static void mark_ptr_or_null_reg(struct bpf_func_state *state,
				 struct bpf_reg_state *reg, u32 id,
				 bool is_null)
{
	if (type_may_be_null(reg->type) && reg->id == id &&
	    !WARN_ON_ONCE(!reg->id)) {
		if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
				 !tnum_equals_const(reg->var_off, 0) ||
				 reg->off)) {
			/* Old offset (both fixed and variable parts) should
			 * have been known-zero, because we don't allow pointer
			 * arithmetic on pointers that might be NULL. If we
			 * see this happening, don't convert the register.
			 */
			return;
		}
		if (is_null) {
			reg->type = SCALAR_VALUE;
			/* We don't need id and ref_obj_id from this point
			 * onwards anymore, thus we should better reset it,
			 * so that state pruning has chances to take effect.
			 */
			reg->id = 0;
			reg->ref_obj_id = 0;

			return;
		}

		mark_ptr_not_null_reg(reg);

		if (!reg_may_point_to_spin_lock(reg)) {
			/* For not-NULL ptr, reg->ref_obj_id will be reset
			 * in release_reg_references().
			 *
			 * reg->id is still used by spin_lock ptr. Other
			 * than spin_lock ptr type, reg->id can be reset.
			 */
			reg->id = 0;
		}
	}
}