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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/106902] [11/12/13 Regression] Program compiled with -O3
 -mfma produces different result
Date: Thu, 29 Sep 2022 06:41:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106902

--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Alexander Monakov from comment #15)
> (In reply to Richard Biener from comment #14)
> > I can't
> > seem to reproduce any vectorization for your smaller example though.
>=20
> My small C samples omit some detail as they were meant to illustrate what
> happened in the IR. Is that a problem?

Not a Problem - it would have made life easier of course ;)

> By the way, I noticed that tree-ssa-math-opts incorrectly handles
> -ffp-contract:
>=20
>   if (FLOAT_TYPE_P (type)
>       && flag_fp_contract_mode =3D=3D FP_CONTRACT_OFF)
>     return false;
>=20
> It should be 'flag_fp_contract_mode !=3D FP_CONTRACT_FAST' instead (the p=
ass
> doesn't have any idea about expression boundaries). It dates back to
> g:1694907238eb

Ah - feel free to fix that (I think such change would be obvious, even bett=
er
when accompanied by a comment).  I do think that since the only way to
preserve expression boundaries is by PAREN_EXPR that the middle-end
shouldn't care about FAST vs. ON (well, it cannot), but the language
frontends need to ensure to emit PAREN_EXPRs for =3DON and omit them for
=3DFAST.

Since we don't implement ON the above check should indeed be changed until
that's fixed.=