+ isl_basic_set_free(context);
+ isl_basic_set_free(bset);
+ return NULL;
+}
+
+/* Remove all information from bset that is redundant in the context
+ * of context. In particular, equalities that are linear combinations
+ * of those in context are removed. Then the inequalities that are
+ * redundant in the context of the equalities and inequalities of
+ * context are removed.
+ *
+ * First of all, we drop those constraints from "context"
+ * that are irrelevant for computing the gist of "bset".
+ * Alternatively, we could factorize the intersection of "context" and "bset".
+ *
+ * We first compute the integer affine hull of the intersection,
+ * compute the gist inside this affine hull and then add back
+ * those equalities that are not implied by the context.
+ *
+ * If two constraints are mutually redundant, then uset_gist_full
+ * will remove the second of those constraints. We therefore first
+ * sort the constraints so that constraints not involving existentially
+ * quantified variables are given precedence over those that do.
+ * We have to perform this sorting before the variable compression,
+ * because that may effect the order of the variables.
+ */
+static __isl_give isl_basic_set *uset_gist(__isl_take isl_basic_set *bset,
+ __isl_take isl_basic_set *context)
+{
+ isl_mat *eq;
+ isl_mat *T, *T2;
+ isl_basic_set *aff;
+ isl_basic_set *aff_context;
+ unsigned total;
+
+ if (!bset || !context)
+ goto error;
+
+ context = drop_irrelevant_constraints(context, bset);
+
+ bset = isl_basic_set_intersect(bset, isl_basic_set_copy(context));
+ if (isl_basic_set_plain_is_empty(bset)) {
+ isl_basic_set_free(context);
+ return bset;
+ }
+ bset = isl_basic_set_sort_constraints(bset);
+ aff = isl_basic_set_affine_hull(isl_basic_set_copy(bset));
+ if (!aff)
+ goto error;
+ if (isl_basic_set_plain_is_empty(aff)) {
+ isl_basic_set_free(aff);
+ isl_basic_set_free(context);
+ return bset;
+ }
+ if (aff->n_eq == 0) {
+ isl_basic_set_free(aff);
+ return uset_gist_full(bset, context);
+ }
+ total = isl_basic_set_total_dim(bset);
+ eq = isl_mat_sub_alloc6(bset->ctx, aff->eq, 0, aff->n_eq, 0, 1 + total);
+ eq = isl_mat_cow(eq);
+ T = isl_mat_variable_compression(eq, &T2);
+ if (T && T->n_col == 0) {
+ isl_mat_free(T);
+ isl_mat_free(T2);
+ isl_basic_set_free(context);
+ isl_basic_set_free(aff);
+ return isl_basic_set_set_to_empty(bset);
+ }
+
+ aff_context = isl_basic_set_affine_hull(isl_basic_set_copy(context));
+
+ bset = isl_basic_set_preimage(bset, isl_mat_copy(T));
+ context = isl_basic_set_preimage(context, T);
+
+ bset = uset_gist_full(bset, context);
+ bset = isl_basic_set_preimage(bset, T2);
+ bset = isl_basic_set_intersect(bset, aff);
+ bset = isl_basic_set_reduce_using_equalities(bset, aff_context);
+
+ if (bset) {
+ ISL_F_SET(bset, ISL_BASIC_SET_NO_IMPLICIT);
+ ISL_F_SET(bset, ISL_BASIC_SET_NO_REDUNDANT);
+ }
+
+ return bset;
+error: