add isl_qpolynomial_fold_scale_val

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

diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index 6f4a2a7..2592a28 100644 (file)
--- a/isl_tab_pip.c
+++ b/isl_tab_pip.c
@@ -3876,6 +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".
  *
@@ -3886,10 +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;
@@ -3939,8 +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);