[Patch][1/3] libgomp: Prepare for reverse offload fn lookup

[Tobias Burnus <tobias@codesourcery.com>]

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Technically, this patch is stand alone, but conceptually it based on the
submitted but not reviewed patch:
"[Patch] OpenMP: Support reverse offload (middle end part)"
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598662.html

With that patch, for reverse offloads ('omp target device(ancestor:1)'),
calls like the following are added:
  GOMP_target_ext (-2 /* initial device */, omp_fn.1
where 'omp_fn.1' on nonhost devices a stub function just required for
looking up the host function pointer via the offload_funcs table.

The attached patch prepare for reverse-offload device->host
function-address lookup by requesting (if needed) the on-device address.

OK for mainline?

Tobias


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libgomp: Prepare for reverse offload fn lookup

Prepare for reverse-offloading function-pointer lookup by passing
a rev_fn_table argument to GOMP_OFFLOAD_load_image.

The argument will be NULL, unless GOMP_REQUIRES_REVERSE_OFFLOAD is
requested and devices not supported it, are filtered out.
(Up to and including this commit, no non-host device claims such
support and the caller currently always passes NULL.)

libgomp/ChangeLog:

	* libgomp-plugin.h (GOMP_OFFLOAD_load_image): Add
	'uint64_t **rev_fn_table' argument.
	* oacc-host.c (host_load_image): Likewise.
	* plugin/plugin-gcn.c (GOMP_OFFLOAD_load_image): Likewise;
	currently unused.
	* plugin/plugin-nvptx.c (GOMP_OFFLOAD_load_image): Likewise.
	* target.c (gomp_load_image_to_device): Update call but pass
	NULL for now.

liboffloadmic/ChangeLog:

	* plugin/libgomp-plugin-intelmic.cpp (GOMP_OFFLOAD_load_image):
	Add (unused) uint64_t **rev_fn_table argument.

 libgomp/libgomp-plugin.h                         | 2 +-
 libgomp/oacc-host.c                              | 3 ++-
 libgomp/plugin/plugin-gcn.c                      | 7 +++++--
 libgomp/plugin/plugin-nvptx.c                    | 7 +++++--
 libgomp/target.c                                 | 2 +-
 liboffloadmic/plugin/libgomp-plugin-intelmic.cpp | 3 ++-
 6 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/libgomp/libgomp-plugin.h b/libgomp/libgomp-plugin.h
index ab3ed638475..57309303e66 100644
--- a/libgomp/libgomp-plugin.h
+++ b/libgomp/libgomp-plugin.h
@@ -130,7 +130,7 @@ extern bool GOMP_OFFLOAD_init_device (int);
 extern bool GOMP_OFFLOAD_fini_device (int);
 extern unsigned GOMP_OFFLOAD_version (void);
 extern int GOMP_OFFLOAD_load_image (int, unsigned, const void *,
-				    struct addr_pair **);
+				    struct addr_pair **, uint64_t **);
 extern bool GOMP_OFFLOAD_unload_image (int, unsigned, const void *);
 extern void *GOMP_OFFLOAD_alloc (int, size_t);
 extern bool GOMP_OFFLOAD_free (int, void *);
diff --git a/libgomp/oacc-host.c b/libgomp/oacc-host.c
index eb11b9cf16a..4e3971ae1a9 100644
--- a/libgomp/oacc-host.c
+++ b/libgomp/oacc-host.c
@@ -81,7 +81,8 @@ static int
 host_load_image (int n __attribute__ ((unused)),
 		 unsigned v __attribute__ ((unused)),
 		 const void *t __attribute__ ((unused)),
-		 struct addr_pair **r __attribute__ ((unused)))
+		 struct addr_pair **r __attribute__ ((unused)),
+		 uint64_t **f __attribute__ ((unused)))
 {
   return 0;
 }
diff --git a/libgomp/plugin/plugin-gcn.c b/libgomp/plugin/plugin-gcn.c
index ea327bf2ca0..363e2950649 100644
--- a/libgomp/plugin/plugin-gcn.c
+++ b/libgomp/plugin/plugin-gcn.c
@@ -3346,11 +3346,14 @@ GOMP_OFFLOAD_init_device (int n)
 
 /* Load GCN object-code module described by struct gcn_image_desc in
    TARGET_DATA and return references to kernel descriptors in TARGET_TABLE.
-   If there are any constructors then run them.  */
+   If there are any constructors then run them.  If not NULL, REV_FN_TABLE will
+   contain the on-device addresses of the functions for reverse offload.  To be
+   freed by the caller.  */
 
 int
 GOMP_OFFLOAD_load_image (int ord, unsigned version, const void *target_data,
-			 struct addr_pair **target_table)
+			 struct addr_pair **target_table,
+			 uint64_t **rev_fn_table __attribute__((unused)))
 {
   if (GOMP_VERSION_DEV (version) != GOMP_VERSION_GCN)
     {
diff --git a/libgomp/plugin/plugin-nvptx.c b/libgomp/plugin/plugin-nvptx.c
index bc63e274cdf..d130665ed19 100644
--- a/libgomp/plugin/plugin-nvptx.c
+++ b/libgomp/plugin/plugin-nvptx.c
@@ -1266,11 +1266,14 @@ nvptx_set_clocktick (CUmodule module, struct ptx_device *dev)
 }
 
 /* Load the (partial) program described by TARGET_DATA to device
-   number ORD.  Allocate and return TARGET_TABLE.  */
+   number ORD.  Allocate and return TARGET_TABLE.  If not NULL, REV_FN_TABLE
+   will contain the on-device addresses of the functions for reverse offload.
+   To be freed by the caller.  */
 
 int
 GOMP_OFFLOAD_load_image (int ord, unsigned version, const void *target_data,
-			 struct addr_pair **target_table)
+			 struct addr_pair **target_table,
+			 uint64_t **rev_fn_table __attribute__((unused)))
 {
   CUmodule module;
   const char *const *var_names;
diff --git a/libgomp/target.c b/libgomp/target.c
index 135db1d88ab..da907a2fb48 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -2137,7 +2137,7 @@ gomp_load_image_to_device (struct gomp_device_descr *devicep, unsigned version,
 
   num_target_entries
     = devicep->load_image_func (devicep->target_id, version,
-				target_data, &target_table);
+				target_data, &target_table, NULL);
 
   if (num_target_entries != num_funcs + num_vars
       /* Others (device_num) are included as trailing entries in pair list.  */
diff --git a/liboffloadmic/plugin/libgomp-plugin-intelmic.cpp b/liboffloadmic/plugin/libgomp-plugin-intelmic.cpp
index 33bae0650b4..7be27f0459d 100644
--- a/liboffloadmic/plugin/libgomp-plugin-intelmic.cpp
+++ b/liboffloadmic/plugin/libgomp-plugin-intelmic.cpp
@@ -349,7 +349,8 @@ GOMP_OFFLOAD_version (void)
 
 extern "C" int
 GOMP_OFFLOAD_load_image (int device, const unsigned version,
-			 const void *target_image, addr_pair **result)
+			 const void *target_image, addr_pair **result,
+			 uint64_t ** /* rev_fn_table */)
 {
   TRACE ("(device = %d, target_image = %p)", device, target_image);