[PATCH] D96980: [amdgpu] Revert agnostic SGPR spill.

[Carl Ritson via Phabricator via llvm-commits]

critson added a comment.

Unfortunately I realized and have verified at least one problem with this and WQM.
With WQM the assumption that the EXEC mask for restore of the SGPR is a subset of the spill EXEC mask is not true.
Specifically an SGPR can be saved before entering WQM, then restored in WQM (so the readfirstlane will return junk).
This could potentially be addressed by ensuring the exec mask mode matches between spills and restores in the WQM pass.
(I can add this to WQM pass if needed, but will think a bit more on it first.)

Note: this issue is not necessarily an immediate problem for graphics, because we try to avoid all spills (particular SGPR spills to memory).
I am explicitly testing with SGPR to VGPR spills disabled and lowered SGPR counts to perturb the problem.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D96980/new/

https://reviews.llvm.org/D96980