https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78742
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> --- The issue is also that bool cst_and_fits_in_hwi (const_tree x) { return (TREE_CODE (x) == INTEGER_CST && TYPE_PRECISION (TREE_TYPE (x)) <= HOST_BITS_PER_WIDE_INT); } returns false for a __int128 constant of value 1. And that tree-data-ref.c happily uses int's to store the result of int_cst_value.