Re: LTO and adding extra information from extra passes

[Richard Guenther <richard dot guenther at gmail dot com>]

On Wed, Sep 2, 2009 at 10:06 PM, Basile
STARYNKEVITCH<basile@starynkevitch.net> wrote:
> Hello All,
>
> My feeling is that the Link Time Optimisation (LTO) effort should be soon
> (=is expected to be, or is already) merged inside GCC trunk (future 4.5).
>
> Several years ago, I asked if there is any possibility for an additional
> pass to profit of LTO infrastructure to add some extra data into LTO stuff
> (which is probably DWARF related inside ELF object files, but I am not sure)
> and to retrieve it. I remember that the answer was of course not.
>
> Now we have a working plugin infrastructure, and I believe it would be very
> sensible for some plugin to register passes which add persistent information
> (as does LTO with its Gimple related representation) into object files and
> to retrieve it.
>
> Is there is still a major objection against that, or is there some API
> usable from plguins for that purpose?
>
> Even the mere ability to add inside the LTO data a chunk of bytes identified
> by the name of the plugin would be great. Of course, some more features
> could be welcome (e.g. the ability to add data specific to each compiled
> function or cgraph_node or whatever, or even to each gimple...).
>
> I could imagine that a plugin might be interested in adding say some
> information into the object file (when ordinary compilation for LTO of a
> single compilation unit happens) and later retrieve it (when link time
> optimisation occur merging several object files.)
>
> A dream case example would be a plugin for whole program static analysis.

The IPA pass infrastructure has all the necessary bits for this.

Richard.

> Regards.
> --
> Basile STARYNKEVITCH ? ? ? ? http://starynkevitch.net/Basile/
> email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
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>