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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102608] [12 regression] Recent change to VN
 causes bogus Wuninitialized warnings & kernel build failures
Date: Wed, 06 Oct 2021 08:39:21 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102608

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|11.0                        |12.0
   Last reconfirmed|                            |2021-10-06
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot =
gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
>    old32_34 =3D .DEFERRED_INIT (4, 2, 0);
>=20
> ...
>=20
> -  _24 =3D .DEFERRED_INIT (4, 2, 0);
> -  __res =3D{v} _24;
> +  __res =3D{v} old32_34;
>=20
>=20
> # 68 "../arch/mips/include/asm/cmpxchg.h"
> This is due to __typeof(*((volatile u32 *)ptr)) __ret
>=20
>=20
>=20
> The warning is kinda of correct but wrong as it uses the wrong decl :).
>=20
> Fre maybe should be disabled for DEFERRED_INIT ....

Hmm, I did consider that but then I thought it wouldn't matter (there were =
no
testsuite FAILs).

But sure, I can easily make .DEFERRED_INIT always produce a VARYING value.=