[llvm] [AMDGPU] Compiler should synthesize private buffer resource descriptor from flat_scratch_init (PR #79586)

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alex-t wrote:

> Also, linking to AMDGPUUsage reminded me that we do document the initial SRSRC setup at https://llvm.org/docs/AMDGPUUsage.html#private-segment-buffer . Would you be able to update that as part of the patch? It lives at `llvm/docs/AMDGPUUsage.rst`. At the very least a FIXME/WARNING in there would be good so we don't mislead anyone while we work out the specifics.

Good Idea. I promise I will do what I can :)

https://github.com/llvm/llvm-project/pull/79586