From: Richard Biener <rguenther@suse.de>
To: Jan Hubicka <hubicka@ucw.cz>
Cc: gcc-patches@gcc.gnu.org, d@dcepelik.cz
Subject: Re: Make nonoverlapping_component_refs work with duplicated main variants
Date: Tue, 09 Jul 2019 13:30:00 -0000 [thread overview]
Message-ID: <alpine.LSU.2.20.1907091527130.2976@zhemvz.fhfr.qr> (raw)
In-Reply-To: <20190709130724.5lnqywgf7xxmlny4@kam.mff.cuni.cz>
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On Tue, 9 Jul 2019, Jan Hubicka wrote:
> > > tree_int_cst_equal will return false if offsets are not INTEGER_CST.
> > > I was not sure if I can safely use operand_equal_p. What happens for
> > > fields with variable offsets when I inline two copies of same function
> > > which takes size as parameter and make the size different? Will I get
> > > here proper SSA name so operand_equal_p will work?
> >
> > No, you get a DECL, but yes, I think operand_equal_p will work.
> > Consider two _same_ variable sizes, you'll not see that you
> > have to return zero then? But yes, in case you have types
> > globbed to the canonical type (but not FIELD_DECLs) then
> > you'll get false !operand_equal_p as well.
> >
> > The question is really what is desired here. If you want/need precision
> > for non-constant offsets then you have to look at the COMPONENT_REF
> > trees because the relevant offset (SSA name) is only there
> > (in TREE_OPERAND (component_ref, 2)).
> >
> > If you want to give up for non-constants and can do that without
> > correctness issue then fine (but Ada probably would like to have
> > it - so also never forget to include Ada in testing here ;))
>
> I would like to have precision here. so perhaps as incremental change I
> can
> 1) reorganize callers to pass refs rather than just field_decls
> 2) check if TREE_OPERAND (component_ref, 2) is non-NULL in both case
> a) if so do operand_equal_p on them and return 0 on match
> b) if there is no match see if I have same canonical types and
> return 1 then
> c) return -1 otherwise
makes sense
> 3) continue with parsing FIELD_DECLS we work on now.
> >
> > Oh, OK ... a bit more explaining commentary might be nice
> > (at the top of the function - basically what the input
> > constraints to the FIELD_DECLs are).
>
> OK, will try to improve comments (though i tried to be relatively
> thorough).
>
> Honza
> >
> > Btw, the offsets in FIELD_DECLs are relative to DECL_CONTEXT so
> > comparing when DECL_CONTEXT are not related at all doesn't make
> > any sense. Well, unless we know _those_ are at the same offset,
> > so - the constraint for the FIELD_DECLs we compare is that
> > the containing structure type object instances live at the same
> > address?
> >
> > Richard.
>
--
Richard Biener <rguenther@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG NÌrnberg)
next prev parent reply other threads:[~2019-07-09 13:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 7:39 Jan Hubicka
2019-07-08 9:10 ` Richard Biener
2019-07-08 10:48 ` Jan Hubicka
2019-07-09 12:02 ` Jan Hubicka
2019-07-09 12:21 ` Richard Biener
2019-07-09 12:41 ` Jan Hubicka
2019-07-09 12:52 ` Richard Biener
2019-07-09 13:10 ` Jan Hubicka
2019-07-09 13:30 ` Richard Biener [this message]
2019-07-09 13:37 ` Jan Hubicka
2019-07-09 13:41 ` Richard Biener
2019-07-09 21:03 ` Bernhard Reutner-Fischer
2019-07-11 8:29 ` Rainer Orth
2019-07-16 9:30 ` Jan Hubicka
2019-07-16 11:58 ` Rainer Orth
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