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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/107190] [aarch64] regression with optimization
 -fexpensive-optimizations
Date: Mon, 10 Oct 2022 16:54:43 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107190

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |rtl-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to vfdff from comment #0)
> This case is simplify from
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107090, and we can see tha=
t the
> codegen of function `test_m` has some regression with optimization
> -fexpensive-optimizations, https://gcc.godbolt.org/z/zbKrEox4j
>=20
> This is because the pass 208t.widening_mul is controlled by
> -fexpensive-optimizations (default on at -O3), it conversion
>=20
> ```
>   m_12 =3D m_9 + m1_10;
>   if (m1_10 > m_12)
> ```
> into
>=20
> ```
>   _17 =3D .ADD_OVERFLOW (m_9, m1_10);
>   m_12 =3D REALPART_EXPR <_17>;
>   _18 =3D IMAGPART_EXPR <_17>;
>   if (_18 !=3D 0)``

This should always be better. If ifcvt.cc does not handle this case, then it
should be improved.=