[libomptarget][nfc] Remove data_sharing type aliasing

[JonChesterfield]

Summary

[libomptarget][nfc] Remove data_sharing type aliasing

Libomptarget previous used kmpc_data_sharing_slot to access values of type
kmpc_data_sharing_{worker,master}_slot_static. This aliasing violation was
benign in practice. The master type has since been removed, so a single type
can be used instead.

This is particularly helpful for the transition to an openmp deviceRTL, as the
c++/openmp compiler for amdgcn currently rejects the flexible array member for
being an incomplete type. Serves the same purpose as abandoned D86324.

[jdoerfert]

LGTM. nice cleanup

openmp/libomptarget/deviceRTLs/common/omptarget.h

private:
   void **args;
   // starts off as MAX_SHARED_ARGS but can increase in size.
   uint32_t nArgs;
 };
 
 extern DEVICE SHARED omptarget_nvptx_SharedArgs
     omptarget_nvptx_globalArgs;
 
+// Worker slot type which is initialized with the default worker slot
+// size of 4*32 bytes.
+struct __kmpc_data_sharing_slot {
+  __kmpc_data_sharing_slot *Next;
+  __kmpc_data_sharing_slot *Prev;
+  void *PrevSlotStackPtr;
+  void *DataEnd;
+  char Data[DS_Worker_Warp_Slot_Size];
+};
+
 // Data structure to keep in shared memory that traces the current slot, stack,
 // and frame pointer as well as the active threads that didn't exit the current
 // environment.
 struct DataSharingStateTy {
   __kmpc_data_sharing_slot *SlotPtr[DS_Max_Warp_Number];
   void *StackPtr[DS_Max_Warp_Number];
   void * volatile FramePtr[DS_Max_Warp_Number];
   __kmpc_impl_lanemask_t ActiveThreads[DS_Max_Warp_Number];
 };
-// Additional worker slot type which is initialized with the default worker slot
-// size of 4*32 bytes.
-struct __kmpc_data_sharing_worker_slot_static {
-  __kmpc_data_sharing_slot *Next;
-  __kmpc_data_sharing_slot *Prev;
-  void *PrevSlotStackPtr;
-  void *DataEnd;
-  char Data[DS_Worker_Warp_Slot_Size];
-};
 
 extern DEVICE SHARED DataSharingStateTy DataSharingState;
 
 ////////////////////////////////////////////////////////////////////////////////
 // task ICV and (implicit & explicit) task state
 
 class omptarget_nvptx_TaskDescr {
 public:

 
 private:
   omptarget_nvptx_TaskDescr
       levelZeroTaskDescr; // icv for team master initial thread
   omptarget_nvptx_WorkDescr
       workDescrForActiveParallel; // one, ONLY for the active par
 
   ALIGN(16)
-  __kmpc_data_sharing_worker_slot_static worker_rootS[DS_Max_Warp_Number];
+  __kmpc_data_sharing_slot worker_rootS[DS_Max_Warp_Number];
 };
 
 ////////////////////////////////////////////////////////////////////////////////
 // thread private data (struct of arrays for better coalescing)
 // tid refers here to the global thread id
 // do not support multiple concurrent kernel a this time
 class omptarget_nvptx_ThreadPrivateContext {
 public:

openmp/libomptarget/deviceRTLs/interface.h

 EXTERN void *__kmpc_data_sharing_coalesced_push_stack(size_t size,
     int16_t UseSharedMemory);
 EXTERN void *__kmpc_data_sharing_push_stack(size_t size, int16_t UseSharedMemory);
 EXTERN void __kmpc_data_sharing_pop_stack(void *a);
 EXTERN void __kmpc_begin_sharing_variables(void ***GlobalArgs, size_t nArgs);
 EXTERN void __kmpc_end_sharing_variables();
 EXTERN void __kmpc_get_shared_variables(void ***GlobalArgs);
 
-// The slot used for data sharing by the master and worker threads. We use a
-// complete (default size version and an incomplete one so that we allow sizes
-// greater than the default).
-struct __kmpc_data_sharing_slot {
-  __kmpc_data_sharing_slot *Next;
-  __kmpc_data_sharing_slot *Prev;
-  void *PrevSlotStackPtr;
-  void *DataEnd;
-  char Data[];
-};
-
 // SPMD execution mode interrogation function.
 EXTERN int8_t __kmpc_is_spmd_exec_mode();
 
 EXTERN void __kmpc_get_team_static_memory(int16_t isSPMDExecutionMode,
                                           const void *buf, size_t size,
                                           int16_t is_shared, const void **res);
 
 EXTERN void __kmpc_restore_team_static_memory(int16_t isSPMDExecutionMode,
                                               int16_t is_shared);
 
 #endif