X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=isl_tab_pip.c;h=2592a285c0e179164254439f4b2c0e0d84bd12ed;hb=63fb8a7f484648c3caa25351c8c94ac2395ec563;hp=8d16d5ca5c8a56f22ea03af296013d7c1edbeb84;hpb=1d767927d11158fe8370e53ef83d79995b2b7bce;p=platform%2Fupstream%2Fisl.git

diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index 8d16d5c..2592a28 100644
--- a/isl_tab_pip.c
+++ b/isl_tab_pip.c
@@ -119,6 +119,14 @@ struct isl_context_lex {
 	struct isl_tab *tab;
 };
 
+/* A stack (linked list) of solutions of subtrees of the search space.
+ *
+ * "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;
 	struct isl_basic_set *dom;
@@ -307,15 +315,26 @@ static void sol_pop(struct isl_sol *sol)
 			sol_pop_one(sol);
 		} else {
 			struct isl_basic_set *bset;
+			isl_mat *M;
+			unsigned n;
 
+			n = isl_basic_set_dim(partial->next->dom, isl_dim_div);
+			n -= n_div;
 			bset = sol_domain(sol);
-			if (!bset)
-				goto error;
-
 			isl_basic_set_free(partial->next->dom);
 			partial->next->dom = bset;
+			M = partial->next->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)
+				goto error;
+
 			sol->partial = partial->next;
 			isl_basic_set_free(partial->dom);
 			isl_mat_free(partial->M);
@@ -2597,6 +2616,14 @@ error:
 	return NULL;
 }
 
+/* Representation of the context when using generalized basis reduction.
+ *
+ * "shifted" contains the offsets of the unit hypercubes that lie inside the
+ * context.  Any rational point in "shifted" can therefore be rounded
+ * up to an integer point in the context.
+ * If the context is constrained by any equality, then "shifted" is not used
+ * as it would be empty.
+ */
 struct isl_context_gbr {
 	struct isl_context context;
 	struct isl_tab *tab;
@@ -2820,6 +2847,15 @@ error:
 	return NULL;
 }
 
+/* Add the equality described by "eq" to the context.
+ * If "check" is set, then we check if the context is empty after
+ * adding the equality.
+ * If "update" is set, then we check if the samples are still valid.
+ *
+ * We do not explicitly add shifted copies of the equality to
+ * cgbr->shifted since they would conflict with each other.
+ * Instead, we directly mark cgbr->shifted empty.
+ */
 static void context_gbr_add_eq(struct isl_context *context, isl_int *eq,
 		int check, int update)
 {
@@ -2827,6 +2863,11 @@ static void context_gbr_add_eq(struct isl_context *context, isl_int *eq,
 
 	cgbr->tab = add_gbr_eq(cgbr->tab, eq);
 
+	if (cgbr->shifted && !cgbr->shifted->empty && use_shifted(cgbr)) {
+		if (isl_tab_mark_empty(cgbr->shifted) < 0)
+			goto error;
+	}
+
 	if (cgbr->cone && cgbr->cone->n_col != cgbr->cone->n_dead) {
 		if (isl_tab_extend_cons(cgbr->cone, 2) < 0)
 			goto error;
@@ -3100,7 +3141,9 @@ static int context_gbr_detect_equalities(struct isl_context *context,
 
 	n_ineq = cgbr->tab->bmap->n_ineq;
 	cgbr->tab = isl_tab_detect_equalities(cgbr->tab, cgbr->cone);
-	if (cgbr->tab && cgbr->tab->bmap->n_ineq > n_ineq)
+	if (!cgbr->tab)
+		return -1;
+	if (cgbr->tab->bmap->n_ineq > n_ineq)
 		propagate_equalities(cgbr, tab, n_ineq);
 
 	return 0;
@@ -3833,6 +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".
  *
@@ -3843,10 +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;
@@ -3896,8 +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);