[turbofan] Introduce dedicated ObjectIsNaN operator.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index b585336a3f52cb1ea04b552b6e08711f657afdf3..e50712762db210aa1e7f04e004f0a9df21bda576 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -285,6 +285,7 @@ class Typer::Visitor : public Reducer {
 #undef DECLARE_METHOD
 
   static Type* ObjectIsDetectableCallable(Type*, Typer*);
+  static Type* ObjectIsNaN(Type*, Typer*);
   static Type* ObjectIsNonCallable(Type*, Typer*);
   static Type* ObjectIsNumber(Type*, Typer*);
   static Type* ObjectIsReceiver(Type*, Typer*);
@@ -512,6 +513,12 @@ Type* Typer::Visitor::ObjectIsDetectableCallable(Type* type, Typer* t) {
   return Type::Boolean();
 }
 
+Type* Typer::Visitor::ObjectIsNaN(Type* type, Typer* t) {
+  if (type->Is(Type::NaN())) return t->singleton_true_;
+  if (!type->Maybe(Type::NaN())) return t->singleton_false_;
+  return Type::Boolean();
+}
+
 Type* Typer::Visitor::ObjectIsNonCallable(Type* type, Typer* t) {
   if (type->Is(Type::NonCallable())) return t->singleton_true_;
   if (!type->Maybe(Type::NonCallable())) return t->singleton_false_;
@@ -1926,6 +1933,10 @@ Type* Typer::Visitor::TypeObjectIsDetectableCallable(Node* node) {
   return TypeUnaryOp(node, ObjectIsDetectableCallable);
 }
 
+Type* Typer::Visitor::TypeObjectIsNaN(Node* node) {
+  return TypeUnaryOp(node, ObjectIsNaN);
+}
+
 Type* Typer::Visitor::TypeObjectIsNonCallable(Node* node) {
   return TypeUnaryOp(node, ObjectIsNonCallable);
 }