[OpenMP] libomp: add UNLIKELY hints to rarely executed branches

Added UNLIKELY hint to one-time or rarely executed branches.
This improves performance of the library on some tasking benchmarks.

Differential Revision: https://reviews.llvm.org/D92322

openmp/runtime/src/kmp_itt.inl

@@ -630,7 +630,7 @@ void __kmp_itt_barrier_finished(int gtid, void *object) {
 void *__kmp_itt_taskwait_object(int gtid) {
  void *object = NULL;
 #if USE_ITT_NOTIFY
- if (__itt_sync_create_ptr) {
+ if (UNLIKELY(__itt_sync_create_ptr)) {
  kmp_info_t *thread = __kmp_thread_from_gtid(gtid);
  kmp_taskdata_t *taskdata = thread->th.th_current_task;
  object = reinterpret_cast<void *>(kmp_uintptr_t(taskdata) +
@@ -677,7 +677,7 @@ void __kmp_itt_task_starting(
  void *object // ITT sync object: barrier or taskwait.
  ) {
 #if USE_ITT_NOTIFY
- if (object != NULL) {
+ if (UNLIKELY(object != NULL)) {
  KMP_ITT_DEBUG_LOCK();
  __itt_sync_cancel(object);
  KMP_ITT_DEBUG_PRINT("[tsk sta] scan( %p )\n", object);

openmp/runtime/src/kmp_tasking.cpp

@@ -275,7 +275,7 @@ static bool __kmp_task_is_allowed(int gtid, const kmp_int32 is_constrained,
  }
  // Check mutexinoutset dependencies, acquire locks
  kmp_depnode_t *node = tasknew->td_depnode;
- if (node && (node->dn.mtx_num_locks > 0)) {
+ if (UNLIKELY(node && (node->dn.mtx_num_locks > 0))) {
  for (int i = 0; i < node->dn.mtx_num_locks; ++i) {
  KMP_DEBUG_ASSERT(node->dn.mtx_locks[i] != NULL);
  if (__kmp_test_lock(node->dn.mtx_locks[i], gtid))
@@ -332,7 +332,7 @@ static kmp_int32 __kmp_push_task(kmp_int32 gtid, kmp_task_t *task) {
  KA_TRACE(20,
  ("__kmp_push_task: T#%d trying to push task %p.\n", gtid, taskdata));
 
- if (taskdata->td_flags.tiedness == TASK_UNTIED) {
+ if (UNLIKELY(taskdata->td_flags.tiedness == TASK_UNTIED)) {
  // untied task needs to increment counter so that the task structure is not
  // freed prematurely
  kmp_int32 counter = 1 + KMP_ATOMIC_INC(&taskdata->td_untied_count);
@@ -344,7 +344,7 @@ static kmp_int32 __kmp_push_task(kmp_int32 gtid, kmp_task_t *task) {
  }
 
  // The first check avoids building task_team thread data if serialized
- if (taskdata->td_flags.task_serial) {
+ if (UNLIKELY(taskdata->td_flags.task_serial)) {
  KA_TRACE(20, ("__kmp_push_task: T#%d team serialized; returning "
  "TASK_NOT_PUSHED for task %p\n",
  gtid, taskdata));
@@ -354,7 +354,7 @@ static kmp_int32 __kmp_push_task(kmp_int32 gtid, kmp_task_t *task) {
  // Now that serialized tasks have returned, we can assume that we are not in
  // immediate exec mode
  KMP_DEBUG_ASSERT(__kmp_tasking_mode != tskm_immediate_exec);
- if (!KMP_TASKING_ENABLED(task_team)) {
+ if (UNLIKELY(!KMP_TASKING_ENABLED(task_team))) {
  __kmp_enable_tasking(task_team, thread);
  }
  KMP_DEBUG_ASSERT(TCR_4(task_team->tt.tt_found_tasks) == TRUE);
@@ -364,7 +364,7 @@ static kmp_int32 __kmp_push_task(kmp_int32 gtid, kmp_task_t *task) {
  thread_data = &task_team->tt.tt_threads_data[tid];
 
  // No lock needed since only owner can allocate
- if (thread_data->td.td_deque == NULL) {
+ if (UNLIKELY(thread_data->td.td_deque == NULL)) {
  __kmp_alloc_task_deque(thread, thread_data);
  }
 
@@ -824,7 +824,7 @@ static void __kmp_task_finish(kmp_int32 gtid, kmp_task_t *task,
  }
 #endif /* BUILD_TIED_TASK_STACK */
 
- if (taskdata->td_flags.tiedness == TASK_UNTIED) {
+ if (UNLIKELY(taskdata->td_flags.tiedness == TASK_UNTIED)) {
  // untied task needs to check the counter so that the task structure is not
  // freed prematurely
  kmp_int32 counter = KMP_ATOMIC_DEC(&taskdata->td_untied_count) - 1;
@@ -1175,7 +1175,7 @@ kmp_task_t *__kmp_task_alloc(ident_t *loc_ref, kmp_int32 gtid,
  kmp_taskdata_t *parent_task = thread->th.th_current_task;
  size_t shareds_offset;
 
- if (!TCR_4(__kmp_init_middle))
+ if (UNLIKELY(!TCR_4(__kmp_init_middle)))
  __kmp_middle_initialize();
 
  KA_TRACE(10, ("__kmp_task_alloc(enter): T#%d loc=%p, flags=(0x%x) "
@@ -1433,8 +1433,8 @@ static void __kmp_invoke_task(kmp_int32 gtid, kmp_task_t *task,
  30, ("__kmp_invoke_task(enter): T#%d invoking task %p, current_task=%p\n",
  gtid, taskdata, current_task));
  KMP_DEBUG_ASSERT(task);
- if (taskdata->td_flags.proxy == TASK_PROXY &&
- taskdata->td_flags.complete == 1) {
+ if (UNLIKELY(taskdata->td_flags.proxy == TASK_PROXY &&
+  taskdata->td_flags.complete == 1)) {
  // This is a proxy task that was already completed but it needs to run
  // its bottom-half finish
  KA_TRACE(
@@ -1476,7 +1476,7 @@ static void __kmp_invoke_task(kmp_int32 gtid, kmp_task_t *task,
  // TODO: cancel tasks if the parallel region has also been cancelled
  // TODO: check if this sequence can be hoisted above __kmp_task_start
  // if cancellation has been enabled for this run ...
- if (__kmp_omp_cancellation) {
+ if (UNLIKELY(__kmp_omp_cancellation)) {
  thread = __kmp_threads[gtid];
  kmp_team_t *this_team = thread->th.th_team;
  kmp_taskgroup_t *taskgroup = taskdata->td_taskgroup;
@@ -1855,7 +1855,7 @@ static kmp_int32 __kmpc_omp_taskwait_template(ident_t *loc_ref, kmp_int32 gtid,
 
 #if USE_ITT_BUILD
  void *itt_sync_obj = __kmp_itt_taskwait_object(gtid);
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_starting(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
 
@@ -1875,7 +1875,7 @@ static kmp_int32 __kmpc_omp_taskwait_template(ident_t *loc_ref, kmp_int32 gtid,
  }
  }
 #if USE_ITT_BUILD
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_finished(gtid, itt_sync_obj);
  KMP_FSYNC_ACQUIRED(taskdata); // acquire self - sync with children
 #endif /* USE_ITT_BUILD */
@@ -1961,7 +1961,7 @@ kmp_int32 __kmpc_omp_taskyield(ident_t *loc_ref, kmp_int32 gtid, int end_part) {
 
 #if USE_ITT_BUILD
  void *itt_sync_obj = __kmp_itt_taskwait_object(gtid);
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_starting(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
  if (!taskdata->td_flags.team_serial) {
@@ -1984,7 +1984,7 @@ kmp_int32 __kmpc_omp_taskyield(ident_t *loc_ref, kmp_int32 gtid, int end_part) {
  }
  }
 #if USE_ITT_BUILD
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_finished(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
 
@@ -2486,7 +2486,7 @@ void __kmpc_end_taskgroup(ident_t *loc, int gtid) {
  // For ITT the taskgroup wait is similar to taskwait until we need to
  // distinguish them
  void *itt_sync_obj = __kmp_itt_taskwait_object(gtid);
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_starting(gtid, itt_sync_obj);
 #endif /* USE_ITT_BUILD */
 
@@ -2520,7 +2520,7 @@ void __kmpc_end_taskgroup(ident_t *loc, int gtid) {
 #endif
 
 #if USE_ITT_BUILD
- if (itt_sync_obj != NULL)
+ if (UNLIKELY(itt_sync_obj != NULL))
  __kmp_itt_taskwait_finished(gtid, itt_sync_obj);
  KMP_FSYNC_ACQUIRED(taskdata); // acquire self - sync with descendants
 #endif /* USE_ITT_BUILD */