[PATCH] D124168: DeadMachineInstructionElim: Switch to using LiveRegUnits

Mon Sep 12 14:22:23 PDT 2022

arsenm added a comment.

In D124168#3784598 <https://reviews.llvm.org/D124168#3784598>, @arsenm wrote:

> 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)

Hopefully d90f7cb559e32c2cbf1f9839d7e8e0cc0be189ba <https://reviews.llvm.org/rGd90f7cb559e32c2cbf1f9839d7e8e0cc0be189ba> fixes this

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124168/new/

https://reviews.llvm.org/D124168