[PATCH] D133902: X86: Stop assigning register costs for longer encodings

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added a comment.

I guess this somewhat of an RFC, if we would accept better regalloc at slightly bigger programs: I found that dropping CostPerUse produced a small but measurable improvement on X86 regalloc.

I would also love to hear if others can explain why the increased register costs for the larger encodings result in slightly smaller programs, even though I don't us prefering registers with more or less uses when ordering eviction and assignment choices (and as far as the AllocationOrder goes the register with longer encodings are still on the back anyway).


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https://reviews.llvm.org/D133902