[llvm] [OFFLOAD] Restore interop functionality (PR #161429)

[Kevin Sala Penades via llvm-commits]

================
@@ -917,6 +917,53 @@ struct CUDADeviceTy : public GenericDeviceTy {
     return Plugin::success();
   }
 
+  interop_spec_t selectInteropPreference(int32_t InteropType,
+                                         int32_t NumPrefers,
+                                         interop_spec_t *Prefers) override {
+    return interop_spec_t{tgt_fr_cuda, {true, 0}, 0};
+  }
+
+  Expected<omp_interop_val_t *>
+  createInterop(int32_t InteropType, interop_spec_t &InteropSpec) override {
+    auto *Ret = new omp_interop_val_t(
+        DeviceId, static_cast<kmp_interop_type_t>(InteropType));
+    Ret->fr_id = tgt_fr_cuda;
+    Ret->vendor_id = omp_vendor_nvidia;
+
+    if (InteropType == kmp_interop_type_target ||
+        InteropType == kmp_interop_type_targetsync) {
+      Ret->device_info.Platform = nullptr;
+      Ret->device_info.Device = reinterpret_cast<void *>(Device);
+      Ret->device_info.Context = Context;
+    }
+
+    if (InteropType == kmp_interop_type_targetsync) {
+      Ret->async_info = new __tgt_async_info();
+      if (auto Err = setContext())
+        return Err;
+      CUstream Stream;
+      if (auto Err = CUDAStreamManager.getResource(
+              *reinterpret_cast<CUstream *>(&Stream)))
+        return Err;
+
+      Ret->async_info->Queue = Stream;
+    }
+    return Ret;
+  }
+
+  Error releaseInterop(omp_interop_val_t *Interop) override {
+    if (!Interop)
+      return Plugin::success();
+
+    if (Interop->async_info) {
+      // TODO: release the stream back to the pool?
----------------
kevinsala wrote:

Isn't `CUDAStreamManager.returnResource(Stream)` what you want here?

https://github.com/llvm/llvm-project/pull/161429