string(), t->zone());
+  } else if (type->IsConstant()) {
+    return Type::Constant(
+        Object::TypeOf(t->isolate(), type->AsConstant()->Value()), t->zone());
   }
   return Type::InternalizedString();
 }
 
 
 Type* Typer::Visitor::TypeJSTypeOf(Node* node) {
   return TypeUnaryOp(node, JSTypeOfTyper);
 }
 
 
@@ skipping 1075 matching lines @@
   }
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::Constant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8