add isl_ast_expr_from_val

[platform/upstream/isl.git] / isl_tab_pip.c

diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index d5ed654..2592a28 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;
@@ -3870,6 +3876,24 @@ error:
        sol->error = 1;
 }
 
+/* Does "sol" contain a pair of partial solutions that could potentially
+ * be merged?
+ *
+ * We currently only check that "sol" is not in an error state
+ * and that there are at least two partial solutions of which the final two
+ * are defined at the same level.
+ */
+static int sol_has_mergeable_solutions(struct isl_sol *sol)
+{
+       if (sol->error)
+               return 0;
+       if (!sol->partial)
+               return 0;
+       if (!sol->partial->next)
+               return 0;
+       return sol->partial->level == sol->partial->next->level;
+}
+
 /* Compute the lexicographic minimum of the set represented by the main
  * tableau "tab" within the context "sol->context_tab".
  *
@@ -3880,10 +3904,20 @@ error:
  * corresponding rows may not be marked as being non-negative.
  * In parts of the context where the added equality does not hold,
  * the main tableau is marked as being empty.
+ *
+ * Before we embark on the actual computation, we save a copy
+ * of the context.  When we return, we check if there are any
+ * partial solutions that can potentially be merged.  If so,
+ * we perform a rollback to the initial state of the context.
+ * The merging of partial solutions happens inside calls to
+ * sol_dec_level that are pushed onto the undo stack of the context.
+ * If there are no partial solutions that can potentially be merged
+ * then the rollback is skipped as it would just be wasted effort.
  */
 static void find_solutions_main(struct isl_sol *sol, struct isl_tab *tab)
 {
        int row;
+       void *saved;
 
        if (!tab)
                goto error;
@@ -3933,8 +3967,15 @@ static void find_solutions_main(struct isl_sol *sol, struct isl_tab *tab)
                row = tab->n_redundant - 1;
        }
 
+       saved = sol->context->op->save(sol->context);
+
        find_solutions(sol, tab);
 
+       if (sol_has_mergeable_solutions(sol))
+               sol->context->op->restore(sol->context, saved);
+       else
+               sol->context->op->discard(saved);
+
        sol->level = 0;
        sol_pop(sol);