2009/2/3 Callum Lerwick <seg@xxxxxxxxxx>: > 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/ -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
