[PATCH] D87050: GlobalISel: Add combines for G_TRUNC

[Jessica Paquette via Phabricator via llvm-commits]

paquette added a comment.

@arsenm

> For AMDGPU this would need a regbank legality check for post-regbankselect combines but I'm not sure what to do about that

Maybe it would make sense for now to add something like

  SelectionStage getSelectionStage(MachineFunction &MF);
  ...
  if (getSelectionStage(MF) < SelectionStage::Legalized)
     return false;
  ...
  if (getSelectionStage(MF) != SelectionStage::RegBankSelected)
     return false;
  ...

So we can at least bail out when something could be unsafe for some target?

Ultimately, it would be nicest to declare which stages each combine is valid/invalid at in the tablegen somehow, but I guess something like this could be useful temporarily? :/


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  https://reviews.llvm.org/D87050/new/

https://reviews.llvm.org/D87050