role of dump_file notably for/in plugins?

role of dump_file notably for/in plugins?

[Basile Starynkevitch]

Hello Folks

What is the intended role of the dump_file [the one known in tree-pass.h
near line 101] for plugins?

May plugins print their arbitrary things (e.g. their own debug printing)
inside? I believe that yea, but I am not sure.

May plugins set the dump_file variable (for instance to stderr). I believe
that no, but I am not sure.

Can dump_file be used outside passes (e.g. in the initialization part of a
plugin)? I believe that no, but I hesitate.

Cheers.


-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
8, rue de la Faiencerie, 92340 Bourg La Reine, France
*** opinions {are only mines, sont seulement les miennes} ***

Re: role of dump_file notably for/in plugins?

[Richard Guenther]

On Wed, Aug 31, 2011 at 4:24 PM, Basile Starynkevitch
<basile@starynkevitch.net> wrote:
> Hello Folks
>
> What is the intended role of the dump_file [the one known in tree-pass.h
> near line 101] for plugins?
>
> May plugins print their arbitrary things (e.g. their own debug printing)
> inside? I believe that yea, but I am not sure.
>
> May plugins set the dump_file variable (for instance to stderr). I believe
> that no, but I am not sure.
>
> Can dump_file be used outside passes (e.g. in the initialization part of a
> plugin)? I believe that no, but I hesitate.

Look at how it is set.. That answers all of your questions.

Richard.

> Cheers.
>
>
> --
> Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
> email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
> 8, rue de la Faiencerie, 92340 Bourg La Reine, France
> *** opinions {are only mines, sont seulement les miennes} ***
>

Re: role of dump_file notably for/in plugins?

[David Malcolm]

On Wed, 2011-08-31 at 16:28 +0200, Richard Guenther wrote:
> On Wed, Aug 31, 2011 at 4:24 PM, Basile Starynkevitch
> <basile@starynkevitch.net> wrote:
> > Hello Folks
> >
> > What is the intended role of the dump_file [the one known in tree-pass.h
> > near line 101] for plugins?
> >
> > May plugins print their arbitrary things (e.g. their own debug printing)
> > inside? I believe that yea, but I am not sure.
> >
> > May plugins set the dump_file variable (for instance to stderr). I believe
> > that no, but I am not sure.
> >
> > Can dump_file be used outside passes (e.g. in the initialization part of a
> > plugin)? I believe that no, but I hesitate.
> 
> Look at how it is set.. That answers all of your questions.

FWIW, I wrapped writing to "dump_file" in my Python gcc plugin as the
API entrypoint:
   gcc.dump(obj)
but given that it didn't seem to be possible to enable dumping for a
given custom pass by name directly from the command-line, it didn't seem
very useful (you can toggle the dfi->state when the pass is created to
manually enable it, which I've wrapped as the "dump_enabled" property of
a gcc.Pass instance).

Given all of this I tend to simply use "dump_base_name", which I wrapped
as:
   gcc.get_dump_base_name()
to supply a meaningful filename, which I use open a regular file for
writing.

See:
http://readthedocs.org/docs/gcc-python-plugin/en/latest/passes.html#dumping-per-pass-information
and
http://readthedocs.org/docs/gcc-python-plugin/en/latest/passes.html#gcc.Pass.dump_enabled
for more notes on how the Python plugin approaches this.

The relevant code is mostly in:
http://git.fedorahosted.org/git/?p=gcc-python-plugin.git;a=blob;f=gcc-python.c;h=f6c5f5f284ffddff61195c40bbf6b8d62f7a7a9d;hb=HEAD#l675
and
http://git.fedorahosted.org/git/?p=gcc-python-plugin.git;a=blob;f=gcc-python-pass.c;h=a54ea9b6d6bd8ecc26f8a305c4e96605d2bd14ab;hb=HEAD#l253

Hope this is helpful
Dave

Re: role of dump_file notably for/in plugins?

[Pierre Vittet]

Hello,

From what I understand, the question is not really how do we dump passes
but what a pass (from a plugin or not) should dump? So the question is
what do you expect from a dump file?

Do you expect to have the full internal representation of the code after
the end of the pass? For many dump files, we just get this (lower,cfg,
ssa...).
Or do you expect something more oriented on what the pass did? Like
"this pass remove three unreable basicblocks, they were located here,
here and here"?

Maybe there is no particular rules and it just depends of the pass.
However I guess there should some clear rules about this. Dump files can
be quite useful to understand the compiler behavior (sometimes it is a
huge task to search using the debugger).

Thanks.

Pierre Vittet