[PATCH 5/n] OpenMP 4.0 offloading infrastructure: libgomp

[Ilya Verbin <iverbin at gmail dot com>]

Hello,

This patch adds plugin support to libgomp, as well as memory mapping and
interaction with target devices through plugin's interface.

Bootstrapped and regtested on top of patch 4.  Is it OK for trunk?

Thanks,
  -- Ilya


2014-10-06  Jakub Jelinek  <jakub@redhat.com>
	    Ilya Verbin  <ilya.verbin@intel.com>
	    Thomas Schwinge  <thomas@codesourcery.com>
	    Andrey Turetskiy  <andrey.turetskiy@intel.com>

libgomp/
	* libgomp.map (GOMP_4.0.1): New symbol version.
	Add GOMP_offload_register.
	* libgomp_target.h: New file.
	* splay-tree.h: New file.
	* target.c: Include config.h, libgomp_target.h, dlfcn.h, splay-tree.h.
	(gomp_target_init): New forward declaration.
	(gomp_is_initialized): New static variable.
	(splay_tree_node, splay_tree, splay_tree_key): New typedefs.
	(struct target_mem_desc, struct splay_tree_key_s, offload_image_descr):
	New structures.
	(offload_images, num_offload_images, devices, num_devices): New static
	variables.
	(splay_compare): New static function.
	(struct gomp_device_descr): New structure.
	(gomp_get_num_devices): Call gomp_target_init.
	(resolve_device, gomp_map_vars_existing, gomp_map_vars, gomp_unmap_tgt)
	(gomp_unmap_vars, gomp_update, gomp_init_device): New static functions.
	(GOMP_offload_register): New function.
	(GOMP_target): Arrange for host callback to be performed in a separate
	initial thread and contention group, inheriting ICVs from
	gomp_global_icv etc.  Call gomp_map_vars and gomp_unmap_vars.
	Add device initialization and lookup for target function in splay tree.
	(GOMP_target_data): Add device initialization and call gomp_map_vars.
	(GOMP_target_end_data): Call gomp_unmap_vars.
	(GOMP_target_update): Add device initialization and call gomp_update.
	(gomp_load_plugin_for_device, gomp_register_images_for_device)
	(gomp_target_init): New static functions.

---

diff --git a/libgomp/libgomp.map b/libgomp/libgomp.map
index b102fd8..f36df23 100644
--- a/libgomp/libgomp.map
+++ b/libgomp/libgomp.map
@@ -227,3 +227,8 @@ GOMP_4.0 {
 	GOMP_target_update;
 	GOMP_teams;
 } GOMP_3.0;
+
+GOMP_4.0.1 {
+  global:
+	GOMP_offload_register;
+} GOMP_4.0;
diff --git a/libgomp/libgomp_target.h b/libgomp/libgomp_target.h
new file mode 100644
index 0000000..f7d19d0
--- /dev/null
+++ b/libgomp/libgomp_target.h
@@ -0,0 +1,44 @@
+/* Copyright (C) 2014 Free Software Foundation, Inc.
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef LIBGOMP_TARGET_H
+#define LIBGOMP_TARGET_H 1
+
+/* Type of offload target device.  */
+enum offload_target_type
+{
+  OFFLOAD_TARGET_TYPE_HOST,
+  OFFLOAD_TARGET_TYPE_INTEL_MIC
+};
+
+/* Auxiliary struct, used for transferring a host-target address range mapping
+   from plugin to libgomp.  */
+struct mapping_table
+{
+  uintptr_t host_start;
+  uintptr_t host_end;
+  uintptr_t tgt_start;
+  uintptr_t tgt_end;
+};
+
+#endif /* LIBGOMP_TARGET_H */
diff --git a/libgomp/splay-tree.h b/libgomp/splay-tree.h
new file mode 100644
index 0000000..eb8011a
--- /dev/null
+++ b/libgomp/splay-tree.h
@@ -0,0 +1,232 @@
+/* A splay-tree datatype.
+   Copyright 1998-2014
+   Free Software Foundation, Inc.
+   Contributed by Mark Mitchell (mark@markmitchell.com).
+
+   This file is part of the GNU OpenMP Library (libgomp).
+
+   Libgomp is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+   more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* The splay tree code copied from include/splay-tree.h and adjusted,
+   so that all the data lives directly in splay_tree_node_s structure
+   and no extra allocations are needed.
+
+   Files including this header should before including it add:
+typedef struct splay_tree_node_s *splay_tree_node;
+typedef struct splay_tree_s *splay_tree;
+typedef struct splay_tree_key_s *splay_tree_key;
+   define splay_tree_key_s structure, and define
+   splay_compare inline function.  */
+
+/* For an easily readable description of splay-trees, see:
+
+     Lewis, Harry R. and Denenberg, Larry.  Data Structures and Their
+     Algorithms.  Harper-Collins, Inc.  1991.
+
+   The major feature of splay trees is that all basic tree operations
+   are amortized O(log n) time for a tree with n nodes.  */
+
+/* The nodes in the splay tree.  */
+struct splay_tree_node_s {
+  struct splay_tree_key_s key;
+  /* The left and right children, respectively.  */
+  splay_tree_node left;
+  splay_tree_node right;
+};
+
+/* The splay tree.  */
+struct splay_tree_s {
+  splay_tree_node root;
+};
+
+/* Rotate the edge joining the left child N with its parent P.  PP is the
+   grandparents' pointer to P.  */
+
+static inline void
+rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
+{
+  splay_tree_node tmp;
+  tmp = n->right;
+  n->right = p;
+  p->left = tmp;
+  *pp = n;
+}
+
+/* Rotate the edge joining the right child N with its parent P.  PP is the
+   grandparents' pointer to P.  */
+
+static inline void
+rotate_right (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
+{
+  splay_tree_node tmp;
+  tmp = n->left;
+  n->left = p;
+  p->right = tmp;
+  *pp = n;
+}
+
+/* Bottom up splay of KEY.  */
+
+static void
+splay_tree_splay (splay_tree sp, splay_tree_key key)
+{
+  if (sp->root == NULL)
+    return;
+
+  do {
+    int cmp1, cmp2;
+    splay_tree_node n, c;
+
+    n = sp->root;
+    cmp1 = splay_compare (key, &n->key);
+
+    /* Found.  */
+    if (cmp1 == 0)
+      return;
+
+    /* Left or right?  If no child, then we're done.  */
+    if (cmp1 < 0)
+      c = n->left;
+    else
+      c = n->right;
+    if (!c)
+      return;
+
+    /* Next one left or right?  If found or no child, we're done
+       after one rotation.  */
+    cmp2 = splay_compare (key, &c->key);
+    if (cmp2 == 0
+	|| (cmp2 < 0 && !c->left)
+	|| (cmp2 > 0 && !c->right))
+      {
+	if (cmp1 < 0)
+	  rotate_left (&sp->root, n, c);
+	else
+	  rotate_right (&sp->root, n, c);
+	return;
+      }
+
+    /* Now we have the four cases of double-rotation.  */
+    if (cmp1 < 0 && cmp2 < 0)
+      {
+	rotate_left (&n->left, c, c->left);
+	rotate_left (&sp->root, n, n->left);
+      }
+    else if (cmp1 > 0 && cmp2 > 0)
+      {
+	rotate_right (&n->right, c, c->right);
+	rotate_right (&sp->root, n, n->right);
+      }
+    else if (cmp1 < 0 && cmp2 > 0)
+      {
+	rotate_right (&n->left, c, c->right);
+	rotate_left (&sp->root, n, n->left);
+      }
+    else if (cmp1 > 0 && cmp2 < 0)
+      {
+	rotate_left (&n->right, c, c->left);
+	rotate_right (&sp->root, n, n->right);
+      }
+  } while (1);
+}
+
+/* Insert a new NODE into SP.  The NODE shouldn't exist in the tree.  */
+
+static void
+splay_tree_insert (splay_tree sp, splay_tree_node node)
+{
+  int comparison = 0;
+
+  splay_tree_splay (sp, &node->key);
+
+  if (sp->root)
+    comparison = splay_compare (&sp->root->key, &node->key);
+
+  if (sp->root && comparison == 0)
+    abort ();
+  else
+    {
+      /* Insert it at the root.  */
+      if (sp->root == NULL)
+	node->left = node->right = NULL;
+      else if (comparison < 0)
+	{
+	  node->left = sp->root;
+	  node->right = node->left->right;
+	  node->left->right = NULL;
+	}
+      else
+	{
+	  node->right = sp->root;
+	  node->left = node->right->left;
+	  node->right->left = NULL;
+	}
+
+      sp->root = node;
+    }
+}
+
+/* Remove node with KEY from SP.  It is not an error if it did not exist.  */
+
+static void
+splay_tree_remove (splay_tree sp, splay_tree_key key)
+{
+  splay_tree_splay (sp, key);
+
+  if (sp->root && splay_compare (&sp->root->key, key) == 0)
+    {
+      splay_tree_node left, right;
+
+      left = sp->root->left;
+      right = sp->root->right;
+
+      /* One of the children is now the root.  Doesn't matter much
+	 which, so long as we preserve the properties of the tree.  */
+      if (left)
+	{
+	  sp->root = left;
+
+	  /* If there was a right child as well, hang it off the
+	     right-most leaf of the left child.  */
+	  if (right)
+	    {
+	      while (left->right)
+		left = left->right;
+	      left->right = right;
+	    }
+	}
+      else
+	sp->root = right;
+    }
+}
+
+/* Lookup KEY in SP, returning NODE if present, and NULL
+   otherwise.  */
+
+static splay_tree_key
+splay_tree_lookup (splay_tree sp, splay_tree_key key)
+{
+  splay_tree_splay (sp, key);
+
+  if (sp->root && splay_compare (&sp->root->key, key) == 0)
+    return &sp->root->key;
+  else
+    return NULL;
+}
diff --git a/libgomp/target.c b/libgomp/target.c
index 46acc58..4ace170 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -22,19 +22,639 @@
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
-/* This file handles the maintainence of threads in response to team
-   creation and termination.  */
+/* This file contains the support of offloading.  */
 
+#include "config.h"
 #include "libgomp.h"
+#include "libgomp_target.h"
 #include <limits.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
 
+#ifdef PLUGIN_SUPPORT
+#include <dlfcn.h>
+#endif
+
+static void gomp_target_init (void);
+
+static pthread_once_t gomp_is_initialized = PTHREAD_ONCE_INIT;
+
+/* Forward declaration for a node in the tree.  */
+typedef struct splay_tree_node_s *splay_tree_node;
+typedef struct splay_tree_s *splay_tree;
+typedef struct splay_tree_key_s *splay_tree_key;
+
+struct target_mem_desc {
+  /* Reference count.  */
+  uintptr_t refcount;
+  /* All the splay nodes allocated together.  */
+  splay_tree_node array;
+  /* Start of the target region.  */
+  uintptr_t tgt_start;
+  /* End of the targer region.  */
+  uintptr_t tgt_end;
+  /* Handle to free.  */
+  void *to_free;
+  /* Previous target_mem_desc.  */
+  struct target_mem_desc *prev;
+  /* Number of items in following list.  */
+  size_t list_count;
+
+  /* Corresponding target device descriptor.  */
+  struct gomp_device_descr *device_descr;
+
+  /* List of splay keys to remove (or decrease refcount)
+     at the end of region.  */
+  splay_tree_key list[];
+};
+
+struct splay_tree_key_s {
+  /* Address of the host object.  */
+  uintptr_t host_start;
+  /* Address immediately after the host object.  */
+  uintptr_t host_end;
+  /* Descriptor of the target memory.  */
+  struct target_mem_desc *tgt;
+  /* Offset from tgt->tgt_start to the start of the target object.  */
+  uintptr_t tgt_offset;
+  /* Reference count.  */
+  uintptr_t refcount;
+  /* True if data should be copied from device to host at the end.  */
+  bool copy_from;
+};
+
+/* This structure describes an offload image.
+   It contains type of the target device, pointer to host table descriptor, and
+   pointer to target data.  */
+struct offload_image_descr {
+  enum offload_target_type type;
+  void *host_table;
+  void *target_data;
+};
+
+/* Array of descriptors of offload images.  */
+static struct offload_image_descr *offload_images;
+
+/* Total number of offload images.  */
+static int num_offload_images;
+
+/* Array of descriptors for all available devices.  */
+static struct gomp_device_descr *devices;
+
+/* Total number of available devices.  */
+static int num_devices;
+
+/* The comparison function.  */
+
+static int
+splay_compare (splay_tree_key x, splay_tree_key y)
+{
+  if (x->host_start == x->host_end
+      && y->host_start == y->host_end)
+    return 0;
+  if (x->host_end <= y->host_start)
+    return -1;
+  if (x->host_start >= y->host_end)
+    return 1;
+  return 0;
+}
+
+#include "splay-tree.h"
+
+/* This structure describes accelerator device.
+   It contains ID-number of the device, its type, function handlers for
+   interaction with the device, and information about mapped memory.  */
+struct gomp_device_descr
+{
+  /* This is the ID number of device.  It could be specified in DEVICE-clause of
+     TARGET construct.  */
+  int id;
+
+  /* This is the ID number of device among devices of the same type.  */
+  int target_id;
+
+  /* This is the TYPE of device.  */
+  enum offload_target_type type;
+
+  /* Set to true when device is initialized.  */
+  bool is_initialized;
+
+  /* Function handlers.  */
+  int (*get_type_func) (void);
+  int (*get_num_devices_func) (void);
+  void (*register_image_func) (void *, void *);
+  void (*init_device_func) (int);
+  int (*get_table_func) (int, void *);
+  void *(*alloc_func) (int, size_t);
+  void (*free_func) (int, void *);
+  void *(*host2dev_func) (int, void *, const void *, size_t);
+  void *(*dev2host_func) (int, void *, const void *, size_t);
+  void (*run_func) (int, void *, void *);
+
+  /* Splay tree containing information about mapped memory regions.  */
+  struct splay_tree_s dev_splay_tree;
+
+  /* Mutex for operating with the splay tree and other shared structures.  */
+  gomp_mutex_t dev_env_lock;
+};
+
 attribute_hidden int
 gomp_get_num_devices (void)
 {
-  return 0;
+  (void) pthread_once (&gomp_is_initialized, gomp_target_init);
+  return num_devices;
+}
+
+static struct gomp_device_descr *
+resolve_device (int device_id)
+{
+  if (device_id == -1)
+    {
+      struct gomp_task_icv *icv = gomp_icv (false);
+      device_id = icv->default_device_var;
+    }
+
+  if (device_id < 0 || device_id >= gomp_get_num_devices ())
+    return NULL;
+
+  return &devices[device_id];
+}
+
+
+/* Handle the case where splay_tree_lookup found oldn for newn.
+   Helper function of gomp_map_vars.  */
+
+static inline void
+gomp_map_vars_existing (splay_tree_key oldn, splay_tree_key newn,
+			unsigned char kind)
+{
+  if (oldn->host_start > newn->host_start
+      || oldn->host_end < newn->host_end)
+    gomp_fatal ("Trying to map into device [%p..%p) object when"
+		"[%p..%p) is already mapped",
+		(void *) newn->host_start, (void *) newn->host_end,
+		(void *) oldn->host_start, (void *) oldn->host_end);
+  oldn->refcount++;
+}
+
+static struct target_mem_desc *
+gomp_map_vars (struct gomp_device_descr *devicep, size_t mapnum,
+	       void **hostaddrs, size_t *sizes, unsigned char *kinds,
+	       bool is_target)
+{
+  size_t i, tgt_align, tgt_size, not_found_cnt = 0;
+  struct splay_tree_key_s cur_node;
+  struct target_mem_desc *tgt
+    = gomp_malloc (sizeof (*tgt) + sizeof (tgt->list[0]) * mapnum);
+  tgt->list_count = mapnum;
+  tgt->refcount = 1;
+  tgt->device_descr = devicep;
+
+  if (mapnum == 0)
+    return tgt;
+
+  tgt_align = sizeof (void *);
+  tgt_size = 0;
+  if (is_target)
+    {
+      size_t align = 4 * sizeof (void *);
+      tgt_align = align;
+      tgt_size = mapnum * sizeof (void *);
+    }
+
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  for (i = 0; i < mapnum; i++)
+    {
+      if (hostaddrs[i] == NULL)
+	{
+	  tgt->list[i] = NULL;
+	  continue;
+	}
+      cur_node.host_start = (uintptr_t) hostaddrs[i];
+      if ((kinds[i] & 7) != 4)
+	cur_node.host_end = cur_node.host_start + sizes[i];
+      else
+	cur_node.host_end = cur_node.host_start + sizeof (void *);
+      splay_tree_key n = splay_tree_lookup (&devicep->dev_splay_tree,
+					    &cur_node);
+      if (n)
+	{
+	  tgt->list[i] = n;
+	  gomp_map_vars_existing (n, &cur_node, kinds[i]);
+	}
+      else
+	{
+	  size_t align = (size_t) 1 << (kinds[i] >> 3);
+	  tgt->list[i] = NULL;
+	  not_found_cnt++;
+	  if (tgt_align < align)
+	    tgt_align = align;
+	  tgt_size = (tgt_size + align - 1) & ~(align - 1);
+	  tgt_size += cur_node.host_end - cur_node.host_start;
+	  if ((kinds[i] & 7) == 5)
+	    {
+	      size_t j;
+	      for (j = i + 1; j < mapnum; j++)
+		if ((kinds[j] & 7) != 4)
+		  break;
+		else if ((uintptr_t) hostaddrs[j] < cur_node.host_start
+			 || ((uintptr_t) hostaddrs[j] + sizeof (void *)
+			     > cur_node.host_end))
+		  break;
+		else
+		  {
+		    tgt->list[j] = NULL;
+		    i++;
+		  }
+	    }
+	}
+    }
+
+  if (not_found_cnt || is_target)
+    {
+      /* Allocate tgt_align aligned tgt_size block of memory.  */
+      /* FIXME: Perhaps change interface to allocate properly aligned
+	 memory.  */
+      tgt->to_free = devicep->alloc_func (devicep->target_id,
+					  tgt_size + tgt_align - 1);
+      tgt->tgt_start = (uintptr_t) tgt->to_free;
+      tgt->tgt_start = (tgt->tgt_start + tgt_align - 1) & ~(tgt_align - 1);
+      tgt->tgt_end = tgt->tgt_start + tgt_size;
+    }
+  else
+    {
+      tgt->to_free = NULL;
+      tgt->tgt_start = 0;
+      tgt->tgt_end = 0;
+    }
+
+  tgt_size = 0;
+  if (is_target)
+    tgt_size = mapnum * sizeof (void *);
+
+  tgt->array = NULL;
+  if (not_found_cnt)
+    {
+      tgt->array = gomp_malloc (not_found_cnt * sizeof (*tgt->array));
+      splay_tree_node array = tgt->array;
+      size_t j;
+
+      for (i = 0; i < mapnum; i++)
+	if (tgt->list[i] == NULL)
+	  {
+	    if (hostaddrs[i] == NULL)
+	      continue;
+	    splay_tree_key k = &array->key;
+	    k->host_start = (uintptr_t) hostaddrs[i];
+	    if ((kinds[i] & 7) != 4)
+	      k->host_end = k->host_start + sizes[i];
+	    else
+	      k->host_end = k->host_start + sizeof (void *);
+	    splay_tree_key n
+	      = splay_tree_lookup (&devicep->dev_splay_tree, k);
+	    if (n)
+	      {
+		tgt->list[i] = n;
+		gomp_map_vars_existing (n, k, kinds[i]);
+	      }
+	    else
+	      {
+		size_t align = (size_t) 1 << (kinds[i] >> 3);
+		tgt->list[i] = k;
+		tgt_size = (tgt_size + align - 1) & ~(align - 1);
+		k->tgt = tgt;
+		k->tgt_offset = tgt_size;
+		tgt_size += k->host_end - k->host_start;
+		k->copy_from = false;
+		if ((kinds[i] & 7) == 2 || (kinds[i] & 7) == 3)
+		  k->copy_from = true;
+		k->refcount = 1;
+		tgt->refcount++;
+		array->left = NULL;
+		array->right = NULL;
+		splay_tree_insert (&devicep->dev_splay_tree, array);
+		switch (kinds[i] & 7)
+		  {
+		  case 0: /* ALLOC */
+		  case 2: /* FROM */
+		    break;
+		  case 1: /* TO */
+		  case 3: /* TOFROM */
+		    /* FIXME: Perhaps add some smarts, like if copying
+		       several adjacent fields from host to target, use some
+		       host buffer to avoid sending each var individually.  */
+		    devicep->host2dev_func (devicep->target_id,
+					    (void *) (tgt->tgt_start
+						      + k->tgt_offset),
+					    (void *) k->host_start,
+					    k->host_end - k->host_start);
+		    break;
+		  case 4: /* POINTER */
+		    cur_node.host_start
+		      = (uintptr_t) *(void **) k->host_start;
+		    if (cur_node.host_start == (uintptr_t) NULL)
+		      {
+			cur_node.tgt_offset = (uintptr_t) NULL;
+			devicep->host2dev_func (devicep->target_id,
+						(void *) (tgt->tgt_start
+							  + k->tgt_offset),
+						(void *) &cur_node.tgt_offset,
+						sizeof (void *));
+			break;
+		      }
+		    /* Add bias to the pointer value.  */
+		    cur_node.host_start += sizes[i];
+		    cur_node.host_end = cur_node.host_start + 1;
+		    n = splay_tree_lookup (&devicep->dev_splay_tree,
+					   &cur_node);
+		    if (n == NULL)
+		      {
+			/* Could be possibly zero size array section.  */
+			cur_node.host_end--;
+			n = splay_tree_lookup (&devicep->dev_splay_tree,
+					       &cur_node);
+			if (n == NULL)
+			  {
+			    cur_node.host_start--;
+			    n = splay_tree_lookup (&devicep->dev_splay_tree,
+						   &cur_node);
+			    cur_node.host_start++;
+			  }
+		      }
+		    if (n == NULL)
+		      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 -= sizes[i];
+		    devicep->host2dev_func (devicep->target_id,
+					    (void *) (tgt->tgt_start
+						      + k->tgt_offset),
+					    (void *) &cur_node.tgt_offset,
+					    sizeof (void *));
+		    break;
+		  case 5: /* TO_PSET */
+		    devicep->host2dev_func (devicep->target_id,
+					    (void *) (tgt->tgt_start
+						      + k->tgt_offset),
+					    (void *) k->host_start,
+					    k->host_end - k->host_start);
+		    for (j = i + 1; j < mapnum; j++)
+		      if ((kinds[j] & 7) != 4)
+			break;
+		      else if ((uintptr_t) hostaddrs[j] < k->host_start
+			       || ((uintptr_t) hostaddrs[j] + sizeof (void *)
+				   > k->host_end))
+			break;
+		      else
+			{
+			  tgt->list[j] = k;
+			  k->refcount++;
+			  cur_node.host_start
+			    = (uintptr_t) *(void **) hostaddrs[j];
+			  if (cur_node.host_start == (uintptr_t) NULL)
+			    {
+			      cur_node.tgt_offset = (uintptr_t) NULL;
+			      devicep->host2dev_func (devicep->target_id,
+				 (void *) (tgt->tgt_start + k->tgt_offset
+					   + ((uintptr_t) hostaddrs[j]
+					      - k->host_start)),
+				 (void *) &cur_node.tgt_offset,
+				 sizeof (void *));
+			      i++;
+			      continue;
+			    }
+			  /* Add bias to the pointer value.  */
+			  cur_node.host_start += sizes[j];
+			  cur_node.host_end = cur_node.host_start + 1;
+			  n = splay_tree_lookup (&devicep->dev_splay_tree,
+						 &cur_node);
+			  if (n == NULL)
+			    {
+			      /* Could be possibly zero size array section.  */
+			      cur_node.host_end--;
+			      n = splay_tree_lookup (&devicep->dev_splay_tree,
+						     &cur_node);
+			      if (n == NULL)
+				{
+				  cur_node.host_start--;
+				  n = splay_tree_lookup
+					(&devicep->dev_splay_tree, &cur_node);
+				  cur_node.host_start++;
+				}
+			    }
+			  if (n == NULL)
+			    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 -= sizes[j];
+			  devicep->host2dev_func (devicep->target_id,
+			     (void *) (tgt->tgt_start + k->tgt_offset
+				       + ((uintptr_t) hostaddrs[j]
+					  - k->host_start)),
+			     (void *) &cur_node.tgt_offset,
+			     sizeof (void *));
+			  i++;
+			}
+		      break;
+		  }
+		array++;
+	      }
+	  }
+    }
+  if (is_target)
+    {
+      for (i = 0; i < mapnum; i++)
+	{
+	  if (tgt->list[i] == NULL)
+	    cur_node.tgt_offset = (uintptr_t) NULL;
+	  else
+	    cur_node.tgt_offset = tgt->list[i]->tgt->tgt_start
+				  + tgt->list[i]->tgt_offset;
+	  devicep->host2dev_func (devicep->target_id,
+				  (void *) (tgt->tgt_start
+					    + i * sizeof (void *)),
+				  (void *) &cur_node.tgt_offset,
+				  sizeof (void *));
+	}
+    }
+
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+  return tgt;
+}
+
+static void
+gomp_unmap_tgt (struct target_mem_desc *tgt)
+{
+  /* Deallocate on target the tgt->tgt_start .. tgt->tgt_end region.  */
+  if (tgt->tgt_end)
+    tgt->device_descr->free_func (tgt->device_descr->target_id, tgt->to_free);
+
+  free (tgt->array);
+  free (tgt);
+}
+
+static void
+gomp_unmap_vars (struct target_mem_desc *tgt)
+{
+  struct gomp_device_descr *devicep = tgt->device_descr;
+
+  if (tgt->list_count == 0)
+    {
+      free (tgt);
+      return;
+    }
+
+  size_t i;
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  for (i = 0; i < tgt->list_count; i++)
+    if (tgt->list[i] == NULL)
+      ;
+    else if (tgt->list[i]->refcount > 1)
+      tgt->list[i]->refcount--;
+    else
+      {
+	splay_tree_key k = tgt->list[i];
+	if (k->copy_from)
+	  devicep->dev2host_func (devicep->target_id, (void *) k->host_start,
+				  (void *) (k->tgt->tgt_start + k->tgt_offset),
+				  k->host_end - k->host_start);
+	splay_tree_remove (&devicep->dev_splay_tree, k);
+	if (k->tgt->refcount > 1)
+	  k->tgt->refcount--;
+	else
+	  gomp_unmap_tgt (k->tgt);
+      }
+
+  if (tgt->refcount > 1)
+    tgt->refcount--;
+  else
+    gomp_unmap_tgt (tgt);
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+}
+
+static void
+gomp_update (struct gomp_device_descr *devicep, size_t mapnum,
+	     void **hostaddrs, size_t *sizes, unsigned char *kinds)
+{
+  size_t i;
+  struct splay_tree_key_s cur_node;
+
+  if (!devicep)
+    return;
+
+  if (mapnum == 0)
+    return;
+
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  for (i = 0; i < mapnum; i++)
+    if (sizes[i])
+      {
+	cur_node.host_start = (uintptr_t) hostaddrs[i];
+	cur_node.host_end = cur_node.host_start + sizes[i];
+	splay_tree_key n = splay_tree_lookup (&devicep->dev_splay_tree,
+					      &cur_node);
+	if (n)
+	  {
+	    if (n->host_start > cur_node.host_start
+		|| n->host_end < cur_node.host_end)
+	      gomp_fatal ("Trying to update [%p..%p) object when"
+			  "only [%p..%p) is mapped",
+			  (void *) cur_node.host_start,
+			  (void *) cur_node.host_end,
+			  (void *) n->host_start,
+			  (void *) n->host_end);
+	    if ((kinds[i] & 7) == 1)
+	      devicep->host2dev_func (devicep->target_id,
+				      (void *) (n->tgt->tgt_start
+						+ n->tgt_offset
+						+ cur_node.host_start
+						- n->host_start),
+				      (void *) cur_node.host_start,
+				      cur_node.host_end - cur_node.host_start);
+	    else if ((kinds[i] & 7) == 2)
+	      devicep->dev2host_func (devicep->target_id,
+				      (void *) cur_node.host_start,
+				      (void *) (n->tgt->tgt_start
+						+ n->tgt_offset
+						+ cur_node.host_start
+						- n->host_start),
+				      cur_node.host_end - cur_node.host_start);
+	  }
+	else
+	  gomp_fatal ("Trying to update [%p..%p) object that is not mapped",
+		      (void *) cur_node.host_start,
+		      (void *) cur_node.host_end);
+      }
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+}
+
+/* This function should be called from every offload image.
+   It gets the descriptor of the host func and var tables HOST_TABLE, TYPE of
+   the target, and TARGET_DATA needed by target plugin.  */
+
+void
+GOMP_offload_register (void *host_table, enum offload_target_type target_type,
+		       void *target_data)
+{
+  offload_images = gomp_realloc (offload_images,
+				 (num_offload_images + 1)
+				 * sizeof (struct offload_image_descr));
+
+  offload_images[num_offload_images].type = target_type;
+  offload_images[num_offload_images].host_table = host_table;
+  offload_images[num_offload_images].target_data = target_data;
+
+  num_offload_images++;
+}
+
+/* This function initializes the target device, specified by DEVICEP.  */
+
+static void
+gomp_init_device (struct gomp_device_descr *devicep)
+{
+  devicep->init_device_func (devicep->target_id);
+
+  /* Get address mapping table for device.  */
+  struct mapping_table *table = NULL;
+  int num_entries = devicep->get_table_func (devicep->target_id, &table);
+
+  /* Insert host-target address mapping into dev_splay_tree.  */
+  int i;
+  for (i = 0; i < num_entries; i++)
+    {
+      struct target_mem_desc *tgt = gomp_malloc (sizeof (*tgt));
+      tgt->refcount = 1;
+      tgt->array = gomp_malloc (sizeof (*tgt->array));
+      tgt->tgt_start = table[i].tgt_start;
+      tgt->tgt_end = table[i].tgt_end;
+      tgt->to_free = NULL;
+      tgt->list_count = 0;
+      tgt->device_descr = devicep;
+      splay_tree_node node = tgt->array;
+      splay_tree_key k = &node->key;
+      k->host_start = table[i].host_start;
+      k->host_end = table[i].host_end;
+      k->tgt_offset = 0;
+      k->tgt = tgt;
+      node->left = NULL;
+      node->right = NULL;
+      splay_tree_insert (&devicep->dev_splay_tree, node);
+    }
+
+  free (table);
+  devicep->is_initialized = true;
 }
 
 /* Called when encountering a target directive.  If DEVICE
@@ -52,7 +672,38 @@ GOMP_target (int device, void (*fn) (void *), const void *openmp_target,
 	     size_t mapnum, void **hostaddrs, size_t *sizes,
 	     unsigned char *kinds)
 {
-  /* Host fallback.  */
+  struct gomp_device_descr *devicep = resolve_device (device);
+  if (devicep == NULL)
+    {
+      /* Host fallback.  */
+      struct gomp_thread old_thr, *thr = gomp_thread ();
+      old_thr = *thr;
+      memset (thr, '\0', sizeof (*thr));
+      if (gomp_places_list)
+	{
+	  thr->place = old_thr.place;
+	  thr->ts.place_partition_len = gomp_places_list_len;
+	}
+      fn (hostaddrs);
+      gomp_free_thread (thr);
+      *thr = old_thr;
+      return;
+    }
+
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  if (!devicep->is_initialized)
+    gomp_init_device (devicep);
+
+  struct splay_tree_key_s k;
+  k.host_start = (uintptr_t) fn;
+  k.host_end = k.host_start + 1;
+  splay_tree_key tgt_fn = splay_tree_lookup (&devicep->dev_splay_tree, &k);
+  if (tgt_fn == NULL)
+    gomp_fatal ("Target function wasn't mapped");
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+
+  struct target_mem_desc *tgt_vars
+    = gomp_map_vars (devicep, mapnum, hostaddrs, sizes, kinds, true);
   struct gomp_thread old_thr, *thr = gomp_thread ();
   old_thr = *thr;
   memset (thr, '\0', sizeof (*thr));
@@ -61,26 +712,74 @@ GOMP_target (int device, void (*fn) (void *), const void *openmp_target,
       thr->place = old_thr.place;
       thr->ts.place_partition_len = gomp_places_list_len;
     }
-  fn (hostaddrs);
+  devicep->run_func (devicep->target_id, (void *) tgt_fn->tgt->tgt_start,
+		     (void *) tgt_vars->tgt_start);
   gomp_free_thread (thr);
   *thr = old_thr;
+  gomp_unmap_vars (tgt_vars);
 }
 
 void
 GOMP_target_data (int device, const void *openmp_target, size_t mapnum,
 		  void **hostaddrs, size_t *sizes, unsigned char *kinds)
 {
+  struct gomp_device_descr *devicep = resolve_device (device);
+  if (devicep == NULL)
+    {
+      /* Host fallback.  */
+      struct gomp_task_icv *icv = gomp_icv (false);
+      if (icv->target_data)
+	{
+	  /* Even when doing a host fallback, if there are any active
+	     #pragma omp target data constructs, need to remember the
+	     new #pragma omp target data, otherwise GOMP_target_end_data
+	     would get out of sync.  */
+	  struct target_mem_desc *tgt
+	    = gomp_map_vars (NULL, 0, NULL, NULL, NULL, false);
+	  tgt->prev = icv->target_data;
+	  icv->target_data = tgt;
+	}
+      return;
+    }
+
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  if (!devicep->is_initialized)
+    gomp_init_device (devicep);
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+
+  struct target_mem_desc *tgt
+    = gomp_map_vars (devicep, mapnum, hostaddrs, sizes, kinds, false);
+  struct gomp_task_icv *icv = gomp_icv (true);
+  tgt->prev = icv->target_data;
+  icv->target_data = tgt;
 }
 
 void
 GOMP_target_end_data (void)
 {
+  struct gomp_task_icv *icv = gomp_icv (false);
+  if (icv->target_data)
+    {
+      struct target_mem_desc *tgt = icv->target_data;
+      icv->target_data = tgt->prev;
+      gomp_unmap_vars (tgt);
+    }
 }
 
 void
 GOMP_target_update (int device, const void *openmp_target, size_t mapnum,
 		    void **hostaddrs, size_t *sizes, unsigned char *kinds)
 {
+  struct gomp_device_descr *devicep = resolve_device (device);
+  if (devicep == NULL)
+    return;
+
+  gomp_mutex_lock (&devicep->dev_env_lock);
+  if (!devicep->is_initialized)
+    gomp_init_device (devicep);
+  gomp_mutex_unlock (&devicep->dev_env_lock);
+
+  gomp_update (devicep, mapnum, hostaddrs, sizes, kinds);
 }
 
 void
@@ -94,3 +793,143 @@ GOMP_teams (unsigned int num_teams, unsigned int thread_limit)
     }
   (void) num_teams;
 }
+
+#ifdef PLUGIN_SUPPORT
+
+/* This function tries to load a plugin for DEVICE.  Name of plugin is passed
+   in PLUGIN_NAME.
+   The handles of the found functions are stored in the corresponding fields
+   of DEVICE.  The function returns TRUE on success and FALSE otherwise.  */
+
+static bool
+gomp_load_plugin_for_device (struct gomp_device_descr *device,
+			     const char *plugin_name)
+{
+  void *plugin_handle = dlopen (plugin_name, RTLD_LAZY);
+  if (!plugin_handle)
+    return false;
+
+  /* Check if all required functions are available in the plugin and store
+     their handlers.  */
+#define DLSYM(f)						    \
+  do								    \
+    {								    \
+      device->f##_func = dlsym (plugin_handle, "GOMP_OFFLOAD_"#f);  \
+      if (!device->f##_func)					    \
+	return false;						    \
+    }								    \
+  while (0)
+  DLSYM (get_type);
+  DLSYM (get_num_devices);
+  DLSYM (register_image);
+  DLSYM (init_device);
+  DLSYM (get_table);
+  DLSYM (alloc);
+  DLSYM (free);
+  DLSYM (dev2host);
+  DLSYM (host2dev);
+  DLSYM (run);
+#undef DLSYM
+
+  return true;
+}
+
+/* This function finds OFFLOAD_IMAGES corresponding to DEVICE type, and
+   registers them in the plugin.  */
+
+static void
+gomp_register_images_for_device (struct gomp_device_descr *device)
+{
+  int i;
+  for (i = 0; i < num_offload_images; i++)
+    {
+      struct offload_image_descr *image = &offload_images[i];
+      if (image->type == device->type)
+	device->register_image_func (image->host_table, image->target_data);
+    }
+}
+
+/* This function initializes the runtime needed for offloading.
+   It parses the list of offload targets and tries to load the plugins for these
+   targets.  Result of the function is properly initialized variable NUM_DEVICES
+   and array DEVICES, containing descriptors for corresponding devices.  */
+
+static void
+gomp_target_init (void)
+{
+  const char *prefix ="libgomp-plugin-";
+  const char *suffix = ".so.1";
+  const char *cur, *next;
+  char *plugin_name;
+  int i, new_num_devices;
+
+  num_devices = 0;
+  devices = NULL;
+
+  cur = OFFLOAD_TARGETS;
+  if (*cur)
+    do
+      {
+	struct gomp_device_descr current_device;
+
+	next = strchr (cur, ',');
+
+	plugin_name = (char *) malloc (1 + (next ? next - cur : strlen (cur))
+				       + strlen (prefix) + strlen (suffix));
+	if (!plugin_name)
+	  {
+	    num_devices = 0;
+	    break;
+	  }
+
+	strcpy (plugin_name, prefix);
+	strncat (plugin_name, cur, next ? next - cur : strlen (cur));
+	strcat (plugin_name, suffix);
+
+	if (gomp_load_plugin_for_device (&current_device, plugin_name))
+	  {
+	    new_num_devices = current_device.get_num_devices_func ();
+	    if (new_num_devices >= 1)
+	      {
+		devices = realloc (devices, (num_devices + new_num_devices)
+				   * sizeof (struct gomp_device_descr));
+		if (!devices)
+		  {
+		    num_devices = 0;
+		    free (plugin_name);
+		    break;
+		  }
+
+		current_device.type = current_device.get_type_func ();
+		current_device.is_initialized = false;
+		current_device.dev_splay_tree.root = NULL;
+		gomp_register_images_for_device (&current_device);
+		for (i = 0; i < new_num_devices; i++)
+		  {
+		    current_device.id = num_devices + 1;
+		    current_device.target_id = i;
+		    devices[num_devices] = current_device;
+		    gomp_mutex_init (&devices[num_devices].dev_env_lock);
+		    num_devices++;
+		  }
+	      }
+	  }
+
+	free (plugin_name);
+	cur = next + 1;
+      }
+    while (next);
+
+  free (offload_images);
+  offload_images = NULL;
+  num_offload_images = 0;
+}
+
+#else /* PLUGIN_SUPPORT */
+/* If dlfcn.h is unavailable we always fallback to host execution.
+   GOMP_target* routines are just stubs for this case.  */
+static void
+gomp_target_init (void)
+{
+}
+#endif /* PLUGIN_SUPPORT */
-- 
1.7.1