Revert " [OpenMP][NFC] Remove DelayedBinDesc (#74360)"

This reverts commit d552ce2.

openmp/libomptarget/include/PluginManager.h

@@ -150,6 +150,24 @@ struct PluginManager {
   HostPtrToTableMapTy HostPtrToTableMap;
   std::mutex TblMapMtx; ///< For HostPtrToTableMap
 
+  // Work around for plugins that call dlopen on shared libraries that call
+  // tgt_register_lib during their initialisation. Stash the pointers in a
+  // vector until the plugins are all initialised and then register them.
+  bool delayRegisterLib(__tgt_bin_desc *Desc) {
+    if (RTLsLoaded)
+      return false;
+    DelayedBinDesc.push_back(Desc);
+    return true;
+  }
+
+  void registerDelayedLibraries() {
+    // Only called by libomptarget constructor
+    RTLsLoaded = true;
+    for (auto *Desc : DelayedBinDesc)
+      __tgt_register_lib(Desc);
+    DelayedBinDesc.clear();
+  }
+
   /// Return the number of usable devices.
   int getNumDevices() { return getExclusiveDevicesAccessor()->size(); }
 
@@ -178,6 +196,9 @@ struct PluginManager {
   void addRequirements(int64_t Flags) { Requirements.addRequirements(Flags); }
 
 private:
+  bool RTLsLoaded = false;
+  llvm::SmallVector<__tgt_bin_desc *> DelayedBinDesc;
+
   // List of all plugin adaptors, in use or not.
   llvm::SmallVector<std::unique_ptr<PluginAdaptorTy>> PluginAdaptors;
 

openmp/libomptarget/src/interface.cpp

@@ -46,6 +46,9 @@ EXTERN void __tgt_register_requires(int64_t Flags) {
 /// adds a target shared library to the target execution image
 EXTERN void __tgt_register_lib(__tgt_bin_desc *Desc) {
   TIMESCOPE();
+  if (PM->delayRegisterLib(Desc))
+    return;
+
   PM->registerLib(Desc);
 }
 

openmp/libomptarget/src/rtl.cpp

@@ -51,6 +51,7 @@ __attribute__((constructor(101))) void init() {
   PM->init();
 
   Profiler::get();
+  PM->registerDelayedLibraries();
 }
 
 __attribute__((destructor(101))) void deinit() {