Index: gcc-interface/utils.c =================================================================== --- gcc-interface/utils.c (revision 251700) +++ gcc-interface/utils.c (working copy) @@ -5257,20 +5257,26 @@ unchecked_convert (tree type, tree expr, ? TYPE_RM_SIZE (etype) : TYPE_SIZE (etype)) == 0))) { - tree base_type - = gnat_type_for_size (TREE_INT_CST_LOW (TYPE_SIZE (type)), - type_unsigned_for_rm (type)); - tree shift_expr - = convert (base_type, - size_binop (MINUS_EXPR, - TYPE_SIZE (type), TYPE_RM_SIZE (type))); - expr - = convert (type, - build_binary_op (RSHIFT_EXPR, base_type, - build_binary_op (LSHIFT_EXPR, base_type, - convert (base_type, expr), - shift_expr), - shift_expr)); + if (integer_zerop (TYPE_RM_SIZE (type))) + expr = build_int_cst (type, 0); + else + { + tree base_type + = gnat_type_for_size (TREE_INT_CST_LOW (TYPE_SIZE (type)), + type_unsigned_for_rm (type)); + tree shift_expr + = convert (base_type, + size_binop (MINUS_EXPR, + TYPE_SIZE (type), TYPE_RM_SIZE (type))); + expr + = convert (type, + build_binary_op (RSHIFT_EXPR, base_type, + build_binary_op (LSHIFT_EXPR, base_type, + convert (base_type, + expr), + shift_expr), + shift_expr)); + } } /* An unchecked conversion should never raise Constraint_Error. The code