[llvm-dev] Call for testing -- new variable location tracking solution

[Jeremy Morse via llvm-dev]

Hi Djordje,

It's great to see that improvement in coverage, particularly when not
all the improvements are landed yet. Note that some substantial
portion of the new locations might be entry values, knowing the
desired values of variables lets us better identify when entry values
can be used,

On Thu, Jul 29, 2021 at 1:40 PM Djordje Todorovic
<Djordje.Todorovic at syrmia.com> wrote:
> The thing I am concerned about is the number of 0% covered variables. It has increased when using this new feature, and I was wondering if there is any reason for that. In addition, the number of debug variables generated is different.

Several things could be going on here, my bet would be that it's
related to D95617 -- unfortunately the different ways that we
represent variables that have been optimised out can have an effect on
the DWARF produced. David points out in this comment [0] that the fix
isn't complete (non-inline functions with abstract origins can
gain/lose variables depending on our internal representation), I took
a look but fixing it wasn't straight forwards (I think subprograms can
acquire abstract origins after they're dwarf-emitted?).

That could explain why there are more zero-percent variables in the
output (different representation leads to different variable count);
however the total number of variables _decreases_, which I wouldn't
expect. If you can get a small reproducer for that I'd really like to
look at it.

[0] https://reviews.llvm.org/D95617#2672839

--
Thanks,
Jeremy