At Tue, 11 Jan 2005 19:03:44 -0600, Marcelo E. Magallon <[EMAIL PROTECTED]> wrote: > > Note that MMX will be removed from the next glibc 2.3.4 upload. It > > will provide only SSE2 (and CMOV, debian-specific for only VIA C3 > > processor). > > Well, there's hand-crafted MMX code, so it's runtime checked. I guess > that would take care of it. After following the advice in other > replies, gcc is generating CMOVs, too.
If your "runtime check" means "hand-crafted MMX code checks the hardware MMX availability and it automatically judges to use MMX instruction on execution time", you don't need to care about library file location. However, if you specify any architecture optimization code like -march=i686, you need to put such library on special HWCAP directory (thus /usr/lib/i686/cmov). > > > My understanding is that this is also significant on sparc > > > (-mcpu=v9) and that this belongs in /usr/lib/v9. Is this right? > > > > Sparc defines HWCAP_SPARC_V9 and HWCAP_SPARC_ULTRA3. So v9 is right. > > See glibc sparc packages. > > Thanks! > > Where would ultra3 libs go? /usr/lib/sparc/ultra3? (sorry about the > naive question, but I had a hardtime finding this sort of > documentation) I think /usr/lib/ultra3 is the right directory if you specify ultra3 optimization option to gcc. Note that unfortunatelly I don't have access to any ev67 or ultra3 machine - so I don't test it. > > > Mesa upstream uses -mcpu=ev5 -mieee on alpha. Is that ok? Where > > > does this belong into? /usr/lib/ev5? > > > > IIRC, alpha does not define any hwcaps. > > Oh... I was looking at the atlas packages (I *think*), and it installed > some libs in /usr/lib/ev5 (or something along those lines). Is that > manually handled by atlas or something like that? Please read README.Debian.gz - atlas2-ev5 package says user needs to use LD_LIBRARY_PATH or to add /usr/lib/ev5 directory into /etc/ld.so.conf. This is another way to use hardware optimization library. However a big drawback is user needs to add such directory under his/her responsibility (if hardware is downgraded from ev56, user needs to edit the configuration again because atlas may start to barf illegal instruction). BTW, I would like to warn about compiler option tuning optimization. I think in most case the hardware specific optimization code does not accelarate uesr application so much (except for HPC apps). 3% speed up is sometimes hard issue for processor architect/creator, but I think it's not large improvement - if your application issues disk IO frequently, the performance is hidden by disk seek slowness. Pure HPC applications pay a lot of efforts of decreasing IO/communication, loop, unrolling and data structure design. Application code optimization makes a lot of performance improvement compared with the lazyness compile option tuning (but some compiler like intel on ia64 is out of scope, though). So, using HWCAP library is not everytime good choise. IIRC, an article said optimization comparison on Gentoo showed no speed gain. Regards, -- gotom -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
