[PATCH 2/2] DWARF: make it possible to emit debug info for declarations only

[Richard Biener]

On Tue, May 30, 2017 at 5:47 PM, Pierre-Marie de Rodat
<derodat@adacore.com> wrote:
> Thank you for your review, Richard.
>
> On 05/30/2017 01:59 PM, Richard Biener wrote:
>>
>> I think the issue is unfortunate in the C frontend as well.  So I believe
>> we can
>> go without a new langhook and instead make sure
>> dwarf2out_early_global_decl
>> is not called for uninteresting decls (which means eventually pushing the
>> call(s) of that hook more towards the FEs).
>
>
> It is called by rest_of_decl_compilation, which seems itself to be called a
> lot on FUNCTION_DECL nodes. Before I dive into this consequent change: this
> would lead for instance to add a parameter to rest_of_compilation to control
> whether it must call the early_global_decl hook, and then to update all
> callers accordingly. Is this what you actually have in mind?

Actually for the bigger picture I'd refactor rest_of_decl_compilation, not
calling it from the frontends but rely on finalize_decl/function.  The missing
part would then be calling the dwarf hook which should eventually be done
at some of the places the frontends now call rest_of_decl_compliation.

>
>> For C/C++ it would be reasonable to output debug info for external
>> declarations
>> that end up being used for example.
>
>
> I guess that could be done indeed. :-)

But for an easier way (you might still explore the above ;)) just remove
the guards from dwarf2out.c and handle it more like types that we
prune if they end up being unused (OTOH I guess we don't refer to
the decl DIEs from "calls" because not all calls are refered to with
standard DWARF -- the GNU callsite stuff refers them I think but those
get generated too late).

That said, when early_finish is called the cgraph and IPA references
exists and thus you can
sort-of see which functions are "used".

Richard.

> --
> Pierre-Marie de Rodat