Re: [RFC] Selective scheduling pass

["Steven Bosscher" <stevenb.gcc@gmail.com>]

On Thu, Jun 5, 2008 at 8:29 PM, Andrey Belevantsev <abel@ispras.ru> wrote:
>> Also, you post a new scheduler and a set of target tunings in one set
>> of patches.  I would like to know what the performance impact is of
>> just the target changes alone.  That is, what happens to e.g. SPEC
>> scores for ia64 with just the tweaks and tunings patch
>> (http://gcc.gnu.org/ml/gcc-patches/2008-06/msg00117.html)?  I assume
>> those target changes alone (the ones not related to sel-sched) also
>> have a positive performance impact.  Since you've globbed everything
>> into one patch set, it's impossible to tell how much of the
>> performance changes can be attributed to sel-sched, and how much is
>> just target tweaks...
>
> AFAIR, the target tunings gave around 1% when we have tested it on -O2.
>  That was a couple of months ago.  We will retest tonight to get fresh
> numbers for this.

Great.

Another thought/suggestion/comment:

Does the selective scheduler also make the register renaming pass
obsolete (pass_regrename and pass_cprop_hardreg)?  I would expect it
does, since the scheduler handles the register renaming itself, as far
as I understand.

These two passes are quite expensive (or at least they were when I
last looked at them).  You could perhaps buy yourself some compile
time back if you can demonstrate you don't need to run these passes if
you do post-regalloc selective scheduling.

Gr.
Steven