[llvm] r200067 - [LPM] Make LCSSA a utility with a FunctionPass that applies it to all

[Chandler Carruth]

On Thu, Dec 11, 2014 at 12:07 PM, Bruno Cardoso Lopes <
bruno.cardoso at gmail.com> wrote:
>
> Do you recall any specific reason for commenting out this assertion?
> Compile time performance?
>

No, it fired constantly and everywhere. =/

Back when I was hacking on this, the loop pass manager would invalidate
LCSSA form for loops outside of the specific layer of the loop nest it was
visiting, and thus this assert would trigger. I tried to fix many such
issues, but while I managed to fix everything I actually saw happen in the
wild, I wasn't able to turn it on without triggering rampant asserts.


> I just sent out a patch to fix a issue in LCSSA and having this on
> would have catch that before, I was wondering about turning it on
> again.
>

Yea, it would be really nice to check this kind of stuff, but I'm quite
worried about how much it will end up firing in places that (today) don't
matter. I left the commented out assert it to help debug actual PRs that
came up in practice which ended up having to do with this. That said, fixes
here seem really good to have; if we could actually turn it on that would
be amazing.
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