How to do executable individualization using optimization options ?

[Byoungyoung Lee <override at postech dot ac dot kr>]

If the optimization options provided in a different way,
the same source codes would be compiled into different executables.

In the different executables,
the register allocation or instruction orders might be easily changed,
but I think that's not that big change.
What I'd like to do is to make their CFG different, while their impact
on executing performance is reasonable.

I'm reading through the compiler books and gcc internal documentations,
but it's really hard for me to pin point what I really need to read
and understand.

So, my question is what kind of optimizing options in gcc could be
used to do such jobs ?
or would you recommend good references for this ?

Regards,
Byoungyoung Lee