Index: tools/libclang/CIndex.cpp
===================================================================
--- tools/libclang/CIndex.cpp
+++ tools/libclang/CIndex.cpp
@@ -8723,9 +8723,7 @@
   if (getenv("LIBCLANG_BGPRIO_DISABLE"))
     return;
 
-#ifdef USE_DARWIN_THREADS
-  setpriority(PRIO_DARWIN_THREAD, 0, PRIO_DARWIN_BG);
-#endif
+  llvm::set_thread_priority(llvm::ThreadPriority::Background);
 }
 
 void cxindex::printDiagsToStderr(ASTUnit *Unit) {