Help with RTL loop invariant motion

[David Edelsohn]

On Mon, Dec 12, 2011 at 3:05 AM, Rohit Arul Raj <rohitarulraj@gmail.com> wrote:

> And with ‘-O3’ and above, we cannot switch OFF the flag
> ‘-fira-loop-pressure’, because it has been explicitly overridden in
> the PPC backend target files.
>
> 1) Is it possible to update the heuristic to allow this optimization.
> 2) If not, the user should have control over the '-fira-loop-pressure'
> flag when passed explicitly.
>
>         File: rs6000.c
>         if (optimize >= 3 && global_init_p &&
> !global_options_set.x_flag_ira_loop_pressure)
>            flag_ira_loop_pressure = 1;

The rs6000 port should allow this option to be overridden.  It would
be better to post an explicit, tested patch to the gcc-patches
mailinglist.

The cost model is a separate issue that also should be corrected to
not inhibit this transformation.

Thanks, David