Is -O9 legitimate?

[Lee Rhodes]

I am studying a Makefile where the author specified the execution of GCC as
follows:

  gcc -O9 -fno-strict-aliasing  ...

I could not find any reference to either -O9 or -fno-strict-aliasing in the
4.2.0 gcc.pdf manual.  I did find -fstrict-aliasing, but most commands that
have a -fno- option are listed in the manual.

What effect does -O9 have?

Would -fno-strict-aliasing turn off strict-aliasing? 

Is there a gcc switch that would issue warnings about either obsolete or
ignored command line switches?

Are there other undocumented switches?

Lee.