llvm-project/libclc/ptx-nvidiacl/lib/workitem/get_group_id.cl

#include <clc/clc.h>

_CLC_DEF size_t get_group_id(uint dim) {
  switch (dim) {
  case 0:  return __builtin_ptx_read_ctaid_x();
  case 1:  return __builtin_ptx_read_ctaid_y();
  case 2:  return __builtin_ptx_read_ctaid_z();
  default: return 0;
  }
}