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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/112653] PTA should handle correctly escape
 information of values returned by a function
Date: Mon, 27 Nov 2023 07:27:25 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112653

--- Comment #9 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 24 Nov 2023, hubicka at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112653
>=20
> --- Comment #8 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
> On ARM32 and other targets methods returns this pointer.  Togher with mak=
ing
> return value escape this probably completely disables any chance for IPA
> tracking of C++ data types...

Note that all call and global var escapes would also go to
"return escape", so the only extra bit you get is the reverse,
what escapes the explicit return doesn't escape through calls.
We'd have

RETURN_ESCAPE =3D ESCAPED

And handle return by adding to RETURN_ESCAPED but not ESCAPED.
Then for example DSE needs to properly query whether sth escaped
through function return (ptr_deref_may_alias_global_p & friends).

The cost is an extra bitmap in struct function.

I will have a look if it's reasonably easy to implement.=