Optimal Optimizations: A Very Preliminary Report

[Nathanael Nerode]

Michael Matz wrote:
> Hi,
> 
> On Tue, 12 Aug 2003, Nathanael Nerode wrote:
> 
> 
>>(Incidentally, the evidence for that particular case indicates that
>>-fschedule-insns should be abandoned entirely, while -fschedule-insns2
>>should be standard.)
> 
> 
> For this particular case!  Scott is testing ooo architectures, which
> generally do not benefit that greatly from scheduling anyway.  The picture
> is wholly different with in-order archs where pre-regalloc scheduling can
> make a horribly high difference (if it's given that there is a reasonable
> number of registers, so that scheduling does not interfere with regalloc
> that much).

Hmm.  Which of our arches are out-of-order and which of them are 
in-order?  I believe that -fschedule-insns has been reported to make 
things worse on sh, powerpc, x86, and ia64.  :-/

Is there a way to set the default optimizations differently on a 
per-architecture basis?  If there isn't, should there be? ;-)