On Thursday 15 July 2010 18:20:07 Konstantinos Margaritis wrote: > On Thursday 15 July 2010 17:34:01 Martin Guy wrote: > > I still doubt that the disruption and extra work for the community of > > Debian package maintainers, and the lower quality of the resulting > > archive, is worth the small increment in speed that is promised. I > > hope > > 30% *measured* (vs promised) speed increase is nothing to sneer at on > low-end cpus like Cortex-A8 is.
Just to reply to myself: In libm.so, I took sinf() -a very often used function, absolutely necessary for any trig stuff- and tried to actually find the differences using objdump: on softfp: $ objdump -S /lib/libm.so.6 --start-address=<startofsinf> --stop- address=<endofsinf>|grep -c vmov 7 on hardfp: $ objdump -S /lib/libm.so.6 --start-address=<startofsinf> --stop- address=<endofsinf>|grep -c vmov 2 Mind you the 2nd vmov in hardfp version, is this: vmov.f32 s16, s0, which definitely does not cost 20 cycles (it's not an mrc instruction). Do the math, there are 6 more vmov instructions (all between rX and sX registers) in the softfp versions. Ok, if one gives a stall of 20 cycles, how many cycles do we lose in sinf() alone? Still not convinced? Konstantinos -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
