From 718ec394030ca2da3973e0135d073e000b366848 Mon Sep 17 00:00:00 2001
Date: Sun, 16 May 2021 12:22:44 -0700
Subject: [PATCH 08/24] Threading: Only call setpriority(PRIO_DARWIN_THREAD, 0,
 PRIO_DARWIN_BG) if it is available

---
 llvm/lib/Support/Unix/Threading.inc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Support/Unix/Threading.inc b/llvm/lib/Support/Unix/Threading.inc
index 99f64b4f553d..ea40db932fc1 100644
--- a/llvm/lib/Support/Unix/Threading.inc
+++ b/llvm/lib/Support/Unix/Threading.inc
@@ -264,7 +264,7 @@ SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
              &priority)
              ? SetThreadPriorityResult::SUCCESS
              : SetThreadPriorityResult::FAILURE;
-#elif defined(__APPLE__)
+#elif defined(__APPLE__) && defined(PRIO_DARWIN_THREAD) && defined(PRIO_DARWIN_BG)
   // https://developer.apple.com/documentation/apple-silicon/tuning-your-code-s-performance-for-apple-silicon
   //
   // Background - Applies to work that isn’t visible to the user and may take significant