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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/106902] [11/12/13/14 Regression] Program compiled with
 -O3 -mfma produces different result
Date: Wed, 17 May 2023 18:49:02 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106902

--- Comment #22 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Created attachment 55105
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D55105&action=3Dedit
patch 1/3

(In reply to Richard Biener from comment #21)
>=20
> Sounds reasonable.  Though I wouldn't use GENERIC folding but instead
> some folding-like code in c-family/ that for example would get invoked
> by genericization or via the gimplification hook?  If we'd add GENERIC
> folding in fold-const.cc or match.pd the chance is that it will pick up
> FMAs "late".

Agreed, thank you. I'm working on it. The attached patch implements this via
c_gimplify_expr and passes bootstrap+regtest under 'configure
--with-cpu=3Dznver2' (i.e. with fma available by default).=