isl_basic_map_foreach_lexopt: properly merge partial empty solutions

b9f95db (isl_basic_map_foreach_lexopt: properly merge partial solutions,
Wed Mar 20 09:55:50 2013 +0100) fixed the merging of partial non-empty
solutions, but did not take into account that partial solutions may
be empty.  If the partial solutions are empty, then M is NULL and we
cannot dereference it.

Note that the new test case only triggers on top of d7e5adb
(isl_tab_basic_map_partial_lexopt: better exploit partial solution cache,
Tue Mar 12 17:25:04 2013 +0100) in the master branch.

Reported-by: Tomofumi Yuki <tomofumi.yuki@gmail.com>
Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>

diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index d5ed654..6f4a2a7 100644 (file)
--- a/isl_tab_pip.c
+++ b/isl_tab_pip.c
@@ -124,6 +124,8 @@ struct isl_context_lex {
  * "M" describes the solution in terms of the dimensions of "dom".
  * The number of columns of "M" is one more than the total number
  * of dimensions of "dom".
+ *
+ * If "M" is NULL, then there is no solution on "dom".
  */
 struct isl_partial_sol {
        int level;
@@ -322,11 +324,15 @@ static void sol_pop(struct isl_sol *sol)
                        isl_basic_set_free(partial->next->dom);
                        partial->next->dom = bset;
                        M = partial->next->M;
-                       M = isl_mat_drop_cols(M, M->n_col - n, n);
-                       partial->next->M = M;
+                       if (M) {
+                               M = isl_mat_drop_cols(M, M->n_col - n, n);
+                               partial->next->M = M;
+                               if (!M)
+                                       goto error;
+                       }
                        partial->next->level = sol->level;
 
-                       if (!bset || !M)
+                       if (!bset)
                                goto error;
 
                        sol->partial = partial->next;

diff --git a/isl_test.c b/isl_test.c
index 7c7b695..951ac75 100644 (file)
--- a/isl_test.c
+++ b/isl_test.c
@@ -1534,6 +1534,20 @@ void test_lexmin(struct isl_ctx *ctx)
        assert(isl_map_is_equal(map, map2));
        isl_map_free(map);
        isl_map_free(map2);
+
+       /* Check that empty pieces are properly combined. */
+       str = "[K, N] -> { [x, y] -> [a, b] : K+2<=N<=K+4 and x>=4 and "
+               "2N-6<=x<K+N and N-1<=a<=K+N-1 and N+b-6<=a<=2N-4 and "
+               "b<=2N-3K+a and 3b<=4N-K+1 and b>=N and a>=x+1 }";
+       map = isl_map_read_from_str(ctx, str);
+       map = isl_map_lexmin(map);
+       str = "[K, N] -> { [x, y] -> [1 + x, N] : x >= -6 + 2N and "
+               "x <= -5 + 2N and x >= -1 + 3K - N and x <= -2 + K + N and "
+               "x >= 4 }";
+       map2 = isl_map_read_from_str(ctx, str);
+       assert(isl_map_is_equal(map, map2));
+       isl_map_free(map);
+       isl_map_free(map2);
 }
 
 struct must_may {