[llvm] [ORC] Fix synchronization in CoreAPIsTest. (PR #144556)

[Jameson Nash via llvm-commits]

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@@ -1559,16 +1559,13 @@ TEST_F(CoreAPIsStandardTest, TestLookupWithThreadedMaterialization) {
 #if LLVM_ENABLE_THREADS
 
   std::mutex WorkThreadsMutex;
-  std::vector<std::thread> WorkThreads;
+  SmallVector<std::thread,0> WorkThreads;
   DispatchOverride = [&](std::unique_ptr<Task> T) {
-    std::promise<void> WaitP;
-    std::lock_guard<std::mutex> Lock(WorkThreadsMutex);
+    std::unique_lock Lock(WorkThreadsMutex);
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vtjnash wrote:

Yeah, I am made slightly uncomfortable by using two completely different RAII locks on the same mutex, though I realize that it is well-defined, so I dropped this part of the chagne. The other changes are all related to the bug fix, so it isn't particularly easy to justify separating them (SmallVector is needed because the iteration structure needed to change and the relevant feature is part of SmallVector not std::vector)

https://github.com/llvm/llvm-project/pull/144556