isl_basic_map_gist: also exploit equalities in gisted set

Some inequalities in the gisted set may only be redundant
wrt the context inside the affine hull of the gisted set.
Although we did add the equalities to the (combined) context
before checking for redundancy, we did not perform any kind
of simplification in the combined context.
In particular, we did not perform any Gaussian elimination,
confusing the heuristic in isl_basic_map_constraint_is_redundant.

diff --git a/isl_map.c b/isl_map.c
index 89f8c84..396b2a8 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -4915,6 +4915,60 @@ error:
        return bset;
 }
 
+static struct isl_basic_set *uset_gist(struct isl_basic_set *bset,
+       struct isl_basic_set *context);
+
+static struct isl_basic_set *uset_gist_context_eq(struct isl_basic_set *bset,
+       struct isl_basic_set *context)
+{
+       struct isl_mat *T;
+       struct isl_mat *T2;
+       struct isl_ctx *ctx = context->ctx;
+       struct isl_basic_set *reduced_context;
+       reduced_context = isl_basic_set_remove_equalities(
+                               isl_basic_set_copy(context), &T, &T2);
+       if (!reduced_context)
+               goto error;
+       bset = isl_basic_set_preimage(ctx, bset, T);
+       bset = uset_gist(bset, reduced_context);
+       bset = isl_basic_set_preimage(ctx, bset, T2);
+       bset = isl_basic_set_reduce_using_equalities(bset, context);
+       return bset;
+error:
+       isl_basic_set_free(context);
+       isl_basic_set_free(bset);
+       return NULL;
+}
+
+static struct isl_basic_set *uset_gist_set_eq(struct isl_basic_set *bset,
+       struct isl_basic_set *context)
+{
+       struct isl_mat *T;
+       struct isl_mat *T2;
+       struct isl_ctx *ctx = context->ctx;
+       struct isl_basic_set *affine_hull = NULL;
+
+       affine_hull = isl_basic_set_copy(bset);
+       affine_hull = isl_basic_set_cow(affine_hull);
+       if (!affine_hull)
+               goto error;
+       isl_basic_set_free_inequality(affine_hull, affine_hull->n_ineq);
+
+       bset = isl_basic_set_remove_equalities(bset, &T, &T2);
+       if (!bset)
+               goto error;
+       context = isl_basic_set_preimage(ctx, context, T);
+       bset = uset_gist(bset, context);
+       bset = isl_basic_set_preimage(ctx, bset, T2);
+       bset = isl_basic_set_intersect(bset, affine_hull);
+       return bset;
+error:
+       isl_basic_set_free(affine_hull);
+       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
@@ -4932,23 +4986,12 @@ static struct isl_basic_set *uset_gist(struct isl_basic_set *bset,
        if (!bset || !context)
                goto error;
 
-       if (context->n_eq > 0) {
-               struct isl_mat *T;
-               struct isl_mat *T2;
-               struct isl_ctx *ctx = context->ctx;
-               struct isl_basic_set *reduced_context;
-               reduced_context = isl_basic_set_remove_equalities(
-                                       isl_basic_set_copy(context), &T, &T2);
-               if (!reduced_context)
-                       goto error;
-               bset = isl_basic_set_preimage(ctx, bset, T);
-               bset = uset_gist(bset, reduced_context);
-               bset = isl_basic_set_preimage(ctx, bset, T2);
-               bset = isl_basic_set_reduce_using_equalities(bset, context);
-               return bset;
-       }
+       if (context->n_eq > 0)
+               return uset_gist_context_eq(bset, context);
        if (!context->n_ineq)
                goto done;
+       if (bset->n_eq > 0)
+               return uset_gist_set_eq(bset, context);
        bset = remove_shifted_constraints(bset, context);
        combined = isl_basic_set_extend_constraints(isl_basic_set_copy(bset),
                        context->n_eq, context->n_ineq);