[turbofan] Introduce proper CheckNumber operator.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 5aaa4cd7e0198ecbb1c4fe4b3b1ab6ae7cc9a314..2e8c3de1530d70daa72bf6b3b0ffef6373e86366 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1828,6 +1828,11 @@ Type* Typer::Visitor::TypeCheckBounds(Node* node) {
   return Type::Unsigned31();
 }
 
+Type* Typer::Visitor::TypeCheckNumber(Node* node) {
+  Type* arg = Operand(node, 0);
+  return Type::Intersect(arg, Type::Number(), zone());
+}
+
 Type* Typer::Visitor::TypeCheckTaggedPointer(Node* node) {
   Type* arg = Operand(node, 0);
   return Type::Intersect(arg, Type::TaggedPointer(), zone());