[llvm-dev] [RFC] Removing debug locations from ConstantSDNodes

[Eric Christopher via llvm-dev]

Yes, this is quite the annoying thing, but consumers are... inconsistent
with how they're using it. I believe I recall a case wehere a debugger
would refuse to stop on lines that didn't have is_stmt on them at all.

-eric

On Thu, Jun 21, 2018 at 9:57 AM via llvm-dev <llvm-dev at lists.llvm.org>
wrote:

> Which brings up yet another big pain point: We don't carry an is_stmt
> annotation around on instructions, we just always set is_stmt=1 on the
> first instruction with a source location different from the previous one,
> without regard to whether it's an "interesting" place to stop.
>
> --paulr
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] *On Behalf Of *Björn
> Pettersson A via llvm-dev
> *Sent:* Thursday, June 21, 2018 12:28 PM
> *To:* llvm-dev at lists.llvm.org
> *Cc:* davidxl at google.com; jbogner at apple.com
>
>
> *Subject:* Re: [llvm-dev] [RFC] Removing debug locations from
> ConstantSDNodes
>
>
>
> Isn’t this a typcial situation when the is_stmt field in the DWARF line
> table should be used?
>
>
>
> If we set is_stmt=0 for the instruction loading the constant, then a
> debugger can choose not to stop on that instruction when doing “step” on
> source level. That way we can keep the original source location for a
> ConstantSDNode, but also telling the debugger that this isn’t a recommended
> breakpoint location for that line. Using is_stmt=0 is ofcourse only
> interesting if the constant load I hoisted so that it isn’t adjacent to
> other is_stmt=1 instructions on the same line.
>
>
>
> /Björn
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of *via
> llvm-dev
> *Sent:* den 21 juni 2018 15:08
> *To:* mbraun at apple.com
> *Cc:* llvm-dev at lists.llvm.org; davidxl at google.com; jbogner at apple.com
> *Subject:* Re: [llvm-dev] [RFC] Removing debug locations from
> ConstantSDNodes
>
>
>
> mbraun at apple.com wrote:
>
>
>
> FWIW: Debug information on constants feels odd to me. They are just values
> not something that is executed so conceptually I would not expect them to
> "happen" at a specific time/place in the program. That said most numbers
> are copied into registers or stored into memory and that is of course an
> interesting action. So in the original example I would hope to see debug
> info on whatever instructions are used to fill the array with values.
>
>
>
> +1.  Constants are not inherently interesting, but loading one as an
> action preparatory to computing a value or setting up a parameter in a
> call, the instruction ought to be associated with the relevant source
> statement.
>
> --paulr
>
>
> _______________________________________________
> 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/20180621/f786a92d/attachment.html>