[llvm][Support] Provide interface to set thread priorities

Summary:
We have a multi-platform thread priority setting function(last piece
landed with D58683), I wanted to make this available to all llvm community,
there seem to be other users of such functionality with portability fixmes:
lib/Support/CrashRecoveryContext.cpp
tools/clang/tools/libclang/CIndex.cpp

Reviewers: gribozavr, ioeric

Subscribers: krytarowski, jfb, kristina, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59130

llvm-svn: 358494

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc
index c53624c0dc9..96649472cc9 100644
--- a/llvm/lib/Support/Windows/Threading.inc
+++ b/llvm/lib/Support/Windows/Threading.inc
@@ -106,3 +106,19 @@ void llvm::get_thread_name(SmallVectorImpl<char> &Name) {
   // value.
   Name.clear();
 }
+
+SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) {
+  // https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-setthreadpriority
+  // Begin background processing mode. The system lowers the resource scheduling
+  // priorities of the thread so that it can perform background work without
+  // significantly affecting activity in the foreground.
+  // End background processing mode. The system restores the resource scheduling
+  // priorities of the thread as they were before the thread entered background
+  // processing mode.
+  return SetThreadPriority(GetCurrentThread(),
+                           Priority == ThreadPriority::Background
+                               ? THREAD_MODE_BACKGROUND_BEGIN
+                               : THREAD_MODE_BACKGROUND_END)
+             ? SetThreadPriorityResult::SUCCESS
+             : SetThreadPriorityResult::FAILURE;
+}