How are -print-stats and -time command line args enabled

The command:
  clang --help shows:
shows:
  -print-stats Print performance metrics and statistics
  -time Time individual commands

However, using either of this command line flags gives the warnings:
  clang: warning: argument unused during compilation: '-time'
  clang: warning: argument unused during compilation: '-print-stats'
How are these flags made useful?

TIA.

-regards,
Larry