On Apr 20, 2007, at 6:42 PM, Robert Dewar wrote:
One possibility would be to have a -Om switch (or whatever) that says "do all optimizations for this machine that help".
Ick, gross. No.
I must say the rule about all optimizations being the same on all machines seems odd to me
I'd look at it this way, it isn't unreasonable to have cost metrics that are in fact different for each cpu and possible each tune choice that greatly effects _any_ codegen choice. Sure, we can unroll the loops always on all targets, but, we can crank up the costs of extra instructions on chips where those costs are high, net result, almost no unrolling. For chips where the costs are cheap and they need to exposed instructions to be able to optimizer further, trivially, the costs involved are totally different. Net result, better code gen for each.
I do however think the concept of not allowing targets to set and unset optimization choices is, well, overly pedantic.
