return op->emitError()
             << "Cannot find function " << sym.getRootReference();
    }
    callees.push_back(callee);
  }
  return success();
}

bool HasSingleBlock(func::FuncOp func) {
  return func->getNumRegions() == 1 && func.getBody().hasOneBlock();
}

  llvm::SmallVector<mlir::func::FuncOp> entry_funcs =
      GetEntryFunctions(*module);
  EXPECT_EQ(entry_funcs.size(), 1);
  EXPECT_EQ(entry_funcs[0].getSymName(), "entry_func");
  EXPECT_TRUE(HasSingleBlock(entry_funcs[0]));
}

TEST(CallGraphUtilTest, MultipleBlocksEntryFunction) {
  const char *const code = R"mlir(
func.func @entry_func(%arg0: tensor<i32>) -> tensor<i32> attributes {tf.entry_function = {}} {

      }
      return WalkResult::advance();
    });
    if (result.wasInterrupted()) return failure();
  }
  return success();
}

// Check if a function has one region and one block only.
bool HasSingleBlock(func::FuncOp func);

}  // namespace mlir