[PATCH] D125102: [RagAllocGreedy] New hook regClassPriorityTrumpsGlobalness

[Jay Foad via Phabricator via llvm-commits]

foad added a comment.

I'm posting this to get feedback on the general idea of allowing targets to tweak live range priority. I'm not sure if there is a precedent for that.

The background is that the AMDGPU target (especially for graphics workloads) tends to use a lot of wide register classes representing a tuple of 2, 3, 4 or 8 gprs. In some cases we get much better packing of the register allocation (i.e. it uses fewer registers overall) if we allocate the wide tuples first, regardless of how long their live ranges are. And for GPUs using fewer registers overall is important because it allows the hardware to launch more kernels simultaneously.


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  https://reviews.llvm.org/D125102/new/

https://reviews.llvm.org/D125102