[llvm] [AMDGPU] Add backward compatibility layer for kernarg preloading (PR #119167)

[Janek van Oirschot via llvm-commits]

================
@@ -0,0 +1,229 @@
+//===- AMDGPUPreloadKernargHeader.cpp - Preload Kernarg Header ------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This pass handles the creation of the backwards compatability layer
+/// for kernarg prealoding. Code may be compiled with the feature enabled, while
----------------
JanekvO wrote:

```suggestion
/// for kernarg preloading. Code may be compiled with the feature enabled, while
```

https://github.com/llvm/llvm-project/pull/119167