[OpenMP] Minor improvement in task allocation

[hbae]

Summary

This patch includes a few changes to improve task allocation
performance slightly. These changes are enough to restore performance
drop observed after introducing hidden helper.

[tianshilei1992]

I can understand the point of setting flag by direct copy, but does inline really help a lot here, or say really inline the function?

[hbae]

Undo the change that introduce __kmp_task_alloc_impl since the outcome may vary depending on the build compiler.

[tianshilei1992]

LGTM. Thanks!

openmp/runtime/src/kmp_tasking.cpp

#endif
   taskdata->td_taskwait_ident = NULL;
   taskdata->td_taskwait_counter = 0;
   taskdata->td_taskwait_thread = 0;
   KMP_DEBUG_ASSERT(taskdata->td_parent != NULL);
   // avoid copying icvs for proxy tasks
   if (flags->proxy == TASK_FULL)
     copy_icvs(&taskdata->td_icvs, &taskdata->td_parent->td_icvs);
 
-  taskdata->td_flags.tiedness = flags->tiedness;
-  taskdata->td_flags.final = flags->final;
-  taskdata->td_flags.merged_if0 = flags->merged_if0;
-  taskdata->td_flags.destructors_thunk = flags->destructors_thunk;
-  taskdata->td_flags.proxy = flags->proxy;
-  taskdata->td_flags.detachable = flags->detachable;
-  taskdata->td_flags.hidden_helper = flags->hidden_helper;
+  taskdata->td_flags = *flags;
   taskdata->encountering_gtid = gtid;
   taskdata->td_task_team = thread->th.th_task_team;
   taskdata->td_size_alloc = shareds_offset + sizeof_shareds;
   taskdata->td_flags.tasktype = TASK_EXPLICIT;
 
   // GEH - TODO: fix this to copy parent task's value of tasking_ser flag
   taskdata->td_flags.tasking_ser = (__kmp_tasking_mode == tskm_immediate_exec);
 
   // GEH - TODO: fix this to copy parent task's value of team_serial flag
   taskdata->td_flags.team_serial = (team->t.t_serialized) ? 1 : 0;
 
   // GEH - Note we serialize the task if the team is serialized to make sure
   // implicit parallel region tasks are not left until program termination to
   // execute. Also, it helps locality to execute immediately.
 
   taskdata->td_flags.task_serial =
       (parent_task->td_flags.final || taskdata->td_flags.team_serial ||
        taskdata->td_flags.tasking_ser || flags->merged_if0);
 
   taskdata->td_flags.started = 0;
   taskdata->td_flags.executing = 0;
   taskdata->td_flags.complete = 0;
   taskdata->td_flags.freed = 0;
 
-  taskdata->td_flags.native = flags->native;
-
   KMP_ATOMIC_ST_RLX(&taskdata->td_incomplete_child_tasks, 0);
   // start at one because counts current task and children
   KMP_ATOMIC_ST_RLX(&taskdata->td_allocated_child_tasks, 1);
   taskdata->td_taskgroup =
       parent_task->td_taskgroup; // task inherits taskgroup from the parent task
   taskdata->td_dephash = NULL;
   taskdata->td_depnode = NULL;
   if (flags->tiedness == TASK_UNTIED)
if (flags->proxy == TASK_PROXY || flags->detachable == TASK_DETACHABLE ||
     KMP_ATOMIC_INC(&parent_task->td_incomplete_child_tasks);
     if (parent_task->td_taskgroup)
       KMP_ATOMIC_INC(&parent_task->td_taskgroup->count);
     // Only need to keep track of allocated child tasks for explicit tasks since
     // implicit not deallocated
     if (taskdata->td_parent->td_flags.tasktype == TASK_EXPLICIT) {
       KMP_ATOMIC_INC(&taskdata->td_parent->td_allocated_child_tasks);
     }
-  }
-
     if (flags->hidden_helper) {
       taskdata->td_flags.task_serial = FALSE;
       // Increment the number of hidden helper tasks to be executed
       KMP_ATOMIC_INC(&__kmp_unexecuted_hidden_helper_tasks);
     }
+  }
 
   KA_TRACE(20, ("__kmp_task_alloc(exit): T#%d created task %p parent=%p\n",
                 gtid, taskdata, taskdata->td_parent));
 
   return task;
 }
 
 kmp_task_t *__kmpc_omp_task_alloc(ident_t *loc_ref, kmp_int32 gtid,