[PATCH] D85737: ARM][MVE] tail-predication: overflow checks for backedge taken count

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added a comment.

Thanks for reviewing!

> It's nice that we have some utility that computes what you need, even if it's not the obvious one.

Yes, that's why I was not entirely happy. Think I have seen a few non-obvious things, and some bugs too hidden by other things, but one step at a time here...



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Comment at: llvm/lib/Target/ARM/MVETailPredication.cpp:374
   auto *BTC = SE->getSCEV(BackedgeTakenCount);
+  auto *MaxBTC = SE->getConstantMaxBackedgeTakenCount(L);
+
----------------
efriedma wrote:
> I'm forgetting, do we have a check somewhere that BackedgeTakenCount is actually the backedge-taken count of the loop?
Good point. I thought we had one, but we have similar checks for the IV, which is done in step 3) below on line 464. Will address this in a follow up.


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