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Re: Changing the default 32-bit x86 arch for Fedora 12



>> Now where does the "i686+SSE2" come into play? Does this SSE2 have any
>> effect on those programs that do not contain SSE(2) related assembly code?
>> Is this 1-2% improvement that you are mentioning only about these kind of
>> programs (that do not contain assembly code)?
>
> One advantage of SSE2 is that it can be used as a replacement for the
> braindead x87 (floating point) instructions.  The x87 instructions are
> architecturally stupid because they arrange the registers as a stack,
> whereas what a compiler wants is a flat register file.
>
> There was an experimental branch of the OCaml/i386 compiler which used
> SSE2 as a replacement for x87 instructions, and it gained a 10-15%
> increase in performance *on floating point benchmarks* [1] (ie. not
> just on any old code, and not code which used specific hand-written
> SSE2 optimizations).
>
> (It's worth noting that SSE2 is always used on ocamlopt/x86_64)

That's because its always been there on x86_64 and most people that
care about performance have already moved to x86_64 to get the other
performance benefits of 64 bit anyway.

Peter


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