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From: "sgk at troutmask dot apl.washington.edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/95053] [11 regression] ICE in f951: gfc_divide()
Date: Thu, 14 May 2020 17:08:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95053

--- Comment #23 from Steve Kargl <sgk at troutmask dot apl.washington.edu> =
---
On Thu, May 14, 2020 at 02:57:37PM +0000, wschmidt at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95053
>=20
> Bill Schmidt <wschmidt at gcc dot gnu.org> changed:
>=20
>            What    |Removed                     |Added
> -------------------------------------------------------------------------=
---
>                  CC|                            |wschmidt at gcc dot gnu.=
org
>=20
> --- Comment #22 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
> Breaking legitimate code, even if "borderline," does not seem right to me=
.=20=20
> Zero division is generally a runtime exception because of such cases.
>=20
> You write code for a general case, then later you discover "oh, well, we =
could
> make this variable zero for our specific usage," and now the compiler thr=
ows a
> fit?  Seems like this is warning-level stuff.
>=20

If Bill's reduction of the several thousand-line file to 10ish
lines is an accurate reduction (and I have no reasons to doubt
that it isn't), then no.  It is an programming error.  This is
not the first time that gfortran has found a programming error
in WRF.  Sure, in this case the 'if (cdleps > 0)' leads to dead
code elimination, but DCE happens after gfortran has done some
constant folding and common subexpression elimination in the
front-end.=