message: [XLA:CPU] Error on unsupported dot instructions
  This is a stopgap measure to avoid silently miscompiling dot operations.
diff: @@ -808,6 +808,19 @@ Status IrEmitter::HandleDot(HloInstruction* dot) {
  return Unimplemented("Dot with batch dimensions not implemented.");
  }
  + if (dnums.lhs_contracting_dimensions_size() != 1) {
  + // This is disallowed by ShapeInference today.
  + return Unimplemented(
  + "Dot with multiple contracting dimensions not implemented.");
  + }
  +
  + if (dnums.lhs_contracting_dimensions(0) !=
  + std::min(lhs->shape().dimensions_size() - 1, 1) ||
  + dnums.rhs_contracting_dimensions(0) != 0) {
  + return Unimplemented(
  + "Dot with non-standard contracting dimensions not implemented.");
  + }
  +
  llvm_ir::IrArray lhs_array(GetIrArrayFor(lhs));
  llvm_ir::IrArray rhs_array(GetIrArrayFor(rhs));
  