[llvm-dev] Completeness of -print-after-all

[Fedor Sergeev via llvm-dev]

чт, 8 нояб. 2018 г., 14:45 Markus Lavin markus.lavin at ericsson.com:

> Fedor,
>
>
>
> Yes that is what happens in my case that the loop is fully unrolled and
> hence ‘removed’.
>
>
>
> My objection though is that there is still IR that could be dumped (i.e.
> the function containing the loop that was removed or the entire module) and
> that is what I want to have dumped after each pass when I specify
> -print-after-all. Of course there may be certain implementation details
> that could make this hard to achieve but ideally I would like to have a
> reliable option that dumps the entire IR (complete enough to import into
> opt and run additional passes on) after each individual pass (module,
> function, loop or whatever).
>
>
>
> Doesn’t that make sense?
>
It does not agree with the semantics of plain - print-before-all, which
intends to prints only the IRunit pass works on.

It does however makes perfect sense for the combo with -print-module-scope.
In fact I was going to try doing that for new-pass-manager implementation.

Legacy one is technically doable as well, though there is a catch that you
can't get module out of invalidated Loop, so there needs to be some
hackstery employed...

Patches welcome! :)

regards,
  Fedor.

>
>
> Regards,
>
> Markus
>
>
>
>
>
> *From:* Fedor Sergeev <fedor.v.sergeev at gmail.com>
> *Sent:* Thursday, November 8, 2018 11:06 AM
> *To:* Markus Lavin <markus.lavin at ericsson.com>
> *Cc:* llvm-dev at lists.llvm.org
> *Subject:* Re: [llvm-dev] Completeness of -print-after-all
>
>
>
> Markus,
>
>
>
> Loop passes are kinda unique compared to func/module passes in that they
> could destroy the loop they worked on. And there might be no loop to print
> after that (btw, there is a known bug in new pass manager where it tries to
> print deleted loop in this situation - nothing good happens!).
>
>
>
> In your case loop unroll can fully uroll the loop, essentially removing
> the Loop.
>
>
>
> If you have suggestions on how to improve behavior in such cases I would
> be happy to discuss this further.
>
>
>
> regards,
>
> Fedor
>
>
>
> 8 нояб. 2018 г. 12:38 пользователь "Markus Lavin via llvm-dev" <
> llvm-dev at lists.llvm.org> написал:
>
> Hi,
>
> I recently worked on an issue where I realized that -print-after-all does
> not
> cover all passes run by the pass manager. E.g. it seems that loop passes
> are
> not fully covered and I could find that loop transformations showed up in
> the
> dump of the next non-loop pass (which happened to be 'Combine redundant
> instructions' and that was rather confusing).
>
> Specifying both -print-before-all and -print-after-all and doing some
> grepping
> gives me the following where we see two back-to-back 'Before' dumps which
> should not be possible.
>
> *** IR Dump Before LCSSA Verifier ***
> *** IR Dump After LCSSA Verifier ***
> *** IR Dump Before Loop-Closed SSA Form Pass ***
> *** IR Dump After Loop-Closed SSA Form Pass ***
> *** IR Dump Before Unroll loops ***
> *** IR Dump Before Combine redundant instructions ***
> *** IR Dump After Combine redundant instructions ***
>
> Maybe there are good reasons for making this hard to fix but to me it seems
> like a rather severe deficiency so I wonder if this is widely known and if
> there
> are any plans to improve it?
>
> -Markus
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181108/c6ee92bf/attachment.html>