[PATCH][OpenMP] Fix resolve_device with -foffload=disable

[Ilya Verbin <iverbin at gmail dot com>]

Hi!

Currently if a compiler is configured with enabled offloading, the 'devices'
array in libgomp is filled properly with a number of available devices.
However, if a program is compiled with -foffload=disable, the resolve_device
function returns a pointer to the device, and host-fallback is not happening.
The patch below fixes this issue.
make check-target-libgomp passed.  OK for trunk?


libgomp/
	* libgomp.h (struct gomp_device_descr): Add num_images.
	* target.c (resolve_device): Call gomp_init_device.  Return NULL if
	there is no image loaded to the device.
	(gomp_offload_image_to_device): Increase num_images.
	(GOMP_offload_unregister): Decrease num_images.
	(GOMP_target): Don't call gomp_init_device.
	(GOMP_target_data): Ditto.
	(GOMP_target_update): Ditto.
	(gomp_target_init): Set num_images to 0.
	* testsuite/libgomp.c/target-1-disable.c: New test.


diff --git a/libgomp/libgomp.h b/libgomp/libgomp.h
index 5272f01..47a064a 100644
--- a/libgomp/libgomp.h
+++ b/libgomp/libgomp.h
@@ -762,6 +762,9 @@ struct gomp_device_descr
   /* Set to true when device is initialized.  */
   bool is_initialized;
 
+  /* Number of images offloaded to the device.  */
+  int num_images;
+
   /* OpenACC-specific data and functions.  */
   /* This is mutable because of its mutable data_environ and target_data
      members.  */
diff --git a/libgomp/target.c b/libgomp/target.c
index d8da783..f5126b9 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -132,6 +132,14 @@ resolve_device (int device_id)
   if (device_id < 0 || device_id >= gomp_get_num_devices ())
     return NULL;
 
+  gomp_mutex_lock (&devices[device_id].lock);
+  if (!devices[device_id].is_initialized)
+    gomp_init_device (&devices[device_id]);
+  gomp_mutex_unlock (&devices[device_id].lock);
+
+  if (devices[device_id].num_images <= 0)
+    return NULL;
+
   return &devices[device_id];
 }
 
@@ -697,6 +705,7 @@ gomp_offload_image_to_device (struct gomp_device_descr *devicep,
   struct addr_pair *target_table = NULL;
   int i, num_target_entries
     = devicep->load_image_func (devicep->target_id, target_data, &target_table);
+  devicep->num_images++;
 
   if (num_target_entries != num_funcs + num_vars)
     {
@@ -831,6 +840,7 @@ GOMP_offload_unregister (void *host_table, enum offload_target_type target_type,
 	}
 
       devicep->unload_image_func (devicep->target_id, target_data);
+      devicep->num_images--;
 
       /* Remove mapping from splay tree.  */
       struct splay_tree_key_s k;
@@ -966,11 +976,6 @@ GOMP_target (int device, void (*fn) (void *), const void *unused,
       return;
     }
 
-  gomp_mutex_lock (&devicep->lock);
-  if (!devicep->is_initialized)
-    gomp_init_device (devicep);
-  gomp_mutex_unlock (&devicep->lock);
-
   void *fn_addr;
 
   if (devicep->capabilities & GOMP_OFFLOAD_CAP_NATIVE_EXEC)
@@ -1034,11 +1039,6 @@ GOMP_target_data (int device, const void *unused, size_t mapnum,
       return;
     }
 
-  gomp_mutex_lock (&devicep->lock);
-  if (!devicep->is_initialized)
-    gomp_init_device (devicep);
-  gomp_mutex_unlock (&devicep->lock);
-
   struct target_mem_desc *tgt
     = gomp_map_vars (devicep, mapnum, hostaddrs, NULL, sizes, kinds, false,
 		     false);
@@ -1069,11 +1069,6 @@ GOMP_target_update (int device, const void *unused, size_t mapnum,
       || !(devicep->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400))
     return;
 
-  gomp_mutex_lock (&devicep->lock);
-  if (!devicep->is_initialized)
-    gomp_init_device (devicep);
-  gomp_mutex_unlock (&devicep->lock);
-
   gomp_update (devicep, mapnum, hostaddrs, sizes, kinds, false);
 }
 
@@ -1265,6 +1260,7 @@ gomp_target_init (void)
 		current_device.type = current_device.get_type_func ();
 		current_device.mem_map.root = NULL;
 		current_device.is_initialized = false;
+		current_device.num_images = 0;
 		current_device.openacc.data_environ = NULL;
 		for (i = 0; i < new_num_devices; i++)
 		  {
diff --git a/libgomp/testsuite/libgomp.c/target-1-disable.c b/libgomp/testsuite/libgomp.c/target-1-disable.c
new file mode 100644
index 0000000..00ea143
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/target-1-disable.c
@@ -0,0 +1,4 @@
+/* { dg-options "-foffload=disable" } */
+/* { dg-require-effective-target offload_device } */
+
+#include "target-1.c"


  -- Ilya