Force honoring nthreads-var and thread-limit-var inside teams constru…

…ct on host

This patch fixes https://bugs.llvm.org/show_bug.cgi?id=42906, via adding
adjustment of number of threads on enter to the teams construct on host
according to user settings. This allows to pass checks and avoid assertions
at time of team of threads creation.

Patch by Andrey Churbanov

Differential Revision: https://reviews.llvm.org/D66351

llvm-svn: 369430

openmp/runtime/src/kmp_runtime.cpp

@@ -7192,19 +7192,32 @@ void __kmp_push_num_teams(ident_t *id, int gtid, int num_teams,
   thr->th.th_set_nproc = thr->th.th_teams_size.nteams = num_teams;
 
   // Remember the number of threads for inner parallel regions
+  if (!TCR_4(__kmp_init_middle))
+    __kmp_middle_initialize(); // get internal globals calculated
+  KMP_DEBUG_ASSERT(__kmp_avail_proc);
+  KMP_DEBUG_ASSERT(__kmp_dflt_team_nth);
   if (num_threads == 0) {
-    if (!TCR_4(__kmp_init_middle))
-      __kmp_middle_initialize(); // get __kmp_avail_proc calculated
     num_threads = __kmp_avail_proc / num_teams;
+    // adjust num_threads w/o warning as it is not user setting
+    // num_threads = min(num_threads, nthreads-var, thread-limit-var)
+    // no thread_limit clause specified -  do not change thread-limit-var ICV
+    if (num_threads > __kmp_dflt_team_nth) {
+      num_threads = __kmp_dflt_team_nth; // honor nthreads-var ICV
+    }
+    if (num_threads > thr->th.th_current_task->td_icvs.thread_limit) {
+      num_threads = thr->th.th_current_task->td_icvs.thread_limit;
+    } // prevent team size to exceed thread-limit-var
     if (num_teams * num_threads > __kmp_teams_max_nth) {
-      // adjust num_threads w/o warning as it is not user setting
       num_threads = __kmp_teams_max_nth / num_teams;
     }
   } else {
     // This thread will be the master of the league masters
     // Store new thread limit; old limit is saved in th_cg_roots list
     thr->th.th_current_task->td_icvs.thread_limit = num_threads;
-
+    // num_threads = min(num_threads, nthreads-var)
+    if (num_threads > __kmp_dflt_team_nth) {
+      num_threads = __kmp_dflt_team_nth; // honor nthreads-var ICV
+    }
     if (num_teams * num_threads > __kmp_teams_max_nth) {
       int new_threads = __kmp_teams_max_nth / num_teams;
       if (!__kmp_reserve_warn) { // user asked for too many threads