https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103406
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- We are folding (1.79769313486231570814527423731704356798070567525844996599e+308 * 2.0e+0) - (1.79769313486231570814527423731704356798070567525844996599e+308 * 2.0e+0) to 0.0 via (simplify (minus @0 @0) (if (!FLOAT_TYPE_P (type) || !tree_expr_maybe_nan_p (@0)) { build_zero_cst (type); })) but appearantly even Inf - Inf is not zero.