isl_affine_hull.c: outside_point: check for obvious candidate first

diff --git a/isl_affine_hull.c b/isl_affine_hull.c
index 9666e20..39075a9 100644 (file)
--- a/isl_affine_hull.c
+++ b/isl_affine_hull.c
@@ -232,6 +232,11 @@ error:
  * Otherwise, look for a point satisfying -e(x) - 1 >= 0 (i.e., e(x) <= -1).
  * The point, if found, is returned as a singleton set.
  * If no point can be found, the empty set is returned.
+ *
+ * Before solving an ILP problem, we first check if simply
+ * adding the normal of the constraint to one of the known
+ * integer points in the basic set yields another point
+ * inside the basic set.
  */
 static struct isl_basic_set *outside_point(struct isl_ctx *ctx,
        struct isl_basic_set *bset, isl_int *eq, int up)
@@ -242,10 +247,22 @@ static struct isl_basic_set *outside_point(struct isl_ctx *ctx,
        unsigned dim;
        int k;
 
+       dim = isl_basic_set_n_dim(bset);
+       sample = isl_vec_alloc(ctx, 1 + dim);
+       if (!sample)
+               return NULL;
+       isl_int_set_si(sample->block.data[0], 1);
+       isl_seq_combine(sample->block.data + 1,
+               ctx->one, bset->sample->block.data + 1,
+               up ? ctx->one : ctx->negone, eq + 1, dim);
+       if (isl_basic_set_contains(bset, sample))
+               return isl_basic_set_from_vec(ctx, sample);
+       isl_vec_free(ctx, sample);
+       sample = NULL;
+
        slice = isl_basic_set_copy(bset);
        if (!slice)
                goto error;
-       dim = isl_basic_set_n_dim(slice);
        slice = isl_basic_set_cow(slice);
        slice = isl_basic_set_extend(slice, 0, dim, 0, 0, 1);
        k = isl_basic_set_alloc_inequality(slice);