On Thursday 19 August 2010 15:11:19 ext Alexander Sack, you wrote: > On Wed, Aug 18, 2010 at 06:09:37AM -0700, Arjan van de Ven wrote: > > couldn't QT read /proc/cpuinfo (or do the equivalent of cpuid) > > instead of looking for the env variable? > > what others are doing is catching the sigill that happens if neon code > is not supported and then runtime falling back to non-neon code paths.
That sounds like a bad idea. If the processor does not support NEON, you do not know how it will interpret the NEON machine code. It might cause an illegal instruction signal. But the trap could be handled in kernel and emulated. You don't want to use emulated NEON, as it would be horribly slow. Worse yet, maybe the NEON machine code would overlap with an incompatible DSP instructions set and be misinterpreted? The fork+SIGILL approach works somewhat for x86, but I wouldn't risk it on ARM. -- Rémi Denis-Courmont Nokia Devices R&D, Maemo Software, Helsinki _______________________________________________ MeeGo-dev mailing list [email protected] http://lists.meego.com/listinfo/meego-dev
