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

[Austin Kerbow via llvm-commits]

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+//===- AMDGPUPreloadKernargHeader.cpp - Preload Kernarg Header ------------===//
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kerbowa wrote:

I'm open to suggestions on the name. By header I just mean I'm adding on a preamble to the kernel. Could be prologue, or we could just name it backward compatibility layer or some variation of that.

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