message: [OPENMP][NVPTX]Fix __kmpc_flush to flush the memory per system, not per block.
  Summary:
  According to the standard, after memory flushing the changes in the
  memory must be visible to all the threads in all teams. Patch fixes
  this.
  Reviewers: gtbercea, kkwli0
  Subscribers: guansong, jfb, caomhin, openmp-commits
diff: @@ -132,7 +132,7 @@ EXTERN void __kmpc_end_single(kmp_Ident *loc, int32_t global_tid) {
  EXTERN void __kmpc_flush(kmp_Ident *loc) {
  PRINT0(LD_IO, "call kmpc_flush\n");
  - __threadfence_block();
  + __threadfence_system();
  }
  ////////////////////////////////////////////////////////////////////////////////
  