On Sat, Jun 1, 2019 at 2:14 AM Indu Bhagat <indu.bha...@oracle.com> wrote:
>
>
>
> On 05/29/2019 12:15 AM, Richard Biener wrote:
>
> Of course. We are merely discussing of where the triggering of processing
> starts: debug hooks, or something like:
>
> dwarf2out_early_finish() {
> ...
> if (ctf)
> ctf_emit();
> }
>
> (and then in addition if the current DWARF info would be the source of CTF
> info, or if it'd be whatever the compiler gives you as trees)
>
> The thing is, with debug hooks you'd have to invent a scheme of stacking
> hooks on top of each other (because we want to generate DWARF and CTF from
> the same compilation). That seems like a wasted effort when our wish is
> for the hooks to go away alltogether.
>
> When the debug hooks go away, the functionality can be folded in. Much like
> above, the ctf proposed implementation will do :
>
> ctf_early_global_decl (tree decl)
> {
> ctf_decl (decl);
>
> real_debug_hooks->early_global_decl (decl);
> }
>
> These ctf_* debug hooks wrappers are as lean as shown above.
>
> I do understand now that if debug hooks are destined to go away, all the
> implementation which wraps debug hooks (go dump hooks, vms debug hooks,
> and now the proposed ctf debug hooks) will need some merging. But to generate
> CTF, I think working on type or decl instead of DWARF dies to is a better
> implementation because if user wants only CTF, no DWARF trees need to be
> created.
>
> This way we keep DWARF and CTF generation independent of each other (as the
> user may want either one of these or both).
>
> The user currently can't have both DWARF and STABS either. That things like
> godump uses debug hooks is just (convenient?) abuse.
>
> In the end frontends will not call sth like dwarf2out_decl but maybe
> gen_subroutine_die () or gen_template_die (). So how do you expect
> the "wrapping" to work there?
>
> I understand you want CTF for "actually emitted" decls so I propose you
> instead hook into the symtab code which would end up calling the
> early_global_decl debug hook. But please don't add new debug hook
> users.
>
> OK.
>
> Will I need to tap both the callsites of the early_global_decl () debug hook
> ? :
> 1. symbol_table::finalize_compilation_unit () in cgraphunit.c
> 2. rest_of_decl_compilation () in passes.c
> Or is the last one for something specific to godump debug hooks and C++ ?
You need to handle both, one is for variables and one for functions.
> I guess the above will take care of the CTF generation bit. For emission,
> something similar should be done because DWARF hooks will not be initialized
> if
> DWARF debuginfo is not requested by the user. So I cannot have the CTF
> emission
> code in the dwarf2out*finish () debug hooks as suggested earlier.
True.
> Curious to know how the current debug hook users like dbx debug hooks will be
> taken care of in the future design ? Is it just the wrapping/stacking of debug
> hooks that's problematic and not the clean instances like dbx debug hooks ?
dbx format support will go away, it's unmaintained and not up to the
task handling
modern languages.
Richard.
>
