]> git.ipfire.org Git - thirdparty/gcc.git/blobdiff - libgomp/target.c
OpenMP: Move omp requires checks to libgomp
[thirdparty/gcc.git] / libgomp / target.c
index 1a8c67c2df5ac5e569ced528ddd3d313a7f0ee86..4dac81862d7f73fece6b05850e60776760e41cd3 100644 (file)
@@ -1,4 +1,4 @@
-/* Copyright (C) 2013-2020 Free Software Foundation, Inc.
+/* Copyright (C) 2013-2022 Free Software Foundation, Inc.
    Contributed by Jakub Jelinek <jakub@redhat.com>.
 
    This file is part of the GNU Offloading and Multi Processing Library
@@ -36,6 +36,7 @@
 # include <inttypes.h>  /* For PRIu64.  */
 #endif
 #include <string.h>
+#include <stdio.h>  /* For snprintf. */
 #include <assert.h>
 #include <errno.h>
 
 #include "plugin-suffix.h"
 #endif
 
+typedef uintptr_t *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"
+
+ialias_redirect (GOMP_task)
+
+static inline hashval_t
+htab_hash (hash_entry_type element)
+{
+  return hash_pointer ((void *) element);
+}
+
+static inline bool
+htab_eq (hash_entry_type x, hash_entry_type y)
+{
+  return x == y;
+}
+
 #define FIELD_TGT_EMPTY (~(size_t) 0)
 
 static void gomp_target_init (void);
@@ -79,6 +99,9 @@ static int num_devices;
 /* Number of GOMP_OFFLOAD_CAP_OPENMP_400 devices.  */
 static int num_devices_openmp;
 
+/* OpenMP requires mask.  */
+static int omp_requires_mask;
+
 /* Similar to gomp_realloc, but release register_lock before gomp_fatal.  */
 
 static void *
@@ -107,18 +130,31 @@ gomp_get_num_devices (void)
 }
 
 static struct gomp_device_descr *
-resolve_device (int device_id)
+resolve_device (int device_id, bool remapped)
 {
-  if (device_id == GOMP_DEVICE_ICV)
+  if (remapped && device_id == GOMP_DEVICE_ICV)
     {
       struct gomp_task_icv *icv = gomp_icv (false);
       device_id = icv->default_device_var;
+      remapped = false;
     }
 
-  if (device_id < 0 || device_id >= gomp_get_num_devices ())
+  if (device_id < 0)
+    {
+      if (device_id == (remapped ? GOMP_DEVICE_HOST_FALLBACK
+                                : omp_initial_device))
+       return NULL;
+      if (device_id == omp_invalid_device)
+       gomp_fatal ("omp_invalid_device encountered");
+      else if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY)
+       gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY, "
+                   "but device not found");
+
+      return NULL;
+    }
+  else if (device_id >= gomp_get_num_devices ())
     {
       if (gomp_target_offload_var == GOMP_TARGET_OFFLOAD_MANDATORY
-         && device_id != GOMP_DEVICE_HOST_FALLBACK
          && device_id != num_devices_openmp)
        gomp_fatal ("OMP_TARGET_OFFLOAD is set to MANDATORY, "
                    "but device not found");
@@ -197,13 +233,24 @@ goacc_device_copy_async (struct gomp_device_descr *devicep,
                                            struct goacc_asyncqueue *),
                         const char *dst, void *dstaddr,
                         const char *src, const void *srcaddr,
+                        const void *srcaddr_orig,
                         size_t size, struct goacc_asyncqueue *aq)
 {
   if (!copy_func (devicep->target_id, dstaddr, srcaddr, size, aq))
     {
       gomp_mutex_unlock (&devicep->lock);
-      gomp_fatal ("Copying of %s object [%p..%p) to %s object [%p..%p) failed",
-                 src, srcaddr, srcaddr + size, dst, dstaddr, dstaddr + size);
+      if (srcaddr_orig && srcaddr_orig != srcaddr)
+       gomp_fatal ("Copying of %s object [%p..%p)"
+                   " via buffer %s object [%p..%p)"
+                   " to %s object [%p..%p) failed",
+                   src, srcaddr_orig, srcaddr_orig + size,
+                   src, srcaddr, srcaddr + size,
+                   dst, dstaddr, dstaddr + size);
+      else
+       gomp_fatal ("Copying of %s object [%p..%p)"
+                   " to %s object [%p..%p) failed",
+                   src, srcaddr, srcaddr + size,
+                   dst, dstaddr, dstaddr + size);
     }
 }
 
@@ -247,7 +294,14 @@ struct gomp_coalesce_buf
    host to device (e.g. map(alloc:), map(from:) etc.).  */
 #define MAX_COALESCE_BUF_GAP   (4 * 1024)
 
-/* Add region with device tgt_start relative offset and length to CBUF.  */
+/* Add region with device tgt_start relative offset and length to CBUF.
+
+   This must not be used for asynchronous copies, because the host data might
+   not be computed yet (by an earlier asynchronous compute region, for
+   example).
+   TODO ... but we could allow CBUF usage for EPHEMERAL data?  (Open question:
+   is it more performant to use libgomp CBUF buffering or individual device
+   asyncronous copying?)  */
 
 static inline void
 gomp_coalesce_buf_add (struct gomp_coalesce_buf *cbuf, size_t start, size_t len)
@@ -300,12 +354,41 @@ gomp_to_device_kind_p (int kind)
     }
 }
 
+/* Copy host memory to an offload device.  In asynchronous mode (if AQ is
+   non-NULL), when the source data is stack or may otherwise be deallocated
+   before the asynchronous copy takes place, EPHEMERAL must be passed as
+   TRUE.  */
+
 attribute_hidden void
 gomp_copy_host2dev (struct gomp_device_descr *devicep,
                    struct goacc_asyncqueue *aq,
                    void *d, const void *h, size_t sz,
-                   struct gomp_coalesce_buf *cbuf)
+                   bool ephemeral, struct gomp_coalesce_buf *cbuf)
 {
+  if (__builtin_expect (aq != NULL, 0))
+    {
+      /* See 'gomp_coalesce_buf_add'.  */
+      assert (!cbuf);
+
+      void *h_buf = (void *) h;
+      if (ephemeral)
+       {
+         /* We're queueing up an asynchronous copy from data that may
+            disappear before the transfer takes place (i.e. because it is a
+            stack local in a function that is no longer executing).  Make a
+            copy of the data into a temporary buffer in those cases.  */
+         h_buf = gomp_malloc (sz);
+         memcpy (h_buf, h, sz);
+       }
+      goacc_device_copy_async (devicep, devicep->openacc.async.host2dev_func,
+                              "dev", d, "host", h_buf, h, sz, aq);
+      if (ephemeral)
+       /* Free temporary buffer once the transfer has completed.  */
+       devicep->openacc.async.queue_callback_func (aq, free, h_buf);
+
+      return;
+    }
+
   if (cbuf)
     {
       uintptr_t doff = (uintptr_t) d - cbuf->tgt->tgt_start;
@@ -321,7 +404,10 @@ gomp_copy_host2dev (struct gomp_device_descr *devicep,
              else if (cbuf->chunks[middle].start <= doff)
                {
                  if (doff + sz > cbuf->chunks[middle].end)
-                   gomp_fatal ("internal libgomp cbuf error");
+                   {
+                     gomp_mutex_unlock (&devicep->lock);
+                     gomp_fatal ("internal libgomp cbuf error");
+                   }
                  memcpy ((char *) cbuf->buf + (doff - cbuf->chunks[0].start),
                          h, sz);
                  return;
@@ -331,11 +417,8 @@ gomp_copy_host2dev (struct gomp_device_descr *devicep,
            }
        }
     }
-  if (__builtin_expect (aq != NULL, 0))
-    goacc_device_copy_async (devicep, devicep->openacc.async.host2dev_func,
-                            "dev", d, "host", h, sz, aq);
-  else
-    gomp_device_copy (devicep, devicep->host2dev_func, "dev", d, "host", h, sz);
+
+  gomp_device_copy (devicep, devicep->host2dev_func, "dev", d, "host", h, sz);
 }
 
 attribute_hidden void
@@ -345,7 +428,7 @@ gomp_copy_dev2host (struct gomp_device_descr *devicep,
 {
   if (__builtin_expect (aq != NULL, 0))
     goacc_device_copy_async (devicep, devicep->openacc.async.dev2host_func,
-                            "host", h, "dev", d, sz, aq);
+                            "host", h, "dev", d, NULL, sz, aq);
   else
     gomp_device_copy (devicep, devicep->dev2host_func, "host", h, "dev", d, sz);
 }
@@ -360,6 +443,113 @@ gomp_free_device_memory (struct gomp_device_descr *devicep, void *devptr)
     }
 }
 
+/* Increment reference count of a splay_tree_key region K by 1.
+   If REFCOUNT_SET != NULL, use it to track already seen refcounts, and only
+   increment the value if refcount is not yet contained in the set (used for
+   OpenMP 5.0, which specifies that a region's refcount is adjusted at most
+   once for each construct).  */
+
+static inline void
+gomp_increment_refcount (splay_tree_key k, htab_t *refcount_set)
+{
+  if (k == NULL || k->refcount == REFCOUNT_INFINITY)
+    return;
+
+  uintptr_t *refcount_ptr = &k->refcount;
+
+  if (REFCOUNT_STRUCTELEM_FIRST_P (k->refcount))
+    refcount_ptr = &k->structelem_refcount;
+  else if (REFCOUNT_STRUCTELEM_P (k->refcount))
+    refcount_ptr = k->structelem_refcount_ptr;
+
+  if (refcount_set)
+    {
+      if (htab_find (*refcount_set, refcount_ptr))
+       return;
+      uintptr_t **slot = htab_find_slot (refcount_set, refcount_ptr, INSERT);
+      *slot = refcount_ptr;
+    }
+
+  *refcount_ptr += 1;
+  return;
+}
+
+/* Decrement reference count of a splay_tree_key region K by 1, or if DELETE_P
+   is true, set reference count to zero. If REFCOUNT_SET != NULL, use it to
+   track already seen refcounts, and only adjust the value if refcount is not
+   yet contained in the set (like gomp_increment_refcount).
+
+   Return out-values: set *DO_COPY to true if we set the refcount to zero, or
+   it is already zero and we know we decremented it earlier. This signals that
+   associated maps should be copied back to host.
+
+   *DO_REMOVE is set to true when we this is the first handling of this refcount
+   and we are setting it to zero. This signals a removal of this key from the
+   splay-tree map.
+
+   Copy and removal are separated due to cases like handling of structure
+   elements, e.g. each map of a structure element representing a possible copy
+   out of a structure field has to be handled individually, but we only signal
+   removal for one (the first encountered) sibing map.  */
+
+static inline void
+gomp_decrement_refcount (splay_tree_key k, htab_t *refcount_set, bool delete_p,
+                        bool *do_copy, bool *do_remove)
+{
+  if (k == NULL || k->refcount == REFCOUNT_INFINITY)
+    {
+      *do_copy = *do_remove = false;
+      return;
+    }
+
+  uintptr_t *refcount_ptr = &k->refcount;
+
+  if (REFCOUNT_STRUCTELEM_FIRST_P (k->refcount))
+    refcount_ptr = &k->structelem_refcount;
+  else if (REFCOUNT_STRUCTELEM_P (k->refcount))
+    refcount_ptr = k->structelem_refcount_ptr;
+
+  bool new_encountered_refcount;
+  bool set_to_zero = false;
+  bool is_zero = false;
+
+  uintptr_t orig_refcount = *refcount_ptr;
+
+  if (refcount_set)
+    {
+      if (htab_find (*refcount_set, refcount_ptr))
+       {
+         new_encountered_refcount = false;
+         goto end;
+       }
+
+      uintptr_t **slot = htab_find_slot (refcount_set, refcount_ptr, INSERT);
+      *slot = refcount_ptr;
+      new_encountered_refcount = true;
+    }
+  else
+    /* If no refcount_set being used, assume all keys are being decremented
+       for the first time.  */
+    new_encountered_refcount = true;
+
+  if (delete_p)
+    *refcount_ptr = 0;
+  else if (*refcount_ptr > 0)
+    *refcount_ptr -= 1;
+
+ end:
+  if (*refcount_ptr == 0)
+    {
+      if (orig_refcount > 0)
+       set_to_zero = true;
+
+      is_zero = true;
+    }
+
+  *do_copy = (set_to_zero || (!new_encountered_refcount && is_zero));
+  *do_remove = (new_encountered_refcount && set_to_zero);
+}
+
 /* Handle the case where gomp_map_lookup, splay_tree_lookup or
    gomp_map_0len_lookup found oldn for newn.
    Helper function of gomp_map_vars.  */
@@ -368,21 +558,34 @@ static inline void
 gomp_map_vars_existing (struct gomp_device_descr *devicep,
                        struct goacc_asyncqueue *aq, splay_tree_key oldn,
                        splay_tree_key newn, struct target_var_desc *tgt_var,
-                       unsigned char kind, bool always_to_flag,
-                       struct gomp_coalesce_buf *cbuf)
+                       unsigned char kind, bool always_to_flag, bool implicit,
+                       struct gomp_coalesce_buf *cbuf,
+                       htab_t *refcount_set)
 {
-  assert (kind != GOMP_MAP_ATTACH);
+  assert (kind != GOMP_MAP_ATTACH
+         || kind != GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION);
 
   tgt_var->key = oldn;
   tgt_var->copy_from = GOMP_MAP_COPY_FROM_P (kind);
   tgt_var->always_copy_from = GOMP_MAP_ALWAYS_FROM_P (kind);
   tgt_var->is_attach = false;
   tgt_var->offset = newn->host_start - oldn->host_start;
-  tgt_var->length = newn->host_end - newn->host_start;
+
+  /* For implicit maps, old contained in new is valid.  */
+  bool implicit_subset = (implicit
+                         && newn->host_start <= oldn->host_start
+                         && oldn->host_end <= newn->host_end);
+  if (implicit_subset)
+    tgt_var->length = oldn->host_end - oldn->host_start;
+  else
+    tgt_var->length = newn->host_end - newn->host_start;
 
   if ((kind & GOMP_MAP_FLAG_FORCE)
-      || oldn->host_start > newn->host_start
-      || oldn->host_end < newn->host_end)
+      /* For implicit maps, old contained in new is valid.  */
+      || !(implicit_subset
+          /* Otherwise, new contained inside old is considered valid.  */
+          || (oldn->host_start <= newn->host_start
+              && newn->host_end <= oldn->host_end)))
     {
       gomp_mutex_unlock (&devicep->lock);
       gomp_fatal ("Trying to map into device [%p..%p) object when "
@@ -392,27 +595,68 @@ gomp_map_vars_existing (struct gomp_device_descr *devicep,
     }
 
   if (GOMP_MAP_ALWAYS_TO_P (kind) || always_to_flag)
-    gomp_copy_host2dev (devicep, aq,
-                       (void *) (oldn->tgt->tgt_start + oldn->tgt_offset
-                                 + newn->host_start - oldn->host_start),
-                       (void *) newn->host_start,
-                       newn->host_end - newn->host_start, cbuf);
+    {
+      /* Implicit + always should not happen. If this does occur, below
+        address/length adjustment is a TODO.  */
+      assert (!implicit_subset);
 
-  if (oldn->refcount != REFCOUNT_INFINITY)
-    oldn->refcount++;
+      if (oldn->aux && oldn->aux->attach_count)
+       {
+         /* We have to be careful not to overwrite still attached pointers
+            during the copyback to host.  */
+         uintptr_t addr = newn->host_start;
+         while (addr < newn->host_end)
+           {
+             size_t i = (addr - oldn->host_start) / sizeof (void *);
+             if (oldn->aux->attach_count[i] == 0)
+               gomp_copy_host2dev (devicep, aq,
+                                   (void *) (oldn->tgt->tgt_start
+                                             + oldn->tgt_offset
+                                             + addr - oldn->host_start),
+                                   (void *) addr,
+                                   sizeof (void *), false, cbuf);
+             addr += sizeof (void *);
+           }
+       }
+      else
+       gomp_copy_host2dev (devicep, aq,
+                           (void *) (oldn->tgt->tgt_start + oldn->tgt_offset
+                                     + newn->host_start - oldn->host_start),
+                           (void *) newn->host_start,
+                           newn->host_end - newn->host_start, false, cbuf);
+    }
+
+  gomp_increment_refcount (oldn, refcount_set);
 }
 
 static int
 get_kind (bool short_mapkind, void *kinds, int idx)
 {
-  return short_mapkind ? ((unsigned short *) kinds)[idx]
-                      : ((unsigned char *) kinds)[idx];
+  if (!short_mapkind)
+    return ((unsigned char *) kinds)[idx];
+
+  int val = ((unsigned short *) kinds)[idx];
+  if (GOMP_MAP_IMPLICIT_P (val))
+    val &= ~GOMP_MAP_IMPLICIT;
+  return val;
+}
+
+
+static bool
+get_implicit (bool short_mapkind, void *kinds, int idx)
+{
+  if (!short_mapkind)
+    return false;
+
+  int val = ((unsigned short *) kinds)[idx];
+  return GOMP_MAP_IMPLICIT_P (val);
 }
 
 static void
 gomp_map_pointer (struct target_mem_desc *tgt, struct goacc_asyncqueue *aq,
                  uintptr_t host_ptr, uintptr_t target_offset, uintptr_t bias,
-                 struct gomp_coalesce_buf *cbuf)
+                 struct gomp_coalesce_buf *cbuf,
+                 bool allow_zero_length_array_sections)
 {
   struct gomp_device_descr *devicep = tgt->device_descr;
   struct splay_tree_s *mem_map = &devicep->mem_map;
@@ -424,8 +668,8 @@ gomp_map_pointer (struct target_mem_desc *tgt, struct goacc_asyncqueue *aq,
       cur_node.tgt_offset = (uintptr_t) NULL;
       gomp_copy_host2dev (devicep, aq,
                          (void *) (tgt->tgt_start + target_offset),
-                         (void *) &cur_node.tgt_offset,
-                         sizeof (void *), cbuf);
+                         (void *) &cur_node.tgt_offset, sizeof (void *),
+                         true, cbuf);
       return;
     }
   /* Add bias to the pointer value.  */
@@ -434,18 +678,27 @@ gomp_map_pointer (struct target_mem_desc *tgt, struct goacc_asyncqueue *aq,
   splay_tree_key n = gomp_map_lookup (mem_map, &cur_node);
   if (n == NULL)
     {
-      gomp_mutex_unlock (&devicep->lock);
-      gomp_fatal ("Pointer target of array section wasn't mapped");
-    }
-  cur_node.host_start -= n->host_start;
-  cur_node.tgt_offset
-    = n->tgt->tgt_start + n->tgt_offset + cur_node.host_start;
-  /* At this point tgt_offset is target address of the
-     array section.  Now subtract bias to get what we want
-     to initialize the pointer with.  */
-  cur_node.tgt_offset -= bias;
+      if (allow_zero_length_array_sections)
+       cur_node.tgt_offset = 0;
+      else
+       {
+         gomp_mutex_unlock (&devicep->lock);
+         gomp_fatal ("Pointer target of array section wasn't mapped");
+       }
+    }
+  else
+    {
+      cur_node.host_start -= n->host_start;
+      cur_node.tgt_offset
+       = n->tgt->tgt_start + n->tgt_offset + cur_node.host_start;
+      /* At this point tgt_offset is target address of the
+        array section.  Now subtract bias to get what we want
+        to initialize the pointer with.  */
+      cur_node.tgt_offset -= bias;
+    }
   gomp_copy_host2dev (devicep, aq, (void *) (tgt->tgt_start + target_offset),
-                     (void *) &cur_node.tgt_offset, sizeof (void *), cbuf);
+                     (void *) &cur_node.tgt_offset, sizeof (void *),
+                     true, cbuf);
 }
 
 static void
@@ -453,12 +706,13 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
                          struct goacc_asyncqueue *aq, splay_tree_key n,
                          size_t first, size_t i, void **hostaddrs,
                          size_t *sizes, void *kinds,
-                         struct gomp_coalesce_buf *cbuf)
+                         struct gomp_coalesce_buf *cbuf, htab_t *refcount_set)
 {
   struct gomp_device_descr *devicep = tgt->device_descr;
   struct splay_tree_s *mem_map = &devicep->mem_map;
   struct splay_tree_key_s cur_node;
   int kind;
+  bool implicit;
   const bool short_mapkind = true;
   const int typemask = short_mapkind ? 0xff : 0x7;
 
@@ -466,12 +720,14 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
   cur_node.host_end = cur_node.host_start + sizes[i];
   splay_tree_key n2 = splay_tree_lookup (mem_map, &cur_node);
   kind = get_kind (short_mapkind, kinds, i);
+  implicit = get_implicit (short_mapkind, kinds, i);
   if (n2
       && n2->tgt == n->tgt
       && n2->host_start - n->host_start == n2->tgt_offset - n->tgt_offset)
     {
       gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-                             kind & typemask, false, cbuf);
+                             kind & typemask, false, implicit, cbuf,
+                             refcount_set);
       return;
     }
   if (sizes[i] == 0)
@@ -487,7 +743,8 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
                 == n2->tgt_offset - n->tgt_offset)
            {
              gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-                                     kind & typemask, false, cbuf);
+                                     kind & typemask, false, implicit, cbuf,
+                                     refcount_set);
              return;
            }
        }
@@ -499,7 +756,8 @@ gomp_map_fields_existing (struct target_mem_desc *tgt,
          && n2->host_start - n->host_start == n2->tgt_offset - n->tgt_offset)
        {
          gomp_map_vars_existing (devicep, aq, n2, &cur_node, &tgt->list[i],
-                                 kind & typemask, false, cbuf);
+                                 kind & typemask, false, implicit, cbuf,
+                                 refcount_set);
          return;
        }
     }
@@ -514,7 +772,8 @@ attribute_hidden void
 gomp_attach_pointer (struct gomp_device_descr *devicep,
                     struct goacc_asyncqueue *aq, splay_tree mem_map,
                     splay_tree_key n, uintptr_t attach_to, size_t bias,
-                    struct gomp_coalesce_buf *cbufp)
+                    struct gomp_coalesce_buf *cbufp,
+                    bool allow_zero_length_array_sections)
 {
   struct splay_tree_key_s s;
   size_t size, idx;
@@ -566,11 +825,19 @@ gomp_attach_pointer (struct gomp_device_descr *devicep,
 
       if (!tn)
        {
-         gomp_mutex_unlock (&devicep->lock);
-         gomp_fatal ("pointer target not mapped for attach");
+         if (allow_zero_length_array_sections)
+           /* When allowing attachment to zero-length array sections, we
+              allow attaching to NULL pointers when the target region is not
+              mapped.  */
+           data = 0;
+         else
+           {
+             gomp_mutex_unlock (&devicep->lock);
+             gomp_fatal ("pointer target not mapped for attach");
+           }
        }
-
-      data = tn->tgt->tgt_start + tn->tgt_offset + target - tn->host_start;
+      else
+       data = tn->tgt->tgt_start + tn->tgt_offset + target - tn->host_start;
 
       gomp_debug (1,
                  "%s: attaching host %p, target %p (struct base %p) to %p\n",
@@ -578,7 +845,7 @@ gomp_attach_pointer (struct gomp_device_descr *devicep,
                  (void *) (n->tgt->tgt_start + n->tgt_offset), (void *) data);
 
       gomp_copy_host2dev (devicep, aq, (void *) devptr, (void *) &data,
-                         sizeof (void *), cbufp);
+                         sizeof (void *), true, cbufp);
     }
   else
     gomp_debug (1, "%s: attach count for %p -> %u\n", __FUNCTION__,
@@ -631,7 +898,7 @@ gomp_detach_pointer (struct gomp_device_descr *devicep,
                  (void *) target);
 
       gomp_copy_host2dev (devicep, aq, (void *) devptr, (void *) &target,
-                         sizeof (void *), cbufp);
+                         sizeof (void *), true, cbufp);
     }
   else
     gomp_debug (1, "%s: attach count for %p -> %u\n", __FUNCTION__,
@@ -671,11 +938,13 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                        struct goacc_asyncqueue *aq, size_t mapnum,
                        void **hostaddrs, void **devaddrs, size_t *sizes,
                        void *kinds, bool short_mapkind,
+                       htab_t *refcount_set,
                        enum gomp_map_vars_kind pragma_kind)
 {
   size_t i, tgt_align, tgt_size, not_found_cnt = 0;
   bool has_firstprivate = false;
   bool has_always_ptrset = false;
+  bool openmp_p = (pragma_kind & GOMP_MAP_VARS_OPENACC) == 0;
   const int rshift = short_mapkind ? 8 : 3;
   const int typemask = short_mapkind ? 0xff : 0x7;
   struct splay_tree_s *mem_map = &devicep->mem_map;
@@ -683,7 +952,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
   struct target_mem_desc *tgt
     = gomp_malloc (sizeof (*tgt) + sizeof (tgt->list[0]) * mapnum);
   tgt->list_count = mapnum;
-  tgt->refcount = pragma_kind == GOMP_MAP_VARS_ENTER_DATA ? 0 : 1;
+  tgt->refcount = (pragma_kind & GOMP_MAP_VARS_ENTER_DATA) ? 0 : 1;
   tgt->device_descr = devicep;
   tgt->prev = NULL;
   struct gomp_coalesce_buf cbuf, *cbufp = NULL;
@@ -729,6 +998,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
   for (i = 0; i < mapnum; i++)
     {
       int kind = get_kind (short_mapkind, kinds, i);
+      bool implicit = get_implicit (short_mapkind, kinds, i);
       if (hostaddrs[i] == NULL
          || (kind & typemask) == GOMP_MAP_FIRSTPRIVATE_INT)
        {
@@ -801,8 +1071,9 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
              for (i = first; i <= last; i++)
                {
                  tgt->list[i].key = NULL;
-                 if (gomp_to_device_kind_p (get_kind (short_mapkind, kinds, i)
-                                            & typemask))
+                 if (!aq
+                     && gomp_to_device_kind_p (get_kind (short_mapkind, kinds, i)
+                                               & typemask))
                    gomp_coalesce_buf_add (&cbuf,
                                           tgt_size - cur_node.host_end
                                           + (uintptr_t) hostaddrs[i],
@@ -813,7 +1084,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
            }
          for (i = first; i <= last; i++)
            gomp_map_fields_existing (tgt, aq, n, first, i, hostaddrs,
-                                     sizes, kinds, NULL);
+                                     sizes, kinds, NULL, refcount_set);
          i--;
          continue;
        }
@@ -824,7 +1095,9 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
          has_firstprivate = true;
          continue;
        }
-      else if ((kind & typemask) == GOMP_MAP_ATTACH)
+      else if ((kind & typemask) == GOMP_MAP_ATTACH
+              || ((kind & typemask)
+                  == GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION))
        {
          tgt->list[i].key = NULL;
          has_firstprivate = true;
@@ -843,8 +1116,9 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
          if (tgt_align < align)
            tgt_align = align;
          tgt_size = (tgt_size + align - 1) & ~(align - 1);
-         gomp_coalesce_buf_add (&cbuf, tgt_size,
-                                cur_node.host_end - cur_node.host_start);
+         if (!aq)
+           gomp_coalesce_buf_add (&cbuf, tgt_size,
+                                  cur_node.host_end - cur_node.host_start);
          tgt_size += cur_node.host_end - cur_node.host_start;
          has_firstprivate = true;
          continue;
@@ -909,7 +1183,8 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                }
            }
          gomp_map_vars_existing (devicep, aq, n, &cur_node, &tgt->list[i],
-                                 kind & typemask, always_to_cnt > 0, NULL);
+                                 kind & typemask, always_to_cnt > 0, implicit,
+                                 NULL, refcount_set);
          i += always_to_cnt;
        }
       else
@@ -936,7 +1211,8 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
          if (tgt_align < align)
            tgt_align = align;
          tgt_size = (tgt_size + align - 1) & ~(align - 1);
-         if (gomp_to_device_kind_p (kind & typemask))
+         if (!aq
+             && gomp_to_device_kind_p (kind & typemask))
            gomp_coalesce_buf_add (&cbuf, tgt_size,
                                   cur_node.host_end - cur_node.host_start);
          tgt_size += cur_node.host_end - cur_node.host_start;
@@ -1020,8 +1296,9 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
       if (not_found_cnt)
        tgt->array = gomp_malloc (not_found_cnt * sizeof (*tgt->array));
       splay_tree_node array = tgt->array;
-      size_t j, field_tgt_offset = 0, field_tgt_clear = ~(size_t) 0;
+      size_t j, field_tgt_offset = 0, field_tgt_clear = FIELD_TGT_EMPTY;
       uintptr_t field_tgt_base = 0;
+      splay_tree_key field_tgt_structelem_first = NULL;
 
       for (i = 0; i < mapnum; i++)
        if (has_always_ptrset
@@ -1064,13 +1341,12 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                    tgt->list[j].copy_from = false;
                    tgt->list[j].always_copy_from = false;
                    tgt->list[j].is_attach = false;
-                   if (k->refcount != REFCOUNT_INFINITY)
-                     k->refcount++;
+                   gomp_increment_refcount (k, refcount_set);
                    gomp_map_pointer (k->tgt, aq,
                                      (uintptr_t) *(void **) hostaddrs[j],
                                      k->tgt_offset + ((uintptr_t) hostaddrs[j]
                                                       - k->host_start),
-                                     sizes[j], cbufp);
+                                     sizes[j], cbufp, false);
                  }
              }
            i = j - 1;
@@ -1078,6 +1354,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
        else if (tgt->list[i].key == NULL)
          {
            int kind = get_kind (short_mapkind, kinds, i);
+           bool implicit = get_implicit (short_mapkind, kinds, i);
            if (hostaddrs[i] == NULL)
              continue;
            switch (kind & typemask)
@@ -1091,8 +1368,25 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                len = sizes[i];
                gomp_copy_host2dev (devicep, aq,
                                    (void *) (tgt->tgt_start + tgt_size),
-                                   (void *) hostaddrs[i], len, cbufp);
+                                   (void *) hostaddrs[i], len, false, cbufp);
+               /* Save device address in hostaddr to permit latter availablity
+                  when doing a deep-firstprivate with pointer attach.  */
+               hostaddrs[i] = (void *) (tgt->tgt_start + tgt_size);
                tgt_size += len;
+
+               /* If followed by GOMP_MAP_ATTACH, pointer assign this
+                  firstprivate to hostaddrs[i+1], which is assumed to contain a
+                  device address.  */
+               if (i + 1 < mapnum
+                   && (GOMP_MAP_ATTACH
+                       == (typemask & get_kind (short_mapkind, kinds, i+1))))
+                 {
+                   uintptr_t target = (uintptr_t) hostaddrs[i];
+                   void *devptr = *(void**) hostaddrs[i+1] + sizes[i+1];
+                   gomp_copy_host2dev (devicep, aq, devptr, &target,
+                                       sizeof (void *), false, cbufp);
+                   ++i;
+                 }
                continue;
              case GOMP_MAP_FIRSTPRIVATE_INT:
              case GOMP_MAP_ZERO_LEN_ARRAY_SECTION:
@@ -1153,13 +1447,14 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                    field_tgt_base = (uintptr_t) hostaddrs[first];
                    field_tgt_offset = tgt_size;
                    field_tgt_clear = last;
+                   field_tgt_structelem_first = NULL;
                    tgt_size += cur_node.host_end
                                - (uintptr_t) hostaddrs[first];
                    continue;
                  }
                for (i = first; i <= last; i++)
                  gomp_map_fields_existing (tgt, aq, n, first, i, hostaddrs,
-                                           sizes, kinds, cbufp);
+                                           sizes, kinds, cbufp, refcount_set);
                i--;
                continue;
              case GOMP_MAP_ALWAYS_POINTER:
@@ -1184,7 +1479,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                                              + cur_node.host_start
                                              - n->host_start),
                                    (void *) &cur_node.tgt_offset,
-                                   sizeof (void *), cbufp);
+                                   sizeof (void *), true, cbufp);
                cur_node.tgt_offset = n->tgt->tgt_start + n->tgt_offset
                                      + cur_node.host_start - n->host_start;
                continue;
@@ -1197,6 +1492,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                  ++i;
                continue;
              case GOMP_MAP_ATTACH:
+             case GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION:
                {
                  cur_node.host_start = (uintptr_t) hostaddrs[i];
                  cur_node.host_end = cur_node.host_start + sizeof (void *);
@@ -1212,15 +1508,19 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                      /* OpenACC 'attach'/'detach' doesn't affect
                         structured/dynamic reference counts ('n->refcount',
                         'n->dynamic_refcount').  */
+
+                     bool zlas
+                       = ((kind & typemask)
+                          == GOMP_MAP_ATTACH_ZERO_LENGTH_ARRAY_SECTION);
+                     gomp_attach_pointer (devicep, aq, mem_map, n,
+                                          (uintptr_t) hostaddrs[i], sizes[i],
+                                          cbufp, zlas);
                    }
-                 else
+                 else if ((pragma_kind & GOMP_MAP_VARS_OPENACC) != 0)
                    {
                      gomp_mutex_unlock (&devicep->lock);
                      gomp_fatal ("outer struct not mapped for attach");
                    }
-                 gomp_attach_pointer (devicep, aq, mem_map, n,
-                                      (uintptr_t) hostaddrs[i], sizes[i],
-                                      cbufp);
                  continue;
                }
              default:
@@ -1235,7 +1535,8 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
            splay_tree_key n = splay_tree_lookup (mem_map, k);
            if (n && n->refcount != REFCOUNT_LINK)
              gomp_map_vars_existing (devicep, aq, n, k, &tgt->list[i],
-                                     kind & typemask, false, cbufp);
+                                     kind & typemask, false, implicit, cbufp,
+                                     refcount_set);
            else
              {
                k->aux = NULL;
@@ -1251,10 +1552,33 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                size_t align = (size_t) 1 << (kind >> rshift);
                tgt->list[i].key = k;
                k->tgt = tgt;
+               k->refcount = 0;
+               k->dynamic_refcount = 0;
                if (field_tgt_clear != FIELD_TGT_EMPTY)
                  {
                    k->tgt_offset = k->host_start - field_tgt_base
                                    + field_tgt_offset;
+                   if (openmp_p)
+                     {
+                       k->refcount = REFCOUNT_STRUCTELEM;
+                       if (field_tgt_structelem_first == NULL)
+                         {
+                           /* Set to first structure element of sequence.  */
+                           k->refcount |= REFCOUNT_STRUCTELEM_FLAG_FIRST;
+                           field_tgt_structelem_first = k;
+                         }
+                       else
+                         /* Point to refcount of leading element, but do not
+                            increment again.  */
+                         k->structelem_refcount_ptr
+                           = &field_tgt_structelem_first->structelem_refcount;
+
+                       if (i == field_tgt_clear)
+                         {
+                           k->refcount |= REFCOUNT_STRUCTELEM_FLAG_LAST;
+                           field_tgt_structelem_first = NULL;
+                         }
+                     }
                    if (i == field_tgt_clear)
                      field_tgt_clear = FIELD_TGT_EMPTY;
                  }
@@ -1264,14 +1588,17 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                    k->tgt_offset = tgt_size;
                    tgt_size += k->host_end - k->host_start;
                  }
+               /* First increment, from 0 to 1. gomp_increment_refcount
+                  encapsulates the different increment cases, so use this
+                  instead of directly setting 1 during initialization.  */
+               gomp_increment_refcount (k, refcount_set);
+
                tgt->list[i].copy_from = GOMP_MAP_COPY_FROM_P (kind & typemask);
                tgt->list[i].always_copy_from
                  = GOMP_MAP_ALWAYS_FROM_P (kind & typemask);
                tgt->list[i].is_attach = false;
                tgt->list[i].offset = 0;
                tgt->list[i].length = k->host_end - k->host_start;
-               k->refcount = 1;
-               k->dynamic_refcount = 0;
                tgt->refcount++;
                array->left = NULL;
                array->right = NULL;
@@ -1294,19 +1621,24 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                                        (void *) (tgt->tgt_start
                                                  + k->tgt_offset),
                                        (void *) k->host_start,
-                                       k->host_end - k->host_start, cbufp);
+                                       k->host_end - k->host_start,
+                                       false, cbufp);
                    break;
                  case GOMP_MAP_POINTER:
-                   gomp_map_pointer (tgt, aq,
-                                     (uintptr_t) *(void **) k->host_start,
-                                     k->tgt_offset, sizes[i], cbufp);
+                 case GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION:
+                   gomp_map_pointer
+                     (tgt, aq, (uintptr_t) *(void **) k->host_start,
+                      k->tgt_offset, sizes[i], cbufp,
+                      ((kind & typemask)
+                       == GOMP_MAP_POINTER_TO_ZERO_LENGTH_ARRAY_SECTION));
                    break;
                  case GOMP_MAP_TO_PSET:
                    gomp_copy_host2dev (devicep, aq,
                                        (void *) (tgt->tgt_start
                                                  + k->tgt_offset),
                                        (void *) k->host_start,
-                                       k->host_end - k->host_start, cbufp);
+                                       k->host_end - k->host_start,
+                                       false, cbufp);
                    tgt->list[i].has_null_ptr_assoc = false;
 
                    for (j = i + 1; j < mapnum; j++)
@@ -1327,14 +1659,20 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                            tgt->list[j].always_copy_from = false;
                            tgt->list[j].is_attach = false;
                            tgt->list[i].has_null_ptr_assoc |= !(*(void **) hostaddrs[j]);
-                           if (k->refcount != REFCOUNT_INFINITY)
-                             k->refcount++;
+                           /* For OpenMP, the use of refcount_sets causes
+                              errors if we set k->refcount = 1 above but also
+                              increment it again here, for decrementing will
+                              not properly match, since we decrement only once
+                              for each key's refcount. Therefore avoid this
+                              increment for OpenMP constructs.  */
+                           if (!openmp_p)
+                             gomp_increment_refcount (k, refcount_set);
                            gomp_map_pointer (tgt, aq,
                                              (uintptr_t) *(void **) hostaddrs[j],
                                              k->tgt_offset
                                              + ((uintptr_t) hostaddrs[j]
                                                 - k->host_start),
-                                             sizes[j], cbufp);
+                                             sizes[j], cbufp, false);
                          }
                        }
                    i = j - 1;
@@ -1363,7 +1701,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                                        (void *) (tgt->tgt_start
                                                  + k->tgt_offset),
                                        (void *) k->host_start,
-                                       sizeof (void *), cbufp);
+                                       sizeof (void *), false, cbufp);
                    break;
                  default:
                    gomp_mutex_unlock (&devicep->lock);
@@ -1379,7 +1717,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
                    /* We intentionally do not use coalescing here, as it's not
                       data allocated by the current call to this function.  */
                    gomp_copy_host2dev (devicep, aq, (void *) n->tgt_offset,
-                                       &tgt_addr, sizeof (void *), NULL);
+                                       &tgt_addr, sizeof (void *), true, NULL);
                  }
                array++;
              }
@@ -1394,19 +1732,23 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
          gomp_copy_host2dev (devicep, aq,
                              (void *) (tgt->tgt_start + i * sizeof (void *)),
                              (void *) &cur_node.tgt_offset, sizeof (void *),
-                             cbufp);
+                             true, cbufp);
        }
     }
 
   if (cbufp)
     {
+      /* See 'gomp_coalesce_buf_add'.  */
+      assert (!aq);
+
       long c = 0;
       for (c = 0; c < cbuf.chunk_cnt; ++c)
        gomp_copy_host2dev (devicep, aq,
                            (void *) (tgt->tgt_start + cbuf.chunks[c].start),
                            (char *) cbuf.buf + (cbuf.chunks[c].start
                                                 - cbuf.chunks[0].start),
-                           cbuf.chunks[c].end - cbuf.chunks[c].start, NULL);
+                           cbuf.chunks[c].end - cbuf.chunks[c].start,
+                           true, NULL);
       free (cbuf.buf);
       cbuf.buf = NULL;
       cbufp = NULL;
@@ -1415,7 +1757,7 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
   /* If the variable from "omp target enter data" map-list was already mapped,
      tgt is not needed.  Otherwise tgt will be freed by gomp_unmap_vars or
      gomp_exit_data.  */
-  if (pragma_kind == GOMP_MAP_VARS_ENTER_DATA && tgt->refcount == 0)
+  if ((pragma_kind & GOMP_MAP_VARS_ENTER_DATA) && tgt->refcount == 0)
     {
       free (tgt);
       tgt = NULL;
@@ -1425,24 +1767,41 @@ gomp_map_vars_internal (struct gomp_device_descr *devicep,
   return tgt;
 }
 
-attribute_hidden struct target_mem_desc *
+static struct target_mem_desc *
 gomp_map_vars (struct gomp_device_descr *devicep, size_t mapnum,
               void **hostaddrs, void **devaddrs, size_t *sizes, void *kinds,
-              bool short_mapkind, enum gomp_map_vars_kind pragma_kind)
+              bool short_mapkind, htab_t *refcount_set,
+              enum gomp_map_vars_kind pragma_kind)
 {
-  return gomp_map_vars_internal (devicep, NULL, mapnum, hostaddrs, devaddrs,
-                                sizes, kinds, short_mapkind, pragma_kind);
+  /* This management of a local refcount_set is for convenience of callers
+     who do not share a refcount_set over multiple map/unmap uses.  */
+  htab_t local_refcount_set = NULL;
+  if (refcount_set == NULL)
+    {
+      local_refcount_set = htab_create (mapnum);
+      refcount_set = &local_refcount_set;
+    }
+
+  struct target_mem_desc *tgt;
+  tgt = gomp_map_vars_internal (devicep, NULL, mapnum, hostaddrs, devaddrs,
+                               sizes, kinds, short_mapkind, refcount_set,
+                               pragma_kind);
+  if (local_refcount_set)
+    htab_free (local_refcount_set);
+
+  return tgt;
 }
 
 attribute_hidden struct target_mem_desc *
-gomp_map_vars_async (struct gomp_device_descr *devicep,
-                    struct goacc_asyncqueue *aq, size_t mapnum,
-                    void **hostaddrs, void **devaddrs, size_t *sizes,
-                    void *kinds, bool short_mapkind,
-                    enum gomp_map_vars_kind pragma_kind)
+goacc_map_vars (struct gomp_device_descr *devicep,
+               struct goacc_asyncqueue *aq, size_t mapnum,
+               void **hostaddrs, void **devaddrs, size_t *sizes,
+               void *kinds, bool short_mapkind,
+               enum gomp_map_vars_kind pragma_kind)
 {
   return gomp_map_vars_internal (devicep, aq, mapnum, hostaddrs, devaddrs,
-                                sizes, kinds, short_mapkind, pragma_kind);
+                                sizes, kinds, short_mapkind, NULL,
+                                GOMP_MAP_VARS_OPENACC | pragma_kind);
 }
 
 static void
@@ -1480,22 +1839,56 @@ gomp_unref_tgt_void (void *ptr)
   (void) gomp_unref_tgt (ptr);
 }
 
-static inline __attribute__((always_inline)) bool
-gomp_remove_var_internal (struct gomp_device_descr *devicep, splay_tree_key k,
-                         struct goacc_asyncqueue *aq)
+static void
+gomp_remove_splay_tree_key (splay_tree sp, splay_tree_key k)
 {
-  bool is_tgt_unmapped = false;
-  splay_tree_remove (&devicep->mem_map, k);
+  splay_tree_remove (sp, k);
   if (k->aux)
     {
       if (k->aux->link_key)
-       splay_tree_insert (&devicep->mem_map,
-                          (splay_tree_node) k->aux->link_key);
+       splay_tree_insert (sp, (splay_tree_node) k->aux->link_key);
       if (k->aux->attach_count)
        free (k->aux->attach_count);
       free (k->aux);
       k->aux = NULL;
     }
+}
+
+static inline __attribute__((always_inline)) bool
+gomp_remove_var_internal (struct gomp_device_descr *devicep, splay_tree_key k,
+                         struct goacc_asyncqueue *aq)
+{
+  bool is_tgt_unmapped = false;
+
+  if (REFCOUNT_STRUCTELEM_P (k->refcount))
+    {
+      if (REFCOUNT_STRUCTELEM_FIRST_P (k->refcount) == false)
+       /* Infer the splay_tree_key of the first structelem key using the
+          pointer to the first structleme_refcount.  */
+       k = (splay_tree_key) ((char *) k->structelem_refcount_ptr
+                             - offsetof (struct splay_tree_key_s,
+                                         structelem_refcount));
+      assert (REFCOUNT_STRUCTELEM_FIRST_P (k->refcount));
+
+      /* The array created by gomp_map_vars is an array of splay_tree_nodes,
+        with the splay_tree_keys embedded inside.  */
+      splay_tree_node node =
+       (splay_tree_node) ((char *) k
+                          - offsetof (struct splay_tree_node_s, key));
+      while (true)
+       {
+         /* Starting from the _FIRST key, and continue for all following
+            sibling keys.  */
+         gomp_remove_splay_tree_key (&devicep->mem_map, k);
+         if (REFCOUNT_STRUCTELEM_LAST_P (k->refcount))
+           break;
+         else
+           k = &(++node)->key;
+       }
+    }
+  else
+    gomp_remove_splay_tree_key (&devicep->mem_map, k);
+
   if (aq)
     devicep->openacc.async.queue_callback_func (aq, gomp_unref_tgt_void,
                                                (void *) k->tgt);
@@ -1529,7 +1922,7 @@ gomp_remove_var_async (struct gomp_device_descr *devicep, splay_tree_key k,
 
 static inline __attribute__((always_inline)) void
 gomp_unmap_vars_internal (struct target_mem_desc *tgt, bool do_copyfrom,
-                         struct goacc_asyncqueue *aq)
+                         htab_t *refcount_set, struct goacc_asyncqueue *aq)
 {
   struct gomp_device_descr *devicep = tgt->device_descr;
 
@@ -1572,23 +1965,17 @@ gomp_unmap_vars_internal (struct target_mem_desc *tgt, bool do_copyfrom,
       if (tgt->list[i].is_attach)
        continue;
 
-      bool do_unmap = false;
-      if (k->refcount > 1 && k->refcount != REFCOUNT_INFINITY)
-       k->refcount--;
-      else if (k->refcount == 1)
-       {
-         k->refcount--;
-         do_unmap = true;
-       }
+      bool do_copy, do_remove;
+      gomp_decrement_refcount (k, refcount_set, false, &do_copy, &do_remove);
 
-      if ((do_unmap && do_copyfrom && tgt->list[i].copy_from)
+      if ((do_copy && do_copyfrom && tgt->list[i].copy_from)
          || tgt->list[i].always_copy_from)
        gomp_copy_dev2host (devicep, aq,
                            (void *) (k->host_start + tgt->list[i].offset),
                            (void *) (k->tgt->tgt_start + k->tgt_offset
                                      + tgt->list[i].offset),
                            tgt->list[i].length);
-      if (do_unmap)
+      if (do_remove)
        {
          struct target_mem_desc *k_tgt = k->tgt;
          bool is_tgt_unmapped = gomp_remove_var (devicep, k);
@@ -1609,17 +1996,30 @@ gomp_unmap_vars_internal (struct target_mem_desc *tgt, bool do_copyfrom,
   gomp_mutex_unlock (&devicep->lock);
 }
 
-attribute_hidden void
-gomp_unmap_vars (struct target_mem_desc *tgt, bool do_copyfrom)
+static void
+gomp_unmap_vars (struct target_mem_desc *tgt, bool do_copyfrom,
+                htab_t *refcount_set)
 {
-  gomp_unmap_vars_internal (tgt, do_copyfrom, NULL);
+  /* This management of a local refcount_set is for convenience of callers
+     who do not share a refcount_set over multiple map/unmap uses.  */
+  htab_t local_refcount_set = NULL;
+  if (refcount_set == NULL)
+    {
+      local_refcount_set = htab_create (tgt->list_count);
+      refcount_set = &local_refcount_set;
+    }
+
+  gomp_unmap_vars_internal (tgt, do_copyfrom, refcount_set, NULL);
+
+  if (local_refcount_set)
+    htab_free (local_refcount_set);
 }
 
 attribute_hidden void
-gomp_unmap_vars_async (struct target_mem_desc *tgt, bool do_copyfrom,
-                      struct goacc_asyncqueue *aq)
+goacc_unmap_vars (struct target_mem_desc *tgt, bool do_copyfrom,
+                 struct goacc_asyncqueue *aq)
 {
-  gomp_unmap_vars_internal (tgt, do_copyfrom, aq);
+  gomp_unmap_vars_internal (tgt, do_copyfrom, NULL, aq);
 }
 
 static void
@@ -1664,17 +2064,45 @@ gomp_update (struct gomp_device_descr *devicep, size_t mapnum, void **hostaddrs,
                            (void *) n->host_end);
              }
 
-
-           void *hostaddr = (void *) cur_node.host_start;
-           void *devaddr = (void *) (n->tgt->tgt_start + n->tgt_offset
-                                     + cur_node.host_start - n->host_start);
-           size_t size = cur_node.host_end - cur_node.host_start;
-
-           if (GOMP_MAP_COPY_TO_P (kind & typemask))
-             gomp_copy_host2dev (devicep, NULL, devaddr, hostaddr, size,
-                                 NULL);
-           if (GOMP_MAP_COPY_FROM_P (kind & typemask))
-             gomp_copy_dev2host (devicep, NULL, hostaddr, devaddr, size);
+           if (n->aux && n->aux->attach_count)
+             {
+               uintptr_t addr = cur_node.host_start;
+               while (addr < cur_node.host_end)
+                 {
+                   /* We have to be careful not to overwrite still attached
+                      pointers during host<->device updates.  */
+                   size_t i = (addr - cur_node.host_start) / sizeof (void *);
+                   if (n->aux->attach_count[i] == 0)
+                     {
+                       void *devaddr = (void *) (n->tgt->tgt_start
+                                                 + n->tgt_offset
+                                                 + addr - n->host_start);
+                       if (GOMP_MAP_COPY_TO_P (kind & typemask))
+                         gomp_copy_host2dev (devicep, NULL,
+                                             devaddr, (void *) addr,
+                                             sizeof (void *), false, NULL);
+                       if (GOMP_MAP_COPY_FROM_P (kind & typemask))
+                         gomp_copy_dev2host (devicep, NULL,
+                                             (void *) addr, devaddr,
+                                             sizeof (void *));
+                     }
+                   addr += sizeof (void *);
+                 }
+             }
+           else
+             {
+               void *hostaddr = (void *) cur_node.host_start;
+               void *devaddr = (void *) (n->tgt->tgt_start + n->tgt_offset
+                                         + cur_node.host_start
+                                         - n->host_start);
+               size_t size = cur_node.host_end - cur_node.host_start;
+
+               if (GOMP_MAP_COPY_TO_P (kind & typemask))
+                 gomp_copy_host2dev (devicep, NULL, devaddr, hostaddr, size,
+                                     false, NULL);
+               if (GOMP_MAP_COPY_FROM_P (kind & typemask))
+                 gomp_copy_dev2host (devicep, NULL, hostaddr, devaddr, size);
+             }
          }
       }
   gomp_mutex_unlock (&devicep->lock);
@@ -1700,6 +2128,9 @@ gomp_load_image_to_device (struct gomp_device_descr *devicep, unsigned version,
   int num_funcs = host_funcs_end - host_func_table;
   int num_vars  = (host_vars_end - host_var_table) / 2;
 
+  /* Others currently is only 'device_num' */
+  int num_others = 1;
+
   /* Load image to device and get target addresses for the image.  */
   struct addr_pair *target_table = NULL;
   int i, num_target_entries;
@@ -1708,7 +2139,9 @@ gomp_load_image_to_device (struct gomp_device_descr *devicep, unsigned version,
     = devicep->load_image_func (devicep->target_id, version,
                                target_data, &target_table);
 
-  if (num_target_entries != num_funcs + num_vars)
+  if (num_target_entries != num_funcs + num_vars
+      /* Others (device_num) are included as trailing entries in pair list.  */
+      && num_target_entries != num_funcs + num_vars + num_others)
     {
       gomp_mutex_unlock (&devicep->lock);
       if (is_register_lock)
@@ -1780,6 +2213,35 @@ gomp_load_image_to_device (struct gomp_device_descr *devicep, unsigned version,
       array++;
     }
 
+  /* Last entry is for the on-device 'device_num' variable. Tolerate case
+     where plugin does not return this entry.  */
+  if (num_funcs + num_vars < num_target_entries)
+    {
+      struct addr_pair *device_num_var = &target_table[num_funcs + num_vars];
+      /* Start address will be non-zero for last entry if GOMP_DEVICE_NUM_VAR
+        was found in this image.  */
+      if (device_num_var->start != 0)
+       {
+         /* The index of the devicep within devices[] is regarded as its
+            'device number', which is different from the per-device type
+            devicep->target_id.  */
+         int device_num_val = (int) (devicep - &devices[0]);
+         if (device_num_var->end - device_num_var->start != sizeof (int))
+           {
+             gomp_mutex_unlock (&devicep->lock);
+             if (is_register_lock)
+               gomp_mutex_unlock (&register_lock);
+             gomp_fatal ("offload plugin managed 'device_num' not of expected "
+                         "format");
+           }
+
+         /* Copy device_num value to place on device memory, hereby actually
+            designating its device number into effect.  */
+         gomp_copy_host2dev (devicep, NULL, (void *) device_num_var->start,
+                             &device_num_val, sizeof (int), false, NULL);
+       }
+    }
+
   free (target_table);
 }
 
@@ -1856,6 +2318,20 @@ gomp_unload_image_from_device (struct gomp_device_descr *devicep,
     }
 }
 
+static void
+gomp_requires_to_name (char *buf, size_t size, int requires_mask)
+{
+  char *end = buf + size, *p = buf;
+  if (requires_mask & GOMP_REQUIRES_UNIFIED_ADDRESS)
+    p += snprintf (p, end - p, "unified_address");
+  if (requires_mask & GOMP_REQUIRES_UNIFIED_SHARED_MEMORY)
+    p += snprintf (p, end - p, "%sunified_shared_memory",
+                  (p == buf ? "" : ", "));
+  if (requires_mask & GOMP_REQUIRES_REVERSE_OFFLOAD)
+    p += snprintf (p, end - p, "%sreverse_offload",
+                  (p == buf ? "" : ", "));
+}
+
 /* This function should be called from every offload image while loading.
    It gets the descriptor of the host func and var tables HOST_TABLE, TYPE of
    the target, and TARGET_DATA needed by target plugin.  */
@@ -1865,13 +2341,43 @@ GOMP_offload_register_ver (unsigned version, const void *host_table,
                           int target_type, const void *target_data)
 {
   int i;
+  int omp_req = 0;
 
   if (GOMP_VERSION_LIB (version) > GOMP_VERSION)
     gomp_fatal ("Library too old for offload (version %u < %u)",
                GOMP_VERSION, GOMP_VERSION_LIB (version));
-  
+
+  if (GOMP_VERSION_LIB (version) > 1)
+    {
+      omp_req = (int) (size_t) ((void **) target_data)[0];
+      target_data = &((void **) target_data)[1];
+    }
+
   gomp_mutex_lock (&register_lock);
 
+  if (omp_req && omp_requires_mask && omp_requires_mask != omp_req)
+    {
+      char buf1[sizeof ("unified_address, unified_shared_memory, "
+                       "reverse_offload")];
+      char buf2[sizeof ("unified_address, unified_shared_memory, "
+                       "reverse_offload")];
+      gomp_requires_to_name (buf2, sizeof (buf2),
+                            omp_req != GOMP_REQUIRES_TARGET_USED
+                            ? omp_req : omp_requires_mask);
+      if (omp_req != GOMP_REQUIRES_TARGET_USED
+         && omp_requires_mask != GOMP_REQUIRES_TARGET_USED)
+       {
+         gomp_requires_to_name (buf1, sizeof (buf1), omp_requires_mask);
+         gomp_fatal ("OpenMP 'requires' directive with non-identical clauses "
+                     "in multiple compilation units: '%s' vs. '%s'",
+                     buf1, buf2);
+       }
+      else
+       gomp_fatal ("OpenMP 'requires' directive with '%s' specified only in "
+                   "some compilation units", buf2);
+    }
+  omp_requires_mask = omp_req;
+
   /* Load image to all initialized devices.  */
   for (i = 0; i < num_devices; i++)
     {
@@ -2011,7 +2517,7 @@ gomp_unload_device (struct gomp_device_descr *devicep)
 
 static void
 gomp_target_fallback (void (*fn) (void *), void **hostaddrs,
-                     struct gomp_device_descr *devicep)
+                     struct gomp_device_descr *devicep, void **args)
 {
   struct gomp_thread old_thr, *thr = gomp_thread ();
 
@@ -2027,6 +2533,25 @@ gomp_target_fallback (void (*fn) (void *), void **hostaddrs,
       thr->place = old_thr.place;
       thr->ts.place_partition_len = gomp_places_list_len;
     }
+  if (args)
+    while (*args)
+      {
+       intptr_t id = (intptr_t) *args++, val;
+       if (id & GOMP_TARGET_ARG_SUBSEQUENT_PARAM)
+         val = (intptr_t) *args++;
+       else
+         val = id >> GOMP_TARGET_ARG_VALUE_SHIFT;
+       if ((id & GOMP_TARGET_ARG_DEVICE_MASK) != GOMP_TARGET_ARG_DEVICE_ALL)
+         continue;
+       id &= GOMP_TARGET_ARG_ID_MASK;
+       if (id != GOMP_TARGET_ARG_THREAD_LIMIT)
+         continue;
+       val = val > INT_MAX ? INT_MAX : val;
+       if (val)
+         gomp_icv (true)->thread_limit_var = val;
+       break;
+      }
+
   fn (hostaddrs);
   gomp_free_thread (thr);
   *thr = old_thr;
@@ -2065,13 +2590,18 @@ copy_firstprivate_data (char *tgt, size_t mapnum, void **hostaddrs,
   tgt_size = 0;
   size_t i;
   for (i = 0; i < mapnum; i++)
-    if ((kinds[i] & 0xff) == GOMP_MAP_FIRSTPRIVATE)
+    if ((kinds[i] & 0xff) == GOMP_MAP_FIRSTPRIVATE && hostaddrs[i] != NULL)
       {
        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]);
        hostaddrs[i] = tgt + tgt_size;
        tgt_size = tgt_size + sizes[i];
+       if (i + 1 < mapnum && (kinds[i+1] & 0xff) == GOMP_MAP_ATTACH)
+         {
+           *(*(uintptr_t**) hostaddrs[i+1] + sizes[i+1]) = (uintptr_t) hostaddrs[i];
+           ++i;
+         }
       }
 }
 
@@ -2119,7 +2649,7 @@ GOMP_target (int device, void (*fn) (void *), const void *unused,
             size_t mapnum, void **hostaddrs, size_t *sizes,
             unsigned char *kinds)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   void *fn_addr;
   if (devicep == NULL
@@ -2127,14 +2657,17 @@ GOMP_target (int device, void (*fn) (void *), const void *unused,
       /* All shared memory devices should use the GOMP_target_ext function.  */
       || devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM
       || !(fn_addr = gomp_get_target_fn_addr (devicep, fn)))
-    return gomp_target_fallback (fn, hostaddrs, devicep);
+    return gomp_target_fallback (fn, hostaddrs, devicep, NULL);
 
+  htab_t refcount_set = htab_create (mapnum);
   struct target_mem_desc *tgt_vars
     = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds, false,
-                    GOMP_MAP_VARS_TARGET);
+                    &refcount_set, GOMP_MAP_VARS_TARGET);
   devicep->run_func (devicep->target_id, fn_addr, (void *) tgt_vars->tgt_start,
                     NULL);
-  gomp_unmap_vars (tgt_vars, true);
+  htab_clear (refcount_set);
+  gomp_unmap_vars (tgt_vars, true, &refcount_set);
+  htab_free (refcount_set);
 }
 
 static inline unsigned int
@@ -2175,7 +2708,7 @@ GOMP_target_ext (int device, void (*fn) (void *), size_t mapnum,
                 void **hostaddrs, size_t *sizes, unsigned short *kinds,
                 unsigned int flags, void **depend, void **args)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
   size_t tgt_align = 0, tgt_size = 0;
   bool fpc_done = false;
 
@@ -2263,11 +2796,13 @@ GOMP_target_ext (int device, void (*fn) (void *), size_t mapnum,
                                      tgt_align, tgt_size);
            }
        }
-      gomp_target_fallback (fn, hostaddrs, devicep);
+      gomp_target_fallback (fn, hostaddrs, devicep, args);
       return;
     }
 
   struct target_mem_desc *tgt_vars;
+  htab_t refcount_set = NULL;
+
   if (devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
     {
       if (!fpc_done)
@@ -2284,13 +2819,21 @@ GOMP_target_ext (int device, void (*fn) (void *), size_t mapnum,
       tgt_vars = NULL;
     }
   else
-    tgt_vars = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds,
-                             true, GOMP_MAP_VARS_TARGET);
+    {
+      refcount_set = htab_create (mapnum);
+      tgt_vars = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds,
+                               true, &refcount_set, GOMP_MAP_VARS_TARGET);
+    }
   devicep->run_func (devicep->target_id, fn_addr,
                     tgt_vars ? (void *) tgt_vars->tgt_start : hostaddrs,
                     args);
   if (tgt_vars)
-    gomp_unmap_vars (tgt_vars, true);
+    {
+      htab_clear (refcount_set);
+      gomp_unmap_vars (tgt_vars, true, &refcount_set);
+    }
+  if (refcount_set)
+    htab_free (refcount_set);
 }
 
 /* Host fallback for GOMP_target_data{,_ext} routines.  */
@@ -2313,7 +2856,7 @@ gomp_target_data_fallback (struct gomp_device_descr *devicep)
          would get out of sync.  */
       struct target_mem_desc *tgt
        = gomp_map_vars (NULL, 0, NULL, NULL, NULL, NULL, false,
-                        GOMP_MAP_VARS_DATA);
+                        NULL, GOMP_MAP_VARS_DATA);
       tgt->prev = icv->target_data;
       icv->target_data = tgt;
     }
@@ -2323,7 +2866,7 @@ void
 GOMP_target_data (int device, const void *unused, size_t mapnum,
                  void **hostaddrs, size_t *sizes, unsigned char *kinds)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   if (devicep == NULL
       || !(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
@@ -2332,7 +2875,7 @@ GOMP_target_data (int device, const void *unused, size_t mapnum,
 
   struct target_mem_desc *tgt
     = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds, false,
-                    GOMP_MAP_VARS_DATA);
+                    NULL, GOMP_MAP_VARS_DATA);
   struct gomp_task_icv *icv = gomp_icv (true);
   tgt->prev = icv->target_data;
   icv->target_data = tgt;
@@ -2342,7 +2885,7 @@ void
 GOMP_target_data_ext (int device, size_t mapnum, void **hostaddrs,
                      size_t *sizes, unsigned short *kinds)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   if (devicep == NULL
       || !(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
@@ -2351,7 +2894,7 @@ GOMP_target_data_ext (int device, size_t mapnum, void **hostaddrs,
 
   struct target_mem_desc *tgt
     = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds, true,
-                    GOMP_MAP_VARS_DATA);
+                    NULL, GOMP_MAP_VARS_DATA);
   struct gomp_task_icv *icv = gomp_icv (true);
   tgt->prev = icv->target_data;
   icv->target_data = tgt;
@@ -2365,7 +2908,7 @@ GOMP_target_end_data (void)
     {
       struct target_mem_desc *tgt = icv->target_data;
       icv->target_data = tgt->prev;
-      gomp_unmap_vars (tgt, true);
+      gomp_unmap_vars (tgt, true, NULL);
     }
 }
 
@@ -2373,7 +2916,7 @@ void
 GOMP_target_update (int device, const void *unused, size_t mapnum,
                    void **hostaddrs, size_t *sizes, unsigned char *kinds)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   if (devicep == NULL
       || !(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
@@ -2388,7 +2931,7 @@ GOMP_target_update_ext (int device, size_t mapnum, void **hostaddrs,
                        size_t *sizes, unsigned short *kinds,
                        unsigned int flags, void **depend)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   /* If there are depend clauses, but nowait is not present,
      block the parent task until the dependencies are resolved
@@ -2464,7 +3007,8 @@ GOMP_target_update_ext (int device, size_t mapnum, void **hostaddrs,
 
 static void
 gomp_exit_data (struct gomp_device_descr *devicep, size_t mapnum,
-               void **hostaddrs, size_t *sizes, unsigned short *kinds)
+               void **hostaddrs, size_t *sizes, unsigned short *kinds,
+               htab_t *refcount_set)
 {
   const int typemask = 0xff;
   size_t i;
@@ -2475,6 +3019,22 @@ gomp_exit_data (struct gomp_device_descr *devicep, size_t mapnum,
       return;
     }
 
+  for (i = 0; i < mapnum; i++)
+    if ((kinds[i] & typemask) == GOMP_MAP_DETACH)
+      {
+       struct splay_tree_key_s cur_node;
+       cur_node.host_start = (uintptr_t) hostaddrs[i];
+       cur_node.host_end = cur_node.host_start + sizeof (void *);
+       splay_tree_key n = splay_tree_lookup (&devicep->mem_map, &cur_node);
+
+       if (n)
+         gomp_detach_pointer (devicep, NULL, n, (uintptr_t) hostaddrs[i],
+                              false, NULL);
+      }
+
+  int nrmvars = 0;
+  splay_tree_key remove_vars[mapnum];
+
   for (i = 0; i < mapnum; i++)
     {
       struct splay_tree_key_s cur_node;
@@ -2496,23 +3056,55 @@ gomp_exit_data (struct gomp_device_descr *devicep, size_t mapnum,
          if (!k)
            continue;
 
-         if (k->refcount > 0 && k->refcount != REFCOUNT_INFINITY)
-           k->refcount--;
-         if ((kind == GOMP_MAP_DELETE
-              || kind == GOMP_MAP_DELETE_ZERO_LEN_ARRAY_SECTION)
-             && k->refcount != REFCOUNT_INFINITY)
-           k->refcount = 0;
+         bool delete_p = (kind == GOMP_MAP_DELETE
+                          || kind == GOMP_MAP_DELETE_ZERO_LEN_ARRAY_SECTION);
+         bool do_copy, do_remove;
+         gomp_decrement_refcount (k, refcount_set, delete_p, &do_copy,
+                                  &do_remove);
 
-         if ((kind == GOMP_MAP_FROM && k->refcount == 0)
+         if ((kind == GOMP_MAP_FROM && do_copy)
              || kind == GOMP_MAP_ALWAYS_FROM)
-           gomp_copy_dev2host (devicep, NULL, (void *) cur_node.host_start,
-                               (void *) (k->tgt->tgt_start + k->tgt_offset
-                                         + cur_node.host_start
-                                         - k->host_start),
-                               cur_node.host_end - cur_node.host_start);
-         if (k->refcount == 0)
-           gomp_remove_var (devicep, k);
+           {
+             if (k->aux && k->aux->attach_count)
+               {
+                 /* We have to be careful not to overwrite still attached
+                    pointers during the copyback to host.  */
+                 uintptr_t addr = k->host_start;
+                 while (addr < k->host_end)
+                   {
+                     size_t i = (addr - k->host_start) / sizeof (void *);
+                     if (k->aux->attach_count[i] == 0)
+                       gomp_copy_dev2host (devicep, NULL, (void *) addr,
+                                           (void *) (k->tgt->tgt_start
+                                                     + k->tgt_offset
+                                                     + addr - k->host_start),
+                                           sizeof (void *));
+                     addr += sizeof (void *);
+                   }
+               }
+             else
+               gomp_copy_dev2host (devicep, NULL, (void *) cur_node.host_start,
+                                   (void *) (k->tgt->tgt_start + k->tgt_offset
+                                             + cur_node.host_start
+                                             - k->host_start),
+                                   cur_node.host_end - cur_node.host_start);
+           }
 
+         /* Structure elements lists are removed altogether at once, which
+            may cause immediate deallocation of the target_mem_desc, causing
+            errors if we still have following element siblings to copy back.
+            While we're at it, it also seems more disciplined to simply
+            queue all removals together for processing below.
+
+            Structured block unmapping (i.e. gomp_unmap_vars_internal) should
+            not have this problem, since they maintain an additional
+            tgt->refcount = 1 reference to the target_mem_desc to start with.
+         */
+         if (do_remove)
+           remove_vars[nrmvars++] = k;
+         break;
+
+       case GOMP_MAP_DETACH:
          break;
        default:
          gomp_mutex_unlock (&devicep->lock);
@@ -2521,6 +3113,9 @@ gomp_exit_data (struct gomp_device_descr *devicep, size_t mapnum,
        }
     }
 
+  for (int i = 0; i < nrmvars; i++)
+    gomp_remove_var (devicep, remove_vars[i]);
+
   gomp_mutex_unlock (&devicep->lock);
 }
 
@@ -2529,7 +3124,7 @@ GOMP_target_enter_exit_data (int device, size_t mapnum, void **hostaddrs,
                             size_t *sizes, unsigned short *kinds,
                             unsigned int flags, void **depend)
 {
-  struct gomp_device_descr *devicep = resolve_device (device);
+  struct gomp_device_descr *devicep = resolve_device (device, true);
 
   /* If there are depend clauses, but nowait is not present,
      block the parent task until the dependencies are resolved
@@ -2600,6 +3195,8 @@ GOMP_target_enter_exit_data (int device, size_t mapnum, void **hostaddrs,
        }
     }
 
+  htab_t refcount_set = htab_create (mapnum);
+
   /* The variables are mapped separately such that they can be released
      independently.  */
   size_t i, j;
@@ -2608,7 +3205,8 @@ GOMP_target_enter_exit_data (int device, size_t mapnum, void **hostaddrs,
       if ((kinds[i] & 0xff) == GOMP_MAP_STRUCT)
        {
          gomp_map_vars (devicep, sizes[i] + 1, &hostaddrs[i], NULL, &sizes[i],
-                        &kinds[i], true, GOMP_MAP_VARS_ENTER_DATA);
+                        &kinds[i], true, &refcount_set,
+                        GOMP_MAP_VARS_ENTER_DATA);
          i += sizes[i];
        }
       else if ((kinds[i] & 0xff) == GOMP_MAP_TO_PSET)
@@ -2618,14 +3216,24 @@ GOMP_target_enter_exit_data (int device, size_t mapnum, void **hostaddrs,
                && !GOMP_MAP_ALWAYS_POINTER_P (get_kind (true, kinds, j) & 0xff))
              break;
          gomp_map_vars (devicep, j-i, &hostaddrs[i], NULL, &sizes[i],
-                        &kinds[i], true, GOMP_MAP_VARS_ENTER_DATA);
+                        &kinds[i], true, &refcount_set,
+                        GOMP_MAP_VARS_ENTER_DATA);
          i += j - i - 1;
        }
+      else if (i + 1 < mapnum && (kinds[i + 1] & 0xff) == GOMP_MAP_ATTACH)
+       {
+         /* An attach operation must be processed together with the mapped
+            base-pointer list item.  */
+         gomp_map_vars (devicep, 2, &hostaddrs[i], NULL, &sizes[i], &kinds[i],
+                        true, &refcount_set, GOMP_MAP_VARS_ENTER_DATA);
+         i += 1;
+       }
       else
        gomp_map_vars (devicep, 1, &hostaddrs[i], NULL, &sizes[i], &kinds[i],
-                      true, GOMP_MAP_VARS_ENTER_DATA);
+                      true, &refcount_set, GOMP_MAP_VARS_ENTER_DATA);
   else
-    gomp_exit_data (devicep, mapnum, hostaddrs, sizes, kinds);
+    gomp_exit_data (devicep, mapnum, hostaddrs, sizes, kinds, &refcount_set);
+  htab_free (refcount_set);
 }
 
 bool
@@ -2643,14 +3251,15 @@ gomp_target_task_fn (void *data)
          || (devicep->can_run_func && !devicep->can_run_func (fn_addr)))
        {
          ttask->state = GOMP_TARGET_TASK_FALLBACK;
-         gomp_target_fallback (ttask->fn, ttask->hostaddrs, devicep);
+         gomp_target_fallback (ttask->fn, ttask->hostaddrs, devicep,
+                               ttask->args);
          return false;
        }
 
       if (ttask->state == GOMP_TARGET_TASK_FINISHED)
        {
          if (ttask->tgt)
-           gomp_unmap_vars (ttask->tgt, true);
+           gomp_unmap_vars (ttask->tgt, true, NULL);
          return false;
        }
 
@@ -2664,7 +3273,7 @@ gomp_target_task_fn (void *data)
        {
          ttask->tgt = gomp_map_vars (devicep, ttask->mapnum, ttask->hostaddrs,
                                      NULL, ttask->sizes, ttask->kinds, true,
-                                     GOMP_MAP_VARS_TARGET);
+                                     NULL, GOMP_MAP_VARS_TARGET);
          actual_arguments = (void *) ttask->tgt->tgt_start;
        }
       ttask->state = GOMP_TARGET_TASK_READY_TO_RUN;
@@ -2683,21 +3292,27 @@ gomp_target_task_fn (void *data)
   if (ttask->flags & GOMP_TARGET_FLAG_UPDATE)
     gomp_update (devicep, ttask->mapnum, ttask->hostaddrs, ttask->sizes,
                 ttask->kinds, true);
-  else if ((ttask->flags & GOMP_TARGET_FLAG_EXIT_DATA) == 0)
-    for (i = 0; i < ttask->mapnum; i++)
-      if ((ttask->kinds[i] & 0xff) == GOMP_MAP_STRUCT)
-       {
-         gomp_map_vars (devicep, ttask->sizes[i] + 1, &ttask->hostaddrs[i],
-                        NULL, &ttask->sizes[i], &ttask->kinds[i], true,
-                        GOMP_MAP_VARS_ENTER_DATA);
-         i += ttask->sizes[i];
-       }
-      else
-       gomp_map_vars (devicep, 1, &ttask->hostaddrs[i], NULL, &ttask->sizes[i],
-                      &ttask->kinds[i], true, GOMP_MAP_VARS_ENTER_DATA);
   else
-    gomp_exit_data (devicep, ttask->mapnum, ttask->hostaddrs, ttask->sizes,
-                   ttask->kinds);
+    {
+      htab_t refcount_set = htab_create (ttask->mapnum);
+      if ((ttask->flags & GOMP_TARGET_FLAG_EXIT_DATA) == 0)
+       for (i = 0; i < ttask->mapnum; i++)
+         if ((ttask->kinds[i] & 0xff) == GOMP_MAP_STRUCT)
+           {
+             gomp_map_vars (devicep, ttask->sizes[i] + 1, &ttask->hostaddrs[i],
+                            NULL, &ttask->sizes[i], &ttask->kinds[i], true,
+                            &refcount_set, GOMP_MAP_VARS_ENTER_DATA);
+             i += ttask->sizes[i];
+           }
+         else
+           gomp_map_vars (devicep, 1, &ttask->hostaddrs[i], NULL, &ttask->sizes[i],
+                          &ttask->kinds[i], true, &refcount_set,
+                          GOMP_MAP_VARS_ENTER_DATA);
+      else
+       gomp_exit_data (devicep, ttask->mapnum, ttask->hostaddrs, ttask->sizes,
+                       ttask->kinds, &refcount_set);
+      htab_free (refcount_set);
+    }
   return false;
 }
 
@@ -2713,16 +3328,40 @@ GOMP_teams (unsigned int num_teams, unsigned int thread_limit)
   (void) num_teams;
 }
 
+bool
+GOMP_teams4 (unsigned int num_teams_low, unsigned int num_teams_high,
+            unsigned int thread_limit, bool first)
+{
+  struct gomp_thread *thr = gomp_thread ();
+  if (first)
+    {
+      if (thread_limit)
+       {
+         struct gomp_task_icv *icv = gomp_icv (true);
+         icv->thread_limit_var
+           = thread_limit > INT_MAX ? UINT_MAX : thread_limit;
+       }
+      (void) num_teams_high;
+      if (num_teams_low == 0)
+       num_teams_low = 1;
+      thr->num_teams = num_teams_low - 1;
+      thr->team_num = 0;
+    }
+  else if (thr->team_num == thr->num_teams)
+    return false;
+  else
+    ++thr->team_num;
+  return true;
+}
+
 void *
 omp_target_alloc (size_t size, int device_num)
 {
-  if (device_num == gomp_get_num_devices ())
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
     return malloc (size);
 
-  if (device_num < 0)
-    return NULL;
-
-  struct gomp_device_descr *devicep = resolve_device (device_num);
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
   if (devicep == NULL)
     return NULL;
 
@@ -2739,20 +3378,15 @@ omp_target_alloc (size_t size, int device_num)
 void
 omp_target_free (void *device_ptr, int device_num)
 {
-  if (device_ptr == NULL)
-    return;
-
-  if (device_num == gomp_get_num_devices ())
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
     {
       free (device_ptr);
       return;
     }
 
-  if (device_num < 0)
-    return;
-
-  struct gomp_device_descr *devicep = resolve_device (device_num);
-  if (devicep == NULL)
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
+  if (devicep == NULL || device_ptr == NULL)
     return;
 
   if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
@@ -2770,19 +3404,17 @@ omp_target_free (void *device_ptr, int device_num)
 int
 omp_target_is_present (const void *ptr, int device_num)
 {
-  if (ptr == NULL)
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
     return 1;
 
-  if (device_num == gomp_get_num_devices ())
-    return 1;
-
-  if (device_num < 0)
-    return 0;
-
-  struct gomp_device_descr *devicep = resolve_device (device_num);
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
   if (devicep == NULL)
     return 0;
 
+  if (ptr == NULL)
+    return 1;
+
   if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
       || devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
     return 1;
@@ -2799,40 +3431,46 @@ omp_target_is_present (const void *ptr, int device_num)
   return ret;
 }
 
-int
-omp_target_memcpy (void *dst, const void *src, size_t length,
-                  size_t dst_offset, size_t src_offset, int dst_device_num,
-                  int src_device_num)
+static int
+omp_target_memcpy_check (int dst_device_num, int src_device_num,
+                        struct gomp_device_descr **dst_devicep,
+                        struct gomp_device_descr **src_devicep)
 {
-  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
-  bool ret;
-
-  if (dst_device_num != gomp_get_num_devices ())
+  if (dst_device_num != gomp_get_num_devices ()
+      /* Above gomp_get_num_devices has to be called unconditionally.  */
+      && dst_device_num != omp_initial_device)
     {
-      if (dst_device_num < 0)
+      *dst_devicep = resolve_device (dst_device_num, false);
+      if (*dst_devicep == NULL)
        return EINVAL;
 
-      dst_devicep = resolve_device (dst_device_num);
-      if (dst_devicep == NULL)
-       return EINVAL;
-
-      if (!(dst_devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
-         || dst_devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
-       dst_devicep = NULL;
+      if (!((*dst_devicep)->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
+         || (*dst_devicep)->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
+       *dst_devicep = NULL;
     }
-  if (src_device_num != num_devices_openmp)
-    {
-      if (src_device_num < 0)
-       return EINVAL;
 
-      src_devicep = resolve_device (src_device_num);
-      if (src_devicep == NULL)
+  if (src_device_num != num_devices_openmp
+      && src_device_num != omp_initial_device)
+    {
+      *src_devicep = resolve_device (src_device_num, false);
+      if (*src_devicep == NULL)
        return EINVAL;
 
-      if (!(src_devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
-         || src_devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
-       src_devicep = NULL;
+      if (!((*src_devicep)->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
+         || (*src_devicep)->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
+       *src_devicep = NULL;
     }
+
+  return 0;
+}
+
+static int
+omp_target_memcpy_copy (void *dst, const void *src, size_t length,
+                       size_t dst_offset, size_t src_offset,
+                       struct gomp_device_descr *dst_devicep,
+                       struct gomp_device_descr *src_devicep)
+{
+  bool ret;
   if (src_devicep == NULL && dst_devicep == NULL)
     {
       memcpy ((char *) dst + dst_offset, (char *) src + src_offset, length);
@@ -2868,6 +3506,85 @@ omp_target_memcpy (void *dst, const void *src, size_t length,
   return EINVAL;
 }
 
+int
+omp_target_memcpy (void *dst, const void *src, size_t length, size_t dst_offset,
+                  size_t src_offset, int dst_device_num, int src_device_num)
+{
+  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
+  int ret = omp_target_memcpy_check (dst_device_num, src_device_num,
+                                    &dst_devicep, &src_devicep);
+
+  if (ret)
+    return ret;
+
+  ret = omp_target_memcpy_copy (dst, src, length, dst_offset, src_offset,
+                               dst_devicep, src_devicep);
+
+  return ret;
+}
+
+typedef struct
+{
+  void *dst;
+  const void *src;
+  size_t length;
+  size_t dst_offset;
+  size_t src_offset;
+  struct gomp_device_descr *dst_devicep;
+  struct gomp_device_descr *src_devicep;
+} omp_target_memcpy_data;
+
+static void
+omp_target_memcpy_async_helper (void *args)
+{
+  omp_target_memcpy_data *a = args;
+  if (omp_target_memcpy_copy (a->dst, a->src, a->length, a->dst_offset,
+                             a->src_offset, a->dst_devicep, a->src_devicep))
+    gomp_fatal ("omp_target_memcpy failed");
+}
+
+int
+omp_target_memcpy_async (void *dst, const void *src, size_t length,
+                        size_t dst_offset, size_t src_offset,
+                        int dst_device_num, int src_device_num,
+                        int depobj_count, omp_depend_t *depobj_list)
+{
+  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
+  unsigned int flags = 0;
+  void *depend[depobj_count + 5];
+  int i;
+  int check = omp_target_memcpy_check (dst_device_num, src_device_num,
+                                      &dst_devicep, &src_devicep);
+
+  omp_target_memcpy_data s = {
+    .dst = dst,
+    .src = src,
+    .length = length,
+    .dst_offset = dst_offset,
+    .src_offset = src_offset,
+    .dst_devicep = dst_devicep,
+    .src_devicep = src_devicep
+  };
+
+  if (check)
+    return check;
+
+  if (depobj_count > 0 && depobj_list != NULL)
+    {
+      flags |= GOMP_TASK_FLAG_DEPEND;
+      depend[0] = 0;
+      depend[1] = (void *) (uintptr_t) depobj_count;
+      depend[2] = depend[3] = depend[4] = 0;
+      for (i = 0; i < depobj_count; ++i)
+       depend[i + 5] = &depobj_list[i];
+    }
+
+  GOMP_task (omp_target_memcpy_async_helper, &s, NULL, sizeof (s),
+            __alignof__ (s), true, flags, depend, 0, NULL);
+
+  return 0;
+}
+
 static int
 omp_target_memcpy_rect_worker (void *dst, const void *src, size_t element_size,
                               int num_dims, const size_t *volume,
@@ -2944,50 +3661,36 @@ omp_target_memcpy_rect_worker (void *dst, const void *src, size_t element_size,
   return 0;
 }
 
-int
-omp_target_memcpy_rect (void *dst, const void *src, size_t element_size,
-                       int num_dims, const size_t *volume,
-                       const size_t *dst_offsets,
-                       const size_t *src_offsets,
-                       const size_t *dst_dimensions,
-                       const size_t *src_dimensions,
-                       int dst_device_num, int src_device_num)
+static int
+omp_target_memcpy_rect_check (void *dst, const void *src, int dst_device_num,
+                             int src_device_num,
+                             struct gomp_device_descr **dst_devicep,
+                             struct gomp_device_descr **src_devicep)
 {
-  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
-
   if (!dst && !src)
     return INT_MAX;
 
-  if (dst_device_num != gomp_get_num_devices ())
-    {
-      if (dst_device_num < 0)
-       return EINVAL;
-
-      dst_devicep = resolve_device (dst_device_num);
-      if (dst_devicep == NULL)
-       return EINVAL;
-
-      if (!(dst_devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
-         || dst_devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
-       dst_devicep = NULL;
-    }
-  if (src_device_num != num_devices_openmp)
-    {
-      if (src_device_num < 0)
-       return EINVAL;
-
-      src_devicep = resolve_device (src_device_num);
-      if (src_devicep == NULL)
-       return EINVAL;
-
-      if (!(src_devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
-         || src_devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
-       src_devicep = NULL;
-    }
+  int ret = omp_target_memcpy_check (dst_device_num, src_device_num,
+                                    dst_devicep, src_devicep);
+  if (ret)
+    return ret;
 
-  if (src_devicep != NULL && dst_devicep != NULL && src_devicep != dst_devicep)
+  if (*src_devicep != NULL && *dst_devicep != NULL && *src_devicep != *dst_devicep)
     return EINVAL;
 
+  return 0;
+}
+
+static int
+omp_target_memcpy_rect_copy (void *dst, const void *src,
+                            size_t element_size, int num_dims,
+                            const size_t *volume, const size_t *dst_offsets,
+                            const size_t *src_offsets,
+                            const size_t *dst_dimensions,
+                            const size_t *src_dimensions,
+                            struct gomp_device_descr *dst_devicep,
+                            struct gomp_device_descr *src_devicep)
+{
   if (src_devicep)
     gomp_mutex_lock (&src_devicep->lock);
   else if (dst_devicep)
@@ -3000,20 +3703,124 @@ omp_target_memcpy_rect (void *dst, const void *src, size_t element_size,
     gomp_mutex_unlock (&src_devicep->lock);
   else if (dst_devicep)
     gomp_mutex_unlock (&dst_devicep->lock);
+
   return ret;
 }
 
+int
+omp_target_memcpy_rect (void *dst, const void *src, size_t element_size,
+                       int num_dims, const size_t *volume,
+                       const size_t *dst_offsets,
+                       const size_t *src_offsets,
+                       const size_t *dst_dimensions,
+                       const size_t *src_dimensions,
+                       int dst_device_num, int src_device_num)
+{
+  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
+
+  int check = omp_target_memcpy_rect_check (dst, src, dst_device_num,
+                                           src_device_num, &dst_devicep,
+                                           &src_devicep);
+
+  if (check)
+    return check;
+
+  int ret = omp_target_memcpy_rect_copy (dst, src, element_size, num_dims,
+                                        volume, dst_offsets, src_offsets,
+                                        dst_dimensions, src_dimensions,
+                                        dst_devicep, src_devicep);
+
+  return ret;
+}
+
+typedef struct
+{
+  void *dst;
+  const void *src;
+  size_t element_size;
+  const size_t *volume;
+  const size_t *dst_offsets;
+  const size_t *src_offsets;
+  const size_t *dst_dimensions;
+  const size_t *src_dimensions;
+  struct gomp_device_descr *dst_devicep;
+  struct gomp_device_descr *src_devicep;
+  int num_dims;
+} omp_target_memcpy_rect_data;
+
+static void
+omp_target_memcpy_rect_async_helper (void *args)
+{
+  omp_target_memcpy_rect_data *a = args;
+  int ret = omp_target_memcpy_rect_copy (a->dst, a->src, a->element_size,
+                                        a->num_dims, a->volume, a->dst_offsets,
+                                        a->src_offsets, a->dst_dimensions,
+                                        a->src_dimensions, a->dst_devicep,
+                                        a->src_devicep);
+  if (ret)
+    gomp_fatal ("omp_target_memcpy_rect failed");
+}
+
+int
+omp_target_memcpy_rect_async (void *dst, const void *src, size_t element_size,
+                             int num_dims, const size_t *volume,
+                             const size_t *dst_offsets,
+                             const size_t *src_offsets,
+                             const size_t *dst_dimensions,
+                             const size_t *src_dimensions,
+                             int dst_device_num, int src_device_num,
+                             int depobj_count, omp_depend_t *depobj_list)
+{
+  struct gomp_device_descr *dst_devicep = NULL, *src_devicep = NULL;
+  unsigned flags = 0;
+  int check = omp_target_memcpy_rect_check (dst, src, dst_device_num,
+                                           src_device_num, &dst_devicep,
+                                           &src_devicep);
+  void *depend[depobj_count + 5];
+  int i;
+
+  omp_target_memcpy_rect_data s = {
+    .dst = dst,
+    .src = src,
+    .element_size = element_size,
+    .num_dims = num_dims,
+    .volume = volume,
+    .dst_offsets = dst_offsets,
+    .src_offsets = src_offsets,
+    .dst_dimensions = dst_dimensions,
+    .src_dimensions = src_dimensions,
+    .dst_devicep = dst_devicep,
+    .src_devicep = src_devicep
+  };
+
+  if (check)
+    return check;
+
+  if (depobj_count > 0 && depobj_list != NULL)
+    {
+      flags |= GOMP_TASK_FLAG_DEPEND;
+      depend[0] = 0;
+      depend[1] = (void *) (uintptr_t) depobj_count;
+      depend[2] = depend[3] = depend[4] = 0;
+      for (i = 0; i < depobj_count; ++i)
+       depend[i + 5] = &depobj_list[i];
+    }
+
+  GOMP_task (omp_target_memcpy_rect_async_helper, &s, NULL, sizeof (s),
+            __alignof__ (s), true, flags, depend, 0, NULL);
+
+  return 0;
+}
+
 int
 omp_target_associate_ptr (const void *host_ptr, const void *device_ptr,
                          size_t size, size_t device_offset, int device_num)
 {
-  if (device_num == gomp_get_num_devices ())
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
     return EINVAL;
 
-  if (device_num < 0)
-    return EINVAL;
-
-  struct gomp_device_descr *devicep = resolve_device (device_num);
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
   if (devicep == NULL)
     return EINVAL;
 
@@ -3070,13 +3877,7 @@ omp_target_associate_ptr (const void *host_ptr, const void *device_ptr,
 int
 omp_target_disassociate_ptr (const void *ptr, int device_num)
 {
-  if (device_num == gomp_get_num_devices ())
-    return EINVAL;
-
-  if (device_num < 0)
-    return EINVAL;
-
-  struct gomp_device_descr *devicep = resolve_device (device_num);
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
   if (devicep == NULL)
     return EINVAL;
 
@@ -3109,14 +3910,70 @@ omp_target_disassociate_ptr (const void *ptr, int device_num)
   return ret;
 }
 
+void *
+omp_get_mapped_ptr (const void *ptr, int device_num)
+{
+  if (device_num == omp_initial_device
+      || device_num == omp_get_initial_device ())
+    return (void *) ptr;
+
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
+  if (devicep == NULL)
+    return NULL;
+
+  if (!(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
+      || devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM)
+    return (void *) ptr;
+
+  gomp_mutex_lock (&devicep->lock);
+
+  struct splay_tree_s *mem_map = &devicep->mem_map;
+  struct splay_tree_key_s cur_node;
+  void *ret = NULL;
+
+  cur_node.host_start = (uintptr_t) ptr;
+  cur_node.host_end = cur_node.host_start;
+  splay_tree_key n = gomp_map_0len_lookup (mem_map, &cur_node);
+
+  if (n)
+    {
+      uintptr_t offset = cur_node.host_start - n->host_start;
+      ret = (void *) (n->tgt->tgt_start + n->tgt_offset + offset);
+    }
+
+  gomp_mutex_unlock (&devicep->lock);
+
+  return ret;
+}
+
+int
+omp_target_is_accessible (const void *ptr, size_t size, int device_num)
+{
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
+    return true;
+
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
+  if (devicep == NULL)
+    return false;
+
+  /* TODO: Unified shared memory must be handled when available.  */
+
+  return devicep->capabilities & GOMP_OFFLOAD_CAP_SHARED_MEM;
+}
+
 int
 omp_pause_resource (omp_pause_resource_t kind, int device_num)
 {
   (void) kind;
-  if (device_num == gomp_get_num_devices ())
+  if (device_num == omp_initial_device
+      || device_num == gomp_get_num_devices ())
     return gomp_pause_host ();
-  if (device_num < 0 || device_num >= num_devices_openmp)
+
+  struct gomp_device_descr *devicep = resolve_device (device_num, false);
+  if (devicep == NULL)
     return -1;
+
   /* Do nothing for target devices for now.  */
   return 0;
 }
@@ -3149,7 +4006,11 @@ gomp_load_plugin_for_device (struct gomp_device_descr *device,
 
   void *plugin_handle = dlopen (plugin_name, RTLD_LAZY);
   if (!plugin_handle)
+#if OFFLOAD_DEFAULTED
+    return 0;
+#else
     goto dl_fail;
+#endif
 
   /* Check if all required functions are available in the plugin and store
      their handlers.  None of the symbols can legitimately be NULL,
@@ -3312,8 +4173,30 @@ gomp_target_init (void)
 
        if (gomp_load_plugin_for_device (&current_device, plugin_name))
          {
-           new_num_devs = current_device.get_num_devices_func ();
-           if (new_num_devs >= 1)
+           int omp_req = omp_requires_mask & ~GOMP_REQUIRES_TARGET_USED;
+           new_num_devs = current_device.get_num_devices_func (omp_req);
+           if (gomp_debug_var > 0 && new_num_devs < 0)
+             {
+               bool found = false;
+               int type = current_device.get_type_func ();
+               for (int img = 0; img < num_offload_images; img++)
+                 if (type == offload_images[img].type)
+                   found = true;
+               if (found)
+                 {
+                   char buf[sizeof ("unified_address, unified_shared_memory, "
+                                    "reverse_offload")];
+                   gomp_requires_to_name (buf, sizeof (buf), omp_req);
+                   char *name = (char *) malloc (cur_len + 1);
+                   memcpy (name, cur, cur_len);
+                   name[cur_len] = '\0';
+                   gomp_debug (1,
+                               "%s devices present but 'omp requires %s' "
+                               "cannot be fulfilled", name, buf);
+                   free (name);
+                 }
+             }
+           else if (new_num_devs >= 1)
              {
                /* Augment DEVICES and NUM_DEVICES.  */