From 9b8b0794b8dd8ebdd17b3653ad29abcc6b7a3583 Mon Sep 17 00:00:00 2001
From: Zachary Turner <zturner@google.com>
Date: Wed, 13 Jun 2018 21:24:19 +0000
Subject: Revert "Enable ThreadPool to queue tasks that return values."

This is failing to compile when LLVM_ENABLE_THREADS is false,
and the fix is not immediately obvious, so reverting while I look
into it.

llvm-svn: 334658
---
 llvm/lib/Support/ThreadPool.cpp | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'llvm/lib/Support/ThreadPool.cpp')

diff --git a/llvm/lib/Support/ThreadPool.cpp b/llvm/lib/Support/ThreadPool.cpp
index fef665ba3d1..d0212ca1346 100644
--- a/llvm/lib/Support/ThreadPool.cpp
+++ b/llvm/lib/Support/ThreadPool.cpp
@@ -32,7 +32,7 @@ ThreadPool::ThreadPool(unsigned ThreadCount)
   for (unsigned ThreadID = 0; ThreadID < ThreadCount; ++ThreadID) {
     Threads.emplace_back([&] {
       while (true) {
-        std::unique_ptr<TaskBase> Task;
+        PackagedTaskTy Task;
         {
           std::unique_lock<std::mutex> LockGuard(QueueLock);
           // Wait for tasks to be pushed in the queue
@@ -54,7 +54,7 @@ ThreadPool::ThreadPool(unsigned ThreadCount)
           Tasks.pop();
         }
         // Run the task we just grabbed
-        Task->execute();
+        Task();
 
         {
           // Adjust `ActiveThreads`, in case someone waits on ThreadPool::wait()
@@ -79,6 +79,23 @@ void ThreadPool::wait() {
                            [&] { return !ActiveThreads && Tasks.empty(); });
 }
 
+std::shared_future<void> ThreadPool::asyncImpl(TaskTy Task) {
+  /// Wrap the Task in a packaged_task to return a future object.
+  PackagedTaskTy PackagedTask(std::move(Task));
+  auto Future = PackagedTask.get_future();
+  {
+    // Lock the queue and push the new task
+    std::unique_lock<std::mutex> LockGuard(QueueLock);
+
+    // Don't allow enqueueing after disabling the pool
+    assert(EnableFlag && "Queuing a thread during ThreadPool destruction");
+
+    Tasks.push(std::move(PackagedTask));
+  }
+  QueueCondition.notify_one();
+  return Future.share();
+}
+
 // The destructor joins all threads, waiting for completion.
 ThreadPool::~ThreadPool() {
   {
-- 
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