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

[via llvm-commits]

alex-t wrote:

> Ah, makes sense; I'm assuming you've seen this, but just in case you haven't we do have ENABLE_SGPR_PRIVATE_SEGMENT_BUFFER (see https://llvm.org/docs/AMDGPUUsage.html#code-object-v3-kernel-descriptor) which might help. If this simply doesn't work (or isn't always available) then I'm similarly not certain how one achieves this uniformly.
> 
I knew we had a bit for this. I mostly was curious how one could set/clear the appropriate bit. Just because I haven't experience with the runtime code and API.  

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