[ThreadPool] Fix Windows failures in the AffinityMask unit test (#155614)

These thread pool tests are typed and one was failing due to the setting
of environment variable `LLVM_THREADPOOL_AFFINITYMASK` leaking out of a
previous run of the test. I suspect that this has mainly succeeded
because the tests have run in separate shards.

Also the re-invocation of the unit test with the process affinity mask
set was not actually running the test because `--gtest_filter=` was not
set correctly. This has been fixed.

The use of the test type (TypeParam) in the AsyncBarrier test has been
restored. Without this the typing of these tests would be completely
redundant.

I suspect that some of these unit tests do not work if
`LLVM_ENABLE_THREADS == 0` but that is beyond the scope of this fix.

Author: nga888

llvm/unittests/Support/ThreadPool.cpp

@@ -140,7 +140,7 @@ TYPED_TEST(ThreadPoolTest, AsyncBarrier) {
 
   std::atomic_int checked_in{0};
 
-  DefaultThreadPool Pool;
+  TypeParam Pool;
   for (size_t i = 0; i < 5; ++i) {
     Pool.async([this, &checked_in] {
       this->waitForMainThread();
@@ -453,15 +453,19 @@ TYPED_TEST(ThreadPoolTest, AffinityMask) {
                         [](auto &T) { return T.getData().front() < 16UL; }) &&
            "Threads ran on more CPUs than expected! The affinity mask does not "
            "seem to work.");
-    GTEST_SKIP();
+    return;
   }
   std::string Executable =
       sys::fs::getMainExecutable(TestMainArgv0, &ThreadPoolTestStringArg1);
-  StringRef argv[] = {Executable, "--gtest_filter=ThreadPoolTest.AffinityMask"};
+  const auto *TestInfo = testing::UnitTest::GetInstance()->current_test_info();
+  std::string Arg = (Twine("--gtest_filter=") + TestInfo->test_suite_name() +
+                     "." + TestInfo->name())
+                        .str();
+  StringRef argv[] = {Executable, Arg};
 
   // Add environment variable to the environment of the child process.
   int Res = setenv("LLVM_THREADPOOL_AFFINITYMASK", "1", false);
-  ASSERT_EQ(Res, 0);
+  ASSERT_EQ(0, Res);
 
   std::string Error;
   bool ExecutionFailed;
@@ -470,6 +474,8 @@ TYPED_TEST(ThreadPoolTest, AffinityMask) {
   Affinity.set(0, 4); // Use CPUs 0,1,2,3.
   int Ret = sys::ExecuteAndWait(Executable, argv, {}, {}, 0, 0, &Error,
                                 &ExecutionFailed, nullptr, &Affinity);
+  Res = setenv("LLVM_THREADPOOL_AFFINITYMASK", "", false);
+  ASSERT_EQ(0, Res);
   ASSERT_EQ(0, Ret);
 }