[PATCH] D59295: [AMDGPU] Pre-allocate WWM registers to reduce VGPR pressure.

[Connor Abbott via Phabricator via llvm-commits]

cwabbott added a comment.

In D59295#1427864 <https://reviews.llvm.org/D59295#1427864>, @arsenm wrote:

> If you can express the constraints with some series of uses and defs, that would be preferable.


Unfortunately that's just not possible. The best thing we could come up with that does this was the current SIFixWWMLiveness pass, and even with subsequent modifications, it's still pretty terrible in practice. We just can't get decent performance without doing something like this hack.


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