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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/94497] Branchless clamp in the general case gets a
 branch in a particular case ?
Date: Mon, 06 Apr 2020 16:31:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94497

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64-*-* i?86-*-*

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Hadrien Grasland from comment #5)
> Thanks for the clarifications! We could probably live with
> -fno-signed-zeros, but I think -ffinite-math-only would be too much as an
> application-wide flag, as I've spotted several occurences of the "do the
> computation, then check if the result is normal" pattern around...
>=20
> I tried to experiment with #pragma optimize as a finer-grained alternative
> to a global fast-math flag, which would probably be acceptable. But that
> seemed to have the side-effect of preventing inlining of the functions to
> which the attributes are applied into other functions that don't have it =
(I
> guess that attribute is implemented by splitting the code into multiple
> compilation units?), whereas in this part of the codebase we want all the
> inlining we can get...

Yeah, since the #pragma optimize works at a function level we cannot permit
inlining of functions with conflicting settings...

> So since I don't have the skills and time to work on GCC myself, I guess I
> will need to wait for now and see what you come up with.

There's also the possibility to use XMM intrinsics or simply fmin()/fmax()
(but the latter is only optimized for targets implementing fmin/fmax expand=
ers
which unfortunately x86 doesn't).=