llvm dev - Oct 2019 - DebugInfo work contribution and update.

On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul <paul.robinson at sony.com>
wrote:
> Welcome Sourabh,
>
>
>
> There are many bits of DWARF-5 that haven’t been implemented.
>
Got a short list, by chance?

>   I know there is currently no big push within Sony to “fill in the
> corners” for v5, as we have been more focused on quality of debug info for
> optimized code (not losing information or reporting incorrect information)
> and the Dexter tool.  There is no shortage of ways in which debug info for
> optimized code could be better; in general we are trying to post bug
> reports for anything we find that we’re not working on right away.
>
>
>
> I think you are doing the right thing as far as coordinating with other
> people: Watch the llvm-commits and cfe-commits lists to notice when people
> are posting patches; post your own patches; and ask on the dev lists.  If
> you decide to work on something that was reported as a bug, post a note
> there or assign the bug to yourself.
>
>
>
> I looked up the two PRs you cited; PR43622 is likely a simple oversight
> that should be easy to fix.  PR43263 doesn’t appear to be related to debug
> info, was that a typo?
>
> --paulr
>
>
>
> *From:* Sourabh Singh Tomar <sourav0311 at gmail.com>
> *Sent:* Wednesday, October 09, 2019 2:38 PM
> *To:* David Blaikie <dblaikie at gmail.com>
> *Cc:* Adrian Prantl <aprantl at apple.com>; Robinson, Paul <
> paul.robinson at sony.com>; Eric Christopher <echristo at
gmail.com>; Jonas
> Devlieghere <jdevlieghere at apple.com>; Ali Tamur <tamur at
google.com>; Pavel
> Labath <pavel at labath.sk>; Pavel Labath <labath at
google.com>;
> llvm-dev at lists.llvm.org; Clang Dev <cfe-dev at lists.llvm.org>;
George, Jini
> Susan <jinisusan.george at amd.com>; sourabhsingh.tomar at amd.com
> *Subject:* Re: [llvm-dev] DebugInfo work contribution and update.
>
>
>
> Thanks, David for updating us.
>
>
>
> Regarding, mail address, can use anyone{@gmail or @amd}. but
> sourav0311 at gmail.com works best for me for mailing lists related stuff.
>
>
>
> Regarding, GDB side of DWARFv5 side of things, we've testing GDB-8.3
WRT
> DWARFv5 clang and gcc binaries to get better idea of debuggability of clang
> generated binaries with GDB.
>
> Primary motivation being GDB better handling of gcc generated binaries,
> compared to clang.
>
>
>
> We've been also tracking Ali's patches in gdb mailing list. Jini
can
> update you better on, this one. Will ask her share update on this one.
>
>
>
> Thanks,
>
> Sourabh
>
>
>
>
>
>
>
> On Wed, Oct 9, 2019 at 10:59 PM David Blaikie <dblaikie at gmail.com>
wrote:
>
> +some other debugger people (Pavel - wasn't sure which email address
you
> prefer, feel free to let me know (privately or publicly) for future
> reference)
>
> I work at Google & we're certainly interested in DWARFv5 compliance
- I'm
> currently working on improving debug_loclist emission to share more address
> pool entries ( https://reviews.llvm.org/D68620 ) which includes some
> improvements to llvm-dwarfdump to go with that. (Pavel's working on
further
> improvements https://reviews.llvm.org/D68271 )
>
> I haven't looked at/started on the loclist issue (PR43622) - so if you
> want to look at that, that's fine by me.
>
> Are you also interested in the debugger side of things? GDB's DWARFv5
> support is pretty incomplete & Ali's already looking at some of
that, and I
> might get to the debug_loclist improvements necessary - but if someone else
> wants to do that before me, I won't complain.
>
> Not sure of any other major holes in LLVM's DWARFv5 support, but they
> might be out there, for sure.
>
>
>
> On Wed, Oct 9, 2019 at 9:37 AM Sourabh Singh Tomar via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi llvm-dev, cfe-dev,
>
>
>
> It's been a while since our team is investigating DebugInfo in LLVM,
we're
> looking forward to contribute and enhance in LLVM DebugInfo.
>
>
>
> We,'ve been investigating mostly on DWARF-5 aspects -- couple of them
to
> mention--
>
> 1. Language aspects
>
> 2. Location mostly optimized out ones
>
> 3. DebugInfo conformance to DWARF-5
>
>
>
> To avoid getting conflicted with some body else's work and avoiding
> redundancy. We would like to know the over-all state of current community
> developments happening WRT DWARF-5.
>
>
>
> As of now, we're working on --
>
> PR 43263, 43622 -- reported today {Just Now}
>
>
>
> we'll be up-streaming patches for these.
>
>
>
> Please let us know your thoughts, and anything else that's relevant
that
> we need to aware of before picking up.
>
>
>
> Thanks in anticipation!
>
> Sourabh Singh Tomar
>
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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> From: David Blaikie <dblaikie at gmail.com> 
>> On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul <mailto:paul.robinson
at sony.com> wrote:
>> There are many bits of DWARF-5 that haven’t been implemented.
>
> Got a short list, by chance?
I can't say I've been keeping track of all that has gone in, but based
on the list that I came up with when I was sizing the initial DWARF 5
work, things that might not be done include:

Default location entry
Inline namespace attribute
Reference-qualified member functions
"auto" return type
Type/item alignment
Defaulted template parameter
Atomic type modifier
DW_OP_implicit_pointer
.debug_macro section
Typed expressions
Supplementary objects

Things I have noticed going in recently:

Call-site and entry-value stuff (is that complete?)
New language/dialect codes
Deleted/defaulted members is in progress
"noreturn" functions is in progress

I can't remember whether split-DWARF is fully v5 compliant...

If any items above are in fact done, my apologies and VERY happy to be 
corrected.
--paulr

> On Oct 9, 2019, at 1:33 PM, Robinson, Paul <paul.robinson at
sony.com> wrote:
> 
>> From: David Blaikie <dblaikie at gmail.com> 
>>> On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul
<mailto:paul.robinson at sony.com> wrote:
>>> There are many bits of DWARF-5 that haven’t been implemented.
>> 
>> Got a short list, by chance?
> 
> I can't say I've been keeping track of all that has gone in, but
based
> on the list that I came up with when I was sizing the initial DWARF 5
> work, things that might not be done include:
> 
> Default location entry
> Inline namespace attribute
I think we may have this one already!

commit dbfda63695272c2d12a6a61b18b52d3961d8e1a8
Author: Adrian Prantl <aprantl at apple.com>
Date:   Thu Nov 3 19:42:02 2016 +0000

    Add DWARF debug info support for C++11 inline namespaces.
    This implements the DWARF 5 DW_AT_export_symbols feature:
    http://dwarfstd.org/ShowIssue.php?issue=141212.1
    
    <rdar://problem/18616046>
    
    llvm-svn: 285959

> Reference-qualified member functions
> "auto" return type
> Type/item alignment
> Defaulted template parameter
> Atomic type modifier
> DW_OP_implicit_pointer
> .debug_macro section
> Typed expressions
> Supplementary objects
> 
> Things I have noticed going in recently:
> 
> Call-site and entry-value stuff (is that complete?)
> New language/dialect codes
> Deleted/defaulted members is in progress
> "noreturn" functions is in progress
> 
> I can't remember whether split-DWARF is fully v5 compliant...
> 
> If any items above are in fact done, my apologies and VERY happy to be 
> corrected.
> --paulr
>

Thanks for the list, Paul. This is quite helpful. DW_OP_implicit_pointer is
something that we are looking into currently. I believe that
"Reference-qualified member functions" has also been implemented.

Thanks!
Jini.



On Thu, Oct 10, 2019 at 2:03 AM Robinson, Paul via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> > From: David Blaikie <dblaikie at gmail.com>
> >> On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul <mailto:
> paul.robinson at sony.com> wrote:
> >> There are many bits of DWARF-5 that haven’t been implemented.
> >
> > Got a short list, by chance?
>
> I can't say I've been keeping track of all that has gone in, but
based
> on the list that I came up with when I was sizing the initial DWARF 5
> work, things that might not be done include:
>
> Default location entry
> Inline namespace attribute
> Reference-qualified member functions
> "auto" return type
> Type/item alignment
> Defaulted template parameter
> Atomic type modifier
> DW_OP_implicit_pointer
> .debug_macro section
> Typed expressions
> Supplementary objects
>
> Things I have noticed going in recently:
>
> Call-site and entry-value stuff (is that complete?)
> New language/dialect codes
> Deleted/defaulted members is in progress
> "noreturn" functions is in progress
>
> I can't remember whether split-DWARF is fully v5 compliant...
>
> If any items above are in fact done, my apologies and VERY happy to be
> corrected.
> --paulr
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Hello Sourabh, David, others,

Like David said I am currently looking at the consumption side of 
debug_loclists, and my main angle is being able to reuse that parser in 
lldb (which has its own dwarf parser for the most part, but it is trying 
to move away from that). However, I've been busy with other stuff lately 
and so I haven't done much work there, but hopefully things will clear 
up now.

On 09/10/2019 21:11, David Blaikie wrote:
> 
> 
> On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul <paul.robinson at
sony.com
> <mailto:paul.robinson at sony.com>> wrote:
> 
>     Welcome Sourabh,____
> 
>     __ __
> 
>     There are many bits of DWARF-5 that haven’t been implemented.
> 
> 
> Got a short list, by chance?
My pet missing feature is the debug_names+type units combo, which 
currently does not work due to the interaction of opportunistic type 
unit creation and eager insertion of type names into the index.

cheers,
pl

On Wed, Oct 9, 2019 at 1:33 PM Robinson, Paul <paul.robinson at sony.com>
wrote:
> > From: David Blaikie <dblaikie at gmail.com>
> >> On Wed, Oct 9, 2019 at 11:59 AM Robinson, Paul <mailto:
> paul.robinson at sony.com> wrote:
> >> There are many bits of DWARF-5 that haven’t been implemented.
> >
> > Got a short list, by chance?
>
> I can't say I've been keeping track of all that has gone in, but
based
> on the list that I came up with when I was sizing the initial DWARF 5
> work, things that might not be done include:
>
> Default location entry
> Inline namespace attribute
> Reference-qualified member functions
> "auto" return type
> Type/item alignment
> Defaulted template parameter
> Atomic type modifier
> DW_OP_implicit_pointer
> .debug_macro section
> Typed expressions
> Supplementary objects
>
Ah, thanks for the list - mostly I'm interested in cases where Clang's
output is not valid DWARFv5 when requested - the new features DWARFv5
enables/allows but doesn't require are lower priority to me. Which I
don't
think too much is left - DWARFv5 loclists in split DWARF is one I know of &
might get to if someone else doesn't do it before me - I'm currently
improving loclist emission (quality of implementation - using fewer address
pool entries & just general code cleanup to share some of teh
implementation with rnglist emission, not a compliance issue)

>
> Things I have noticed going in recently:
>
> Call-site and entry-value stuff (is that complete?)
> New language/dialect codes
> Deleted/defaulted members is in progress
> "noreturn" functions is in progress
>
> I can't remember whether split-DWARF is fully v5 compliant...
>
> If any items above are in fact done, my apologies and VERY happy to be
> corrected.
> --paulr
>
>
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