Features/ArchitectureSupport - changing what we build for

[Colin Walters]

2009/2/3 Callum Lerwick <seg at haxxed.com>:
> On Tue, 2009-02-03 at 01:01 -0500, Gregory Maxwell wrote:
>> We would see much more substantial gains from things like -msse2 &
>> fpmath=sse but, unfortunately, unlike i586 there are a *lot* of
>> systems out there (and still being sold) which do not have all the
>> fancy instruction set extensions.
>
> I've found -mfpmath=sse to actually be slightly slower than x87. GCC
> just isn't very good at SSE yet, but people have been tuning its x87
> output for decades now.
>
> And at this point, all really performance critical bits of code I've
> ever seen, are already using runtime selection of hand-tuned SSE/MMX/etc
> inner loops. This is absolutely key. There's little gain to be had from
> diddling with GCC's instruction set usage because most performance
> critical software is already using hand-tuned assembly in their hotpaths
> on CPUs that support them.

Speaking of, it's worth mentioning liboil:
http://liboil.freedesktop.org/wiki/