[llvm] [Libomptarget] Rework device initialization and image registration (PR #93844)

[Joseph Huber via llvm-commits]

================
@@ -188,54 +95,107 @@ void PluginManager::registerLib(__tgt_bin_desc *Desc) {
     // Scan the RTLs that have associated images until we find one that supports
     // the current image.
     for (auto &R : PM->plugins()) {
-      if (!R.number_of_devices())
+      if (!R.is_plugin_compatible(Img))
         continue;
 
-      if (!R.is_valid_binary(Img, /*Initialized=*/true)) {
-        DP("Image " DPxMOD " is NOT compatible with RTL %s!\n",
-           DPxPTR(Img->ImageStart), R.getName());
-        continue;
+      if (!R.is_initialized()) {
+        if (auto Err = R.init()) {
+          [[maybe_unused]] std::string InfoMsg = toString(std::move(Err));
+          DP("Failed to init plugin: %s\n", InfoMsg.c_str());
+          continue;
+        }
+        DP("Registered plugin %s with %d visible device(s)\n", R.getName(),
+           R.number_of_devices());
       }
 
-      DP("Image " DPxMOD " is compatible with RTL %s!\n",
-         DPxPTR(Img->ImageStart), R.getName());
-
-      PM->initDevices(R);
-
-      // Initialize (if necessary) translation table for this library.
-      PM->TrlTblMtx.lock();
-      if (!PM->HostEntriesBeginToTransTable.count(Desc->HostEntriesBegin)) {
-        PM->HostEntriesBeginRegistrationOrder.push_back(Desc->HostEntriesBegin);
-        TranslationTable &TransTable =
-            (PM->HostEntriesBeginToTransTable)[Desc->HostEntriesBegin];
-        TransTable.HostTable.EntriesBegin = Desc->HostEntriesBegin;
-        TransTable.HostTable.EntriesEnd = Desc->HostEntriesEnd;
+      if (!R.number_of_devices()) {
+        DP("Skipping plugin %s with no visible devices\n", R.getName());
+        continue;
       }
 
-      // Retrieve translation table for this library.
-      TranslationTable &TransTable =
-          (PM->HostEntriesBeginToTransTable)[Desc->HostEntriesBegin];
+      for (int32_t DeviceId = 0; DeviceId < R.number_of_devices(); ++DeviceId) {
+        if (!R.is_device_compatible(DeviceId, Img))
+          continue;
+
+        DP("Image " DPxMOD " is compatible with RTL %s device %d!\n",
+           DPxPTR(Img->ImageStart), R.getName(), DeviceId);
+
+        if (!R.is_device_initialized(DeviceId)) {
+          // Initialize the device information for the RTL we are about to use.
+          auto ExclusiveDevicesAccessor = getExclusiveDevicesAccessor();
+
+          int32_t DeviceOffset = ExclusiveDevicesAccessor->size();
+
+          // Set the device identifier offset in the plugin.
+          R.set_device_offset(DeviceOffset);
----------------
jhuber6 wrote:

The concept of "device offset" was always terrible. The only user of this is OMPT which uses it for some callbacks that want to have the OpenMP device ID. I could probably replace this with some map, basically "device id x goes to OpenMP id y" and that would be more correct.

https://github.com/llvm/llvm-project/pull/93844