[llvm-dev] How to help improve debug experience w/ optimizations enabled?

[Greg Bedwell via llvm-dev]

Hi Pierre,

I'll put up a change at the old dexter repo to redirect to its new home. I
should have done that a long time ago. Sorry for the inconvenience!

-Greg

On Wed, 26 Feb 2020 at 14:36, Pierre van Houtryve via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
> Thank you very much for your detailed answer.
>
> I didn't know DExTer was in the monorepo, I have been working on the "old"
> Dexter repo and I even made several changes/fixes to Dexter.
> I'll need to move my changes to the new version then (I hope to upstream a
> few of them, but it still needs some work)
>
> I already picked up one bug from the umbrella bug (and it's now waiting
> for review), I'll try to pick up more of them in the next few days.
>
> Kind regards,
> Pierre van Houtryve
> ------------------------------
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Jeremy
> Morse via llvm-dev <llvm-dev at lists.llvm.org>
> *Sent:* 26 February 2020 12:40
> *To:* Vedant Kumar <vedant_kumar at apple.com>
> *Cc:* llvm-dev at lists.llvm.org <llvm-dev at lists.llvm.org>
> *Subject:* Re: [llvm-dev] How to help improve debug experience w/
> optimizations enabled?
>
> Hi Pierre,
>
> > Is there any bug in this list that isn't being looked at (and that
> doesn't require a lot of knowledge) that I could work on?
>
> As others say, please do pick up any unassigned bug. Some of the bugs
> in the umbrella bugs haven't been touched in roughly a year -- just
> identifying whether they reproduce or not on the master branch today
> is worthwhile, so that we know what to focus on,
>
> > In general, if I want to find bug reports about missing debug info/poor
> debug experience, where should I look at?
> > e.g. bug trackers for clang-built projects, particular code examples,
> issues you encountered but haven't reported yet, etc.
>
> A while back I wrote some small Dexter tests to stimulate different
> optimisations in LLVM [0], on the principle that this should generate
> a suite of programs with different behaviours, that we could look at
> the debuginfo for. Most of the worst errors were reported under the
> umbrella bug, but there were some strange behaviours that didn't end
> up being reported. It might be worth re-running Dexter over these
> tests to see if there are still weird behaviours present. Note that
> differences in the code generated in the meantime may have altered or
> even invalidated the tests since then (alas), and a certain amount of
> analysis is needed to determine whether debuginfo can really be
> improved.
>
> > I also tried using Dexter (https://github.com/SNSystems/dexter ) to
> find issues, but it's hard to find something that I can fix in a reasonable
> amount of time using Dexter alone as I don't have enough LLVM experience to
> know where to look at/what to look for.
>
> (Note that Dexter is now in the 'debuginfo-tests' dir of the
> monorepo). I've tended to use Dexter in a very tight loop of modifying
> code and then running Dexter to see what the debugger observes about
> that code, to quickly try out code patterns that might be faulty. If I
> had to pick an area, I'd say that manipulating structs / passing them
> between functions might be an area worth analysing, we've had a few
> bugs with struct fragments being misinterpreted recently.
>
> [0]
> https://github.com/jmorse/dexter/tree/92f8ee722dda9710eb33969f00d29b48059b95bb/tests/nostdlib/llvm_passes
>
> --
> Thanks,
> Jeremy
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