How to dump all the optimization flags enabled?

[Vladimir Simonov]

Andrew Haley wrote:
> Vladimir Simonov writes:
>  > 
>  > Andrew Haley wrote:
>  > > Wei Hu writes:
>  > >  > Hello,
>  > >  > 
>  > >  > Is there a way to tell gcc to print out all the effective optimization
>  > >  > flags when it compiles a C file?
>  > >  > I know the manual tells you what flags are set at different
>  > >  > optimization levels, but I'm still looking for an answer to my
>  > >  > question because it will be useful to my project.
>  > > 
>  > > Yes.  -fverbose-asm dumps the flags to the .s file.
>   > 
>  > Sorry, if probably a bit offtopic from subj.
>  > 
>  > I've created flags lists for -O0 and -O2,
>  > made diff (see attach) and built my project
>  > both with -O0 and -O2 -fno-{all options marked by + in diff}.
>  > 
>  > I've expected that results(binaries) will be equal.
>  > But they are different.
>  > 
>  > Are my expectations correct?
>  > Or -O0 and -O2 -fno-{all options marked
>  > by + in diff} are not the same?
> 
> I don't really understand your question, but if you're asking "if I
> set all individual optimization flags but don't set -O, will that
> still optimize?" the answer is no.  If you're asking "f I unset all
> individual optimization flags but set -O2, will that be the same as
> -O0", the answer is no.
> 
> Andrew.
> 

The second one.

Do you know a way to turn on optimization
flags step by step from -O0 till -O2?

Thank you.
Vladimir