+/* Remove divs that do not appear in the quasi-polynomial, nor in any
+ * of the divs that do appear in the quasi-polynomial.
+ */
+static __isl_give isl_qpolynomial *remove_redundant_divs(
+ __isl_take isl_qpolynomial *qp)
+{
+ int i, j;
+ int d;
+ int len;
+ int skip;
+ int *active = NULL;
+ int *reordering = NULL;
+ int redundant = 0;
+ int n_div;
+ isl_ctx *ctx;
+
+ if (!qp)
+ return NULL;
+ if (qp->div->n_row == 0)
+ return qp;
+
+ d = isl_space_dim(qp->dim, isl_dim_all);
+ len = qp->div->n_col - 2;
+ ctx = isl_qpolynomial_get_ctx(qp);
+ active = isl_calloc_array(ctx, int, len);
+ if (!active)
+ goto error;
+
+ if (up_set_active(qp->upoly, active, len) < 0)
+ goto error;
+
+ for (i = qp->div->n_row - 1; i >= 0; --i) {
+ if (!active[d + i]) {
+ redundant = 1;
+ continue;
+ }
+ for (j = 0; j < i; ++j) {
+ if (isl_int_is_zero(qp->div->row[i][2 + d + j]))
+ continue;
+ active[d + j] = 1;
+ break;
+ }
+ }
+
+ if (!redundant) {
+ free(active);
+ return qp;
+ }
+
+ reordering = isl_alloc_array(qp->div->ctx, int, len);
+ if (!reordering)
+ goto error;
+
+ for (i = 0; i < d; ++i)
+ reordering[i] = i;
+
+ skip = 0;
+ n_div = qp->div->n_row;
+ for (i = 0; i < n_div; ++i) {
+ if (!active[d + i]) {
+ qp->div = isl_mat_drop_rows(qp->div, i - skip, 1);
+ qp->div = isl_mat_drop_cols(qp->div,
+ 2 + d + i - skip, 1);
+ skip++;
+ }
+ reordering[d + i] = d + i - skip;
+ }
+
+ qp->upoly = reorder(qp->upoly, reordering);
+
+ if (!qp->upoly || !qp->div)
+ goto error;
+
+ free(active);
+ free(reordering);
+
+ return qp;
+error:
+ free(active);
+ free(reordering);
+ isl_qpolynomial_free(qp);
+ return NULL;
+}
+