On 12/04/12 16:48, Richard Earnshaw wrote:
If negation in Neon needs a scratch register, it seems to me to be somewhat odd that we're disparaging the ARM version.
Good point, I'm really meaning to provide missing functionality in NEON to prevent unnecessary moves, rather than cause them, so I should remove the '?'s.
It probably doesn't need disparaging on A8, etiher?
Also, wouldn't it be sensible to support a variant that was early-clobber on operand 0, but loaded immediate zero into that value first: vmov Dd, #0 vsub Dd, Dd, Dm That way you'll never need more than two registers, whereas today you want three.
That does seem like a good option. I'll have a go and see what happens. Andrew