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Re: Why you are wrong [Was: On linux kernel packaging issue]

On Mon, Nov 10, 2003 at 05:08:48PM -0600, Joe Wreschnig wrote:
> Of course, I'm far from a compiler and chip design expert (or even
> novice); this is what I remember from my classes last year. :) But it
> shows how complicated optimizing compilers can get, and why you can't
> say any optimization is always good/safe/faster/etc. The only truly safe
> way to tell is extensive, controlled benchmarking.

An optimisation that makes things unsafe or slower isn't an
optimisation. The compiler shouldn't produce any code that is incorrect
or slower. Of course, it can't stop you from taking a P4-optimised
binary and running it on an Athlon.

I think you could say that any optimisation is safe and not slower;
otherwise it's not an optimisation.

The job of compiling for modern processors does seem daunting
(especially VLIW architectures like ia64).

Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>

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