/path/to/sellhip.hip.cpp:309:3: warning: loop not unrolled: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering [-Wpass-failed=transform-warning]
  for (int offset = WARP_SIZE / 2; offset >= sliceheight; offset /= 2) { t += __shfl_down(t, offset); }