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[RISCV][WIP][RFC] Fix stack slot for argument type sizes not a multiple of 64 bits (Bug 49500)
AbandonedPublic

Authored by luismarques on Mar 22 2021, 4:06 AM.

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Summary

This is a fix for: https://bugs.llvm.org/show_bug.cgi?id=49500.

As it stands, this patch is basically just a copy of D97514. Originally I suspected that there might be a better way to solve it, but eventually I realized I had arrived at roughly the same approach. I'm not sure there's much point in using getRegisterTypeForCallingConv and getNumRegistersForCallingConv versus something more direct, but I've left that unchanged.

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Event Timeline

luismarques created this revision.Mar 22 2021, 4:06 AM
luismarques requested review of this revision.Mar 22 2021, 4:06 AM
Herald added a project: Restricted Project. · View Herald TranscriptMar 22 2021, 4:06 AM
luismarques edited reviewers, added: mundaym; removed: Michael.Mar 22 2021, 4:06 AM
luismarques edited the summary of this revision. (Show Details)Mar 22 2021, 4:09 AM
luismarques added inline comments.Mar 22 2021, 4:18 AM
llvm/lib/Target/RISCV/RISCVISelLowering.cpp
6196–6197

Is OrigArgVT always going to be equal to Outs[i].ArgVT?

Does this happen to fix D95025? It's certainly in a similar area as my (WIP) fix that I never got round to publishing.

Does this happen to fix D95025? It's certainly in a similar area as my (WIP) fix that I never got round to publishing.

At first glance it looks like it does.

At first glance it looks like it does.

Excellent!

My fix was more direct: I went over ArgValue and all of the SDValue PartValue = OutVals[i + 1]; as in the loop later in this block, and summed up all of the required getStoreSizes of their VTs, and took the maximum required alignment of each. Then created a stack temporary of that summed size and max alignment. I wasn't sufficiently happy with it and since I didn't get much indication that this was an urgent fix I didn't put it up for discussion - sorry about that. I can share my patch with you if you're interested.

My fix was more direct: I went over ArgValue and all of the SDValue PartValue = OutVals[i + 1]; as in the loop later in this block, and summed up all of the required getStoreSizes of their VTs, and took the maximum required alignment of each. Then created a stack temporary of that summed size and max alignment. I wasn't sufficiently happy with it and since I didn't get much indication that this was an urgent fix I didn't put it up for discussion - sorry about that. I can share my patch with you if you're interested.

That sounds like it has the potential for being a better alternative than this one. Please post it for review. Thanks!

luismarques updated this revision to Diff 332295.EditedMar 22 2021, 8:24 AM
  • Precommitted the original test, to better show the difference caused by the patch.
  • Updated the existing tests. They seem to more broadly show the issue I noted about the excessive alignment/overly conservative stack size.
luismarques abandoned this revision.Apr 4 2021, 8:33 AM

Abandoned in favor of D99087. Thanks @frasercrmck!

luismarques edited the summary of this revision. (Show Details)

Fixing alignment before truly abandoning, in case it's useful for D97514.