[PATCH] D109958: [LoopFlatten] Enable it by default

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks added a comment.

In D109958#3055809 <https://reviews.llvm.org/D109958#3055809>, @alanphipps wrote:

>> Thanks for the suggestion, I am happy to enable LoopFlatten by default only for the new PM, so will look into that.
>
> My team presently relies on loop flattening with a downstream compiler, and we presently use the LPM and will move to the NPM after the 14.x branch.  It would be great if this functionality didn't diverge between the two, although I understand the frustration.  At the very least, I would like to understand what is different, and we could perhaps enable by default downstream until we migrate to the NPM.

There are already a good number of divergences between the two pass managers, I don't see the harm in keeping the LPM pipeline the same. Do you specifically care about this pass?

The changes to the test show that this would affect execution order of passes which could actually affect optimizations. People have requested that the LPM not regress even though it's deprecated, and I'm hesitant to touch LPM pass execution order.
I'd say that somebody cares about this pass and is using the LPM, they can investigate the weirdness and turn it on in a separate change for the LPM.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D109958/new/

https://reviews.llvm.org/D109958