]> git.ipfire.org Git - thirdparty/gcc.git/blobdiff - libgomp/task.c
nvptx: In mkoffload.cc, call diagnostic_color_init + gcc_init_libintl: Restore 'libgo...
[thirdparty/gcc.git] / libgomp / task.c
index d3d72663f35c0762a2f4c0557240350eb08c9dd5..e2d7f21de62b3fb182a55adbfd2c47659a49cf7d 100644 (file)
@@ -1,7 +1,8 @@
-/* Copyright (C) 2007, 2008, 2009, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2007-2024 Free Software Foundation, Inc.
    Contributed by Richard Henderson <rth@redhat.com>.
 
-   This file is part of the GNU OpenMP Library (libgomp).
+   This file is part of the GNU Offloading and Multi Processing Library
+   (libgomp).
 
    Libgomp is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-/* This file handles the maintainence of tasks in response to task
+/* This file handles the maintenance of tasks in response to task
    creation and termination.  */
 
 #include "libgomp.h"
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
+#include "gomp-constants.h"
 
+typedef struct gomp_task_depend_entry *hash_entry_type;
+
+static inline void *
+htab_alloc (size_t size)
+{
+  return gomp_malloc (size);
+}
+
+static inline void
+htab_free (void *ptr)
+{
+  free (ptr);
+}
+
+#include "hashtab.h"
+
+static inline hashval_t
+htab_hash (hash_entry_type element)
+{
+  return hash_pointer (element->addr);
+}
+
+static inline bool
+htab_eq (hash_entry_type x, hash_entry_type y)
+{
+  return x->addr == y->addr;
+}
 
 /* Create a new task data structure.  */
 
@@ -36,14 +66,30 @@ void
 gomp_init_task (struct gomp_task *task, struct gomp_task *parent_task,
                struct gomp_task_icv *prev_icv)
 {
+  /* It would seem that using memset here would be a win, but it turns
+     out that partially filling gomp_task allows us to keep the
+     overhead of task creation low.  In the nqueens-1.c test, for a
+     sufficiently large N, we drop the overhead from 5-6% to 1%.
+
+     Note, the nqueens-1.c test in serial mode is a good test to
+     benchmark the overhead of creating tasks as there are millions of
+     tiny tasks created that all run undeferred.  */
   task->parent = parent_task;
+  priority_queue_init (&task->children_queue);
+  task->taskgroup = NULL;
+  task->dependers = NULL;
+  task->depend_hash = NULL;
+  task->taskwait = NULL;
+  task->depend_all_memory = NULL;
+  task->depend_count = 0;
+  task->completion_sem = NULL;
+  task->deferred_p = false;
   task->icv = *prev_icv;
   task->kind = GOMP_TASK_IMPLICIT;
-  task->in_taskwait = false;
   task->in_tied_task = false;
   task->final_task = false;
-  task->children = NULL;
-  gomp_sem_init (&task->taskwait_sem, 0);
+  task->copy_ctors_done = false;
+  task->parent_depends_on = false;
 }
 
 /* Clean up a task, after completing it.  */
@@ -58,30 +104,399 @@ gomp_end_task (void)
   thr->task = task->parent;
 }
 
+/* Clear the parent field of every task in LIST.  */
+
 static inline void
-gomp_clear_parent (struct gomp_task *children)
+gomp_clear_parent_in_list (struct priority_list *list)
 {
-  struct gomp_task *task = children;
-
-  if (task)
+  struct priority_node *p = list->tasks;
+  if (p)
     do
       {
-       task->parent = NULL;
-       task = task->next_child;
+       priority_node_to_task (PQ_CHILDREN, p)->parent = NULL;
+       p = p->next;
       }
-    while (task != children);
+    while (p != list->tasks);
+}
+
+/* Splay tree version of gomp_clear_parent_in_list.
+
+   Clear the parent field of every task in NODE within SP, and free
+   the node when done.  */
+
+static void
+gomp_clear_parent_in_tree (prio_splay_tree sp, prio_splay_tree_node node)
+{
+  if (!node)
+    return;
+  prio_splay_tree_node left = node->left, right = node->right;
+  gomp_clear_parent_in_list (&node->key.l);
+#if _LIBGOMP_CHECKING_
+  memset (node, 0xaf, sizeof (*node));
+#endif
+  /* No need to remove the node from the tree.  We're nuking
+     everything, so just free the nodes and our caller can clear the
+     entire splay tree.  */
+  free (node);
+  gomp_clear_parent_in_tree (sp, left);
+  gomp_clear_parent_in_tree (sp, right);
+}
+
+/* Clear the parent field of every task in Q and remove every task
+   from Q.  */
+
+static inline void
+gomp_clear_parent (struct priority_queue *q)
+{
+  if (priority_queue_multi_p (q))
+    {
+      gomp_clear_parent_in_tree (&q->t, q->t.root);
+      /* All the nodes have been cleared in gomp_clear_parent_in_tree.
+        No need to remove anything.  We can just nuke everything.  */
+      q->t.root = NULL;
+    }
+  else
+    gomp_clear_parent_in_list (&q->l);
+}
+
+/* Helper function for GOMP_task and gomp_create_target_task.
+
+   For a TASK with in/out dependencies, fill in the various dependency
+   queues.  PARENT is the parent of said task.  DEPEND is as in
+   GOMP_task.  */
+
+static void
+gomp_task_handle_depend (struct gomp_task *task, struct gomp_task *parent,
+                        void **depend)
+{
+  size_t ndepend = (uintptr_t) depend[0];
+  size_t i;
+  hash_entry_type ent;
+  bool all_memory = false;
+
+  if (ndepend)
+    {
+      /* depend[0] is total # */
+      size_t nout = (uintptr_t) depend[1]; /* # of out: and inout: */
+      /* ndepend - nout is # of in: */
+      for (i = 0; i < ndepend; i++)
+       {
+         task->depend[i].addr = depend[2 + i];
+         task->depend[i].is_in = i >= nout;
+         all_memory |= i < nout && depend[2 + i] == NULL;
+       }
+    }
+  else
+    {
+      ndepend = (uintptr_t) depend[1]; /* total # */
+      size_t nout = (uintptr_t) depend[2]; /* # of out: and inout: */
+      size_t nmutexinoutset = (uintptr_t) depend[3]; /* # of mutexinoutset: */
+      /* For now we treat mutexinoutset like out, which is compliant, but
+        inefficient.  */
+      size_t nin = (uintptr_t) depend[4]; /* # of in: */
+      /* ndepend - nout - nmutexinoutset - nin is # of depobjs */
+      size_t normal = nout + nmutexinoutset + nin;
+      size_t n = 0;
+      bool has_in = false;
+      for (i = normal; i < ndepend; i++)
+       {
+         void **d = (void **) (uintptr_t) depend[5 + i];
+         switch ((uintptr_t) d[1])
+           {
+           case GOMP_DEPEND_OUT:
+           case GOMP_DEPEND_INOUT:
+             all_memory |= d[0] == NULL;
+             break;
+           case GOMP_DEPEND_MUTEXINOUTSET:
+             break;
+           case GOMP_DEPEND_IN:
+           case GOMP_DEPEND_INOUTSET:
+             has_in = true;
+             continue;
+           default:
+             gomp_fatal ("unknown omp_depend_t dependence type %d",
+                         (int) (uintptr_t) d[1]);
+           }
+         task->depend[n].addr = d[0];
+         task->depend[n++].is_in = 0;
+       }
+      for (i = 0; i < normal; i++)
+       {
+         task->depend[n].addr = depend[5 + i];
+         task->depend[n++].is_in = i >= nout + nmutexinoutset;
+       }
+      if (has_in)
+       for (i = normal; i < ndepend; i++)
+         {
+           void **d = (void **) (uintptr_t) depend[5 + i];
+           if ((uintptr_t) d[1] != GOMP_DEPEND_IN
+               && (uintptr_t) d[1] != GOMP_DEPEND_INOUTSET)
+             continue;
+           task->depend[n].addr = d[0];
+           task->depend[n++].is_in
+             = 1 + ((uintptr_t) d[1] == GOMP_DEPEND_INOUTSET);
+         }
+    }
+  task->num_dependees = 0;
+  if (__builtin_expect (parent->depend_all_memory && ndepend, false))
+    {
+      struct gomp_task *tsk = parent->depend_all_memory;
+      if (tsk->dependers == NULL)
+       {
+         tsk->dependers
+           = gomp_malloc (sizeof (struct gomp_dependers_vec)
+                          + 6 * sizeof (struct gomp_task *));
+         tsk->dependers->n_elem = 1;
+         tsk->dependers->allocated = 6;
+         tsk->dependers->elem[0] = task;
+       }
+      else
+       {
+         if (tsk->dependers->n_elem == tsk->dependers->allocated)
+           {
+             tsk->dependers->allocated
+               = tsk->dependers->allocated * 2 + 2;
+             tsk->dependers
+               = gomp_realloc (tsk->dependers,
+                               sizeof (struct gomp_dependers_vec)
+                               + (tsk->dependers->allocated
+                                  * sizeof (struct gomp_task *)));
+           }
+         tsk->dependers->elem[tsk->dependers->n_elem++] = task;
+       }
+      task->num_dependees++;
+    }
+  if (__builtin_expect (all_memory, false))
+    {
+      /* A task with depend(inout: omp_all_memory) depends on all previous
+        sibling tasks which have any dependencies and all later sibling
+        tasks which have any dependencies depend on it.  */
+      task->depend_count = 1;
+      task->depend[0].addr = NULL;
+      task->depend[0].next = NULL;
+      task->depend[0].prev = NULL;
+      task->depend[0].task = task;
+      task->depend[0].redundant = true;
+      task->depend[0].redundant_out = false;
+      if (parent->depend_hash)
+       {
+         /* Inlined htab_traverse + htab_clear.  All newer siblings can
+            just depend on this task.  Add dependencies on all previous
+            sibling tasks with dependencies and make them redundant and
+            clear the hash table.  */
+         hash_entry_type *slot = &parent->depend_hash->entries[0];
+         hash_entry_type *end = slot + htab_size (parent->depend_hash);
+         for (; slot != end; ++slot)
+           {
+             if (*slot == HTAB_EMPTY_ENTRY)
+               continue;
+             if (*slot != HTAB_DELETED_ENTRY)
+               {
+                 for (ent = *slot; ent; ent = ent->next)
+                   {
+                     struct gomp_task *tsk = ent->task;
+
+                     if (ent->redundant_out)
+                       break;
+
+                     ent->redundant = true;
+                     if (tsk->dependers == NULL)
+                       {
+                         tsk->dependers
+                           = gomp_malloc (sizeof (struct gomp_dependers_vec)
+                                          + 6 * sizeof (struct gomp_task *));
+                         tsk->dependers->n_elem = 1;
+                         tsk->dependers->allocated = 6;
+                         tsk->dependers->elem[0] = task;
+                         task->num_dependees++;
+                         continue;
+                       }
+                     /* We already have some other dependency on tsk from
+                        earlier depend clause.  */
+                     else if (tsk->dependers->n_elem
+                              && (tsk->dependers->elem[tsk->dependers->n_elem
+                                                       - 1] == task))
+                       continue;
+                     else if (tsk->dependers->n_elem
+                              == tsk->dependers->allocated)
+                       {
+                         tsk->dependers->allocated
+                           = tsk->dependers->allocated * 2 + 2;
+                         tsk->dependers
+                           = gomp_realloc (tsk->dependers,
+                                           sizeof (struct gomp_dependers_vec)
+                                           + (tsk->dependers->allocated
+                                              * sizeof (struct gomp_task *)));
+                       }
+                     tsk->dependers->elem[tsk->dependers->n_elem++] = task;
+                     task->num_dependees++;
+                   }
+                 while (ent)
+                   {
+                     ent->redundant = true;
+                     ent = ent->next;
+                   }
+               }
+             *slot = HTAB_EMPTY_ENTRY;
+           }
+         if (htab_size (parent->depend_hash) <= 32)
+           {
+             parent->depend_hash->n_elements = 0;
+             parent->depend_hash->n_deleted = 0;
+           }
+         else
+           {
+             /* Shrink the hash table if it would be too large.
+                We don't want to walk e.g. megabytes of empty hash
+                table for every depend(inout: omp_all_memory).  */
+             free (parent->depend_hash);
+             parent->depend_hash = htab_create (12);
+           }
+       }
+      parent->depend_all_memory = task;
+      return;
+    }
+  task->depend_count = ndepend;
+  if (parent->depend_hash == NULL)
+    parent->depend_hash = htab_create (2 * ndepend > 12 ? 2 * ndepend : 12);
+  for (i = 0; i < ndepend; i++)
+    {
+      task->depend[i].next = NULL;
+      task->depend[i].prev = NULL;
+      task->depend[i].task = task;
+      task->depend[i].redundant = false;
+      task->depend[i].redundant_out = false;
+
+      hash_entry_type *slot = htab_find_slot (&parent->depend_hash,
+                                             &task->depend[i], INSERT);
+      hash_entry_type out = NULL, last = NULL;
+      if (*slot)
+       {
+         /* If multiple depends on the same task are the same, all but the
+            first one are redundant.  As inout/out come first, if any of them
+            is inout/out, it will win, which is the right semantics.  */
+         if ((*slot)->task == task)
+           {
+             task->depend[i].redundant = true;
+             continue;
+           }
+         for (ent = *slot; ent; ent = ent->next)
+           {
+             if (ent->redundant_out)
+               break;
+
+             last = ent;
+
+             /* depend(in:...) doesn't depend on earlier depend(in:...).
+                Similarly depend(inoutset:...) doesn't depend on earlier
+                depend(inoutset:...).  */
+             if (task->depend[i].is_in && task->depend[i].is_in == ent->is_in)
+               continue;
+
+             if (!ent->is_in)
+               out = ent;
+
+             struct gomp_task *tsk = ent->task;
+             if (tsk->dependers == NULL)
+               {
+                 tsk->dependers
+                   = gomp_malloc (sizeof (struct gomp_dependers_vec)
+                                  + 6 * sizeof (struct gomp_task *));
+                 tsk->dependers->n_elem = 1;
+                 tsk->dependers->allocated = 6;
+                 tsk->dependers->elem[0] = task;
+                 task->num_dependees++;
+                 continue;
+               }
+             /* We already have some other dependency on tsk from earlier
+                depend clause.  */
+             else if (tsk->dependers->n_elem
+                      && (tsk->dependers->elem[tsk->dependers->n_elem - 1]
+                          == task))
+               continue;
+             else if (tsk->dependers->n_elem == tsk->dependers->allocated)
+               {
+                 tsk->dependers->allocated
+                   = tsk->dependers->allocated * 2 + 2;
+                 tsk->dependers
+                   = gomp_realloc (tsk->dependers,
+                                   sizeof (struct gomp_dependers_vec)
+                                   + (tsk->dependers->allocated
+                                      * sizeof (struct gomp_task *)));
+               }
+             tsk->dependers->elem[tsk->dependers->n_elem++] = task;
+             task->num_dependees++;
+           }
+         task->depend[i].next = *slot;
+         (*slot)->prev = &task->depend[i];
+       }
+      *slot = &task->depend[i];
+
+      /* There is no need to store more than one depend({,in}out:) task per
+        address in the hash table chain for the purpose of creation of
+        deferred tasks, because each out depends on all earlier outs, thus it
+        is enough to record just the last depend({,in}out:).  For depend(in:),
+        we need to keep all of the previous ones not terminated yet, because
+        a later depend({,in}out:) might need to depend on all of them.  So, if
+        the new task's clause is depend({,in}out:), we know there is at most
+        one other depend({,in}out:) clause in the list (out).  For
+        non-deferred tasks we want to see all outs, so they are moved to the
+        end of the chain, after first redundant_out entry all following
+        entries should be redundant_out.  */
+      if (!task->depend[i].is_in && out)
+       {
+         if (out != last)
+           {
+             out->next->prev = out->prev;
+             out->prev->next = out->next;
+             out->next = last->next;
+             out->prev = last;
+             last->next = out;
+             if (out->next)
+               out->next->prev = out;
+           }
+         out->redundant_out = true;
+       }
+    }
+}
+
+/* Body of empty task like taskwait nowait depend.  */
+
+static void
+empty_task (void *data __attribute__((unused)))
+{
 }
 
+static void gomp_task_run_post_handle_depend_hash (struct gomp_task *);
+static inline size_t gomp_task_run_post_handle_depend (struct gomp_task *,
+                                                      struct gomp_team *);
+
 /* Called when encountering an explicit task directive.  If IF_CLAUSE is
    false, then we must not delay in executing the task.  If UNTIED is true,
-   then the task may be executed by any member of the team.  */
+   then the task may be executed by any member of the team.
+
+   DEPEND is an array containing:
+     if depend[0] is non-zero, then:
+       depend[0]: number of depend elements.
+       depend[1]: number of depend elements of type "out/inout".
+       depend[2..N+1]: address of [1..N]th depend element.
+     otherwise, when depend[0] is zero, then:
+       depend[1]: number of depend elements.
+       depend[2]: number of depend elements of type "out/inout".
+       depend[3]: number of depend elements of type "mutexinoutset".
+       depend[4]: number of depend elements of type "in".
+       depend[5..4+depend[2]+depend[3]+depend[4]]: address of depend elements
+       depend[5+depend[2]+depend[3]+depend[4]..4+depend[1]]: address of
+                  omp_depend_t objects.  */
 
 void
 GOMP_task (void (*fn) (void *), void *data, void (*cpyfn) (void *, void *),
-          long arg_size, long arg_align, bool if_clause, unsigned flags)
+          long arg_size, long arg_align, bool if_clause, unsigned flags,
+          void **depend, int priority_arg, void *detach)
 {
   struct gomp_thread *thr = gomp_thread ();
   struct gomp_team *team = thr->ts.team;
+  int priority = 0;
 
 #ifdef HAVE_BROKEN_POSIX_SEMAPHORES
   /* If pthread_mutex_* is used for omp_*lock*, then each task must be
@@ -90,21 +505,72 @@ GOMP_task (void (*fn) (void *), void *data, void (*cpyfn) (void *, void *),
      might be running on different thread than FN.  */
   if (cpyfn)
     if_clause = false;
-  if (flags & 1)
-    flags &= ~1;
+  flags &= ~GOMP_TASK_FLAG_UNTIED;
 #endif
 
+  /* If parallel or taskgroup has been cancelled, don't start new tasks.  */
+  if (__builtin_expect (gomp_cancel_var, 0) && team)
+    {
+      if (gomp_team_barrier_cancelled (&team->barrier))
+       return;
+      if (thr->task->taskgroup)
+       {
+         if (thr->task->taskgroup->cancelled)
+           return;
+         if (thr->task->taskgroup->workshare
+             && thr->task->taskgroup->prev
+             && thr->task->taskgroup->prev->cancelled)
+           return;
+       }
+    }
+
+  if (__builtin_expect ((flags & GOMP_TASK_FLAG_PRIORITY) != 0, 0))
+    {
+      priority = priority_arg;
+      if (priority > gomp_max_task_priority_var)
+       priority = gomp_max_task_priority_var;
+    }
+
   if (!if_clause || team == NULL
       || (thr->task && thr->task->final_task)
       || team->task_count > 64 * team->nthreads)
     {
       struct gomp_task task;
+      gomp_sem_t completion_sem;
+
+      /* If there are depend clauses and earlier deferred sibling tasks
+        with depend clauses, check if there isn't a dependency.  If there
+        is, we need to wait for them.  There is no need to handle
+        depend clauses for non-deferred tasks other than this, because
+        the parent task is suspended until the child task finishes and thus
+        it can't start further child tasks.  */
+      if ((flags & GOMP_TASK_FLAG_DEPEND)
+         && thr->task && thr->task->depend_hash)
+       gomp_task_maybe_wait_for_dependencies (depend);
 
       gomp_init_task (&task, thr->task, gomp_icv (false));
-      task.kind = GOMP_TASK_IFFALSE;
-      task.final_task = (thr->task && thr->task->final_task) || (flags & 2);
+      task.kind = GOMP_TASK_UNDEFERRED;
+      task.final_task = (thr->task && thr->task->final_task)
+                       || (flags & GOMP_TASK_FLAG_FINAL);
+      task.priority = priority;
+
+      if ((flags & GOMP_TASK_FLAG_DETACH) != 0)
+       {
+         gomp_sem_init (&completion_sem, 0);
+         task.completion_sem = &completion_sem;
+         *(void **) detach = &task;
+         if (data)
+           *(void **) data = &task;
+
+         gomp_debug (0, "Thread %d: new event: %p\n",
+                     thr->ts.team_id, &task);
+       }
+
       if (thr->task)
-       task.in_tied_task = thr->task->in_tied_task;
+       {
+         task.in_tied_task = thr->task->in_tied_task;
+         task.taskgroup = thr->task->taskgroup;
+       }
       thr->task = &task;
       if (__builtin_expect (cpyfn != NULL, 0))
        {
@@ -116,10 +582,26 @@ GOMP_task (void (*fn) (void *), void *data, void (*cpyfn) (void *, void *),
        }
       else
        fn (data);
-      if (task.children)
+
+      if ((flags & GOMP_TASK_FLAG_DETACH) != 0)
+       {
+         gomp_sem_wait (&completion_sem);
+         gomp_sem_destroy (&completion_sem);
+       }
+
+      /* Access to "children" is normally done inside a task_lock
+        mutex region, but the only way this particular task.children
+        can be set is if this thread's task work function (fn)
+        creates children.  So since the setter is *this* thread, we
+        need no barriers here when testing for non-NULL.  We can have
+        task.children set by the current thread then changed by a
+        child thread, but seeing a stale non-NULL value is not a
+        problem.  Once past the task_lock acquisition, this thread
+        will see the real value of task.children.  */
+      if (!priority_queue_empty_p (&task.children_queue, MEMMODEL_RELAXED))
        {
          gomp_mutex_lock (&team->task_lock);
-         gomp_clear_parent (task.children);
+         gomp_clear_parent (&task.children_queue);
          gomp_mutex_unlock (&team->task_lock);
        }
       gomp_end_task ();
@@ -128,54 +610,122 @@ GOMP_task (void (*fn) (void *), void *data, void (*cpyfn) (void *, void *),
     {
       struct gomp_task *task;
       struct gomp_task *parent = thr->task;
+      struct gomp_taskgroup *taskgroup = parent->taskgroup;
       char *arg;
       bool do_wake;
+      size_t depend_size = 0;
 
-      task = gomp_malloc (sizeof (*task) + arg_size + arg_align - 1);
-      arg = (char *) (((uintptr_t) (task + 1) + arg_align - 1)
+      if (flags & GOMP_TASK_FLAG_DEPEND)
+       depend_size = ((uintptr_t) (depend[0] ? depend[0] : depend[1])
+                      * sizeof (struct gomp_task_depend_entry));
+      task = gomp_malloc (sizeof (*task) + depend_size
+                         + arg_size + arg_align - 1);
+      arg = (char *) (((uintptr_t) (task + 1) + depend_size + arg_align - 1)
                      & ~(uintptr_t) (arg_align - 1));
       gomp_init_task (task, parent, gomp_icv (false));
-      task->kind = GOMP_TASK_IFFALSE;
+      task->priority = priority;
+      task->kind = GOMP_TASK_UNDEFERRED;
       task->in_tied_task = parent->in_tied_task;
+      task->taskgroup = taskgroup;
+      task->deferred_p = true;
+      if ((flags & GOMP_TASK_FLAG_DETACH) != 0)
+       {
+         task->detach_team = team;
+
+         *(void **) detach = task;
+         if (data)
+           *(void **) data = task;
+
+         gomp_debug (0, "Thread %d: new event: %p\n", thr->ts.team_id, task);
+       }
       thr->task = task;
       if (cpyfn)
-       cpyfn (arg, data);
+       {
+         cpyfn (arg, data);
+         task->copy_ctors_done = true;
+       }
       else
        memcpy (arg, data, arg_size);
       thr->task = parent;
       task->kind = GOMP_TASK_WAITING;
       task->fn = fn;
       task->fn_data = arg;
-      task->in_tied_task = true;
-      task->final_task = (flags & 2) >> 1;
+      task->final_task = (flags & GOMP_TASK_FLAG_FINAL) >> 1;
       gomp_mutex_lock (&team->task_lock);
-      if (parent->children)
+      /* If parallel or taskgroup has been cancelled, don't start new
+        tasks.  */
+      if (__builtin_expect (gomp_cancel_var, 0)
+         && !task->copy_ctors_done)
        {
-         task->next_child = parent->children;
-         task->prev_child = parent->children->prev_child;
-         task->next_child->prev_child = task;
-         task->prev_child->next_child = task;
-       }
-      else
-       {
-         task->next_child = task;
-         task->prev_child = task;
-       }
-      parent->children = task;
-      if (team->task_queue)
-       {
-         task->next_queue = team->task_queue;
-         task->prev_queue = team->task_queue->prev_queue;
-         task->next_queue->prev_queue = task;
-         task->prev_queue->next_queue = task;
+         if (gomp_team_barrier_cancelled (&team->barrier))
+           {
+           do_cancel:
+             gomp_mutex_unlock (&team->task_lock);
+             gomp_finish_task (task);
+             free (task);
+             return;
+           }
+         if (taskgroup)
+           {
+             if (taskgroup->cancelled)
+               goto do_cancel;
+             if (taskgroup->workshare
+                 && taskgroup->prev
+                 && taskgroup->prev->cancelled)
+               goto do_cancel;
+           }
        }
-      else
+      if (taskgroup)
+       taskgroup->num_children++;
+      if (depend_size)
        {
-         task->next_queue = task;
-         task->prev_queue = task;
-         team->task_queue = task;
+         gomp_task_handle_depend (task, parent, depend);
+         if (task->num_dependees)
+           {
+             /* Tasks that depend on other tasks are not put into the
+                various waiting queues, so we are done for now.  Said
+                tasks are instead put into the queues via
+                gomp_task_run_post_handle_dependers() after their
+                dependencies have been satisfied.  After which, they
+                can be picked up by the various scheduling
+                points.  */
+             gomp_mutex_unlock (&team->task_lock);
+             return;
+           }
+         /* Check for taskwait nowait depend which doesn't need to wait for
+            anything.  */
+         if (__builtin_expect (fn == empty_task, 0))
+           {
+             if (taskgroup)
+               taskgroup->num_children--;
+             gomp_task_run_post_handle_depend_hash (task);
+             gomp_mutex_unlock (&team->task_lock);
+             gomp_finish_task (task);
+             free (task);
+             return;
+           }
        }
+
+      priority_queue_insert (PQ_CHILDREN, &parent->children_queue,
+                            task, priority,
+                            PRIORITY_INSERT_BEGIN,
+                            /*adjust_parent_depends_on=*/false,
+                            task->parent_depends_on);
+      if (taskgroup)
+       priority_queue_insert (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                              task, priority,
+                              PRIORITY_INSERT_BEGIN,
+                              /*adjust_parent_depends_on=*/false,
+                              task->parent_depends_on);
+
+      priority_queue_insert (PQ_TEAM, &team->task_queue,
+                            task, priority,
+                            PRIORITY_INSERT_END,
+                            /*adjust_parent_depends_on=*/false,
+                            task->parent_depends_on);
+
       ++team->task_count;
+      ++team->task_queued_count;
       gomp_team_barrier_set_task_pending (&team->barrier);
       do_wake = team->task_running_count + !parent->in_tied_task
                < team->nthreads;
@@ -185,151 +735,1366 @@ GOMP_task (void (*fn) (void *), void *data, void (*cpyfn) (void *, void *),
     }
 }
 
-void
-gomp_barrier_handle_tasks (gomp_barrier_state_t state)
-{
-  struct gomp_thread *thr = gomp_thread ();
-  struct gomp_team *team = thr->ts.team;
-  struct gomp_task *task = thr->task;
-  struct gomp_task *child_task = NULL;
-  struct gomp_task *to_free = NULL;
+ialias (GOMP_task)
+ialias (GOMP_taskgroup_start)
+ialias (GOMP_taskgroup_end)
+ialias (GOMP_taskgroup_reduction_register)
 
-  gomp_mutex_lock (&team->task_lock);
-  if (gomp_barrier_last_thread (state))
+#define TYPE long
+#define UTYPE unsigned long
+#define TYPE_is_long 1
+#include "taskloop.c"
+#undef TYPE
+#undef UTYPE
+#undef TYPE_is_long
+
+#define TYPE unsigned long long
+#define UTYPE TYPE
+#define GOMP_taskloop GOMP_taskloop_ull
+#include "taskloop.c"
+#undef TYPE
+#undef UTYPE
+#undef GOMP_taskloop
+
+static void inline
+priority_queue_move_task_first (enum priority_queue_type type,
+                               struct priority_queue *head,
+                               struct gomp_task *task)
+{
+#if _LIBGOMP_CHECKING_
+  if (!priority_queue_task_in_queue_p (type, head, task))
+    gomp_fatal ("Attempt to move first missing task %p", task);
+#endif
+  struct priority_list *list;
+  if (priority_queue_multi_p (head))
     {
-      if (team->task_count == 0)
-       {
-         gomp_team_barrier_done (&team->barrier, state);
-         gomp_mutex_unlock (&team->task_lock);
-         gomp_team_barrier_wake (&team->barrier, 0);
-         return;
-       }
-      gomp_team_barrier_set_waiting_for_tasks (&team->barrier);
+      list = priority_queue_lookup_priority (head, task->priority);
+#if _LIBGOMP_CHECKING_
+      if (!list)
+       gomp_fatal ("Unable to find priority %d", task->priority);
+#endif
     }
+  else
+    list = &head->l;
+  priority_list_remove (list, task_to_priority_node (type, task), 0);
+  priority_list_insert (type, list, task, task->priority,
+                       PRIORITY_INSERT_BEGIN, type == PQ_CHILDREN,
+                       task->parent_depends_on);
+}
 
-  while (1)
-    {
-      if (team->task_queue != NULL)
-       {
-         struct gomp_task *parent;
+/* Actual body of GOMP_PLUGIN_target_task_completion that is executed
+   with team->task_lock held, or is executed in the thread that called
+   gomp_target_task_fn if GOMP_PLUGIN_target_task_completion has been
+   run before it acquires team->task_lock.  */
 
-         child_task = team->task_queue;
-         parent = child_task->parent;
-         if (parent && parent->children == child_task)
-           parent->children = child_task->next_child;
-         child_task->prev_queue->next_queue = child_task->next_queue;
-         child_task->next_queue->prev_queue = child_task->prev_queue;
-         if (child_task->next_queue != child_task)
-           team->task_queue = child_task->next_queue;
-         else
-           team->task_queue = NULL;
-         child_task->kind = GOMP_TASK_TIED;
-         team->task_running_count++;
-         if (team->task_count == team->task_running_count)
-           gomp_team_barrier_clear_task_pending (&team->barrier);
-       }
-      gomp_mutex_unlock (&team->task_lock);
-      if (to_free)
-       {
-         gomp_finish_task (to_free);
-         free (to_free);
-         to_free = NULL;
-       }
-      if (child_task)
+static void
+gomp_target_task_completion (struct gomp_team *team, struct gomp_task *task)
+{
+  struct gomp_task *parent = task->parent;
+  if (parent)
+    priority_queue_move_task_first (PQ_CHILDREN, &parent->children_queue,
+                                   task);
+
+  struct gomp_taskgroup *taskgroup = task->taskgroup;
+  if (taskgroup)
+    priority_queue_move_task_first (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                                   task);
+
+  priority_queue_insert (PQ_TEAM, &team->task_queue, task, task->priority,
+                        PRIORITY_INSERT_BEGIN, false,
+                        task->parent_depends_on);
+  task->kind = GOMP_TASK_WAITING;
+  if (parent && parent->taskwait)
+    {
+      if (parent->taskwait->in_taskwait)
        {
-         thr->task = child_task;
-         child_task->fn (child_task->fn_data);
-         thr->task = task;
+         /* One more task has had its dependencies met.
+            Inform any waiters.  */
+         parent->taskwait->in_taskwait = false;
+         gomp_sem_post (&parent->taskwait->taskwait_sem);
        }
-      else
-       return;
-      gomp_mutex_lock (&team->task_lock);
-      if (child_task)
+      else if (parent->taskwait->in_depend_wait)
        {
-         struct gomp_task *parent = child_task->parent;
-         if (parent)
-           {
-             child_task->prev_child->next_child = child_task->next_child;
-             child_task->next_child->prev_child = child_task->prev_child;
-             if (parent->children == child_task)
-               {
-                 if (child_task->next_child != child_task)
-                   parent->children = child_task->next_child;
-                 else
-                   {
-                     parent->children = NULL;
-                     if (parent->in_taskwait)
-                       gomp_sem_post (&parent->taskwait_sem);
-                   }
-               }
-           }
-         gomp_clear_parent (child_task->children);
-         to_free = child_task;
-         child_task = NULL;
-         team->task_running_count--;
-         if (--team->task_count == 0
-             && gomp_team_barrier_waiting_for_tasks (&team->barrier))
-           {
-             gomp_team_barrier_done (&team->barrier, state);
-             gomp_mutex_unlock (&team->task_lock);
-             gomp_team_barrier_wake (&team->barrier, 0);
-             gomp_mutex_lock (&team->task_lock);
-           }
+         /* One more task has had its dependencies met.
+            Inform any waiters.  */
+         parent->taskwait->in_depend_wait = false;
+         gomp_sem_post (&parent->taskwait->taskwait_sem);
        }
     }
+  if (taskgroup && taskgroup->in_taskgroup_wait)
+    {
+      /* One more task has had its dependencies met.
+        Inform any waiters.  */
+      taskgroup->in_taskgroup_wait = false;
+      gomp_sem_post (&taskgroup->taskgroup_sem);
+    }
+
+  ++team->task_queued_count;
+  gomp_team_barrier_set_task_pending (&team->barrier);
+  /* I'm afraid this can't be done after releasing team->task_lock,
+     as gomp_target_task_completion is run from unrelated thread and
+     therefore in between gomp_mutex_unlock and gomp_team_barrier_wake
+     the team could be gone already.  */
+  if (team->nthreads > team->task_running_count)
+    gomp_team_barrier_wake (&team->barrier, 1);
 }
 
-/* Called when encountering a taskwait directive.  */
+/* Signal that a target task TTASK has completed the asynchronously
+   running phase and should be requeued as a task to handle the
+   variable unmapping.  */
 
 void
-GOMP_taskwait (void)
+GOMP_PLUGIN_target_task_completion (void *data)
+{
+  struct gomp_target_task *ttask = (struct gomp_target_task *) data;
+  struct gomp_task *task = ttask->task;
+  struct gomp_team *team = ttask->team;
+
+  gomp_mutex_lock (&team->task_lock);
+  if (ttask->state == GOMP_TARGET_TASK_READY_TO_RUN)
+    {
+      ttask->state = GOMP_TARGET_TASK_FINISHED;
+      gomp_mutex_unlock (&team->task_lock);
+      return;
+    }
+  ttask->state = GOMP_TARGET_TASK_FINISHED;
+  gomp_target_task_completion (team, task);
+  gomp_mutex_unlock (&team->task_lock);
+}
+
+/* Called for nowait target tasks.  */
+
+bool
+gomp_create_target_task (struct gomp_device_descr *devicep,
+                        void (*fn) (void *), size_t mapnum, void **hostaddrs,
+                        size_t *sizes, unsigned short *kinds,
+                        unsigned int flags, void **depend, void **args,
+                        enum gomp_target_task_state state)
 {
   struct gomp_thread *thr = gomp_thread ();
   struct gomp_team *team = thr->ts.team;
-  struct gomp_task *task = thr->task;
-  struct gomp_task *child_task = NULL;
-  struct gomp_task *to_free = NULL;
 
-  if (task == NULL || task->children == NULL)
-    return;
-  gomp_mutex_lock (&team->task_lock);
-  while (1)
+  /* If parallel or taskgroup has been cancelled, don't start new tasks.  */
+  if (__builtin_expect (gomp_cancel_var, 0) && team)
     {
-      if (task->children == NULL)
+      if (gomp_team_barrier_cancelled (&team->barrier))
+       return true;
+      if (thr->task->taskgroup)
        {
-         gomp_mutex_unlock (&team->task_lock);
-         if (to_free)
-           {
-             gomp_finish_task (to_free);
-             free (to_free);
-           }
-         return;
+         if (thr->task->taskgroup->cancelled)
+           return true;
+         if (thr->task->taskgroup->workshare
+             && thr->task->taskgroup->prev
+             && thr->task->taskgroup->prev->cancelled)
+           return true;
        }
-      if (task->children->kind == GOMP_TASK_WAITING)
+    }
+
+  struct gomp_target_task *ttask;
+  struct gomp_task *task;
+  struct gomp_task *parent = thr->task;
+  struct gomp_taskgroup *taskgroup = parent->taskgroup;
+  bool do_wake;
+  size_t depend_size = 0;
+  uintptr_t depend_cnt = 0;
+  size_t tgt_align = 0, tgt_size = 0;
+  uintptr_t args_cnt = 0;
+
+  if (depend != NULL)
+    {
+      depend_cnt = (uintptr_t) (depend[0] ? depend[0] : depend[1]);
+      depend_size = depend_cnt * sizeof (struct gomp_task_depend_entry);
+    }
+  if (fn)
+    {
+      /* GOMP_MAP_FIRSTPRIVATE need to be copied first, as they are
+        firstprivate on the target task.  */
+      size_t i;
+      for (i = 0; i < mapnum; i++)
+       if ((kinds[i] & 0xff) == GOMP_MAP_FIRSTPRIVATE)
+         {
+           size_t align = (size_t) 1 << (kinds[i] >> 8);
+           if (tgt_align < align)
+             tgt_align = align;
+           tgt_size = (tgt_size + align - 1) & ~(align - 1);
+           tgt_size += sizes[i];
+         }
+      if (tgt_align)
+       tgt_size += tgt_align - 1;
+      else
+       tgt_size = 0;
+      if (args)
        {
-         child_task = task->children;
-         task->children = child_task->next_child;
-         child_task->prev_queue->next_queue = child_task->next_queue;
-         child_task->next_queue->prev_queue = child_task->prev_queue;
-         if (team->task_queue == child_task)
+         void **cargs = args;
+         while (*cargs)
            {
-             if (child_task->next_queue != child_task)
-               team->task_queue = child_task->next_queue;
-             else
-               team->task_queue = NULL;
+             intptr_t id = (intptr_t) *cargs++;
+             if (id & GOMP_TARGET_ARG_SUBSEQUENT_PARAM)
+               cargs++;
            }
-         child_task->kind = GOMP_TASK_TIED;
-         team->task_running_count++;
-         if (team->task_count == team->task_running_count)
-           gomp_team_barrier_clear_task_pending (&team->barrier);
+         args_cnt = cargs + 1 - args;
        }
-      else
-       /* All tasks we are waiting for are already running
-          in other threads.  Wait for them.  */
-       task->in_taskwait = true;
-      gomp_mutex_unlock (&team->task_lock);
-      if (to_free)
-       {
+    }
+
+  task = gomp_malloc (sizeof (*task) + depend_size
+                     + sizeof (*ttask)
+                     + args_cnt * sizeof (void *)
+                     + mapnum * (sizeof (void *) + sizeof (size_t)
+                                 + sizeof (unsigned short))
+                     + tgt_size);
+  gomp_init_task (task, parent, gomp_icv (false));
+  task->priority = 0;
+  task->kind = GOMP_TASK_WAITING;
+  task->in_tied_task = parent->in_tied_task;
+  task->taskgroup = taskgroup;
+  ttask = (struct gomp_target_task *) &task->depend[depend_cnt];
+  ttask->devicep = devicep;
+  ttask->fn = fn;
+  ttask->mapnum = mapnum;
+  memcpy (ttask->hostaddrs, hostaddrs, mapnum * sizeof (void *));
+  if (args_cnt)
+    {
+      ttask->args = (void **) &ttask->hostaddrs[mapnum];
+      memcpy (ttask->args, args, args_cnt * sizeof (void *));
+      ttask->sizes = (size_t *) &ttask->args[args_cnt];
+    }
+  else
+    {
+      ttask->args = args;
+      ttask->sizes = (size_t *) &ttask->hostaddrs[mapnum];
+    }
+  memcpy (ttask->sizes, sizes, mapnum * sizeof (size_t));
+  ttask->kinds = (unsigned short *) &ttask->sizes[mapnum];
+  memcpy (ttask->kinds, kinds, mapnum * sizeof (unsigned short));
+  if (tgt_align)
+    {
+      char *tgt = (char *) &ttask->kinds[mapnum];
+      size_t i;
+      uintptr_t al = (uintptr_t) tgt & (tgt_align - 1);
+      if (al)
+       tgt += tgt_align - al;
+      tgt_size = 0;
+      for (i = 0; i < mapnum; i++)
+       if ((kinds[i] & 0xff) == GOMP_MAP_FIRSTPRIVATE)
+         {
+           size_t align = (size_t) 1 << (kinds[i] >> 8);
+           tgt_size = (tgt_size + align - 1) & ~(align - 1);
+           memcpy (tgt + tgt_size, hostaddrs[i], sizes[i]);
+           ttask->hostaddrs[i] = tgt + tgt_size;
+           tgt_size = tgt_size + sizes[i];
+         }
+    }
+  ttask->flags = flags;
+  ttask->state = state;
+  ttask->task = task;
+  ttask->team = team;
+  task->fn = NULL;
+  task->fn_data = ttask;
+  task->final_task = 0;
+  gomp_mutex_lock (&team->task_lock);
+  /* If parallel or taskgroup has been cancelled, don't start new tasks.  */
+  if (__builtin_expect (gomp_cancel_var, 0))
+    {
+      if (gomp_team_barrier_cancelled (&team->barrier))
+       {
+       do_cancel:
+         gomp_mutex_unlock (&team->task_lock);
+         gomp_finish_task (task);
+         free (task);
+         return true;
+       }
+      if (taskgroup)
+       {
+         if (taskgroup->cancelled)
+           goto do_cancel;
+         if (taskgroup->workshare
+             && taskgroup->prev
+             && taskgroup->prev->cancelled)
+           goto do_cancel;
+       }
+    }
+  if (depend_size)
+    {
+      gomp_task_handle_depend (task, parent, depend);
+      if (task->num_dependees)
+       {
+         if (taskgroup)
+           taskgroup->num_children++;
+         gomp_mutex_unlock (&team->task_lock);
+         return true;
+       }
+    }
+  if (state == GOMP_TARGET_TASK_DATA)
+    {
+      gomp_task_run_post_handle_depend_hash (task);
+      gomp_mutex_unlock (&team->task_lock);
+      gomp_finish_task (task);
+      free (task);
+      return false;
+    }
+  if (taskgroup)
+    taskgroup->num_children++;
+  /* For async offloading, if we don't need to wait for dependencies,
+     run the gomp_target_task_fn right away, essentially schedule the
+     mapping part of the task in the current thread.  */
+  if (devicep != NULL
+      && (devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400))
+    {
+      priority_queue_insert (PQ_CHILDREN, &parent->children_queue, task, 0,
+                            PRIORITY_INSERT_END,
+                            /*adjust_parent_depends_on=*/false,
+                            task->parent_depends_on);
+      if (taskgroup)
+       priority_queue_insert (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                              task, 0, PRIORITY_INSERT_END,
+                              /*adjust_parent_depends_on=*/false,
+                              task->parent_depends_on);
+      task->pnode[PQ_TEAM].next = NULL;
+      task->pnode[PQ_TEAM].prev = NULL;
+      task->kind = GOMP_TASK_TIED;
+      ++team->task_count;
+      gomp_mutex_unlock (&team->task_lock);
+
+      thr->task = task;
+      gomp_target_task_fn (task->fn_data);
+      thr->task = parent;
+
+      gomp_mutex_lock (&team->task_lock);
+      task->kind = GOMP_TASK_ASYNC_RUNNING;
+      /* If GOMP_PLUGIN_target_task_completion has run already
+        in between gomp_target_task_fn and the mutex lock,
+        perform the requeuing here.  */
+      if (ttask->state == GOMP_TARGET_TASK_FINISHED)
+       gomp_target_task_completion (team, task);
+      else
+       ttask->state = GOMP_TARGET_TASK_RUNNING;
+      gomp_mutex_unlock (&team->task_lock);
+      return true;
+    }
+  priority_queue_insert (PQ_CHILDREN, &parent->children_queue, task, 0,
+                        PRIORITY_INSERT_BEGIN,
+                        /*adjust_parent_depends_on=*/false,
+                        task->parent_depends_on);
+  if (taskgroup)
+    priority_queue_insert (PQ_TASKGROUP, &taskgroup->taskgroup_queue, task, 0,
+                          PRIORITY_INSERT_BEGIN,
+                          /*adjust_parent_depends_on=*/false,
+                          task->parent_depends_on);
+  priority_queue_insert (PQ_TEAM, &team->task_queue, task, 0,
+                        PRIORITY_INSERT_END,
+                        /*adjust_parent_depends_on=*/false,
+                        task->parent_depends_on);
+  ++team->task_count;
+  ++team->task_queued_count;
+  gomp_team_barrier_set_task_pending (&team->barrier);
+  do_wake = team->task_running_count + !parent->in_tied_task
+           < team->nthreads;
+  gomp_mutex_unlock (&team->task_lock);
+  if (do_wake)
+    gomp_team_barrier_wake (&team->barrier, 1);
+  return true;
+}
+
+/* Given a parent_depends_on task in LIST, move it to the front of its
+   priority so it is run as soon as possible.
+
+   Care is taken to update the list's LAST_PARENT_DEPENDS_ON field.
+
+   We rearrange the queue such that all parent_depends_on tasks are
+   first, and last_parent_depends_on points to the last such task we
+   rearranged.  For example, given the following tasks in a queue
+   where PD[123] are the parent_depends_on tasks:
+
+       task->children
+       |
+       V
+       C1 -> C2 -> C3 -> PD1 -> PD2 -> PD3 -> C4
+
+       We rearrange such that:
+
+       task->children
+       |              +--- last_parent_depends_on
+       |              |
+       V              V
+       PD1 -> PD2 -> PD3 -> C1 -> C2 -> C3 -> C4.  */
+
+static void inline
+priority_list_upgrade_task (struct priority_list *list,
+                           struct priority_node *node)
+{
+  struct priority_node *last_parent_depends_on
+    = list->last_parent_depends_on;
+  if (last_parent_depends_on)
+    {
+      node->prev->next = node->next;
+      node->next->prev = node->prev;
+      node->prev = last_parent_depends_on;
+      node->next = last_parent_depends_on->next;
+      node->prev->next = node;
+      node->next->prev = node;
+    }
+  else if (node != list->tasks)
+    {
+      node->prev->next = node->next;
+      node->next->prev = node->prev;
+      node->prev = list->tasks->prev;
+      node->next = list->tasks;
+      list->tasks = node;
+      node->prev->next = node;
+      node->next->prev = node;
+    }
+  list->last_parent_depends_on = node;
+}
+
+/* Given a parent_depends_on TASK in its parent's children_queue, move
+   it to the front of its priority so it is run as soon as possible.
+
+   PARENT is passed as an optimization.
+
+   (This function could be defined in priority_queue.c, but we want it
+   inlined, and putting it in priority_queue.h is not an option, given
+   that gomp_task has not been properly defined at that point).  */
+
+static void inline
+priority_queue_upgrade_task (struct gomp_task *task,
+                            struct gomp_task *parent)
+{
+  struct priority_queue *head = &parent->children_queue;
+  struct priority_node *node = &task->pnode[PQ_CHILDREN];
+#if _LIBGOMP_CHECKING_
+  if (!task->parent_depends_on)
+    gomp_fatal ("priority_queue_upgrade_task: task must be a "
+               "parent_depends_on task");
+  if (!priority_queue_task_in_queue_p (PQ_CHILDREN, head, task))
+    gomp_fatal ("priority_queue_upgrade_task: cannot find task=%p", task);
+#endif
+  if (priority_queue_multi_p (head))
+    {
+      struct priority_list *list
+       = priority_queue_lookup_priority (head, task->priority);
+      priority_list_upgrade_task (list, node);
+    }
+  else
+    priority_list_upgrade_task (&head->l, node);
+}
+
+/* Given a CHILD_TASK in LIST that is about to be executed, move it out of
+   the way in LIST so that other tasks can be considered for
+   execution.  LIST contains tasks of type TYPE.
+
+   Care is taken to update the queue's LAST_PARENT_DEPENDS_ON field
+   if applicable.  */
+
+static void inline
+priority_list_downgrade_task (enum priority_queue_type type,
+                             struct priority_list *list,
+                             struct gomp_task *child_task)
+{
+  struct priority_node *node = task_to_priority_node (type, child_task);
+  if (list->tasks == node)
+    list->tasks = node->next;
+  else if (node->next != list->tasks)
+    {
+      /* The task in NODE is about to become TIED and TIED tasks
+        cannot come before WAITING tasks.  If we're about to
+        leave the queue in such an indeterminate state, rewire
+        things appropriately.  However, a TIED task at the end is
+        perfectly fine.  */
+      struct gomp_task *next_task = priority_node_to_task (type, node->next);
+      if (next_task->kind == GOMP_TASK_WAITING)
+       {
+         /* Remove from list.  */
+         node->prev->next = node->next;
+         node->next->prev = node->prev;
+         /* Rewire at the end.  */
+         node->next = list->tasks;
+         node->prev = list->tasks->prev;
+         list->tasks->prev->next = node;
+         list->tasks->prev = node;
+       }
+    }
+
+  /* If the current task is the last_parent_depends_on for its
+     priority, adjust last_parent_depends_on appropriately.  */
+  if (__builtin_expect (child_task->parent_depends_on, 0)
+      && list->last_parent_depends_on == node)
+    {
+      struct gomp_task *prev_child = priority_node_to_task (type, node->prev);
+      if (node->prev != node
+         && prev_child->kind == GOMP_TASK_WAITING
+         && prev_child->parent_depends_on)
+       list->last_parent_depends_on = node->prev;
+      else
+       {
+         /* There are no more parent_depends_on entries waiting
+            to run, clear the list.  */
+         list->last_parent_depends_on = NULL;
+       }
+    }
+}
+
+/* Given a TASK in HEAD that is about to be executed, move it out of
+   the way so that other tasks can be considered for execution.  HEAD
+   contains tasks of type TYPE.
+
+   Care is taken to update the queue's LAST_PARENT_DEPENDS_ON field
+   if applicable.
+
+   (This function could be defined in priority_queue.c, but we want it
+   inlined, and putting it in priority_queue.h is not an option, given
+   that gomp_task has not been properly defined at that point).  */
+
+static void inline
+priority_queue_downgrade_task (enum priority_queue_type type,
+                              struct priority_queue *head,
+                              struct gomp_task *task)
+{
+#if _LIBGOMP_CHECKING_
+  if (!priority_queue_task_in_queue_p (type, head, task))
+    gomp_fatal ("Attempt to downgrade missing task %p", task);
+#endif
+  if (priority_queue_multi_p (head))
+    {
+      struct priority_list *list
+       = priority_queue_lookup_priority (head, task->priority);
+      priority_list_downgrade_task (type, list, task);
+    }
+  else
+    priority_list_downgrade_task (type, &head->l, task);
+}
+
+/* Setup CHILD_TASK to execute.  This is done by setting the task to
+   TIED, and updating all relevant queues so that CHILD_TASK is no
+   longer chosen for scheduling.  Also, remove CHILD_TASK from the
+   overall team task queue entirely.
+
+   Return TRUE if task or its containing taskgroup has been
+   cancelled.  */
+
+static inline bool
+gomp_task_run_pre (struct gomp_task *child_task, struct gomp_task *parent,
+                  struct gomp_team *team)
+{
+#if _LIBGOMP_CHECKING_
+  if (child_task->parent)
+    priority_queue_verify (PQ_CHILDREN,
+                          &child_task->parent->children_queue, true);
+  if (child_task->taskgroup)
+    priority_queue_verify (PQ_TASKGROUP,
+                          &child_task->taskgroup->taskgroup_queue, false);
+  priority_queue_verify (PQ_TEAM, &team->task_queue, false);
+#endif
+
+  /* Task is about to go tied, move it out of the way.  */
+  if (parent)
+    priority_queue_downgrade_task (PQ_CHILDREN, &parent->children_queue,
+                                  child_task);
+
+  /* Task is about to go tied, move it out of the way.  */
+  struct gomp_taskgroup *taskgroup = child_task->taskgroup;
+  if (taskgroup)
+    priority_queue_downgrade_task (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                                  child_task);
+
+  priority_queue_remove (PQ_TEAM, &team->task_queue, child_task,
+                        MEMMODEL_RELAXED);
+  child_task->pnode[PQ_TEAM].next = NULL;
+  child_task->pnode[PQ_TEAM].prev = NULL;
+  child_task->kind = GOMP_TASK_TIED;
+
+  if (--team->task_queued_count == 0)
+    gomp_team_barrier_clear_task_pending (&team->barrier);
+  if (__builtin_expect (gomp_cancel_var, 0)
+      && !child_task->copy_ctors_done)
+    {
+      if (gomp_team_barrier_cancelled (&team->barrier))
+       return true;
+      if (taskgroup)
+       {
+         if (taskgroup->cancelled)
+           return true;
+         if (taskgroup->workshare
+             && taskgroup->prev
+             && taskgroup->prev->cancelled)
+           return true;
+       }
+    }
+  return false;
+}
+
+static void
+gomp_task_run_post_handle_depend_hash (struct gomp_task *child_task)
+{
+  struct gomp_task *parent = child_task->parent;
+  size_t i;
+
+  if (parent->depend_all_memory == child_task)
+    parent->depend_all_memory = NULL;
+  for (i = 0; i < child_task->depend_count; i++)
+    if (!child_task->depend[i].redundant)
+      {
+       if (child_task->depend[i].next)
+         child_task->depend[i].next->prev = child_task->depend[i].prev;
+       if (child_task->depend[i].prev)
+         child_task->depend[i].prev->next = child_task->depend[i].next;
+       else
+         {
+           hash_entry_type *slot
+             = htab_find_slot (&parent->depend_hash, &child_task->depend[i],
+                               NO_INSERT);
+           if (*slot != &child_task->depend[i])
+             abort ();
+           if (child_task->depend[i].next)
+             *slot = child_task->depend[i].next;
+           else
+             htab_clear_slot (parent->depend_hash, slot);
+         }
+      }
+}
+
+/* After a CHILD_TASK has been run, adjust the dependency queue for
+   each task that depends on CHILD_TASK, to record the fact that there
+   is one less dependency to worry about.  If a task that depended on
+   CHILD_TASK now has no dependencies, place it in the various queues
+   so it gets scheduled to run.
+
+   TEAM is the team to which CHILD_TASK belongs to.  */
+
+static size_t
+gomp_task_run_post_handle_dependers (struct gomp_task *child_task,
+                                    struct gomp_team *team)
+{
+  struct gomp_task *parent = child_task->parent;
+  size_t i, count = child_task->dependers->n_elem, ret = 0;
+  for (i = 0; i < count; i++)
+    {
+      struct gomp_task *task = child_task->dependers->elem[i];
+
+      /* CHILD_TASK satisfies a dependency for TASK.  Keep track of
+        TASK's remaining dependencies.  Once TASK has no other
+        dependencies, put it into the various queues so it will get
+        scheduled for execution.  */
+      if (--task->num_dependees != 0)
+       continue;
+
+      struct gomp_taskgroup *taskgroup = task->taskgroup;
+      if (__builtin_expect (task->fn == empty_task, 0))
+       {
+         if (!parent)
+           task->parent = NULL;
+         else if (__builtin_expect (task->parent_depends_on, 0)
+                  && --parent->taskwait->n_depend == 0
+                  && parent->taskwait->in_depend_wait)
+           {
+             parent->taskwait->in_depend_wait = false;
+             gomp_sem_post (&parent->taskwait->taskwait_sem);
+           }
+         if (gomp_task_run_post_handle_depend (task, team))
+           ++ret;
+         if (taskgroup)
+           {
+             if (taskgroup->num_children > 1)
+               --taskgroup->num_children;
+             else
+               {
+                 __atomic_store_n (&taskgroup->num_children, 0,
+                                   MEMMODEL_RELEASE);
+                 if (taskgroup->in_taskgroup_wait)
+                   {
+                     taskgroup->in_taskgroup_wait = false;
+                     gomp_sem_post (&taskgroup->taskgroup_sem);
+                   }
+               }
+           }
+         gomp_finish_task (task);
+         free (task);
+         continue;
+       }
+      if (parent)
+       {
+         priority_queue_insert (PQ_CHILDREN, &parent->children_queue,
+                                task, task->priority,
+                                PRIORITY_INSERT_BEGIN,
+                                /*adjust_parent_depends_on=*/true,
+                                task->parent_depends_on);
+         if (parent->taskwait)
+           {
+             if (parent->taskwait->in_taskwait)
+               {
+                 /* One more task has had its dependencies met.
+                    Inform any waiters.  */
+                 parent->taskwait->in_taskwait = false;
+                 gomp_sem_post (&parent->taskwait->taskwait_sem);
+               }
+             else if (parent->taskwait->in_depend_wait)
+               {
+                 /* One more task has had its dependencies met.
+                    Inform any waiters.  */
+                 parent->taskwait->in_depend_wait = false;
+                 gomp_sem_post (&parent->taskwait->taskwait_sem);
+               }
+           }
+       }
+      else
+       task->parent = NULL;
+      if (taskgroup)
+       {
+         priority_queue_insert (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                                task, task->priority,
+                                PRIORITY_INSERT_BEGIN,
+                                /*adjust_parent_depends_on=*/false,
+                                task->parent_depends_on);
+         if (taskgroup->in_taskgroup_wait)
+           {
+             /* One more task has had its dependencies met.
+                Inform any waiters.  */
+             taskgroup->in_taskgroup_wait = false;
+             gomp_sem_post (&taskgroup->taskgroup_sem);
+           }
+       }
+      priority_queue_insert (PQ_TEAM, &team->task_queue,
+                            task, task->priority,
+                            PRIORITY_INSERT_END,
+                            /*adjust_parent_depends_on=*/false,
+                            task->parent_depends_on);
+      ++team->task_count;
+      ++team->task_queued_count;
+      ++ret;
+    }
+  free (child_task->dependers);
+  child_task->dependers = NULL;
+  if (ret > 1)
+    gomp_team_barrier_set_task_pending (&team->barrier);
+  return ret;
+}
+
+static inline size_t
+gomp_task_run_post_handle_depend (struct gomp_task *child_task,
+                                 struct gomp_team *team)
+{
+  if (child_task->depend_count == 0)
+    return 0;
+
+  /* If parent is gone already, the hash table is freed and nothing
+     will use the hash table anymore, no need to remove anything from it.  */
+  if (child_task->parent != NULL)
+    gomp_task_run_post_handle_depend_hash (child_task);
+
+  if (child_task->dependers == NULL)
+    return 0;
+
+  return gomp_task_run_post_handle_dependers (child_task, team);
+}
+
+/* Remove CHILD_TASK from its parent.  */
+
+static inline void
+gomp_task_run_post_remove_parent (struct gomp_task *child_task)
+{
+  struct gomp_task *parent = child_task->parent;
+  if (parent == NULL)
+    return;
+
+  /* If this was the last task the parent was depending on,
+     synchronize with gomp_task_maybe_wait_for_dependencies so it can
+     clean up and return.  */
+  if (__builtin_expect (child_task->parent_depends_on, 0)
+      && --parent->taskwait->n_depend == 0
+      && parent->taskwait->in_depend_wait)
+    {
+      parent->taskwait->in_depend_wait = false;
+      gomp_sem_post (&parent->taskwait->taskwait_sem);
+    }
+
+  if (priority_queue_remove (PQ_CHILDREN, &parent->children_queue,
+                            child_task, MEMMODEL_RELEASE)
+      && parent->taskwait && parent->taskwait->in_taskwait)
+    {
+      parent->taskwait->in_taskwait = false;
+      gomp_sem_post (&parent->taskwait->taskwait_sem);
+    }
+  child_task->pnode[PQ_CHILDREN].next = NULL;
+  child_task->pnode[PQ_CHILDREN].prev = NULL;
+}
+
+/* Remove CHILD_TASK from its taskgroup.  */
+
+static inline void
+gomp_task_run_post_remove_taskgroup (struct gomp_task *child_task)
+{
+  struct gomp_taskgroup *taskgroup = child_task->taskgroup;
+  if (taskgroup == NULL)
+    return;
+  bool empty = priority_queue_remove (PQ_TASKGROUP,
+                                     &taskgroup->taskgroup_queue,
+                                     child_task, MEMMODEL_RELAXED);
+  child_task->pnode[PQ_TASKGROUP].next = NULL;
+  child_task->pnode[PQ_TASKGROUP].prev = NULL;
+  if (taskgroup->num_children > 1)
+    --taskgroup->num_children;
+  else
+    {
+      /* We access taskgroup->num_children in GOMP_taskgroup_end
+        outside of the task lock mutex region, so
+        need a release barrier here to ensure memory
+        written by child_task->fn above is flushed
+        before the NULL is written.  */
+      __atomic_store_n (&taskgroup->num_children, 0, MEMMODEL_RELEASE);
+    }
+  if (empty && taskgroup->in_taskgroup_wait)
+    {
+      taskgroup->in_taskgroup_wait = false;
+      gomp_sem_post (&taskgroup->taskgroup_sem);
+    }
+}
+
+void
+gomp_barrier_handle_tasks (gomp_barrier_state_t state)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task = thr->task;
+  struct gomp_task *child_task = NULL;
+  struct gomp_task *to_free = NULL;
+  int do_wake = 0;
+
+  gomp_mutex_lock (&team->task_lock);
+  if (gomp_barrier_last_thread (state))
+    {
+      if (team->task_count == 0)
+       {
+         gomp_team_barrier_done (&team->barrier, state);
+         gomp_mutex_unlock (&team->task_lock);
+         gomp_team_barrier_wake (&team->barrier, 0);
+         return;
+       }
+      gomp_team_barrier_set_waiting_for_tasks (&team->barrier);
+    }
+
+  while (1)
+    {
+      bool cancelled = false;
+
+      if (!priority_queue_empty_p (&team->task_queue, MEMMODEL_RELAXED))
+       {
+         bool ignored;
+         child_task
+           = priority_queue_next_task (PQ_TEAM, &team->task_queue,
+                                       PQ_IGNORED, NULL,
+                                       &ignored);
+         cancelled = gomp_task_run_pre (child_task, child_task->parent,
+                                        team);
+         if (__builtin_expect (cancelled, 0))
+           {
+             if (to_free)
+               {
+                 gomp_finish_task (to_free);
+                 free (to_free);
+                 to_free = NULL;
+               }
+             goto finish_cancelled;
+           }
+         team->task_running_count++;
+         child_task->in_tied_task = true;
+       }
+      else if (team->task_count == 0
+              && gomp_team_barrier_waiting_for_tasks (&team->barrier))
+       {
+         gomp_team_barrier_done (&team->barrier, state);
+         gomp_mutex_unlock (&team->task_lock);
+         gomp_team_barrier_wake (&team->barrier, 0);
+         if (to_free)
+           {
+             gomp_finish_task (to_free);
+             free (to_free);
+           }
+         return;
+       }
+      gomp_mutex_unlock (&team->task_lock);
+      if (do_wake)
+       {
+         gomp_team_barrier_wake (&team->barrier, do_wake);
+         do_wake = 0;
+       }
+      if (to_free)
+       {
+         gomp_finish_task (to_free);
+         free (to_free);
+         to_free = NULL;
+       }
+      if (child_task)
+       {
+         thr->task = child_task;
+         if (__builtin_expect (child_task->fn == NULL, 0))
+           {
+             if (gomp_target_task_fn (child_task->fn_data))
+               {
+                 thr->task = task;
+                 gomp_mutex_lock (&team->task_lock);
+                 child_task->kind = GOMP_TASK_ASYNC_RUNNING;
+                 team->task_running_count--;
+                 struct gomp_target_task *ttask
+                   = (struct gomp_target_task *) child_task->fn_data;
+                 /* If GOMP_PLUGIN_target_task_completion has run already
+                    in between gomp_target_task_fn and the mutex lock,
+                    perform the requeuing here.  */
+                 if (ttask->state == GOMP_TARGET_TASK_FINISHED)
+                   gomp_target_task_completion (team, child_task);
+                 else
+                   ttask->state = GOMP_TARGET_TASK_RUNNING;
+                 child_task = NULL;
+                 continue;
+               }
+           }
+         else
+           child_task->fn (child_task->fn_data);
+         thr->task = task;
+       }
+      else
+       return;
+      gomp_mutex_lock (&team->task_lock);
+      if (child_task)
+       {
+         if (child_task->detach_team)
+           {
+             assert (child_task->detach_team == team);
+             child_task->kind = GOMP_TASK_DETACHED;
+             ++team->task_detach_count;
+             --team->task_running_count;
+             gomp_debug (0,
+                         "thread %d: task with event %p finished without "
+                         "completion event fulfilled in team barrier\n",
+                         thr->ts.team_id, child_task);
+             child_task = NULL;
+             continue;
+           }
+
+        finish_cancelled:;
+         size_t new_tasks
+           = gomp_task_run_post_handle_depend (child_task, team);
+         gomp_task_run_post_remove_parent (child_task);
+         gomp_clear_parent (&child_task->children_queue);
+         gomp_task_run_post_remove_taskgroup (child_task);
+         to_free = child_task;
+         if (!cancelled)
+           team->task_running_count--;
+         child_task = NULL;
+         if (new_tasks > 1)
+           {
+             do_wake = team->nthreads - team->task_running_count;
+             if (do_wake > new_tasks)
+               do_wake = new_tasks;
+           }
+         --team->task_count;
+       }
+    }
+}
+
+/* Called when encountering a taskwait directive.
+
+   Wait for all children of the current task.  */
+
+void
+GOMP_taskwait (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task = thr->task;
+  struct gomp_task *child_task = NULL;
+  struct gomp_task *to_free = NULL;
+  struct gomp_taskwait taskwait;
+  int do_wake = 0;
+
+  /* The acquire barrier on load of task->children here synchronizes
+     with the write of a NULL in gomp_task_run_post_remove_parent.  It is
+     not necessary that we synchronize with other non-NULL writes at
+     this point, but we must ensure that all writes to memory by a
+     child thread task work function are seen before we exit from
+     GOMP_taskwait.  */
+  if (task == NULL
+      || priority_queue_empty_p (&task->children_queue, MEMMODEL_ACQUIRE))
+    return;
+
+  memset (&taskwait, 0, sizeof (taskwait));
+  bool child_q = false;
+  gomp_mutex_lock (&team->task_lock);
+  while (1)
+    {
+      bool cancelled = false;
+      if (priority_queue_empty_p (&task->children_queue, MEMMODEL_RELAXED))
+       {
+         bool destroy_taskwait = task->taskwait != NULL;
+         task->taskwait = NULL;
+         gomp_mutex_unlock (&team->task_lock);
+         if (to_free)
+           {
+             gomp_finish_task (to_free);
+             free (to_free);
+           }
+         if (destroy_taskwait)
+           gomp_sem_destroy (&taskwait.taskwait_sem);
+         return;
+       }
+      struct gomp_task *next_task
+       = priority_queue_next_task (PQ_CHILDREN, &task->children_queue,
+                                   PQ_TEAM, &team->task_queue, &child_q);
+      if (next_task->kind == GOMP_TASK_WAITING)
+       {
+         child_task = next_task;
+         cancelled
+           = gomp_task_run_pre (child_task, task, team);
+         if (__builtin_expect (cancelled, 0))
+           {
+             if (to_free)
+               {
+                 gomp_finish_task (to_free);
+                 free (to_free);
+                 to_free = NULL;
+               }
+             goto finish_cancelled;
+           }
+       }
+      else
+       {
+       /* All tasks we are waiting for are either running in other
+          threads, are detached and waiting for the completion event to be
+          fulfilled, or they are tasks that have not had their
+          dependencies met (so they're not even in the queue).  Wait
+          for them.  */
+         if (task->taskwait == NULL)
+           {
+             taskwait.in_depend_wait = false;
+             gomp_sem_init (&taskwait.taskwait_sem, 0);
+             task->taskwait = &taskwait;
+           }
+         taskwait.in_taskwait = true;
+       }
+      gomp_mutex_unlock (&team->task_lock);
+      if (do_wake)
+       {
+         gomp_team_barrier_wake (&team->barrier, do_wake);
+         do_wake = 0;
+       }
+      if (to_free)
+       {
+         gomp_finish_task (to_free);
+         free (to_free);
+         to_free = NULL;
+       }
+      if (child_task)
+       {
+         thr->task = child_task;
+         if (__builtin_expect (child_task->fn == NULL, 0))
+           {
+             if (gomp_target_task_fn (child_task->fn_data))
+               {
+                 thr->task = task;
+                 gomp_mutex_lock (&team->task_lock);
+                 child_task->kind = GOMP_TASK_ASYNC_RUNNING;
+                 struct gomp_target_task *ttask
+                   = (struct gomp_target_task *) child_task->fn_data;
+                 /* If GOMP_PLUGIN_target_task_completion has run already
+                    in between gomp_target_task_fn and the mutex lock,
+                    perform the requeuing here.  */
+                 if (ttask->state == GOMP_TARGET_TASK_FINISHED)
+                   gomp_target_task_completion (team, child_task);
+                 else
+                   ttask->state = GOMP_TARGET_TASK_RUNNING;
+                 child_task = NULL;
+                 continue;
+               }
+           }
+         else
+           child_task->fn (child_task->fn_data);
+         thr->task = task;
+       }
+      else
+       gomp_sem_wait (&taskwait.taskwait_sem);
+      gomp_mutex_lock (&team->task_lock);
+      if (child_task)
+       {
+         if (child_task->detach_team)
+           {
+             assert (child_task->detach_team == team);
+             child_task->kind = GOMP_TASK_DETACHED;
+             ++team->task_detach_count;
+             gomp_debug (0,
+                         "thread %d: task with event %p finished without "
+                         "completion event fulfilled in taskwait\n",
+                         thr->ts.team_id, child_task);
+             child_task = NULL;
+             continue;
+           }
+
+        finish_cancelled:;
+         size_t new_tasks
+           = gomp_task_run_post_handle_depend (child_task, team);
+
+         if (child_q)
+           {
+             priority_queue_remove (PQ_CHILDREN, &task->children_queue,
+                                    child_task, MEMMODEL_RELAXED);
+             child_task->pnode[PQ_CHILDREN].next = NULL;
+             child_task->pnode[PQ_CHILDREN].prev = NULL;
+           }
+
+         gomp_clear_parent (&child_task->children_queue);
+
+         gomp_task_run_post_remove_taskgroup (child_task);
+
+         to_free = child_task;
+         child_task = NULL;
+         team->task_count--;
+         if (new_tasks > 1)
+           {
+             do_wake = team->nthreads - team->task_running_count
+                       - !task->in_tied_task;
+             if (do_wake > new_tasks)
+               do_wake = new_tasks;
+           }
+       }
+    }
+}
+
+/* Called when encountering a taskwait directive with depend clause(s).
+   Wait as if it was an mergeable included task construct with empty body.  */
+
+void
+GOMP_taskwait_depend (void **depend)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+
+  /* If parallel or taskgroup has been cancelled, return early.  */
+  if (__builtin_expect (gomp_cancel_var, 0) && team)
+    {
+      if (gomp_team_barrier_cancelled (&team->barrier))
+       return;
+      if (thr->task->taskgroup)
+       {
+         if (thr->task->taskgroup->cancelled)
+           return;
+         if (thr->task->taskgroup->workshare
+             && thr->task->taskgroup->prev
+             && thr->task->taskgroup->prev->cancelled)
+           return;
+       }
+    }
+
+  if (thr->task && thr->task->depend_hash)
+    gomp_task_maybe_wait_for_dependencies (depend);
+}
+
+/* Called when encountering a taskwait directive with nowait and depend
+   clause(s).  Create a possibly deferred task construct with empty body.  */
+
+void
+GOMP_taskwait_depend_nowait (void **depend)
+{
+  ialias_call (GOMP_task) (empty_task, "", NULL, 0, 1, true,
+                          GOMP_TASK_FLAG_DEPEND, depend, 0, NULL);
+}
+
+/* An undeferred task is about to run.  Wait for all tasks that this
+   undeferred task depends on.
+
+   This is done by first putting all known ready dependencies
+   (dependencies that have their own dependencies met) at the top of
+   the scheduling queues.  Then we iterate through these imminently
+   ready tasks (and possibly other high priority tasks), and run them.
+   If we run out of ready dependencies to execute, we either wait for
+   the remaining dependencies to finish, or wait for them to get
+   scheduled so we can run them.
+
+   DEPEND is as in GOMP_task.  */
+
+void
+gomp_task_maybe_wait_for_dependencies (void **depend)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_task *task = thr->task;
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task_depend_entry elem, *ent = NULL;
+  struct gomp_taskwait taskwait;
+  size_t orig_ndepend = (uintptr_t) depend[0];
+  size_t nout = (uintptr_t) depend[1];
+  size_t ndepend = orig_ndepend;
+  size_t normal = ndepend;
+  size_t n = 2;
+  size_t i;
+  size_t num_awaited = 0;
+  struct gomp_task *child_task = NULL;
+  struct gomp_task *to_free = NULL;
+  int do_wake = 0;
+
+  if (ndepend == 0)
+    {
+      ndepend = nout;
+      nout = (uintptr_t) depend[2] + (uintptr_t) depend[3];
+      normal = nout + (uintptr_t) depend[4];
+      n = 5;
+    }
+  gomp_mutex_lock (&team->task_lock);
+  if (__builtin_expect (task->depend_all_memory && ndepend, false))
+    {
+      struct gomp_task *tsk = task->depend_all_memory;
+      if (!tsk->parent_depends_on)
+       {
+         tsk->parent_depends_on = true;
+         ++num_awaited;
+         if (tsk->num_dependees == 0 && tsk->kind == GOMP_TASK_WAITING)
+           priority_queue_upgrade_task (tsk, task);
+       }
+    }
+  for (i = 0; i < ndepend; i++)
+    {
+      elem.addr = depend[i + n];
+      elem.is_in = i >= nout;
+      if (__builtin_expect (i >= normal, 0))
+       {
+         void **d = (void **) elem.addr;
+         switch ((uintptr_t) d[1])
+           {
+           case GOMP_DEPEND_IN:
+             break;
+           case GOMP_DEPEND_OUT:
+           case GOMP_DEPEND_INOUT:
+           case GOMP_DEPEND_MUTEXINOUTSET:
+             elem.is_in = 0;
+             break;
+           case GOMP_DEPEND_INOUTSET:
+             elem.is_in = 2;
+             break;
+           default:
+             gomp_fatal ("unknown omp_depend_t dependence type %d",
+                         (int) (uintptr_t) d[1]);
+           }
+         elem.addr = d[0];
+       }
+      if (__builtin_expect (elem.addr == NULL && !elem.is_in, false))
+       {
+         size_t size = htab_size (task->depend_hash);
+         if (htab_elements (task->depend_hash) * 8 < size && size > 32)
+           htab_expand (task->depend_hash);
+
+         /* depend(inout: omp_all_memory) - depend on all previous
+            sibling tasks that do have dependencies.  Inlined
+            htab_traverse.  */
+         hash_entry_type *slot = &task->depend_hash->entries[0];
+         hash_entry_type *end = slot + htab_size (task->depend_hash);
+         for (; slot != end; ++slot)
+           {
+             if (*slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
+               continue;
+             for (ent = *slot; ent; ent = ent->next)
+               {
+                 struct gomp_task *tsk = ent->task;
+                 if (!tsk->parent_depends_on)
+                   {
+                     tsk->parent_depends_on = true;
+                     ++num_awaited;
+                     if (tsk->num_dependees == 0
+                         && tsk->kind == GOMP_TASK_WAITING)
+                       priority_queue_upgrade_task (tsk, task);
+                   }
+               }
+           }
+         break;
+       }
+      ent = htab_find (task->depend_hash, &elem);
+      for (; ent; ent = ent->next)
+       if (elem.is_in && elem.is_in == ent->is_in)
+         continue;
+       else
+         {
+           struct gomp_task *tsk = ent->task;
+           if (!tsk->parent_depends_on)
+             {
+               tsk->parent_depends_on = true;
+               ++num_awaited;
+               /* If dependency TSK itself has no dependencies and is
+                  ready to run, move it up front so that we run it as
+                  soon as possible.  */
+               if (tsk->num_dependees == 0 && tsk->kind == GOMP_TASK_WAITING)
+                 priority_queue_upgrade_task (tsk, task);
+             }
+         }
+    }
+  if (num_awaited == 0)
+    {
+      gomp_mutex_unlock (&team->task_lock);
+      return;
+    }
+
+  memset (&taskwait, 0, sizeof (taskwait));
+  taskwait.n_depend = num_awaited;
+  gomp_sem_init (&taskwait.taskwait_sem, 0);
+  task->taskwait = &taskwait;
+
+  while (1)
+    {
+      bool cancelled = false;
+      if (taskwait.n_depend == 0)
+       {
+         task->taskwait = NULL;
+         gomp_mutex_unlock (&team->task_lock);
+         if (to_free)
+           {
+             gomp_finish_task (to_free);
+             free (to_free);
+           }
+         gomp_sem_destroy (&taskwait.taskwait_sem);
+         return;
+       }
+
+      /* Theoretically when we have multiple priorities, we should
+        chose between the highest priority item in
+        task->children_queue and team->task_queue here, so we should
+        use priority_queue_next_task().  However, since we are
+        running an undeferred task, perhaps that makes all tasks it
+        depends on undeferred, thus a priority of INF?  This would
+        make it unnecessary to take anything into account here,
+        but the dependencies.
+
+        On the other hand, if we want to use priority_queue_next_task(),
+        care should be taken to only use priority_queue_remove()
+        below if the task was actually removed from the children
+        queue.  */
+      bool ignored;
+      struct gomp_task *next_task
+       = priority_queue_next_task (PQ_CHILDREN, &task->children_queue,
+                                   PQ_IGNORED, NULL, &ignored);
+
+      if (next_task->kind == GOMP_TASK_WAITING)
+       {
+         child_task = next_task;
+         cancelled
+           = gomp_task_run_pre (child_task, task, team);
+         if (__builtin_expect (cancelled, 0))
+           {
+             if (to_free)
+               {
+                 gomp_finish_task (to_free);
+                 free (to_free);
+                 to_free = NULL;
+               }
+             goto finish_cancelled;
+           }
+       }
+      else
+       /* All tasks we are waiting for are either running in other
+          threads, or they are tasks that have not had their
+          dependencies met (so they're not even in the queue).  Wait
+          for them.  */
+       taskwait.in_depend_wait = true;
+      gomp_mutex_unlock (&team->task_lock);
+      if (do_wake)
+       {
+         gomp_team_barrier_wake (&team->barrier, do_wake);
+         do_wake = 0;
+       }
+      if (to_free)
+       {
          gomp_finish_task (to_free);
          free (to_free);
          to_free = NULL;
@@ -337,42 +2102,580 @@ GOMP_taskwait (void)
       if (child_task)
        {
          thr->task = child_task;
-         child_task->fn (child_task->fn_data);
+         if (__builtin_expect (child_task->fn == NULL, 0))
+           {
+             if (gomp_target_task_fn (child_task->fn_data))
+               {
+                 thr->task = task;
+                 gomp_mutex_lock (&team->task_lock);
+                 child_task->kind = GOMP_TASK_ASYNC_RUNNING;
+                 struct gomp_target_task *ttask
+                   = (struct gomp_target_task *) child_task->fn_data;
+                 /* If GOMP_PLUGIN_target_task_completion has run already
+                    in between gomp_target_task_fn and the mutex lock,
+                    perform the requeuing here.  */
+                 if (ttask->state == GOMP_TARGET_TASK_FINISHED)
+                   gomp_target_task_completion (team, child_task);
+                 else
+                   ttask->state = GOMP_TARGET_TASK_RUNNING;
+                 child_task = NULL;
+                 continue;
+               }
+           }
+         else
+           child_task->fn (child_task->fn_data);
          thr->task = task;
        }
       else
+       gomp_sem_wait (&taskwait.taskwait_sem);
+      gomp_mutex_lock (&team->task_lock);
+      if (child_task)
        {
-         gomp_sem_wait (&task->taskwait_sem);
-         task->in_taskwait = false;
-         return;
+        finish_cancelled:;
+         size_t new_tasks
+           = gomp_task_run_post_handle_depend (child_task, team);
+         if (child_task->parent_depends_on)
+           --taskwait.n_depend;
+
+         priority_queue_remove (PQ_CHILDREN, &task->children_queue,
+                                child_task, MEMMODEL_RELAXED);
+         child_task->pnode[PQ_CHILDREN].next = NULL;
+         child_task->pnode[PQ_CHILDREN].prev = NULL;
+
+         gomp_clear_parent (&child_task->children_queue);
+         gomp_task_run_post_remove_taskgroup (child_task);
+         to_free = child_task;
+         child_task = NULL;
+         team->task_count--;
+         if (new_tasks > 1)
+           {
+             do_wake = team->nthreads - team->task_running_count
+                       - !task->in_tied_task;
+             if (do_wake > new_tasks)
+               do_wake = new_tasks;
+           }
+       }
+    }
+}
+
+/* Called when encountering a taskyield directive.  */
+
+void
+GOMP_taskyield (void)
+{
+  /* Nothing at the moment.  */
+}
+
+static inline struct gomp_taskgroup *
+gomp_taskgroup_init (struct gomp_taskgroup *prev)
+{
+  struct gomp_taskgroup *taskgroup
+    = gomp_malloc (sizeof (struct gomp_taskgroup));
+  taskgroup->prev = prev;
+  priority_queue_init (&taskgroup->taskgroup_queue);
+  taskgroup->reductions = prev ? prev->reductions : NULL;
+  taskgroup->in_taskgroup_wait = false;
+  taskgroup->cancelled = false;
+  taskgroup->workshare = false;
+  taskgroup->num_children = 0;
+  gomp_sem_init (&taskgroup->taskgroup_sem, 0);
+  return taskgroup;
+}
+
+void
+GOMP_taskgroup_start (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task = thr->task;
+
+  /* If team is NULL, all tasks are executed as
+     GOMP_TASK_UNDEFERRED tasks and thus all children tasks of
+     taskgroup and their descendant tasks will be finished
+     by the time GOMP_taskgroup_end is called.  */
+  if (team == NULL)
+    return;
+  task->taskgroup = gomp_taskgroup_init (task->taskgroup);
+}
+
+void
+GOMP_taskgroup_end (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task = thr->task;
+  struct gomp_taskgroup *taskgroup;
+  struct gomp_task *child_task = NULL;
+  struct gomp_task *to_free = NULL;
+  int do_wake = 0;
+
+  if (team == NULL)
+    return;
+  taskgroup = task->taskgroup;
+  if (__builtin_expect (taskgroup == NULL, 0)
+      && thr->ts.level == 0)
+    {
+      /* This can happen if GOMP_taskgroup_start is called when
+        thr->ts.team == NULL, but inside of the taskgroup there
+        is #pragma omp target nowait that creates an implicit
+        team with a single thread.  In this case, we want to wait
+        for all outstanding tasks in this team.  */
+      gomp_team_barrier_wait (&team->barrier);
+      return;
+    }
+
+  /* The acquire barrier on load of taskgroup->num_children here
+     synchronizes with the write of 0 in gomp_task_run_post_remove_taskgroup.
+     It is not necessary that we synchronize with other non-0 writes at
+     this point, but we must ensure that all writes to memory by a
+     child thread task work function are seen before we exit from
+     GOMP_taskgroup_end.  */
+  if (__atomic_load_n (&taskgroup->num_children, MEMMODEL_ACQUIRE) == 0)
+    goto finish;
+
+  bool unused;
+  gomp_mutex_lock (&team->task_lock);
+  while (1)
+    {
+      bool cancelled = false;
+      if (priority_queue_empty_p (&taskgroup->taskgroup_queue,
+                                 MEMMODEL_RELAXED))
+       {
+         if (taskgroup->num_children)
+           {
+             if (priority_queue_empty_p (&task->children_queue,
+                                         MEMMODEL_RELAXED))
+               goto do_wait;
+             child_task
+               = priority_queue_next_task (PQ_CHILDREN, &task->children_queue,
+                                           PQ_TEAM, &team->task_queue,
+                                           &unused);
+           }
+         else
+           {
+             gomp_mutex_unlock (&team->task_lock);
+             if (to_free)
+               {
+                 gomp_finish_task (to_free);
+                 free (to_free);
+               }
+             goto finish;
+           }
+       }
+      else
+       child_task
+         = priority_queue_next_task (PQ_TASKGROUP, &taskgroup->taskgroup_queue,
+                                     PQ_TEAM, &team->task_queue, &unused);
+      if (child_task->kind == GOMP_TASK_WAITING)
+       {
+         cancelled
+           = gomp_task_run_pre (child_task, child_task->parent, team);
+         if (__builtin_expect (cancelled, 0))
+           {
+             if (to_free)
+               {
+                 gomp_finish_task (to_free);
+                 free (to_free);
+                 to_free = NULL;
+               }
+             goto finish_cancelled;
+           }
        }
+      else
+       {
+         child_task = NULL;
+        do_wait:
+       /* All tasks we are waiting for are either running in other
+          threads, or they are tasks that have not had their
+          dependencies met (so they're not even in the queue).  Wait
+          for them.  */
+         taskgroup->in_taskgroup_wait = true;
+       }
+      gomp_mutex_unlock (&team->task_lock);
+      if (do_wake)
+       {
+         gomp_team_barrier_wake (&team->barrier, do_wake);
+         do_wake = 0;
+       }
+      if (to_free)
+       {
+         gomp_finish_task (to_free);
+         free (to_free);
+         to_free = NULL;
+       }
+      if (child_task)
+       {
+         thr->task = child_task;
+         if (__builtin_expect (child_task->fn == NULL, 0))
+           {
+             if (gomp_target_task_fn (child_task->fn_data))
+               {
+                 thr->task = task;
+                 gomp_mutex_lock (&team->task_lock);
+                 child_task->kind = GOMP_TASK_ASYNC_RUNNING;
+                 struct gomp_target_task *ttask
+                   = (struct gomp_target_task *) child_task->fn_data;
+                 /* If GOMP_PLUGIN_target_task_completion has run already
+                    in between gomp_target_task_fn and the mutex lock,
+                    perform the requeuing here.  */
+                 if (ttask->state == GOMP_TARGET_TASK_FINISHED)
+                   gomp_target_task_completion (team, child_task);
+                 else
+                   ttask->state = GOMP_TARGET_TASK_RUNNING;
+                 child_task = NULL;
+                 continue;
+               }
+           }
+         else
+           child_task->fn (child_task->fn_data);
+         thr->task = task;
+       }
+      else
+       gomp_sem_wait (&taskgroup->taskgroup_sem);
       gomp_mutex_lock (&team->task_lock);
       if (child_task)
        {
-         child_task->prev_child->next_child = child_task->next_child;
-         child_task->next_child->prev_child = child_task->prev_child;
-         if (task->children == child_task)
+         if (child_task->detach_team)
            {
-             if (child_task->next_child != child_task)
-               task->children = child_task->next_child;
-             else
-               task->children = NULL;
+             assert (child_task->detach_team == team);
+             child_task->kind = GOMP_TASK_DETACHED;
+             ++team->task_detach_count;
+             gomp_debug (0,
+                         "thread %d: task with event %p finished without "
+                         "completion event fulfilled in taskgroup\n",
+                         thr->ts.team_id, child_task);
+             child_task = NULL;
+             continue;
            }
-         gomp_clear_parent (child_task->children);
+
+        finish_cancelled:;
+         size_t new_tasks
+           = gomp_task_run_post_handle_depend (child_task, team);
+         gomp_task_run_post_remove_parent (child_task);
+         gomp_clear_parent (&child_task->children_queue);
+         gomp_task_run_post_remove_taskgroup (child_task);
          to_free = child_task;
          child_task = NULL;
          team->task_count--;
-         team->task_running_count--;
+         if (new_tasks > 1)
+           {
+             do_wake = team->nthreads - team->task_running_count
+                       - !task->in_tied_task;
+             if (do_wake > new_tasks)
+               do_wake = new_tasks;
+           }
        }
     }
+
+ finish:
+  task->taskgroup = taskgroup->prev;
+  gomp_sem_destroy (&taskgroup->taskgroup_sem);
+  free (taskgroup);
 }
 
-/* Called when encountering a taskyield directive.  */
+static inline __attribute__((always_inline)) void
+gomp_reduction_register (uintptr_t *data, uintptr_t *old, uintptr_t *orig,
+                        unsigned nthreads)
+{
+  size_t total_cnt = 0;
+  uintptr_t *d = data;
+  struct htab *old_htab = NULL, *new_htab;
+  do
+    {
+      if (__builtin_expect (orig != NULL, 0))
+       {
+         /* For worksharing task reductions, memory has been allocated
+            already by some other thread that encountered the construct
+            earlier.  */
+         d[2] = orig[2];
+         d[6] = orig[6];
+         orig = (uintptr_t *) orig[4];
+       }
+      else
+       {
+         size_t sz = d[1] * nthreads;
+         /* Should use omp_alloc if d[3] is not -1.  */
+         void *ptr = gomp_aligned_alloc (d[2], sz);
+         memset (ptr, '\0', sz);
+         d[2] = (uintptr_t) ptr;
+         d[6] = d[2] + sz;
+       }
+      d[5] = 0;
+      total_cnt += d[0];
+      if (d[4] == 0)
+       {
+         d[4] = (uintptr_t) old;
+         break;
+       }
+      else
+       d = (uintptr_t *) d[4];
+    }
+  while (1);
+  if (old && old[5])
+    {
+      old_htab = (struct htab *) old[5];
+      total_cnt += htab_elements (old_htab);
+    }
+  new_htab = htab_create (total_cnt);
+  if (old_htab)
+    {
+      /* Copy old hash table, like in htab_expand.  */
+      hash_entry_type *p, *olimit;
+      new_htab->n_elements = htab_elements (old_htab);
+      olimit = old_htab->entries + old_htab->size;
+      p = old_htab->entries;
+      do
+       {
+         hash_entry_type x = *p;
+         if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
+           *find_empty_slot_for_expand (new_htab, htab_hash (x)) = x;
+         p++;
+       }
+      while (p < olimit);
+    }
+  d = data;
+  do
+    {
+      size_t j;
+      for (j = 0; j < d[0]; ++j)
+       {
+         uintptr_t *p = d + 7 + j * 3;
+         p[2] = (uintptr_t) d;
+         /* Ugly hack, hash_entry_type is defined for the task dependencies,
+            which hash on the first element which is a pointer.  We need
+            to hash also on the first sizeof (uintptr_t) bytes which contain
+            a pointer.  Hide the cast from the compiler.  */
+         hash_entry_type n;
+         __asm ("" : "=g" (n) : "0" (p));
+         *htab_find_slot (&new_htab, n, INSERT) = n;
+       }
+      if (d[4] == (uintptr_t) old)
+       break;
+      else
+       d = (uintptr_t *) d[4];
+    }
+  while (1);
+  d[5] = (uintptr_t) new_htab;
+}
+
+static void
+gomp_create_artificial_team (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_task_icv *icv;
+  struct gomp_team *team = gomp_new_team (1);
+  struct gomp_task *task = thr->task;
+  struct gomp_task **implicit_task = &task;
+  icv = task ? &task->icv : &gomp_global_icv;
+  team->prev_ts = thr->ts;
+  thr->ts.team = team;
+  thr->ts.team_id = 0;
+  thr->ts.work_share = &team->work_shares[0];
+  thr->ts.last_work_share = NULL;
+#ifdef HAVE_SYNC_BUILTINS
+  thr->ts.single_count = 0;
+#endif
+  thr->ts.static_trip = 0;
+  thr->task = &team->implicit_task[0];
+  gomp_init_task (thr->task, NULL, icv);
+  while (*implicit_task
+        && (*implicit_task)->kind != GOMP_TASK_IMPLICIT)
+    implicit_task = &(*implicit_task)->parent;
+  if (*implicit_task)
+    {
+      thr->task = *implicit_task;
+      gomp_end_task ();
+      free (*implicit_task);
+      thr->task = &team->implicit_task[0];
+    }
+#ifdef LIBGOMP_USE_PTHREADS
+  else
+    pthread_setspecific (gomp_thread_destructor, thr);
+#endif
+  if (implicit_task != &task)
+    {
+      *implicit_task = thr->task;
+      thr->task = task;
+    }
+}
+
+/* The format of data is:
+   data[0]     cnt
+   data[1]     size
+   data[2]     alignment (on output array pointer)
+   data[3]     allocator (-1 if malloc allocator)
+   data[4]     next pointer
+   data[5]     used internally (htab pointer)
+   data[6]     used internally (end of array)
+   cnt times
+   ent[0]      address
+   ent[1]      offset
+   ent[2]      used internally (pointer to data[0])
+   The entries are sorted by increasing offset, so that a binary
+   search can be performed.  Normally, data[8] is 0, exception is
+   for worksharing construct task reductions in cancellable parallel,
+   where at offset 0 there should be space for a pointer and an integer
+   which are used internally.  */
 
 void
-GOMP_taskyield (void)
+GOMP_taskgroup_reduction_register (uintptr_t *data)
 {
-  /* Nothing at the moment.  */
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task;
+  unsigned nthreads;
+  if (__builtin_expect (team == NULL, 0))
+    {
+      /* The task reduction code needs a team and task, so for
+        orphaned taskgroups just create the implicit team.  */
+      gomp_create_artificial_team ();
+      ialias_call (GOMP_taskgroup_start) ();
+      team = thr->ts.team;
+    }
+  nthreads = team->nthreads;
+  task = thr->task;
+  gomp_reduction_register (data, task->taskgroup->reductions, NULL, nthreads);
+  task->taskgroup->reductions = data;
+}
+
+void
+GOMP_taskgroup_reduction_unregister (uintptr_t *data)
+{
+  uintptr_t *d = data;
+  htab_free ((struct htab *) data[5]);
+  do
+    {
+      gomp_aligned_free ((void *) d[2]);
+      d = (uintptr_t *) d[4];
+    }
+  while (d && !d[5]);
+}
+ialias (GOMP_taskgroup_reduction_unregister)
+
+/* For i = 0 to cnt-1, remap ptrs[i] which is either address of the
+   original list item or address of previously remapped original list
+   item to address of the private copy, store that to ptrs[i].
+   For i < cntorig, additionally set ptrs[cnt+i] to the address of
+   the original list item.  */
+
+void
+GOMP_task_reduction_remap (size_t cnt, size_t cntorig, void **ptrs)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_task *task = thr->task;
+  unsigned id = thr->ts.team_id;
+  uintptr_t *data = task->taskgroup->reductions;
+  uintptr_t *d;
+  struct htab *reduction_htab = (struct htab *) data[5];
+  size_t i;
+  for (i = 0; i < cnt; ++i)
+    {
+      hash_entry_type ent, n;
+      __asm ("" : "=g" (ent) : "0" (ptrs + i));
+      n = htab_find (reduction_htab, ent);
+      if (n)
+       {
+         uintptr_t *p;
+         __asm ("" : "=g" (p) : "0" (n));
+         /* At this point, p[0] should be equal to (uintptr_t) ptrs[i],
+            p[1] is the offset within the allocated chunk for each
+            thread, p[2] is the array registered with
+            GOMP_taskgroup_reduction_register, d[2] is the base of the
+            allocated memory and d[1] is the size of the allocated chunk
+            for one thread.  */
+         d = (uintptr_t *) p[2];
+         ptrs[i] = (void *) (d[2] + id * d[1] + p[1]);
+         if (__builtin_expect (i < cntorig, 0))
+           ptrs[cnt + i] = (void *) p[0];
+         continue;
+       }
+      d = data;
+      while (d != NULL)
+       {
+         if ((uintptr_t) ptrs[i] >= d[2] && (uintptr_t) ptrs[i] < d[6])
+           break;
+         d = (uintptr_t *) d[4];
+       }
+      if (d == NULL)
+       gomp_fatal ("couldn't find matching task_reduction or reduction with "
+                   "task modifier for %p", ptrs[i]);
+      uintptr_t off = ((uintptr_t) ptrs[i] - d[2]) % d[1];
+      ptrs[i] = (void *) (d[2] + id * d[1] + off);
+      if (__builtin_expect (i < cntorig, 0))
+       {
+         size_t lo = 0, hi = d[0] - 1;
+         while (lo <= hi)
+           {
+             size_t m = (lo + hi) / 2;
+             if (d[7 + 3 * m + 1] < off)
+               lo = m + 1;
+             else if (d[7 + 3 * m + 1] == off)
+               {
+                 ptrs[cnt + i] = (void *) d[7 + 3 * m];
+                 break;
+               }
+             else
+               hi = m - 1;
+           }
+         if (lo > hi)
+           gomp_fatal ("couldn't find matching task_reduction or reduction "
+                       "with task modifier for %p", ptrs[i]);
+       }
+    }
+}
+
+struct gomp_taskgroup *
+gomp_parallel_reduction_register (uintptr_t *data, unsigned nthreads)
+{
+  struct gomp_taskgroup *taskgroup = gomp_taskgroup_init (NULL);
+  gomp_reduction_register (data, NULL, NULL, nthreads);
+  taskgroup->reductions = data;
+  return taskgroup;
+}
+
+void
+gomp_workshare_task_reduction_register (uintptr_t *data, uintptr_t *orig)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task = thr->task;
+  unsigned nthreads = team->nthreads;
+  gomp_reduction_register (data, task->taskgroup->reductions, orig, nthreads);
+  task->taskgroup->reductions = data;
+}
+
+void
+gomp_workshare_taskgroup_start (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_team *team = thr->ts.team;
+  struct gomp_task *task;
+
+  if (team == NULL)
+    {
+      gomp_create_artificial_team ();
+      team = thr->ts.team;
+    }
+  task = thr->task;
+  task->taskgroup = gomp_taskgroup_init (task->taskgroup);
+  task->taskgroup->workshare = true;
+}
+
+void
+GOMP_workshare_task_reduction_unregister (bool cancelled)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_task *task = thr->task;
+  struct gomp_team *team = thr->ts.team;
+  uintptr_t *data = task->taskgroup->reductions;
+  ialias_call (GOMP_taskgroup_end) ();
+  if (thr->ts.team_id == 0)
+    ialias_call (GOMP_taskgroup_reduction_unregister) (data);
+  else
+    htab_free ((struct htab *) data[5]);
+
+  if (!cancelled)
+    gomp_team_barrier_wait (&team->barrier);
 }
 
 int
@@ -383,3 +2686,90 @@ omp_in_final (void)
 }
 
 ialias (omp_in_final)
+
+int
+omp_in_explicit_task (void)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  struct gomp_task *task = thr->task;
+  return task && task->kind != GOMP_TASK_IMPLICIT;
+}
+
+ialias (omp_in_explicit_task)
+
+void
+omp_fulfill_event (omp_event_handle_t event)
+{
+  struct gomp_task *task = (struct gomp_task *) event;
+  if (!task->deferred_p)
+    {
+      if (gomp_sem_getcount (task->completion_sem) > 0)
+       gomp_fatal ("omp_fulfill_event: %p event already fulfilled!\n", task);
+
+      gomp_debug (0, "omp_fulfill_event: %p event for undeferred task\n",
+                 task);
+      gomp_sem_post (task->completion_sem);
+      return;
+    }
+
+  struct gomp_team *team = __atomic_load_n (&task->detach_team,
+                                           MEMMODEL_RELAXED);
+  if (!team)
+    gomp_fatal ("omp_fulfill_event: %p event is invalid or has already "
+               "been fulfilled!\n", task);
+
+  gomp_mutex_lock (&team->task_lock);
+  if (task->kind != GOMP_TASK_DETACHED)
+    {
+      /* The task has not finished running yet.  */
+      gomp_debug (0,
+                 "omp_fulfill_event: %p event fulfilled for unfinished "
+                 "task\n", task);
+      __atomic_store_n (&task->detach_team, NULL, MEMMODEL_RELAXED);
+      gomp_mutex_unlock (&team->task_lock);
+      return;
+    }
+
+  gomp_debug (0, "omp_fulfill_event: %p event fulfilled for finished task\n",
+             task);
+  size_t new_tasks = gomp_task_run_post_handle_depend (task, team);
+  gomp_task_run_post_remove_parent (task);
+  gomp_clear_parent (&task->children_queue);
+  gomp_task_run_post_remove_taskgroup (task);
+  team->task_count--;
+  team->task_detach_count--;
+
+  int do_wake = 0;
+  bool shackled_thread_p = team == gomp_thread ()->ts.team;
+  if (new_tasks > 0)
+    {
+      /* Wake up threads to run new tasks.  */
+      gomp_team_barrier_set_task_pending (&team->barrier);
+      do_wake = team->nthreads - team->task_running_count;
+      if (do_wake > new_tasks)
+       do_wake = new_tasks;
+    }
+
+  if (!shackled_thread_p
+      && !do_wake
+      && team->task_detach_count == 0
+      && gomp_team_barrier_waiting_for_tasks (&team->barrier))
+    /* Ensure that at least one thread is woken up to signal that the
+       barrier can finish.  */
+    do_wake = 1;
+
+  /* If we are running in an unshackled thread, the team might vanish before
+     gomp_team_barrier_wake is run if we release the lock first, so keep the
+     lock for the call in that case.  */
+  if (shackled_thread_p)
+    gomp_mutex_unlock (&team->task_lock);
+  if (do_wake)
+    gomp_team_barrier_wake (&team->barrier, do_wake);
+  if (!shackled_thread_p)
+    gomp_mutex_unlock (&team->task_lock);
+
+  gomp_finish_task (task);
+  free (task);
+}
+
+ialias (omp_fulfill_event)