[PATCH] D124168: DeadMachineInstructionElim: Switch to using LiveRegUnits

Mon Sep 12 11:50:33 PDT 2022

arsenm added a comment.

In D124168#3784108 <https://reviews.llvm.org/D124168#3784108>, @nikic wrote:

>> Theoretically improves compile time for targets with many overlapping registers
>
> In practice, this is a major compile time regression instead: http://llvm-compile-time-tracker.com/compare.php?from=6c44a7179f1747ec38d580e6b50bde98555ad811&to=b5041527c75de2f409aa9e2e6deba12b17834c59&stat=instructions

This doesn't make much sense. My preliminary analysis says that this is somehow phys_regs_and_masks fault (which really doesn't buy any real code simplification over iterating the operands)

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https://reviews.llvm.org/D124168