Remove possibility of failures to due race in ThreadPool unittest

Remove all checks that required main thread to run faster than tasks in
ThreadPool, and yields which are now unnecessary. This should fix some
bot failures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256056 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Support/ThreadPool.cpp

@@ -18,18 +18,6 @@
 #include "gtest/gtest.h"
 
 using namespace llvm;
-using namespace std::chrono;
-
-/// Try best to make this thread not progress faster than the main thread
-static void yield() {
-#ifdef LLVM_ENABLE_THREADS
-  std::this_thread::yield();
-#endif
-  std::this_thread::sleep_for(milliseconds(200));
-#ifdef LLVM_ENABLE_THREADS
-  std::this_thread::yield();
-#endif
-}
 
 // Fixture for the unittests, allowing to *temporarily* disable the unittests
 // on a particular platform
@@ -83,11 +71,9 @@ TEST_F(ThreadPoolTest, AsyncBarrier) {
   ThreadPool Pool;
   for (size_t i = 0; i < 5; ++i) {
     Pool.async([&checked_in, i] {
-      yield();
       ++checked_in;
     });
   }
-  ASSERT_EQ(0, checked_in);
   Pool.wait();
   ASSERT_EQ(5, checked_in);
 }
@@ -111,13 +97,10 @@ TEST_F(ThreadPoolTest, Async) {
   CHECK_UNSUPPORTED();
   ThreadPool Pool;
   std::atomic_int i{0};
-  // sleep here just to ensure that the not-equal is correct.
   Pool.async([&i] {
-    yield();
     ++i;
   });
   Pool.async([&i] { ++i; });
-  ASSERT_NE(2, i.load());
   Pool.wait();
   ASSERT_EQ(2, i.load());
 }
@@ -126,14 +109,11 @@ TEST_F(ThreadPoolTest, GetFuture) {
   CHECK_UNSUPPORTED();
   ThreadPool Pool;
   std::atomic_int i{0};
-  // sleep here just to ensure that the not-equal is correct.
   Pool.async([&i] {
-    yield();
     ++i;
   });
   // Force the future using get()
   Pool.async([&i] { ++i; }).get();
-  ASSERT_NE(2, i.load());
   Pool.wait();
   ASSERT_EQ(2, i.load());
 }
@@ -147,11 +127,9 @@ TEST_F(ThreadPoolTest, PoolDestruction) {
     ThreadPool Pool;
     for (size_t i = 0; i < 5; ++i) {
       Pool.async([&checked_in, i] {
-        yield();
         ++checked_in;
       });
     }
-    ASSERT_EQ(0, checked_in);
   }
   ASSERT_EQ(5, checked_in);
 }