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From: "anlauf at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/103707] Stray "Array operands are incommensurate"
Date: Sun, 26 Jun 2022 21:21:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103707

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-06-26
                 CC|                            |anlauf at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #6 from anlauf at gcc dot gnu.org ---
(In reply to Thomas Koenig from comment #5)
> Thanks for the quick reduction, Gerhard.
>=20
> This originally came from something like
>=20
> program p
>    real, parameter :: fmin(1) =3D 0.
>    real, parameter :: fmax(1) =3D 1.
>    real :: x(1)
>    where (fmin <=3D 0)
>       x =3D fmin + (fmax-fmin)
>    elsewhere
>       x =3D (fmax/fmin)**2
>    end where
>    print *,x
> end
>=20
> so there is no division by zero at runtime.

Some data points from other compiler that reject the code:

NAG prints

NAG Fortran Compiler Release 7.0(Yurakucho) Build 7009
Error: pr103707.f90, line 8: Floating-point divide by zero


Cray versions 10 thru 14 print:

      x =3D (fmax/fmin)**2
               ^=20=20=20=20=20=20=20=20=20
ftn-1184 crayftn: WARNING P, File =3D pr103707.f90, Line =3D 8, Column =3D =
16=20
  Evaluation of this constant expression produced a NaN or other abnormal
value.
                     ^=20=20=20
ftn-1184 crayftn: WARNING P, File =3D pr103707.f90, Line =3D 8, Column =3D =
22=20
  Evaluation of this constant expression produced a NaN or other abnormal
value.

Cray Fortran : Version 14.0.0
(20220420160222_c98838affc7b58fed2a72f164d77c35e1bc8772f)


Intel and Nvidia are silent.

While gfortran's error message is misleading, what is our plan?
Avoid simplification in the frontend?=