On 24 Jan 2007 09:56:55 -0800, Ian Lance Taylor <[EMAIL PROTECTED]> wrote:
"Paulo J. Matos" <[EMAIL PROTECTED]> writes:
> Which optimization levels affect gimple?
> I've tried for a program to check what kind of gimple code you get
> with -fdump-tree-gimple and -O0 and -O3 have different results,
> however, -O3 and -O9 have exactly the same output. Will -Ox for x > 3,
> generate the same gimple trees? (i.e., are done in backend of gcc?)
At present, as far as I know, the highest defined optimization level
is -O3. -ONUMBER where NUMBER > 3 is equivalent to -O3. There is no
particular guarantee that will remain true in the future, although
there are also no current plans to change it.
That's quite curious. I always thought that O3 was different to O4,
O5, ... O9. Still, beyond O3 optimizations were not safe... maybe an
old gcc myth! :-)
Thanks for clearing that up to me.
Ian
--
Paulo Jorge Matos - pocm at soton.ac.uk
http://www.personal.soton.ac.uk/pocm
PhD Student @ ECS
University of Southampton, UK
