[PATCH] D151276: Weaken MFI Max Call Frame Size Assertion

[Oskar Wirga via Phabricator via llvm-commits]

oskarwirga added a comment.

In D151276#4366712 <https://reviews.llvm.org/D151276#4366712>, @barannikov88 wrote:

> I'm not sure this is the correct fix. The assertion specifically checks that MaxCallFrameSize and AdjustsStack computed here are the same as computed by `MachineFrameInfo::computeMaxCallFrameSize`.
> Have you been able to figure out why the results of the calculations are different?

Yes, bcl5980 commented on the github issue:

> In the AArch64TargetLowering::finalizeLowering it call MFI.computeMaxCallFrameSize(MF) to get MaxCallFrameSize
>  MaxCallFrameSize is 8 because a ADJCALLSTACKDOWN/ADJCALLSTACKUP in bb.2
>  And in the pass unreachable-mbb-elimination, bb.2 will be removed
>  Then the assert will be triggered in the pass prologepilog
>  Not sure how to fix the assert

I was able to fix this assertion by appending to `UnreachableMachineBlockElim::runOnMachineFunction`

  MachineFrameInfo &MFI = F.getFrameInfo();
  MFI.computeMaxCallFrameSize(F);

but was advised to weaken this assertion by @MatzeB with his reasoning being that the assertion was mostly to catch cases where the value //grew// later, rather than shrank.


Repository:
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  https://reviews.llvm.org/D151276/new/

https://reviews.llvm.org/D151276