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Re: GCC mini-summit - compiling for a particular architecture
Diego Novillo wrote:
H. J. Lu wrote on 04/20/07 21:30:
-fprefetch-loop-arrays shouldn't be on by default since HW prefetch
usually will have negative performance impact on Intel.
We are talking about one specific architecture where it usually helps: ia64.
Right, but the follow on discussion was *if* we have to have the same
set of optimization options for all architectures, *then* could we
consider turning on loop unrolling by default.
One possibility would be to have a -Om switch (or whatever) that
says "do all optimizations for this machine that help".
I must say the rule about all optimizations being the same on
all machines seems odd to me in another respect. What if you
have an optimziation that applies *only* to one machine (ia64
has a number of such possibilities!)