// The pattern we're matching is
  // ^block(arg0, arg1, ..., argN):
  //   r0, r1, ..., rN = func.call @foo(arg0, arg1, ..., argN)
  //   "tf.yield"(r0, r1, ..., rN)
  if (!region.hasOneBlock()) return std::nullopt;
  Block& block = region.front();
  if (std::distance(block.begin(), block.end()) != 2) return std::nullopt;
  TF::YieldOp yield =
      llvm::dyn_cast_or_null<TF::YieldOp>(block.getTerminator());