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

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,229 @@
+//===- AMDGPUPreloadKernargHeader.cpp - Preload Kernarg Header ------------===//
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arsenm wrote:

Prolog or preamble would be better 

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