The statement was that L4 was getting this right. Neither the L4 kernel nor the Coyotos kernel use the XMM registers at all aside from saving and restoring them in context switch. They are compiled to avoid floating point as well.
Contrary to what was said earlier in the thread, the block zero instructions on the scalar unit are quite good on x86/x64. Though nowadays the SIMD and Float registers are so universally used that the case for avoiding them in the kernel is pretty weak. shap On Tue, Aug 17, 2010 at 6:56 PM, Ben Kloosterman <[email protected]> wrote: > Were talking about the use of the XMM registers ( rather than SIMD but > its an extention). > > > > Now there are several approaches here > > > > 1) You can give the language first grade support for 128 and 256 GP > registers ( which are limited to 32 bits for + - / * but 128/256 for all > other ops ) . > > 2) You can try to get most common use cases and hand craft them in > assembly in libs eg memcpy > > 3) You can try to let the compiler optimize it by trying to work out > if SSE can be used but at present this just works for some stores and > writes and suffers from alignment issues. Hence 2. > > > > Now the 2) case is common but not very portable ( hence my comments as the > L4 guys are very concerned about the IPC speed) and inferior to a language > solution . Note it’s true that L4 don’t use much SSE in their OS , but > Linux does > > > > This probably should be a spate thread but it does relate. > > > > Regards, > > > > Ben > > > > *From:* [email protected] [mailto:[email protected]] > *On Behalf Of *Jonathan S. Shapiro > *Sent:* Wednesday, August 18, 2010 6:37 AM > > *To:* [email protected]; Discussions about the BitC language > *Subject:* Re: [bitc-dev] Bitc and Simd > > > > Tyler certainly doesn't speak for me on this, but the L4 guys aren't doing > much SIMD support in their OS, so I'm not sure what the point of this > exchange is, exactly. > > On Mon, Aug 16, 2010 at 12:36 AM, Ben Kloosterman <[email protected]> > wrote: > > It seems wrong that all the guys working on the L4 series OS have got it to > the point where they removed ( most of ?) the asm and made it more portable > while the libs are going the other way and we are seeing more assembly. > > > > Ben > > > > <snip> > > _______________________________________________ > bitc-dev mailing list > [email protected] > http://www.coyotos.org/mailman/listinfo/bitc-dev > >
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