add isl_map_fast_is_single_valued

This is mainly meant to deal with the easy cases in isl_map_is_single_valued.

Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>

diff --git a/isl_map.c b/isl_map.c
index c8b15aa..41d2ca0 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -7463,6 +7463,56 @@ int isl_basic_set_dims_get_sign(__isl_keep isl_basic_set *bset,
        return isl_basic_set_vars_get_sign(bset, first, n, signs);
 }
 
+/* Check if the given basic map is obviously single-valued.
+ * In particular, for each output dimension, check that there is
+ * an equality that defines the output dimension in terms of
+ * earlier dimensions.
+ */
+int isl_basic_map_fast_is_single_valued(__isl_keep isl_basic_map *bmap)
+{
+       int i, j;
+       unsigned total;
+       unsigned n_out;
+       unsigned o_out;
+
+       if (!bmap)
+               return -1;
+
+       total = 1 + isl_basic_map_total_dim(bmap);
+       n_out = isl_basic_map_dim(bmap, isl_dim_out);
+       o_out = isl_basic_map_offset(bmap, isl_dim_out);
+
+       for (i = 0; i < n_out; ++i) {
+               for (j = 0; j < bmap->n_eq; ++j) {
+                       if (isl_int_is_zero(bmap->eq[j][o_out + i]))
+                               continue;
+                       if (isl_seq_first_non_zero(bmap->eq[j] + o_out + i + 1,
+                                               total - (o_out + i + 1)) == -1)
+                               break;
+               }
+               if (j >= bmap->n_eq)
+                       return 0;
+       }
+
+       return 1;
+}
+
+/* Check if the given map is obviously single-valued.
+ */
+int isl_map_fast_is_single_valued(__isl_keep isl_map *map)
+{
+       int sv;
+
+       if (!map)
+               return -1;
+       if (map->n == 0)
+               return 1;
+       if (map->n >= 2)
+               return 0;
+
+       return isl_basic_map_fast_is_single_valued(map->p[0]);
+}
+
 /* Check if the given map is single-valued.
  * We simply compute
  *
@@ -7476,6 +7526,10 @@ int isl_map_is_single_valued(__isl_keep isl_map *map)
        isl_map *id;
        int sv;
 
+       sv = isl_map_fast_is_single_valued(map);
+       if (sv < 0 || sv)
+               return sv;
+
        test = isl_map_reverse(isl_map_copy(map));
        test = isl_map_apply_range(test, isl_map_copy(map));