diff --git a/llvm/include/llvm/ADT/STLArrayExtras.h b/llvm/include/llvm/ADT/STLArrayExtras.h
deleted file mode 100644
--- a/llvm/include/llvm/ADT/STLArrayExtras.h
+++ /dev/null
@@ -1,38 +0,0 @@
-//===- llvm/ADT/STLArrayExtras.h - additions to <array> ---------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file contains some templates that are useful if you are working with the
-// STL at all.
-//
-// No library is required when using these functions.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_ADT_STLARRAYEXTRAS_H
-#define LLVM_ADT_STLARRAYEXTRAS_H
-
-#include <cstddef>
-
-#include "llvm/Support/Compiler.h"
-
-namespace llvm {
-
-//===----------------------------------------------------------------------===//
-//     Extra additions for arrays
-//===----------------------------------------------------------------------===//
-
-/// Find the length of an array.
-template <class T, std::size_t N>
-LLVM_DEPRECATED("Use std::size instead.", "std::size")
-constexpr inline size_t array_lengthof(T (&)[N]) {
-  return N;
-}
-
-} // end namespace llvm
-
-#endif // LLVM_ADT_STLARRAYEXTRAS_H