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From: "juergen.reuter at desy dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/110311] [14 Regression] regression in
 tree-optimizer
Date: Sat, 24 Jun 2023 13:04:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110311

--- Comment #16 from J=C3=BCrgen Reuter <juergen.reuter at desy dot de> ---
It seems that it is this function where the NaNs appear:
  function mult_mod (a, b, c, m) result (v)
    real(default), intent(in) :: a
    real(default), intent(in) :: b
    real(default), intent(in) :: c
    real(default), intent(in) :: m
    real(default) :: v
    integer :: a1
    real(default) :: a2
    v =3D a * b + c
    if (v >=3D two53 .or. v <=3D -two53) then
       a1 =3D int (a / two17)
       a2 =3D a - a1 * two17
       v =3D mod (a1 * b, m)
       v =3D v * two17 + a2 * b + c
    end if
    v =3D mod (v, m)
    if (v < 0.0_default) v =3D v + m
  end function mult_mod

particularly mod (v, m) gets evaluated to NaN, even if a replace it with
v =3D mod (v0, m) to avoid potential aliasing problems. It appears only in =
a very
complex setup, not in a 100 line program.=