message: Add counter to MLIR dumps in bridge
  Now MLIR files dumped from bridge have a 4-digit counter as prefix so the order
  of the passes is obvious.
diff: @@ -15,6 +15,8 @@ limitations under the License.
  #include "tensorflow/compiler/mlir/tensorflow/utils/bridge_logger.h"
  +#include <atomic>
  +
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/FormatVariadic.h"
  #include "mlir/IR/Operation.h" // from @llvm-project
  @@ -23,17 +25,24 @@ limitations under the License.
  namespace tensorflow {
  +// Counter is used as a prefix for filenames.
  +static std::atomic<int> log_counter(0);
  +
  BridgeLoggerConfig::BridgeLoggerConfig(bool print_module_scope,
  bool print_after_only_on_change)
  : mlir::PassManager::IRPrinterConfig(print_module_scope,
  print_after_only_on_change) {}
  -// Logs op to file with name of format `mlir_bridge-pass_name-file_suffix.mlir`.
  +// Logs op to file with name of format
  +// `<log_counter>_mlir_bridge_<pass_name>_<file_suffix>.mlir`.
  inline static void Log(BridgeLoggerConfig::PrintCallbackFn print_callback,
  mlir::Pass* pass, mlir::Operation* op,
  llvm::StringRef file_suffix) {
  - std::string name =
  - llvm::formatv("mlir_bridge_{0}_{1}", pass->getName(), file_suffix).str();
  + std::string pass_name = pass->getName().str();
  +
  + // Add 4-digit counter as prefix so the order of the passes is obvious.
  + std::string name = llvm::formatv("{0,0+4}_mlir_bridge_{1}_{2}", log_counter++,
  + pass_name, file_suffix);
  std::unique_ptr<llvm::raw_ostream> os;
  std::string filepath;
  