[turbofan] Add Symbol feedback to Equal/StrictEqual.

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 <iomanip>
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
@@ skipping 1842 matching lines @@
 Type* Typer::Visitor::TypeCheckSmi(Node* node) {
   Type* arg = Operand(node, 0);
   return Type::Intersect(arg, Type::SignedSmall(), zone());
 }
 
 Type* Typer::Visitor::TypeCheckString(Node* node) {
   Type* arg = Operand(node, 0);
   return Type::Intersect(arg, Type::String(), zone());
 }
 
+Type* Typer::Visitor::TypeCheckSymbol(Node* node) {
+  Type* arg = Operand(node, 0);
+  return Type::Intersect(arg, Type::Symbol(), zone());
+}
+
 Type* Typer::Visitor::TypeCheckFloat64Hole(Node* node) {
   return typer_->operation_typer_.CheckFloat64Hole(Operand(node, 0));
 }
 
 Type* Typer::Visitor::TypeCheckTaggedHole(Node* node) {
   Type* type = Operand(node, 0);
   type = Type::Intersect(type, Type::NonInternal(), zone());
   return type;
 }
 
@@ skipping 125 matching lines @@
 Type* Typer::Visitor::TypeConstant(Handle<Object> value) {
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::NewConstant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8