How disable backend?

[pang long]

Dear:
    I want to know how to disable the backend output by commond
options or any way. I just want to run the analysis or optimization
pass excluding generating asm or executable file output. This is
because I am planning to implement some static analysis passes of GCC,
and I just want to get the result of my own passes but all other
further output such as final executable program.
    I find a static global variable no_backend in toplev.c(GCC 4.3.0
Core). It is defined in line1734:" no_backend =
lang_hooks.post_options (&main_input_filename);" I have read the
corresponding implementation "c_common_post_options" for language C,
but I don't catch the corresponding commond options for GCC. Please
give some hints.

Yours sincerely
PANG Long
Thanks a lot for ur help!