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From: "tkoenig at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/41453] use INTENT(out) for optimization
Date: Sun, 25 Sep 2022 20:32:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D41453

--- Comment #16 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
(In reply to Mikael Morin from comment #15)
> Status update:

A lot of progress :-)

> (In reply to Thomas Koenig from comment #5)
> > Still missing: To clobber
> >=20
> > - variables passed by reference to the caller
> > - saved variables
> > - associated variables (there are passed as pointers to
> >   the associate blocsk)
> These have been done now.
>=20
> Still missing: pointer or allocatable dummy.
> Seems doable, probably a low hanging fruit.

For an allocatable dummy, we have to deallocate on intent(out)
anyway, and we do this on the caller's side, so we should not clobber.=20
For pointers, it could be an advantage.

> > - intent(out) variables on entry to the procedure.
> This remains to do.

Again, sounds doable


> Another case that could be handled is the case of arrays:
> when the full array is passed as argument, and it is contiguous, and maybe
> some other condition, we can clobber its decl.  The hard part is the "may=
be
> some other condition".

Not sure what that other condition could be.  If we have a full array ref, =
as
per gfc_full_array_ref_p, and we pass this to an intent(out) argument,
then that should be enough.

> Not sure it's worth keeping this PR open.
> Surely the initial test works as expected, and has been working for a long
> time.

There are still a few open points in relation to this.  I would be in
favor of keeping this open (to not lose the discussion) until we have
them all fixed, or decide not to fix some or all of them.=