[ORC] Fix race when checking isComplete (llvm#165063)

After llvm#164340 there is a tsan race on `OutstandingSymbolsCount` when
decrementing it in `notifySymbolMetRequiredState` vs reading it in
`isComplete()`. Fix this by having `IL_emit` filter out non-completed
queries when it has the lock to do so, and that way we avoid needing to
call `isComplete()` later.

Author: rupprecht

llvm/include/llvm/ExecutionEngine/Orc/Core.h

@@ -1768,7 +1768,7 @@ class ExecutionSession {
   // FIXME: We should be able to derive FailedSymsForQuery from each query once
   //        we fix how the detach operation works.
   struct EmitQueries {
-    JITDylib::AsynchronousSymbolQuerySet Updated;
+    JITDylib::AsynchronousSymbolQuerySet Completed;
     JITDylib::AsynchronousSymbolQuerySet Failed;
     DenseMap<AsynchronousSymbolQuery *, std::shared_ptr<SymbolDependenceMap>>
         FailedSymsForQuery;

llvm/lib/ExecutionEngine/Orc/Core.cpp

@@ -2901,13 +2901,23 @@ ExecutionSession::IL_emit(MaterializationResponsibility &MR,
 
   for (auto &SN : ER.Ready)
     IL_collectQueries(
-        EQ.Updated, SN->defs(),
+        EQ.Completed, SN->defs(),
         [](JITDylib::SymbolTableEntry &E) { E.setState(SymbolState::Ready); },
         [](AsynchronousSymbolQuery &Q, JITDylib &JD,
            NonOwningSymbolStringPtr Name, JITDylib::SymbolTableEntry &E) {
           Q.notifySymbolMetRequiredState(SymbolStringPtr(Name), E.getSymbol());
         });
 
+  // std::erase_if is not available in C++17, and llvm::erase_if does not work
+  // here.
+  for (auto it = EQ.Completed.begin(), end = EQ.Completed.end(); it != end;) {
+    if ((*it)->isComplete()) {
+      ++it;
+    } else {
+      it = EQ.Completed.erase(it);
+    }
+  }
+
 #ifdef EXPENSIVE_CHECKS
   verifySessionState("exiting ExecutionSession::IL_emit");
 #endif
@@ -3043,9 +3053,8 @@ Error ExecutionSession::OL_notifyEmitted(
     }
   }
 
-  for (auto &UQ : EmitQueries->Updated)
-    if (UQ->isComplete())
-      UQ->handleComplete(*this);
+  for (auto &UQ : EmitQueries->Completed)
+    UQ->handleComplete(*this);
 
   // If there are any bad dependencies then return an error.
   if (!BadDeps.empty()) {