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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libquadmath/114140] different results for std::fmin/std::fmax
 and quadmath fminq/fmaxq if one argument=signaling_NaN
Date: Wed, 28 Feb 2024 02:00:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114140

--- Comment #14 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to g.peterhoff from comment #13)
> > The cppreference page is wrong.
> But then *all* of your implementations for fmin/fmax (float, double, long
> double, std::floatN_t) would be wrong, because they give exactly the resu=
lts
> as described on cppreference.
> Is this really the case (which I don't believe)? And if so, that still
> doesn't solve the original problem: std::math-functions and
> quadmath-functions *must* of course return the same results - no matter
> which implementation is correct.

Again read what I mentioned, adding -fsignaling-nans changes the behavior of
std::fmin/fmax even for float/double,etc.
As I mentioned, it is about constant folding of fmin (inside the compiler) =
vs
what the function actually does.

> Is this really the case (which I don't believe)?=20

You can test it yourself by changing const to volatile and you will see it =
is
different in the middle-end's constant folding vs libc's version.

libc (and libquadmath) version is correct based on those 2 sourceware issue=
s.
The question becomes is the constant folding version correct without
-fsignaling-nans ?=