[llvm] [AMDGPU] Add amdgpu-lower-special-lds pass to lower named-barrier LDS (PR #165692)

[Pierre van Houtryve via llvm-commits]

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@@ -0,0 +1,234 @@
+//===-- AMDGPULowerSpecialLDS.cpp -----------------------------------------===//
+//
+// 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 pass lowers the named barriers LDS globals which needs
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Pierre-vh wrote:

Elaborate a bit more, add a little code snippet with before/after. e.g.: This assigns a unique barrier ID to every !amdgpu.named.barrier GV, and encodes the barrier ID in the !absolute_symbol metadata of the GV so LDS lowering pass can safely handle it.

https://github.com/llvm/llvm-project/pull/165692