some cleanup, race condition fix

Author: vtjnash

llvm/include/llvm/ExecutionEngine/Orc/TaskDispatch.h

@@ -266,6 +266,46 @@ class promise {
   std::shared_ptr<typename future<T>::state> state_;
 };
 
+/// Specialization of future<void>
+template <> class future<void> : public future_base {
+public:
+  using state = future_base::state_base;
+
+  future() = default;
+  future(const future &) = delete;
+  future &operator=(const future &) = delete;
+  future(future &&) = default;
+  future &operator=(future &&) = default;
+
+  /// Get the value (void), helping with task dispatch while waiting.
+  void get(TaskDispatcher &D) { wait(D); }
+
+private:
+  friend class promise<void>;
+
+  explicit future(std::shared_ptr<state> state) : future_base(state) {}
+};
+
+/// Specialization of promise<void>
+template <> class promise<void> {
+  friend class future<void>;
+
+public:
+  promise() : state_(std::make_shared<future<void>::state>()) {}
+  promise(const promise &) = delete;
+  promise &operator=(const promise &) = delete;
+  promise(promise &&) = default;
+  promise &operator=(promise &&) = default;
+
+  /// Get the associated future
+  future<void> get_future() { return future<void>(state_); }
+
+  /// Set the value (void)
+  void set_value() { state_->status_.store(1, std::memory_order_release); }
+
+private:
+  std::shared_ptr<future<void>::state> state_;
+};
 
 } // End namespace orc
 } // End namespace llvm

llvm/lib/ExecutionEngine/Orc/Core.cpp

@@ -1463,16 +1463,19 @@ Expected<DenseMap<JITDylib *, SymbolMap>> Platform::lookupInitSymbols(
 
   DenseMap<JITDylib *, SymbolMap> CompoundResult;
   Error CompoundErr = Error::success();
+  orc::promise<void> ResultReady;
+  auto ReadyF = ResultReady.get_future();
   std::mutex LookupMutex;
-  std::condition_variable CV;
-  uint64_t Count = InitSyms.size();
+  volatile uint64_t Count = InitSyms.size();
 
   LLVM_DEBUG({
     dbgs() << "Issuing init-symbol lookup:\n";
     for (auto &KV : InitSyms)
       dbgs() << "  " << KV.first->getName() << ": " << KV.second << "\n";
   });
 
+  if (Count == 0)
+    ResultReady.set_value();
   for (auto &KV : InitSyms) {
     auto *JD = KV.first;
     auto Names = std::move(KV.second);
@@ -1491,14 +1494,14 @@ Expected<DenseMap<JITDylib *, SymbolMap>> Platform::lookupInitSymbols(
             } else
               CompoundErr =
                   joinErrors(std::move(CompoundErr), Result.takeError());
+            if (Count == 0)
+              ResultReady.set_value();
           }
-          CV.notify_one();
         },
         NoDependenciesToRegister);
   }
 
-  std::unique_lock<std::mutex> Lock(LookupMutex);
-  CV.wait(Lock, [&] { return Count == 0; });
+  ReadyF.get(ES.getExecutorProcessControl().getDispatcher());
 
   if (CompoundErr)
     return std::move(CompoundErr);