[PATCH] D31081: [ARM] ScheduleDAGRRList::DelayForLiveRegsBottomUp must consider OptionalDefs

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Oh... looking a bit more closely, the "fast" scheduler is basically dead, and the VLIW scheduler is obviously irrelevant here.  And I guess this is pretty low risk, given that ARM is the only backend using optional defs.

This needs a much better comment explaining why this is necessary (covering the important points discussed in this review).  Otherwise, I'm okay with this (but I'm really not familiar with this code, so I'd like someone else to confirm that judgement).

------

I spent a little time experimenting with multiclassing the Thumb1 instructions to avoid optional defs; it seems like it's viable, and it's substantially simpler in some ways, but it would take a lot of time to finish.


Repository:
  rL LLVM

https://reviews.llvm.org/D31081