openmp: Add support for thread_limit clause on target

OpenMP 5.1 says that thread_limit clause can also appear on target,
and similarly to teams should affect the thread-limit-var ICV.
On combined target teams, the clause goes to both.

We actually passed thread_limit internally on target already before,
but only used it for gcn/ptx offloading to hint how many threads should be
created and for ptx didn't set thread_limit_var in that case.
Similarly for host fallback.
Also, I found that we weren't copying the args array that contains encoded
thread_limit and num_teams clause for target (etc.) for async target.

2021-11-15  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* gimplify.c (optimize_target_teams): Only add OMP_CLAUSE_THREAD_LIMIT
	to OMP_TARGET_CLAUSES if it isn't there already.
gcc/c-family/
	* c-omp.c (c_omp_split_clauses) <case OMP_CLAUSE_THREAD_LIMIT>:
	Duplicate to both OMP_TARGET and OMP_TEAMS.
gcc/c/
	* c-parser.c (OMP_TARGET_CLAUSE_MASK): Add
	PRAGMA_OMP_CLAUSE_THREAD_LIMIT.
gcc/cp/
	* parser.c (OMP_TARGET_CLAUSE_MASK): Add
	PRAGMA_OMP_CLAUSE_THREAD_LIMIT.
libgomp/
	* task.c (gomp_create_target_task): Copy args array as well.
	* target.c (gomp_target_fallback): Add args argument.
	Set gomp_icv (true)->thread_limit_var if thread_limit is present.
	(GOMP_target): Adjust gomp_target_fallback caller.
	(GOMP_target_ext): Likewise.
	(gomp_target_task_fn): Likewise.
	* config/nvptx/team.c (gomp_nvptx_main): Set
	gomp_global_icv.thread_limit_var.
	* testsuite/libgomp.c-c++-common/thread-limit-1.c: New test.

1 files changed, 23 insertions, 0 deletions

diff --git a/libgomp/testsuite/libgomp.c-c++-common/thread-limit-1.c b/libgomp/testsuite/libgomp.c-c++-common/thread-limit-1.c
new file mode 100644
index 0000000..cac2202
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/thread-limit-1.c
@@ -0,0 +1,23 @@
+#include <omp.h>
+#include <stdlib.h>
+
+void
+foo ()
+{
+  {
+    #pragma omp target parallel nowait thread_limit (4) num_threads (1)
+    if (omp_get_thread_limit () > 4)
+      abort ();
+  }
+  #pragma omp taskwait
+}
+
+int
+main ()
+{
+  #pragma omp target thread_limit (6)
+  if (omp_get_thread_limit () > 6)
+    abort ();
+  foo ();
+  return 0;
+}