[Bug middle-end/128313] -fsignaling-nans: x != 1.0 with a signaling NaN x is folded at -O1 and above, so FE_INVALID is not raised

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128313

Drea Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2026-10-30
     Ever confirmed|0                           |1

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---

Setting value number of x.0_1 to  Nan (changed)
Replaced x with  Nan in all uses of x.0_1 = x;
Value numbering stmt = _2 = x.0_1 != 1.0e+0;
Match-and-simplified x.0_1 != 1.0e+0 to 1
RHS x.0_1 != 1.0e+0 simplified to 1


That is fold_relational_const does not have a check for signaling nans.

Needs something like:
      /* Don't perform operation if we honor signaling NaNs and
         either operand is a signaling NaN.  */
      if (HONOR_SNANS (mode)
          && (REAL_VALUE_ISSIGNALING_NAN (c0)
              || REAL_VALUE_ISSIGNALING_NAN (c1)))
        return NULL_TREE;

Under:
      /* Handle the cases where either operand is a NaN.  */