doc: update supported versions of clang
[isl.git] / isl_flow.c
index 6e2a9a3..c083a96 100644 (file)
@@ -16,6 +16,8 @@
  * and Ecole Normale Superieure, 45 rue d'Ulm, 75230 Paris, France
  */
 
+#include <isl/val.h>
+#include <isl/space.h>
 #include <isl/set.h>
 #include <isl/map.h>
 #include <isl/union_set.h>
@@ -23,6 +25,7 @@
 #include <isl/flow.h>
 #include <isl/schedule_node.h>
 #include <isl_sort.h>
+#include <isl/stream.h>
 
 enum isl_restriction_type {
        isl_restriction_type_empty,
@@ -159,10 +162,15 @@ struct isl_labeled_map {
        int             must;
 };
 
+typedef isl_bool (*isl_access_coscheduled)(void *first, void *second);
+
 /* A structure containing the input for dependence analysis:
  * - a sink
  * - n_must + n_may (<= max_source) sources
  * - a function for determining the relative order of sources and sink
+ * - an optional function "coscheduled" for determining whether sources
+ *   may be coscheduled.  If "coscheduled" is NULL, then the sources
+ *   are assumed not to be coscheduled.
  * The must sources are placed before the may sources.
  *
  * domain_map is an auxiliary map that maps the sink access relation
@@ -177,6 +185,7 @@ struct isl_access_info {
        isl_map                         *domain_map;
        struct isl_labeled_map          sink;
        isl_access_level_before         level_before;
+       isl_access_coscheduled          coscheduled;
 
        isl_access_restrict             restrict_fn;
        void                            *restrict_user;
@@ -304,6 +313,13 @@ error:
        return NULL;
 }
 
+/* A helper struct carrying the isl_access_info and an error condition.
+ */
+struct access_sort_info {
+       isl_access_info *access_info;
+       int error;
+};
+
 /* Return -n, 0 or n (with n a positive value), depending on whether
  * the source access identified by p1 should be sorted before, together
  * or after that identified by p2.
@@ -316,10 +332,18 @@ error:
  * If not, we try to order the two statements based on the description
  * of the iteration domains.  This results in an arbitrary, but fairly
  * stable ordering.
+ *
+ * In case of an error, sort_info.error is set to true and all elements are
+ * reported to be equal.
  */
 static int access_sort_cmp(const void *p1, const void *p2, void *user)
 {
-       isl_access_info *acc = user;
+       struct access_sort_info *sort_info = user;
+       isl_access_info *acc = sort_info->access_info;
+
+       if (sort_info->error)
+               return 0;
+
        const struct isl_labeled_map *i1, *i2;
        int level1, level2;
        uint32_t h1, h2;
@@ -327,16 +351,23 @@ static int access_sort_cmp(const void *p1, const void *p2, void *user)
        i2 = (const struct isl_labeled_map *) p2;
 
        level1 = acc->level_before(i1->data, i2->data);
+       if (level1 < 0)
+               goto error;
        if (level1 % 2)
                return -1;
 
        level2 = acc->level_before(i2->data, i1->data);
+       if (level2 < 0)
+               goto error;
        if (level2 % 2)
                return 1;
 
        h1 = isl_map_get_hash(i1->map);
        h2 = isl_map_get_hash(i2->map);
        return h1 > h2 ? 1 : h1 < h2 ? -1 : 0;
+error:
+       sort_info->error = 1;
+       return 0;
 }
 
 /* Sort the must source accesses in their textual order.
@@ -344,13 +375,20 @@ static int access_sort_cmp(const void *p1, const void *p2, void *user)
 static __isl_give isl_access_info *isl_access_info_sort_sources(
        __isl_take isl_access_info *acc)
 {
+       struct access_sort_info sort_info;
+
+       sort_info.access_info = acc;
+       sort_info.error = 0;
+
        if (!acc)
                return NULL;
        if (acc->n_must <= 1)
                return acc;
 
        if (isl_sort(acc->source, acc->n_must, sizeof(struct isl_labeled_map),
-                   access_sort_cmp, acc) < 0)
+                   access_sort_cmp, &sort_info) < 0)
+               return isl_access_info_free(acc);
+       if (sort_info.error)
                return isl_access_info_free(acc);
 
        return acc;
@@ -362,12 +400,21 @@ static __isl_give isl_access_info *isl_access_info_sort_sources(
 static __isl_give isl_space *space_align_and_join(__isl_take isl_space *left,
        __isl_take isl_space *right)
 {
-       if (isl_space_match(left, isl_dim_param, right, isl_dim_param))
+       isl_bool equal_params;
+
+       equal_params = isl_space_has_equal_params(left, right);
+       if (equal_params < 0)
+               goto error;
+       if (equal_params)
                return isl_space_join(left, right);
 
        left = isl_space_align_params(left, isl_space_copy(right));
        right = isl_space_align_params(right, isl_space_copy(left));
        return isl_space_join(left, right);
+error:
+       isl_space_free(left);
+       isl_space_free(right);
+       return NULL;
 }
 
 /* Initialize an empty isl_flow structure corresponding to a given
@@ -401,11 +448,11 @@ static __isl_give isl_flow *isl_flow_alloc(__isl_keep isl_access_info *acc)
 
        dep->n_source = n;
        for (i = 0; i < acc->n_must; ++i) {
-               isl_space *dim;
-               dim = space_align_and_join(
+               isl_space *space;
+               space = space_align_and_join(
                        isl_map_get_space(acc->source[i].map),
                        isl_space_reverse(isl_map_get_space(acc->sink.map)));
-               dep->dep[2 * i].map = isl_map_empty(dim);
+               dep->dep[2 * i].map = isl_map_empty(space);
                dep->dep[2 * i + 1].map = isl_map_copy(dep->dep[2 * i].map);
                dep->dep[2 * i].data = acc->source[i].data;
                dep->dep[2 * i + 1].data = acc->source[i].data;
@@ -415,11 +462,11 @@ static __isl_give isl_flow *isl_flow_alloc(__isl_keep isl_access_info *acc)
                        goto error;
        }
        for (i = acc->n_must; i < acc->n_must + acc->n_may; ++i) {
-               isl_space *dim;
-               dim = space_align_and_join(
+               isl_space *space;
+               space = space_align_and_join(
                        isl_map_get_space(acc->source[i].map),
                        isl_space_reverse(isl_map_get_space(acc->sink.map)));
-               dep->dep[acc->n_must + i].map = isl_map_empty(dim);
+               dep->dep[acc->n_must + i].map = isl_map_empty(space);
                dep->dep[acc->n_must + i].data = acc->source[i].data;
                dep->dep[acc->n_must + i].must = 0;
                if (!dep->dep[acc->n_must + i].map)
@@ -472,12 +519,12 @@ __isl_give isl_map *isl_flow_get_no_source(__isl_keep isl_flow *deps, int must)
                return isl_set_unwrap(isl_set_copy(deps->may_no_source));
 }
 
-void isl_flow_free(__isl_take isl_flow *deps)
+__isl_null isl_flow *isl_flow_free(__isl_take isl_flow *deps)
 {
        int i;
 
        if (!deps)
-               return;
+               return NULL;
        isl_set_free(deps->must_no_source);
        isl_set_free(deps->may_no_source);
        if (deps->dep) {
@@ -486,6 +533,8 @@ void isl_flow_free(__isl_take isl_flow *deps)
                free(deps->dep);
        }
        free(deps);
+
+       return NULL;
 }
 
 isl_ctx *isl_flow_get_ctx(__isl_keep isl_flow *deps)
@@ -503,14 +552,15 @@ isl_ctx *isl_flow_get_ctx(__isl_keep isl_flow *deps)
  * be greater than the loop iterator of the range at the last
  * of the level/2 shared loops, i.e., loop level/2 - 1.
  */
-static __isl_give isl_map *after_at_level(__isl_take isl_space *dim, int level)
+static __isl_give isl_map *after_at_level(__isl_take isl_space *space,
+       int level)
 {
        struct isl_basic_map *bmap;
 
        if (level % 2)
-               bmap = isl_basic_map_equal(dim, level/2);
+               bmap = isl_basic_map_equal(space, level/2);
        else
-               bmap = isl_basic_map_more_at(dim, level/2 - 1);
+               bmap = isl_basic_map_more_at(space, level/2 - 1);
 
        return isl_map_from_basic_map(bmap);
 }
@@ -617,7 +667,7 @@ static struct isl_map *last_later_source(struct isl_access_info *acc,
                                         int k, int after_level,
                                         struct isl_set **empty)
 {
-       isl_space *dim;
+       isl_space *space;
        struct isl_set *set_C;
        struct isl_map *read_map;
        struct isl_map *write_map;
@@ -632,9 +682,9 @@ static struct isl_map *last_later_source(struct isl_access_info *acc,
 
        write_map = isl_map_reverse(write_map);
        dep_map = isl_map_apply_range(read_map, write_map);
-       dim = space_align_and_join(isl_map_get_space(acc->source[k].map),
+       space = space_align_and_join(isl_map_get_space(acc->source[k].map),
                    isl_space_reverse(isl_map_get_space(acc->source[j].map)));
-       after_write = after_at_level(dim, after_level);
+       after_write = after_at_level(space, after_level);
        after_write = isl_map_apply_range(after_write, old_map);
        after_write = isl_map_reverse(after_write);
        dep_map = isl_map_intersect(dep_map, after_write);
@@ -674,24 +724,34 @@ static int can_precede_at_level(int shared_level, int target_level)
  *
  * If temp_rel[j] is empty, then there can be no improvement and
  * we return immediately.
+ *
+ * This function returns isl_stat_ok in case it was executed successfully and
+ * isl_stat_error in case of errors during the execution of this function.
  */
-static int intermediate_sources(__isl_keep isl_access_info *acc,
+static isl_stat intermediate_sources(__isl_keep isl_access_info *acc,
        struct isl_map **temp_rel, int j, int sink_level)
 {
        int k, level;
-       int depth = 2 * isl_map_dim(acc->source[j].map, isl_dim_in) + 1;
+       isl_size n_in = isl_map_dim(acc->source[j].map, isl_dim_in);
+       int depth = 2 * n_in + 1;
 
+       if (n_in < 0)
+               return isl_stat_error;
        if (isl_map_plain_is_empty(temp_rel[j]))
-               return 0;
+               return isl_stat_ok;
 
        for (k = j - 1; k >= 0; --k) {
                int plevel, plevel2;
                plevel = acc->level_before(acc->source[k].data, acc->sink.data);
+               if (plevel < 0)
+                       return isl_stat_error;
                if (!can_precede_at_level(plevel, sink_level))
                        continue;
 
                plevel2 = acc->level_before(acc->source[j].data,
                                                acc->source[k].data);
+               if (plevel2 < 0)
+                       return isl_stat_error;
 
                for (level = sink_level; level <= depth; ++level) {
                        struct isl_map *T;
@@ -714,7 +774,7 @@ static int intermediate_sources(__isl_keep isl_access_info *acc,
                }
        }
 
-       return 0;
+       return isl_stat_ok;
 }
 
 /* Compute all iterations of may source j that precedes the sink at the given
@@ -740,7 +800,7 @@ static __isl_give isl_map *all_sources(__isl_keep isl_access_info *acc,
 }
 
 /* For a given mapping between iterations of must source k and iterations
- * of the sink, compute the all iteration of may source j preceding
+ * of the sink, compute all iterations of may source j preceding
  * the sink at level before_level for any of the sink iterations,
  * but following the corresponding iteration of must source k at level
  * after_level.
@@ -749,7 +809,7 @@ static __isl_give isl_map *all_later_sources(__isl_keep isl_access_info *acc,
        __isl_take isl_map *old_map,
        int j, int before_level, int k, int after_level)
 {
-       isl_space *dim;
+       isl_space *space;
        isl_set *set_C;
        isl_map *read_map;
        isl_map *write_map;
@@ -764,9 +824,10 @@ static __isl_give isl_map *all_later_sources(__isl_keep isl_access_info *acc,
 
        write_map = isl_map_reverse(write_map);
        dep_map = isl_map_apply_range(read_map, write_map);
-       dim = isl_space_join(isl_map_get_space(acc->source[acc->n_must + j].map),
+       space = isl_space_join(isl_map_get_space(
+                   acc->source[acc->n_must + j].map),
                    isl_space_reverse(isl_map_get_space(acc->source[k].map)));
-       after_write = after_at_level(dim, after_level);
+       after_write = after_at_level(space, after_level);
        after_write = isl_map_apply_range(after_write, old_map);
        after_write = isl_map_reverse(after_write);
        dep_map = isl_map_intersect(dep_map, after_write);
@@ -788,9 +849,12 @@ static __isl_give isl_map *all_intermediate_sources(
        int j, int sink_level)
 {
        int k, level;
-       int depth = 2 * isl_map_dim(acc->source[acc->n_must + j].map,
-                                       isl_dim_in) + 1;
+       isl_size n_in = isl_map_dim(acc->source[acc->n_must + j].map,
+                                   isl_dim_in);
+       int depth = 2 * n_in + 1;
 
+       if (n_in < 0)
+               return isl_map_free(map);
        for (k = 0; k < acc->n_must; ++k) {
                int plevel;
 
@@ -800,6 +864,8 @@ static __isl_give isl_map *all_intermediate_sources(
 
                plevel = acc->level_before(acc->source[k].data,
                                        acc->source[acc->n_must + j].data);
+               if (plevel < 0)
+                       return isl_map_free(map);
 
                for (level = sink_level; level <= depth; ++level) {
                        isl_map *T;
@@ -831,6 +897,157 @@ static __isl_give isl_map *all_intermediate_sources(
        return map;
 }
 
+/* Given a dependence relation "old_map" between a must-source and the sink,
+ * return a subset of the dependences, augmented with instances
+ * of the source at position "pos" in "acc" that are coscheduled
+ * with the must-source and that access the same element.
+ * That is, if the input lives in a space T -> K, then the output
+ * lives in the space [T -> S] -> K, with S the space of source "pos", and
+ * the domain factor of the domain product is a subset of the input.
+ * The sources are considered to be coscheduled if they have the same values
+ * for the initial "depth" coordinates.
+ *
+ * First construct a dependence relation S -> K and a mapping
+ * between coscheduled sources T -> S.
+ * The second is combined with the original dependence relation T -> K
+ * to form a relation in T -> [S -> K], which is subsequently
+ * uncurried to [T -> S] -> K.
+ * This result is then intersected with the dependence relation S -> K
+ * to form the output.
+ *
+ * In case a negative depth is given, NULL is returned to indicate an error.
+ */
+static __isl_give isl_map *coscheduled_source(__isl_keep isl_access_info *acc,
+       __isl_keep isl_map *old_map, int pos, int depth)
+{
+       isl_space *space;
+       isl_set *set_C;
+       isl_map *read_map;
+       isl_map *write_map;
+       isl_map *dep_map;
+       isl_map *equal;
+       isl_map *map;
+
+       if (depth < 0)
+               return NULL;
+
+       set_C = isl_map_range(isl_map_copy(old_map));
+       read_map = isl_map_copy(acc->sink.map);
+       read_map = isl_map_intersect_domain(read_map, set_C);
+       write_map = isl_map_copy(acc->source[pos].map);
+       dep_map = isl_map_domain_product(write_map, read_map);
+       dep_map = isl_set_unwrap(isl_map_domain(dep_map));
+       space = isl_space_join(isl_map_get_space(old_map),
+                               isl_space_reverse(isl_map_get_space(dep_map)));
+       equal = isl_map_from_basic_map(isl_basic_map_equal(space, depth));
+       map = isl_map_range_product(equal, isl_map_copy(old_map));
+       map = isl_map_uncurry(map);
+       map = isl_map_intersect_domain_factor_range(map, dep_map);
+
+       return map;
+}
+
+/* After the dependences derived from a must-source have been computed
+ * at a certain level, check if any of the sources of the must-dependences
+ * may be coscheduled with other sources.
+ * If they are any such sources, then there is no way of determining
+ * which of the sources actually comes last and the must-dependences
+ * need to be turned into may-dependences, while dependences from
+ * the other sources need to be added to the may-dependences as well.
+ * "acc" describes the sources and a callback for checking whether
+ * two sources may be coscheduled.  If acc->coscheduled is NULL then
+ * the sources are assumed not to be coscheduled.
+ * "must_rel" and "may_rel" describe the must and may-dependence relations
+ * computed at the current level for the must-sources.  Some of the dependences
+ * may be moved from "must_rel" to "may_rel".
+ * "flow" contains all dependences computed so far (apart from those
+ * in "must_rel" and "may_rel") and may be updated with additional
+ * dependences derived from may-sources.
+ *
+ * In particular, consider all the must-sources with a non-empty
+ * dependence relation in "must_rel".  They are considered in reverse
+ * order because that is the order in which they are considered in the caller.
+ * If any of the must-sources are coscheduled, then the last one
+ * is the one that will have a corresponding dependence relation.
+ * For each must-source i, consider both all the previous must-sources
+ * and all the may-sources.  If any of those may be coscheduled with
+ * must-source i, then compute the coscheduled instances that access
+ * the same memory elements.  The result is a relation [T -> S] -> K.
+ * The projection onto T -> K is a subset of the must-dependence relation
+ * that needs to be turned into may-dependences.
+ * The projection onto S -> K needs to be added to the may-dependences
+ * of source S.
+ * Since a given must-source instance may be coscheduled with several
+ * other source instances, the dependences that need to be turned
+ * into may-dependences are first collected and only actually removed
+ * from the must-dependences after all other sources have been considered.
+ */
+static __isl_give isl_flow *handle_coscheduled(__isl_keep isl_access_info *acc,
+       __isl_keep isl_map **must_rel, __isl_keep isl_map **may_rel,
+       __isl_take isl_flow *flow)
+{
+       int i, j;
+
+       if (!acc->coscheduled)
+               return flow;
+       for (i = acc->n_must - 1; i >= 0; --i) {
+               isl_map *move;
+
+               if (isl_map_plain_is_empty(must_rel[i]))
+                       continue;
+               move = isl_map_empty(isl_map_get_space(must_rel[i]));
+               for (j = i - 1; j >= 0; --j) {
+                       int depth;
+                       isl_bool coscheduled;
+                       isl_map *map, *factor;
+
+                       coscheduled = acc->coscheduled(acc->source[i].data,
+                                                       acc->source[j].data);
+                       if (coscheduled < 0) {
+                               isl_map_free(move);
+                               return isl_flow_free(flow);
+                       }
+                       if (!coscheduled)
+                               continue;
+                       depth = acc->level_before(acc->source[i].data,
+                                               acc->source[j].data) / 2;
+                       map = coscheduled_source(acc, must_rel[i], j, depth);
+                       factor = isl_map_domain_factor_range(isl_map_copy(map));
+                       may_rel[j] = isl_map_union(may_rel[j], factor);
+                       map = isl_map_domain_factor_domain(map);
+                       move = isl_map_union(move, map);
+               }
+               for (j = 0; j < acc->n_may; ++j) {
+                       int depth, pos;
+                       isl_bool coscheduled;
+                       isl_map *map, *factor;
+
+                       pos = acc->n_must + j;
+                       coscheduled = acc->coscheduled(acc->source[i].data,
+                                                       acc->source[pos].data);
+                       if (coscheduled < 0) {
+                               isl_map_free(move);
+                               return isl_flow_free(flow);
+                       }
+                       if (!coscheduled)
+                               continue;
+                       depth = acc->level_before(acc->source[i].data,
+                                               acc->source[pos].data) / 2;
+                       map = coscheduled_source(acc, must_rel[i], pos, depth);
+                       factor = isl_map_domain_factor_range(isl_map_copy(map));
+                       pos = 2 * acc->n_must + j;
+                       flow->dep[pos].map = isl_map_union(flow->dep[pos].map,
+                                                           factor);
+                       map = isl_map_domain_factor_domain(map);
+                       move = isl_map_union(move, map);
+               }
+               must_rel[i] = isl_map_subtract(must_rel[i], isl_map_copy(move));
+               may_rel[i] = isl_map_union(may_rel[i], move);
+       }
+
+       return flow;
+}
+
 /* Compute dependences for the case where all accesses are "may"
  * accesses, which boils down to computing memory based dependences.
  * The generic algorithm would also work in this case, but it would
@@ -854,19 +1071,22 @@ static __isl_give isl_flow *compute_mem_based_dependences(
        for (i = 0; i < acc->n_may; ++i) {
                int plevel;
                int is_before;
-               isl_space *dim;
+               isl_space *space;
                isl_map *before;
                isl_map *dep;
 
                plevel = acc->level_before(acc->source[i].data, acc->sink.data);
+               if (plevel < 0)
+                       goto error;
+
                is_before = plevel & 1;
                plevel >>= 1;
 
-               dim = isl_map_get_space(res->dep[i].map);
+               space = isl_map_get_space(res->dep[i].map);
                if (is_before)
-                       before = isl_map_lex_le_first(dim, plevel);
+                       before = isl_map_lex_le_first(space, plevel);
                else
-                       before = isl_map_lex_lt_first(dim, plevel);
+                       before = isl_map_lex_lt_first(space, plevel);
                dep = isl_map_apply_range(isl_map_copy(acc->source[i].map),
                        isl_map_reverse(isl_map_copy(acc->sink.map)));
                dep = isl_map_intersect(dep, before);
@@ -879,6 +1099,11 @@ static __isl_give isl_flow *compute_mem_based_dependences(
        res->must_no_source = mustdo;
 
        return res;
+error:
+       isl_set_free(mustdo);
+       isl_set_free(maydo);
+       isl_flow_free(res);
+       return NULL;
 }
 
 /* Compute dependences for the case where there is at least one
@@ -908,7 +1133,12 @@ static __isl_give isl_flow *compute_mem_based_dependences(
  * need to be considered.  These iterations are split into those that
  * haven't been matched to any source access (mustdo) and those that have only
  * been matched to may accesses (maydo).
- * At the end of each level, we also consider the may accesses.
+ * At the end of each level, must-sources and may-sources that are coscheduled
+ * with the sources of the must-dependences at that level are considered.
+ * If any coscheduled instances are found, then corresponding may-dependences
+ * are added and the original must-dependences are turned into may-dependences.
+ * Afterwards, the may accesses that occur after must-dependence sources
+ * are considered.
  * In particular, we consider may accesses that precede the remaining
  * sink iterations, moving elements from mustdo to maydo when appropriate,
  * and may accesses that occur between a must source and a sink of any 
@@ -924,6 +1154,7 @@ static __isl_give isl_flow *compute_val_based_dependences(
        isl_set *mustdo = NULL;
        isl_set *maydo = NULL;
        int level, j;
+       isl_size n_in;
        int depth;
        isl_map **must_rel = NULL;
        isl_map **may_rel = NULL;
@@ -936,7 +1167,10 @@ static __isl_give isl_flow *compute_val_based_dependences(
                goto error;
        ctx = isl_map_get_ctx(acc->sink.map);
 
-       depth = 2 * isl_map_dim(acc->sink.map, isl_dim_in) + 1;
+       n_in = isl_map_dim(acc->sink.map, isl_dim_in);
+       if (n_in < 0)
+               goto error;
+       depth = 2 * n_in + 1;
        mustdo = isl_map_domain(isl_map_copy(acc->sink.map));
        maydo = isl_set_empty(isl_set_get_space(mustdo));
        if (!mustdo || !maydo)
@@ -944,8 +1178,8 @@ static __isl_give isl_flow *compute_val_based_dependences(
        if (isl_set_plain_is_empty(mustdo))
                goto done;
 
-       must_rel = isl_alloc_array(ctx, struct isl_map *, acc->n_must);
-       may_rel = isl_alloc_array(ctx, struct isl_map *, acc->n_must);
+       must_rel = isl_calloc_array(ctx, struct isl_map *, acc->n_must);
+       may_rel = isl_calloc_array(ctx, struct isl_map *, acc->n_must);
        if (!must_rel || !may_rel)
                goto error;
 
@@ -964,6 +1198,8 @@ static __isl_give isl_flow *compute_val_based_dependences(
 
                        plevel = acc->level_before(acc->source[j].data,
                                                     acc->sink.data);
+                       if (plevel < 0)
+                               goto error;
                        if (!can_precede_at_level(plevel, level))
                                continue;
 
@@ -971,13 +1207,15 @@ static __isl_give isl_flow *compute_val_based_dependences(
                        must_rel[j] = isl_map_union_disjoint(must_rel[j], T);
                        mustdo = rest;
 
-                       intermediate_sources(acc, must_rel, j, level);
+                       if (intermediate_sources(acc, must_rel, j, level) < 0)
+                               goto error;
 
                        T = last_source(acc, maydo, j, level, &rest);
                        may_rel[j] = isl_map_union_disjoint(may_rel[j], T);
                        maydo = rest;
 
-                       intermediate_sources(acc, may_rel, j, level);
+                       if (intermediate_sources(acc, may_rel, j, level) < 0)
+                               goto error;
 
                        if (isl_set_plain_is_empty(mustdo) &&
                            isl_set_plain_is_empty(maydo))
@@ -988,13 +1226,21 @@ static __isl_give isl_flow *compute_val_based_dependences(
 
                        plevel = acc->level_before(acc->source[j].data,
                                                     acc->sink.data);
+                       if (plevel < 0)
+                               goto error;
                        if (!can_precede_at_level(plevel, level))
                                continue;
 
-                       intermediate_sources(acc, must_rel, j, level);
-                       intermediate_sources(acc, may_rel, j, level);
+                       if (intermediate_sources(acc, must_rel, j, level) < 0)
+                               goto error;
+                       if (intermediate_sources(acc, may_rel, j, level) < 0)
+                               goto error;
                }
 
+               res = handle_coscheduled(acc, must_rel, may_rel, res);
+               if (!res)
+                       goto error;
+
                for (j = 0; j < acc->n_may; ++j) {
                        int plevel;
                        isl_map *T;
@@ -1002,6 +1248,8 @@ static __isl_give isl_flow *compute_val_based_dependences(
 
                        plevel = acc->level_before(acc->source[acc->n_must + j].data,
                                                     acc->sink.data);
+                       if (plevel < 0)
+                               goto error;
                        if (!can_precede_at_level(plevel, level))
                                continue;
 
@@ -1042,6 +1290,12 @@ done:
        res->may_no_source = maydo;
        return res;
 error:
+       if (must_rel)
+               for (j = 0; j < acc->n_must; ++j)
+                       isl_map_free(must_rel[j]);
+       if (may_rel)
+               for (j = 0; j < acc->n_must; ++j)
+                       isl_map_free(may_rel[j]);
        isl_flow_free(res);
        isl_set_free(mustdo);
        isl_set_free(maydo);
@@ -1169,18 +1423,21 @@ static __isl_give struct isl_sched_info *sched_info_alloc(
        __isl_keep isl_map *map)
 {
        isl_ctx *ctx;
-       isl_space *dim;
+       isl_space *space;
        struct isl_sched_info *info;
-       int i, n;
+       int i;
+       isl_size n;
 
        if (!map)
                return NULL;
 
-       dim = isl_space_unwrap(isl_space_domain(isl_map_get_space(map)));
-       if (!dim)
+       space = isl_space_unwrap(isl_space_domain(isl_map_get_space(map)));
+       if (!space)
+               return NULL;
+       n = isl_space_dim(space, isl_dim_in);
+       isl_space_free(space);
+       if (n < 0)
                return NULL;
-       n = isl_space_dim(dim, isl_dim_in);
-       isl_space_free(dim);
 
        ctx = isl_map_get_ctx(map);
        info = isl_alloc_type(ctx, struct isl_sched_info);
@@ -1210,11 +1467,28 @@ error:
        return NULL;
 }
 
+/* The different types of access relations that isl_union_access_info
+ * keeps track of.
+
+ * "isl_access_sink" represents the sink accesses.
+ * "isl_access_must_source" represents the definite source accesses.
+ * "isl_access_may_source" represents the possible source accesses.
+ * "isl_access_kill" represents the kills.
+ *
+ * isl_access_sink is sometimes treated differently and
+ * should therefore appear first.
+ */
+enum isl_access_type {
+       isl_access_sink,
+       isl_access_must_source,
+       isl_access_may_source,
+       isl_access_kill,
+       isl_access_end
+};
+
 /* This structure represents the input for a dependence analysis computation.
  *
- * "sink" represents the sink accesses.
- * "must_source" represents the definite source accesses.
- * "may_source" represents the possible source accesses.
+ * "access" contains the access relations.
  *
  * "schedule" or "schedule_map" represents the execution order.
  * Exactly one of these fields should be NULL.  The other field
@@ -1227,9 +1501,7 @@ error:
  * the "schedule_map" field no longer contains useful information.
  */
 struct isl_union_access_info {
-       isl_union_map *sink;
-       isl_union_map *must_source;
-       isl_union_map *may_source;
+       isl_union_map *access[isl_access_end];
 
        isl_schedule *schedule;
        isl_union_map *schedule_map;
@@ -1240,12 +1512,13 @@ struct isl_union_access_info {
 __isl_null isl_union_access_info *isl_union_access_info_free(
        __isl_take isl_union_access_info *access)
 {
+       enum isl_access_type i;
+
        if (!access)
                return NULL;
 
-       isl_union_map_free(access->sink);
-       isl_union_map_free(access->must_source);
-       isl_union_map_free(access->may_source);
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               isl_union_map_free(access->access[i]);
        isl_schedule_free(access->schedule);
        isl_union_map_free(access->schedule_map);
        free(access);
@@ -1257,85 +1530,174 @@ __isl_null isl_union_access_info *isl_union_access_info_free(
  */
 isl_ctx *isl_union_access_info_get_ctx(__isl_keep isl_union_access_info *access)
 {
-       return access ? isl_union_map_get_ctx(access->sink) : NULL;
+       if (!access)
+               return NULL;
+       return isl_union_map_get_ctx(access->access[isl_access_sink]);
 }
 
-/* Create a new isl_union_access_info with the given sink accesses and
- * and no source accesses or schedule information.
+/* Construct an empty (invalid) isl_union_access_info object.
+ * The caller is responsible for setting the sink access relation and
+ * initializing all the other fields, e.g., by calling
+ * isl_union_access_info_init.
+ */
+static __isl_give isl_union_access_info *isl_union_access_info_alloc(
+       isl_ctx *ctx)
+{
+       return isl_calloc_type(ctx, isl_union_access_info);
+}
+
+/* Initialize all the fields of "info", except the sink access relation,
+ * which is assumed to have been set by the caller.
  *
  * By default, we use the schedule field of the isl_union_access_info,
  * but this may be overridden by a call
  * to isl_union_access_info_set_schedule_map.
  */
+static __isl_give isl_union_access_info *isl_union_access_info_init(
+       __isl_take isl_union_access_info *info)
+{
+       isl_space *space;
+       isl_union_map *empty;
+       enum isl_access_type i;
+
+       if (!info)
+               return NULL;
+       if (!info->access[isl_access_sink])
+               return isl_union_access_info_free(info);
+
+       space = isl_union_map_get_space(info->access[isl_access_sink]);
+       empty = isl_union_map_empty(isl_space_copy(space));
+       for (i = isl_access_sink + 1; i < isl_access_end; ++i)
+               if (!info->access[i])
+                       info->access[i] = isl_union_map_copy(empty);
+       isl_union_map_free(empty);
+       if (!info->schedule && !info->schedule_map)
+               info->schedule = isl_schedule_empty(isl_space_copy(space));
+       isl_space_free(space);
+
+       for (i = isl_access_sink + 1; i < isl_access_end; ++i)
+               if (!info->access[i])
+                       return isl_union_access_info_free(info);
+       if (!info->schedule && !info->schedule_map)
+               return isl_union_access_info_free(info);
+
+       return info;
+}
+
+/* Create a new isl_union_access_info with the given sink accesses and
+ * and no other accesses or schedule information.
+ */
 __isl_give isl_union_access_info *isl_union_access_info_from_sink(
        __isl_take isl_union_map *sink)
 {
        isl_ctx *ctx;
-       isl_space *space;
-       isl_union_map *empty;
        isl_union_access_info *access;
 
        if (!sink)
                return NULL;
        ctx = isl_union_map_get_ctx(sink);
-       access = isl_alloc_type(ctx, isl_union_access_info);
+       access = isl_union_access_info_alloc(ctx);
        if (!access)
                goto error;
-
-       space = isl_union_map_get_space(sink);
-       empty = isl_union_map_empty(isl_space_copy(space));
-       access->sink = sink;
-       access->must_source = isl_union_map_copy(empty);
-       access->may_source = empty;
-       access->schedule = isl_schedule_empty(space);
-       access->schedule_map = NULL;
-
-       if (!access->sink || !access->must_source ||
-           !access->may_source || !access->schedule)
-               return isl_union_access_info_free(access);
-
-       return access;
+       access->access[isl_access_sink] = sink;
+       return isl_union_access_info_init(access);
 error:
        isl_union_map_free(sink);
        return NULL;
 }
 
-/* Replace the definite source accesses of "access" by "must_source".
+/* Replace the access relation of type "type" of "info" by "access".
  */
-__isl_give isl_union_access_info *isl_union_access_info_set_must_source(
-       __isl_take isl_union_access_info *access,
-       __isl_take isl_union_map *must_source)
+static __isl_give isl_union_access_info *isl_union_access_info_set(
+       __isl_take isl_union_access_info *info,
+       enum isl_access_type type, __isl_take isl_union_map *access)
 {
-       if (!access || !must_source)
+       if (!info || !access)
                goto error;
 
-       isl_union_map_free(access->must_source);
-       access->must_source = must_source;
+       isl_union_map_free(info->access[type]);
+       info->access[type] = access;
 
-       return access;
+       return info;
 error:
-       isl_union_access_info_free(access);
-       isl_union_map_free(must_source);
+       isl_union_access_info_free(info);
+       isl_union_map_free(access);
        return NULL;
 }
 
+/* Replace the definite source accesses of "access" by "must_source".
+ */
+__isl_give isl_union_access_info *isl_union_access_info_set_must_source(
+       __isl_take isl_union_access_info *access,
+       __isl_take isl_union_map *must_source)
+{
+       return isl_union_access_info_set(access, isl_access_must_source,
+                                       must_source);
+}
+
 /* Replace the possible source accesses of "access" by "may_source".
  */
 __isl_give isl_union_access_info *isl_union_access_info_set_may_source(
        __isl_take isl_union_access_info *access,
        __isl_take isl_union_map *may_source)
 {
-       if (!access || !may_source)
-               goto error;
+       return isl_union_access_info_set(access, isl_access_may_source,
+                                       may_source);
+}
 
-       isl_union_map_free(access->may_source);
-       access->may_source = may_source;
+/* Replace the kills of "info" by "kill".
+ */
+__isl_give isl_union_access_info *isl_union_access_info_set_kill(
+       __isl_take isl_union_access_info *info, __isl_take isl_union_map *kill)
+{
+       return isl_union_access_info_set(info, isl_access_kill, kill);
+}
 
-       return access;
-error:
-       isl_union_access_info_free(access);
-       isl_union_map_free(may_source);
-       return NULL;
+/* Return the access relation of type "type" of "info".
+ */
+static __isl_give isl_union_map *isl_union_access_info_get(
+       __isl_keep isl_union_access_info *info, enum isl_access_type type)
+{
+       if (!info)
+               return NULL;
+       return isl_union_map_copy(info->access[type]);
+}
+
+/* Return the definite source accesses of "info".
+ */
+__isl_give isl_union_map *isl_union_access_info_get_must_source(
+       __isl_keep isl_union_access_info *info)
+{
+       return isl_union_access_info_get(info, isl_access_must_source);
+}
+
+/* Return the possible source accesses of "info".
+ */
+__isl_give isl_union_map *isl_union_access_info_get_may_source(
+       __isl_keep isl_union_access_info *info)
+{
+       return isl_union_access_info_get(info, isl_access_may_source);
+}
+
+/* Return the kills of "info".
+ */
+__isl_give isl_union_map *isl_union_access_info_get_kill(
+       __isl_keep isl_union_access_info *info)
+{
+       return isl_union_access_info_get(info, isl_access_kill);
+}
+
+/* Does "info" specify any kills?
+ */
+static isl_bool isl_union_access_has_kill(
+       __isl_keep isl_union_access_info *info)
+{
+       isl_bool empty;
+
+       if (!info)
+               return isl_bool_error;
+       empty = isl_union_map_is_empty(info->access[isl_access_kill]);
+       return isl_bool_not(empty);
 }
 
 /* Replace the schedule of "access" by "schedule".
@@ -1384,15 +1746,15 @@ __isl_give isl_union_access_info *isl_union_access_info_copy(
        __isl_keep isl_union_access_info *access)
 {
        isl_union_access_info *copy;
+       enum isl_access_type i;
 
        if (!access)
                return NULL;
        copy = isl_union_access_info_from_sink(
-                               isl_union_map_copy(access->sink));
-       copy = isl_union_access_info_set_must_source(copy,
-                               isl_union_map_copy(access->must_source));
-       copy = isl_union_access_info_set_may_source(copy,
-                               isl_union_map_copy(access->may_source));
+                   isl_union_map_copy(access->access[isl_access_sink]));
+       for (i = isl_access_sink + 1; i < isl_access_end; ++i)
+               copy = isl_union_access_info_set(copy, i,
+                                       isl_union_map_copy(access->access[i]));
        if (access->schedule)
                copy = isl_union_access_info_set_schedule(copy,
                                isl_schedule_copy(access->schedule));
@@ -1403,20 +1765,57 @@ __isl_give isl_union_access_info *isl_union_access_info_copy(
        return copy;
 }
 
-/* Print a key-value pair of a YAML mapping to "p",
- * with key "name" and value "umap".
+#undef BASE
+#define BASE union_map
+#include "print_yaml_field_templ.c"
+
+/* An enumeration of the various keys that may appear in a YAML mapping
+ * of an isl_union_access_info object.
+ * The keys for the access relation types are assumed to have the same values
+ * as the access relation types in isl_access_type.
+ */
+enum isl_ai_key {
+       isl_ai_key_error = -1,
+       isl_ai_key_sink = isl_access_sink,
+       isl_ai_key_must_source = isl_access_must_source,
+       isl_ai_key_may_source = isl_access_may_source,
+       isl_ai_key_kill = isl_access_kill,
+       isl_ai_key_schedule_map,
+       isl_ai_key_schedule,
+       isl_ai_key_end
+};
+
+/* Textual representations of the YAML keys for an isl_union_access_info
+ * object.
+ */
+static char *key_str[] = {
+       [isl_ai_key_sink] = "sink",
+       [isl_ai_key_must_source] = "must_source",
+       [isl_ai_key_may_source] = "may_source",
+       [isl_ai_key_kill] = "kill",
+       [isl_ai_key_schedule_map] = "schedule_map",
+       [isl_ai_key_schedule] = "schedule",
+};
+
+/* Print a key-value pair corresponding to the access relation of type "type"
+ * of a YAML mapping of "info" to "p".
+ *
+ * The sink access relation is always printed, but any other access relation
+ * is only printed if it is non-empty.
  */
-static __isl_give isl_printer *print_union_map_field(__isl_take isl_printer *p,
-       const char *name, __isl_keep isl_union_map *umap)
+static __isl_give isl_printer *print_access_field(__isl_take isl_printer *p,
+       __isl_keep isl_union_access_info *info, enum isl_access_type type)
 {
-       p = isl_printer_print_str(p, name);
-       p = isl_printer_yaml_next(p);
-       p = isl_printer_print_str(p, "\"");
-       p = isl_printer_print_union_map(p, umap);
-       p = isl_printer_print_str(p, "\"");
-       p = isl_printer_yaml_next(p);
+       if (type != isl_access_sink) {
+               isl_bool empty;
 
-       return p;
+               empty = isl_union_map_is_empty(info->access[type]);
+               if (empty < 0)
+                       return isl_printer_free(p);
+               if (empty)
+                       return p;
+       }
+       return print_yaml_field_union_map(p, key_str[type], info->access[type]);
 }
 
 /* Print the information contained in "access" to "p".
@@ -1425,21 +1824,22 @@ static __isl_give isl_printer *print_union_map_field(__isl_take isl_printer *p,
 __isl_give isl_printer *isl_printer_print_union_access_info(
        __isl_take isl_printer *p, __isl_keep isl_union_access_info *access)
 {
+       enum isl_access_type i;
+
        if (!access)
                return isl_printer_free(p);
 
        p = isl_printer_yaml_start_mapping(p);
-       p = print_union_map_field(p, "sink", access->sink);
-       p = print_union_map_field(p, "must_source", access->must_source);
-       p = print_union_map_field(p, "may_source", access->may_source);
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               p = print_access_field(p, access, i);
        if (access->schedule) {
-               p = isl_printer_print_str(p, "schedule");
+               p = isl_printer_print_str(p, key_str[isl_ai_key_schedule]);
                p = isl_printer_yaml_next(p);
                p = isl_printer_print_schedule(p, access->schedule);
                p = isl_printer_yaml_next(p);
        } else {
-               p = print_union_map_field(p, "schedule_map",
-                                               access->schedule_map);
+               p = print_yaml_field_union_map(p,
+                       key_str[isl_ai_key_schedule_map], access->schedule_map);
        }
        p = isl_printer_yaml_end_mapping(p);
 
@@ -1467,6 +1867,125 @@ __isl_give char *isl_union_access_info_to_str(
        return s;
 }
 
+#undef KEY
+#define KEY enum isl_ai_key
+#undef KEY_ERROR
+#define KEY_ERROR isl_ai_key_error
+#undef KEY_END
+#define KEY_END isl_ai_key_end
+#undef KEY_STR
+#define KEY_STR key_str
+#undef KEY_EXTRACT
+#define KEY_EXTRACT extract_key
+#undef KEY_GET
+#define KEY_GET get_key
+#include "extract_key.c"
+
+#undef BASE
+#define BASE union_map
+#include "read_in_string_templ.c"
+
+/* Read an isl_union_access_info object from "s".
+ *
+ * Start off with an empty (invalid) isl_union_access_info object and
+ * then fill up the fields based on the input.
+ * The input needs to contain at least a description of the sink
+ * access relation as well as some form of schedule.
+ * The other access relations are set to empty relations
+ * by isl_union_access_info_init if they are not specified in the input.
+ */
+__isl_give isl_union_access_info *isl_stream_read_union_access_info(
+       isl_stream *s)
+{
+       isl_ctx *ctx;
+       isl_union_access_info *info;
+       isl_bool more;
+       int sink_set = 0;
+       int schedule_set = 0;
+
+       if (isl_stream_yaml_read_start_mapping(s) < 0)
+               return NULL;
+
+       ctx = isl_stream_get_ctx(s);
+       info = isl_union_access_info_alloc(ctx);
+       while ((more = isl_stream_yaml_next(s)) == isl_bool_true) {
+               enum isl_ai_key key;
+               enum isl_access_type type;
+               isl_union_map *access, *schedule_map;
+               isl_schedule *schedule;
+
+               key = get_key(s);
+               if (isl_stream_yaml_next(s) < 0)
+                       return isl_union_access_info_free(info);
+               switch (key) {
+               case isl_ai_key_end:
+               case isl_ai_key_error:
+                       return isl_union_access_info_free(info);
+               case isl_ai_key_sink:
+                       sink_set = 1;
+               case isl_ai_key_must_source:
+               case isl_ai_key_may_source:
+               case isl_ai_key_kill:
+                       type = (enum isl_access_type) key;
+                       access = read_union_map(s);
+                       info = isl_union_access_info_set(info, type, access);
+                       if (!info)
+                               return NULL;
+                       break;
+               case isl_ai_key_schedule_map:
+                       schedule_set = 1;
+                       schedule_map = read_union_map(s);
+                       info = isl_union_access_info_set_schedule_map(info,
+                                                               schedule_map);
+                       if (!info)
+                               return NULL;
+                       break;
+               case isl_ai_key_schedule:
+                       schedule_set = 1;
+                       schedule = isl_stream_read_schedule(s);
+                       info = isl_union_access_info_set_schedule(info,
+                                                               schedule);
+                       if (!info)
+                               return NULL;
+                       break;
+               }
+       }
+       if (more < 0)
+               return isl_union_access_info_free(info);
+
+       if (isl_stream_yaml_read_end_mapping(s) < 0)
+               return isl_union_access_info_free(info);
+
+       if (!sink_set) {
+               isl_stream_error(s, NULL, "no sink specified");
+               return isl_union_access_info_free(info);
+       }
+
+       if (!schedule_set) {
+               isl_stream_error(s, NULL, "no schedule specified");
+               return isl_union_access_info_free(info);
+       }
+
+       return isl_union_access_info_init(info);
+}
+
+/* Read an isl_union_access_info object from the file "input".
+ */
+__isl_give isl_union_access_info *isl_union_access_info_read_from_file(
+       isl_ctx *ctx, FILE *input)
+{
+       isl_stream *s;
+       isl_union_access_info *access;
+
+       s = isl_stream_new_file(ctx, input);
+       if (!s)
+               return NULL;
+       access = isl_stream_read_union_access_info(s);
+       isl_stream_free(s);
+
+       return access;
+}
+
 /* Update the fields of "access" such that they all have the same parameters,
  * keeping in mind that the schedule_map field may be NULL and ignoring
  * the schedule field.
@@ -1475,23 +1994,21 @@ static __isl_give isl_union_access_info *isl_union_access_info_align_params(
        __isl_take isl_union_access_info *access)
 {
        isl_space *space;
+       enum isl_access_type i;
 
        if (!access)
                return NULL;
 
-       space = isl_union_map_get_space(access->sink);
-       space = isl_space_align_params(space,
-                               isl_union_map_get_space(access->must_source));
-       space = isl_space_align_params(space,
-                               isl_union_map_get_space(access->may_source));
+       space = isl_union_map_get_space(access->access[isl_access_sink]);
+       for (i = isl_access_sink + 1; i < isl_access_end; ++i)
+               space = isl_space_align_params(space,
+                               isl_union_map_get_space(access->access[i]));
        if (access->schedule_map)
                space = isl_space_align_params(space,
                                isl_union_map_get_space(access->schedule_map));
-       access->sink = isl_union_map_align_params(access->sink,
-                                                       isl_space_copy(space));
-       access->must_source = isl_union_map_align_params(access->must_source,
-                                                       isl_space_copy(space));
-       access->may_source = isl_union_map_align_params(access->may_source,
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               access->access[i] =
+                       isl_union_map_align_params(access->access[i],
                                                        isl_space_copy(space));
        if (!access->schedule_map) {
                isl_space_free(space);
@@ -1502,8 +2019,9 @@ static __isl_give isl_union_access_info *isl_union_access_info_align_params(
                        return isl_union_access_info_free(access);
        }
 
-       if (!access->sink || !access->must_source || !access->may_source)
-               return isl_union_access_info_free(access);
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               if (!access->access[i])
+                       return isl_union_access_info_free(access);
 
        return access;
 }
@@ -1535,22 +2053,23 @@ isl_union_access_info_introduce_schedule(
        __isl_take isl_union_access_info *access)
 {
        isl_union_map *sm;
+       enum isl_access_type i;
 
        if (!access)
                return NULL;
 
        sm = isl_union_map_reverse(access->schedule_map);
        sm = isl_union_map_range_map(sm);
-       access->sink = isl_union_map_apply_range(isl_union_map_copy(sm),
-                                               access->sink);
-       access->may_source = isl_union_map_apply_range(isl_union_map_copy(sm),
-                                               access->may_source);
-       access->must_source = isl_union_map_apply_range(isl_union_map_copy(sm),
-                                               access->must_source);
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               access->access[i] =
+                       isl_union_map_apply_range(isl_union_map_copy(sm),
+                                               access->access[i]);
        access->schedule_map = sm;
 
-       if (!access->sink || !access->must_source ||
-           !access->may_source || !access->schedule_map)
+       for (i = isl_access_sink; i < isl_access_end; ++i)
+               if (!access->access[i])
+                       return isl_union_access_info_free(access);
+       if (!access->schedule_map)
                return isl_union_access_info_free(access);
 
        return access;
@@ -1829,16 +2348,16 @@ struct isl_compute_flow_data {
 static isl_stat count_matching_array(__isl_take isl_map *map, void *user)
 {
        int eq;
-       isl_space *dim;
+       isl_space *space;
        struct isl_compute_flow_data *data;
 
        data = (struct isl_compute_flow_data *)user;
 
-       dim = isl_space_range(isl_map_get_space(map));
+       space = isl_space_range(isl_map_get_space(map));
 
-       eq = isl_space_is_equal(dim, data->dim);
+       eq = isl_space_is_equal(space, data->dim);
 
-       isl_space_free(dim);
+       isl_space_free(space);
        isl_map_free(map);
 
        if (eq < 0)
@@ -1852,17 +2371,17 @@ static isl_stat count_matching_array(__isl_take isl_map *map, void *user)
 static isl_stat collect_matching_array(__isl_take isl_map *map, void *user)
 {
        int eq;
-       isl_space *dim;
+       isl_space *space;
        struct isl_sched_info *info;
        struct isl_compute_flow_data *data;
 
        data = (struct isl_compute_flow_data *)user;
 
-       dim = isl_space_range(isl_map_get_space(map));
+       space = isl_space_range(isl_map_get_space(map));
 
-       eq = isl_space_is_equal(dim, data->dim);
+       eq = isl_space_is_equal(space, data->dim);
 
-       isl_space_free(dim);
+       isl_space_free(space);
 
        if (eq < 0)
                goto error;
@@ -1901,11 +2420,13 @@ static int before(void *first, void *second)
 {
        struct isl_sched_info *info1 = first;
        struct isl_sched_info *info2 = second;
-       int n1, n2;
+       isl_size n1, n2;
        int i;
 
        n1 = isl_vec_size(info1->cst);
        n2 = isl_vec_size(info2->cst);
+       if (n1 < 0 || n2 < 0)
+               return -1;
 
        if (n2 < n1)
                n1 = n2;
@@ -1930,6 +2451,42 @@ static int before(void *first, void *second)
        return 2 * n1;
 }
 
+/* Check if the given two accesses may be coscheduled.
+ * If so, return isl_bool_true.  Otherwise return isl_bool_false.
+ *
+ * Two accesses may only be coscheduled if the fixed schedule
+ * coordinates have the same values.
+ */
+static isl_bool coscheduled(void *first, void *second)
+{
+       struct isl_sched_info *info1 = first;
+       struct isl_sched_info *info2 = second;
+       isl_size n1, n2;
+       int i;
+
+       n1 = isl_vec_size(info1->cst);
+       n2 = isl_vec_size(info2->cst);
+       if (n1 < 0 || n2 < 0)
+               return isl_bool_error;
+
+       if (n2 < n1)
+               n1 = n2;
+
+       for (i = 0; i < n1; ++i) {
+               int cmp;
+
+               if (!info1->is_cst[i])
+                       continue;
+               if (!info2->is_cst[i])
+                       continue;
+               cmp = isl_vec_cmp_element(info1->cst, info2->cst, i);
+               if (cmp != 0)
+                       return isl_bool_false;
+       }
+
+       return isl_bool_true;
+}
+
 /* Given a sink access, look for all the source accesses that access
  * the same array and perform dataflow analysis on them using
  * isl_access_info_compute_flow_core.
@@ -1969,6 +2526,7 @@ static isl_stat compute_flow(__isl_take isl_map *map, void *user)
        if (!data->sink_info || (data->count && !data->source_info) ||
            !data->accesses)
                goto error;
+       data->accesses->coscheduled = &coscheduled;
        data->count = 0;
        data->must = 1;
        if (isl_union_map_foreach_map(data->must_source,
@@ -2025,6 +2583,69 @@ error:
        return isl_stat_error;
 }
 
+/* Add the kills of "info" to the must-sources.
+ */
+static __isl_give isl_union_access_info *
+isl_union_access_info_add_kill_to_must_source(
+       __isl_take isl_union_access_info *info)
+{
+       isl_union_map *must, *kill;
+
+       must = isl_union_access_info_get_must_source(info);
+       kill = isl_union_access_info_get_kill(info);
+       must = isl_union_map_union(must, kill);
+       return isl_union_access_info_set_must_source(info, must);
+}
+
+/* Drop dependences from "flow" that purely originate from kills.
+ * That is, only keep those dependences that originate from
+ * the original must-sources "must" and/or the original may-sources "may".
+ * In particular, "must" contains the must-sources from before
+ * the kills were added and "may" contains the may-source from before
+ * the kills were removed.
+ *
+ * The dependences are of the form
+ *
+ *     Source -> [Sink -> Data]
+ *
+ * Only those dependences are kept where the Source -> Data part
+ * is a subset of the original may-sources or must-sources.
+ * Of those, only the must-dependences that intersect with the must-sources
+ * remain must-dependences.
+ * If there is some overlap between the may-sources and the must-sources,
+ * then the may-dependences and must-dependences may also overlap.
+ * This should be fine since the may-dependences are only kept
+ * disjoint from the must-dependences for the isl_union_map_compute_flow
+ * interface.  This interface does not support kills, so it will
+ * not end up calling this function.
+ */
+static __isl_give isl_union_flow *isl_union_flow_drop_kill_source(
+       __isl_take isl_union_flow *flow, __isl_take isl_union_map *must,
+       __isl_take isl_union_map *may)
+{
+       isl_union_map *move;
+
+       if (!flow)
+               goto error;
+       move = isl_union_map_copy(flow->must_dep);
+       move = isl_union_map_intersect_range_factor_range(move,
+                               isl_union_map_copy(may));
+       may = isl_union_map_union(may, isl_union_map_copy(must));
+       flow->may_dep = isl_union_map_intersect_range_factor_range(
+                               flow->may_dep, may);
+       flow->must_dep = isl_union_map_intersect_range_factor_range(
+                               flow->must_dep, must);
+       flow->may_dep = isl_union_map_union(flow->may_dep, move);
+       if (!flow->must_dep || !flow->may_dep)
+               return isl_union_flow_free(flow);
+
+       return flow;
+error:
+       isl_union_map_free(must);
+       isl_union_map_free(may);
+       return NULL;
+}
+
 /* Remove the must accesses from the may accesses.
  *
  * A must access always trumps a may access, so there is no need
@@ -2037,9 +2658,10 @@ static __isl_give isl_union_access_info *isl_union_access_info_normalize(
 {
        if (!access)
                return NULL;
-       access->may_source = isl_union_map_subtract(access->may_source,
-                                   isl_union_map_copy(access->must_source));
-       if (!access->may_source)
+       access->access[isl_access_may_source] =
+               isl_union_map_subtract(access->access[isl_access_may_source],
+                   isl_union_map_copy(access->access[isl_access_must_source]));
+       if (!access->access[isl_access_may_source])
                return isl_union_access_info_free(access);
 
        return access;
@@ -2068,18 +2690,20 @@ static __isl_give isl_union_flow *compute_flow_union_map(
        __isl_take isl_union_access_info *access)
 {
        struct isl_compute_flow_data data;
+       isl_union_map *sink;
 
        access = isl_union_access_info_align_params(access);
        access = isl_union_access_info_introduce_schedule(access);
        if (!access)
                return NULL;
 
-       data.must_source = access->must_source;
-       data.may_source = access->may_source;
+       data.must_source = access->access[isl_access_must_source];
+       data.may_source = access->access[isl_access_may_source];
 
-       data.flow = isl_union_flow_alloc(isl_union_map_get_space(access->sink));
+       sink = access->access[isl_access_sink];
+       data.flow = isl_union_flow_alloc(isl_union_map_get_space(sink));
 
-       if (isl_union_map_foreach_map(access->sink, &compute_flow, &data) < 0)
+       if (isl_union_map_foreach_map(sink, &compute_flow, &data) < 0)
                goto error;
 
        data.flow = isl_union_flow_drop_schedule(data.flow);
@@ -2203,31 +2827,32 @@ static isl_bool count_sink_source(__isl_keep isl_schedule_node *node,
        isl_union_set *domain;
        isl_union_map *umap;
        isl_bool r = isl_bool_false;
+       isl_size n;
 
        if (isl_schedule_node_get_type(node) != isl_schedule_node_leaf)
                return isl_bool_true;
 
        domain = isl_schedule_node_get_universe_domain(node);
 
-       umap = isl_union_map_copy(data->access->sink);
+       umap = isl_union_map_copy(data->access->access[isl_access_sink]);
        umap = isl_union_map_intersect_domain(umap, isl_union_set_copy(domain));
-       data->n_sink += isl_union_map_n_map(umap);
+       data->n_sink += n = isl_union_map_n_map(umap);
        isl_union_map_free(umap);
-       if (!umap)
+       if (n < 0)
                r = isl_bool_error;
 
-       umap = isl_union_map_copy(data->access->must_source);
+       umap = isl_union_map_copy(data->access->access[isl_access_must_source]);
        umap = isl_union_map_intersect_domain(umap, isl_union_set_copy(domain));
-       data->n_source += isl_union_map_n_map(umap);
+       data->n_source += n = isl_union_map_n_map(umap);
        isl_union_map_free(umap);
-       if (!umap)
+       if (n < 0)
                r = isl_bool_error;
 
-       umap = isl_union_map_copy(data->access->may_source);
+       umap = isl_union_map_copy(data->access->access[isl_access_may_source]);
        umap = isl_union_map_intersect_domain(umap, isl_union_set_copy(domain));
-       data->n_source += isl_union_map_n_map(umap);
+       data->n_source += n = isl_union_map_n_map(umap);
        isl_union_map_free(umap);
-       if (!umap)
+       if (n < 0)
                r = isl_bool_error;
 
        isl_union_set_free(domain);
@@ -2298,7 +2923,7 @@ static isl_bool collect_sink_source(__isl_keep isl_schedule_node *node,
        prefix = isl_union_map_range_map(prefix);
 
        data->set_sink = 1;
-       umap = isl_union_map_copy(data->access->sink);
+       umap = isl_union_map_copy(data->access->access[isl_access_sink]);
        umap = isl_union_map_apply_range(isl_union_map_copy(prefix), umap);
        if (isl_union_map_foreach_map(umap, &extract_sink_source, data) < 0)
                r = isl_bool_error;
@@ -2306,7 +2931,7 @@ static isl_bool collect_sink_source(__isl_keep isl_schedule_node *node,
 
        data->set_sink = 0;
        data->must = 1;
-       umap = isl_union_map_copy(data->access->must_source);
+       umap = isl_union_map_copy(data->access->access[isl_access_must_source]);
        umap = isl_union_map_apply_range(isl_union_map_copy(prefix), umap);
        if (isl_union_map_foreach_map(umap, &extract_sink_source, data) < 0)
                r = isl_bool_error;
@@ -2314,7 +2939,7 @@ static isl_bool collect_sink_source(__isl_keep isl_schedule_node *node,
 
        data->set_sink = 0;
        data->must = 0;
-       umap = isl_union_map_copy(data->access->may_source);
+       umap = isl_union_map_copy(data->access->access[isl_access_may_source]);
        umap = isl_union_map_apply_range(isl_union_map_copy(prefix), umap);
        if (isl_union_map_foreach_map(umap, &extract_sink_source, data) < 0)
                r = isl_bool_error;
@@ -2346,21 +2971,27 @@ static int before_node(void *first, void *second)
        isl_schedule_node *node1 = first;
        isl_schedule_node *node2 = second;
        isl_schedule_node *shared;
-       int depth;
+       isl_size depth;
        int before = 0;
 
        shared = isl_schedule_node_get_shared_ancestor(node1, node2);
-       if (!shared)
+       depth = isl_schedule_node_get_schedule_depth(shared);
+       if (depth < 0) {
+               isl_schedule_node_free(shared);
                return -1;
+       }
 
-       depth = isl_schedule_node_get_schedule_depth(shared);
        if (isl_schedule_node_get_type(shared) == isl_schedule_node_sequence) {
-               int pos1, pos2;
+               isl_size pos1, pos2;
 
                pos1 = isl_schedule_node_get_ancestor_child_position(node1,
                                                                    shared);
                pos2 = isl_schedule_node_get_ancestor_child_position(node2,
                                                                    shared);
+               if (pos1 < 0 || pos2 < 0) {
+                       isl_schedule_node_free(shared);
+                       return -1;
+               }
                before = pos1 < pos2;
        }
 
@@ -2369,6 +3000,19 @@ static int before_node(void *first, void *second)
        return 2 * depth + before;
 }
 
+/* Check if the given two accesses may be coscheduled.
+ * If so, return isl_bool_true.  Otherwise return isl_bool_false.
+ *
+ * Two accesses may only be coscheduled if they appear in the same leaf.
+ */
+static isl_bool coscheduled_node(void *first, void *second)
+{
+       isl_schedule_node *node1 = first;
+       isl_schedule_node *node2 = second;
+
+       return isl_bool_ok(node1 == node2);
+}
+
 /* Add the scheduled sources from "data" that access
  * the same data space as "sink" to "access".
  */
@@ -2439,6 +3083,8 @@ static __isl_give isl_union_flow *compute_single_flow(
 
        access = isl_access_info_alloc(isl_map_copy(sink->access), sink->node,
                                        &before_node, data->n_source);
+       if (access)
+               access->coscheduled = &coscheduled_node;
        access = add_matching_sources(access, sink, data);
 
        flow = access_info_compute_flow_core(access);
@@ -2496,6 +3142,7 @@ static __isl_give isl_union_flow *compute_flow_schedule(
        struct isl_compute_flow_schedule_data data = { access };
        int i, n;
        isl_ctx *ctx;
+       isl_space *space;
        isl_union_flow *flow;
 
        ctx = isl_union_access_info_get_ctx(access);
@@ -2518,7 +3165,8 @@ static __isl_give isl_union_flow *compute_flow_schedule(
                                            &collect_sink_source, &data) < 0)
                goto error;
 
-       flow = isl_union_flow_alloc(isl_union_map_get_space(access->sink));
+       space = isl_union_map_get_space(access->access[isl_access_sink]);
+       flow = isl_union_flow_alloc(space);
 
        isl_compute_flow_schedule_data_align_params(&data);
 
@@ -2547,20 +3195,44 @@ error:
  * map domain elements of access->{may,must)_source to
  * domain elements of access->sink.
  *
+ * If any kills have been specified, then they are treated as
+ * must-sources internally.  Any dependence that purely derives
+ * from an original kill is removed from the output.
+ *
  * We check whether the schedule is available as a schedule tree
- * or a schedule map and call the correpsonding function to perform
+ * or a schedule map and call the corresponding function to perform
  * the analysis.
  */
 __isl_give isl_union_flow *isl_union_access_info_compute_flow(
        __isl_take isl_union_access_info *access)
 {
+       isl_bool has_kill;
+       isl_union_map *must = NULL, *may = NULL;
+       isl_union_flow *flow;
+
+       has_kill = isl_union_access_has_kill(access);
+       if (has_kill < 0)
+               goto error;
+       if (has_kill) {
+               must = isl_union_access_info_get_must_source(access);
+               may = isl_union_access_info_get_may_source(access);
+       }
+       access = isl_union_access_info_add_kill_to_must_source(access);
        access = isl_union_access_info_normalize(access);
        if (!access)
-               return NULL;
+               goto error;
        if (access->schedule)
-               return compute_flow_schedule(access);
+               flow = compute_flow_schedule(access);
        else
-               return compute_flow_union_map(access);
+               flow = compute_flow_union_map(access);
+       if (has_kill)
+               flow = isl_union_flow_drop_kill_source(flow, must, may);
+       return flow;
+error:
+       isl_union_access_info_free(access);
+       isl_union_map_free(must);
+       isl_union_map_free(may);
+       return NULL;
 }
 
 /* Print the information contained in "flow" to "p".
@@ -2575,13 +3247,16 @@ __isl_give isl_printer *isl_printer_print_union_flow(
                return isl_printer_free(p);
 
        p = isl_printer_yaml_start_mapping(p);
-       p = print_union_map_field(p, "must_dependence", flow->must_dep);
-       umap = isl_union_flow_get_may_dependence(flow);
-       p = print_union_map_field(p, "may_dependence", umap);
+       umap = isl_union_flow_get_full_must_dependence(flow);
+       p = print_yaml_field_union_map(p, "must_dependence", umap);
+       isl_union_map_free(umap);
+       umap = isl_union_flow_get_full_may_dependence(flow);
+       p = print_yaml_field_union_map(p, "may_dependence", umap);
        isl_union_map_free(umap);
-       p = print_union_map_field(p, "must_no_source", flow->must_no_source);
+       p = print_yaml_field_union_map(p, "must_no_source",
+                                       flow->must_no_source);
        umap = isl_union_flow_get_may_no_source(flow);
-       p = print_union_map_field(p, "may_no_source", umap);
+       p = print_yaml_field_union_map(p, "may_no_source", umap);
        isl_union_map_free(umap);
        p = isl_printer_yaml_end_mapping(p);