[OpenMP] Fixed an issue that taskwait doesn't work on detachable task (llvm#3005)

It appears that this patch (fixing SWDEV-510164) got lost during (many)
merges from mainline. This PR reapplies it.

Original log (by Shilei Tian) follows:

D77609 mistakenly changed the bebavior of task waiting on detachable
task that a detachable task is not waited, based on
https://lists.llvm.org/pipermail/openmp-dev/2021-February/003836.html.
This patch fixed it. Thank Raúl for the report.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D95798

Co-authored-by: Shilei Tian <[email protected]>

Author: jtb20

openmp/runtime/src/kmp_tasking.cpp

@@ -1517,7 +1517,7 @@ kmp_task_t *__kmp_task_alloc(ident_t *loc_ref, kmp_int32 gtid,
       }
     }
 
-    if (flags->proxy == TASK_PROXY &&
+    if ((flags->proxy == TASK_PROXY || flags->detachable == TASK_DETACHABLE) &&
         task_team->tt.tt_found_proxy_tasks == FALSE)
       TCW_4(task_team->tt.tt_found_proxy_tasks, TRUE);
     if (flags->hidden_helper &&

openmp/runtime/test/tasking/bug_taskwait_detach.cpp

@@ -0,0 +1,115 @@
+// RUN: %libomp-cxx-compile-and-run
+
+#include <omp.h>
+
+#include <chrono>
+#include <iostream>
+#include <thread>
+
+// detached
+#define PTASK_FLAG_DETACHABLE 0x40
+
+// OpenMP RTL interfaces
+typedef long long kmp_int64;
+
+typedef struct ID {
+  int reserved_1;
+  int flags;
+  int reserved_2;
+  int reserved_3;
+  char *psource;
+} id;
+
+// Compiler-generated code (emulation)
+typedef struct ident {
+  void *dummy; // not used in the library
+} ident_t;
+
+typedef enum kmp_event_type_t {
+  KMP_EVENT_UNINITIALIZED = 0,
+  KMP_EVENT_ALLOW_COMPLETION = 1
+} kmp_event_type_t;
+
+typedef struct {
+  kmp_event_type_t type;
+  union {
+    void *task;
+  } ed;
+} kmp_event_t;
+
+typedef struct shar { // shareds used in the task
+} * pshareds;
+
+typedef struct task {
+  pshareds shareds;
+  int (*routine)(int, struct task *);
+  int part_id;
+  // void *destructor_thunk; // optional, needs flag setting if provided
+  // int priority; // optional, needs flag setting if provided
+  // ------------------------------
+  // privates used in the task:
+  omp_event_handle_t evt;
+} * ptask, kmp_task_t;
+
+typedef int (*task_entry_t)(int, ptask);
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+extern int __kmpc_global_thread_num(void *id_ref);
+extern int **__kmpc_omp_task_alloc(id *loc, int gtid, int flags, size_t sz,
+                                   size_t shar, task_entry_t rtn);
+extern int __kmpc_omp_task(id *loc, kmp_int64 gtid, kmp_task_t *task);
+extern omp_event_handle_t __kmpc_task_allow_completion_event(ident_t *loc_ref,
+                                                             int gtid,
+                                                             kmp_task_t *task);
+#ifdef __cplusplus
+}
+#endif
+
+int volatile checker;
+
+void target(ptask task) {
+  std::this_thread::sleep_for(std::chrono::seconds(3));
+  checker = 1;
+  omp_fulfill_event(task->evt);
+}
+
+// User's code
+int task_entry(int gtid, ptask task) {
+  std::thread t(target, task);
+  t.detach();
+  return 0;
+}
+
+int main(int argc, char *argv[]) {
+  int gtid = __kmpc_global_thread_num(nullptr);
+  checker = 0;
+
+  /*
+    #pragma omp task detach(evt)
+    {}
+  */
+  std::cout << "detaching...\n";
+  ptask task = (ptask)__kmpc_omp_task_alloc(
+      nullptr, gtid, PTASK_FLAG_DETACHABLE, sizeof(struct task),
+      sizeof(struct shar), &task_entry);
+  omp_event_handle_t evt =
+      (omp_event_handle_t)__kmpc_task_allow_completion_event(nullptr, gtid,
+                                                             task);
+  task->evt = evt;
+
+  __kmpc_omp_task(nullptr, gtid, task);
+
+#pragma omp taskwait
+
+  // check results
+  if (checker == 1) {
+    std::cout << "PASS\n";
+    return 0;
+  }
+
+  return 1;
+}
+
+// CHECK: PASS