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From: "malat at debian dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/110622] x87: Miscompilation at O2 level (O1 is working)
Date: Thu, 21 Sep 2023 13:42:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110622

--- Comment #14 from Mathieu Malaterre <malat at debian dot org> ---
(In reply to Andrew Pinski from comment #13)
> (In reply to Mathieu Malaterre from comment #12)
> > I am seeing a difference in result (log1p computation) in the range:
> >=20
> > 4318952042648305665 - 0x1.0000000000001p-64
> > 4368493837572636672 - 0x1.002p-53
> >=20
> > the other values seems to match expectation of log1p computation.
>=20
> But you used excess-precision=3Dfast
>=20
> *** This bug has been marked as a duplicate of bug 323 ***

AFAIK bug #323 does not mention my trick:

  asm volatile("" : "+r"(y.raw[0]) : : "memory");

That simple line totally changed the optimizer code generation.=