message: [XLA] Use Iota in Cholesky rather than a std::iota constant.
  NFC intended, just a cleanup noticed in passing.
diff: @@ -68,29 +68,26 @@ XlaOp CholeskyUnblocked(XlaOp a, PrecisionConfig::Precision precision) {
  auto body_fn =
  [&](XlaOp i, absl::Span<const XlaOp> loop_vars,
  XlaBuilder* body_builder) -> StatusOr<std::vector<XlaOp>> {
  - Shape col_shape;
  - Shape row_shape;
  - for (int64 d : major_dims) {
  - row_shape.add_dimensions(d);
  - col_shape.add_dimensions(d);
  - }
  - row_shape.add_dimensions(1);
  - row_shape.add_dimensions(n);
  - row_shape.set_element_type(a_shape.element_type());
  - auto mask_zeros_row = Zeros(body_builder, row_shape);
  -
  - col_shape.add_dimensions(n);
  - col_shape.add_dimensions(1);
  - col_shape.set_element_type(a_shape.element_type());
  - auto mask_zeros_col = Zeros(body_builder, col_shape);
  -
  - std::vector<int32> mask_vector(n);
  - std::iota(mask_vector.begin(), mask_vector.end(), 0);
  - auto mask_range = ConstantR1<int32>(body_builder, mask_vector);
  + std::vector<int64> row_shape_dims(major_dims.begin(), major_dims.end());
  + std::vector<int64> col_shape_dims(major_dims.begin(), major_dims.end());
  + row_shape_dims.push_back(1);
  + row_shape_dims.push_back(n);
  + auto mask_zeros_row =
  + Zeros(body_builder,
  + ShapeUtil::MakeShape(a_shape.element_type(), row_shape_dims));
  +
  + col_shape_dims.push_back(n);
  + col_shape_dims.push_back(1);
  + auto mask_zeros_col =
  + Zeros(body_builder,
  + ShapeUtil::MakeShape(a_shape.element_type(), col_shape_dims));
  +
  auto mask_range_row =
  - Broadcast(Reshape(mask_range, {0}, {1, n}), major_dims);
  + Iota(body_builder, ShapeUtil::MakeShape(S32, row_shape_dims),
  + /*iota_dimension=*/n_dims - 1);
  auto mask_range_col =
  - Broadcast(Reshape(mask_range, {0}, {n, 1}), major_dims);
  + Iota(body_builder, ShapeUtil::MakeShape(S32, col_shape_dims),
  + /*iota_dimension=*/n_dims - 2);
  auto body_a = loop_vars[0];
  auto body_l = loop_vars[1];
  