xla

f2cab69c - Remove the expand pass and implement the SumToSize operation.

Remove the expand pass and implement the SumToSize operation. https://github.com/pytorch/pytorch/blob/master/torch/csrc/jit/register_prim_ops.cpp#L475 https://github.com/zdevito/ATen/blob/master/aten/src/ATen/ExpandUtils.h#L139