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Re: Optimal Optimizations: A Very Preliminary Report


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? ;-)


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