> On Tue, Mar 30, 1999 at 02:42:55PM -0600, Brandon Black wrote:
> > I'm actually way past taking my life in my own hands, in that the
> > binutils, compiler, and kernel have all been built using egcs-1.1.2 with
> > the following optimization flags:
> >
> > -march=pentiumpro -O6 -fomit-frame-pointer -malign-loops=0
> > -malign-functions=0 -malign-jumps=0
> > (yes, even the kernel at O6).
>
> well, if you have a pentiumpro, that should really be
> -malign-loops=4 etc. You might also try adding -funroll-loops.
>
> I wonder if -fno-strict-aliasing might be better for the kernel?
>
> btw, egcs doesn't really have -O levels beyond 3.
>
> -- arvind
hmmm... I've tried -fstrcit-aliasing and -fno-strict-aliasing, and I can't
see any notable difference, but I don't have any way of qualitatively
profiling the kernel's performance, they both compile and work though.
About alignment.... the info I have found was that pentiums like -malign-*=2,
and PPro's supposedly liked either 2 or 4 depending on who you ask, and then
I read somewhere else that PII (at least the latest Deschutes ones) and later
processors should go back to 0, because for some reason the alignment didn't
help them much, and removing the padding would save space in the L2 (and to a
small degree the L1) cache.... so that's why I went with zero. Do you (or
anybody on the list) no for sure the optimal alignment for the PII Deschutes?
I kind-of assumed since gcc (I think) does thigns at least to 6, and so does
pgcc, both of which go into egcs, that egcs would have an O6... oh well :)
Brandon
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