Re: cortex / arm-hardfloat-linux-gnueabi (was Re: armelfp: new architecture name for an armel variant)
+++ Paul Brook [2010-07-15 22:29 +0100]:
> > > 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?
> >
> > Depends how the function is called. Worst case we loose 17 cycles, best
> > case we should be ~10 cycles faster.
>
> A simple benchmark confirms this hypothesis.
> softfp is actually faster in many cases.
>
> // uncomment one of these.
> //x[i] = sinf(y[i]); // hard 15% slower
> //x[i] = sinf(y[i]) + 1.0; // hard 5% slower
> //x[i] = sinf(y[i] + 1.0); // hard 0.5% slower
> //x[i] = sinf(y[i] + 1.0) + 1.0; // softfp 2.5% slower
Hmm, interesting.
What hardware/CPU/emulator did you test this on? I guess the answers
will vary to some degree depending what it is run on.
Wookey
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