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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/106785] ICE in fail, at selftest.cc:47 since
 r13-2266-g8bb1df032cc080
Date: Wed, 31 Aug 2022 12:41:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106785

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
If !MODE_HAS_NANS, then NANs can't appear ever, that is the VAX case.
Some floating point formats simply have no representation for those.
If MODE_HAS_NANS && !HONOR_NANS, it is user promising NaNs won't appear but=
 the
floating point format supports them.  Code where NaN would appear is UB, we=
 can
do anything we want, just shouldn't break code where the NaN wouldn't appea=
r at
runtime.  Say
if (cond)
  x =3D __builtin_nan ("");
else
  x =3D 1.24;
we can assume that x will never be NaN with -ffinite-math-only.=