[PATCH] D108141: [PowerPC][AIX] Set the HasAlloca flag in the AIX Traceback Table only if R31 is used as a frame pointer

[Zarko Todorovski via Phabricator via llvm-commits]

ZarkoCA added a comment.

In D108141#2948615 <https://reviews.llvm.org/D108141#2948615>, @lkail wrote:

> Is the `AllocaUsed` bit indicating LLVM instruction `alloca` is used? If so, I'm assuming this patches refers to dynamic alloca, since r31 is used under this condition. There is a flag in `MachineFrameInfo::hasVarSizedObjects` for dynamic alloca. There are some other cases also using r31 as frame pointer, so use r31 here might be not accurate.

Yes, that's a good suggestion howeever, according to the AIX convention:

  The `function calls alloca' bit seems to be set whenever reg 31 is
  set up as a frame pointer, even when there is no alloca call.

And this is why we have this implementation. As per your good offline suggestion I will also edit the description of the patch to make this clear.


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https://reviews.llvm.org/D108141