On 12/04/12 17:16, Andrew Stubbs wrote:
> 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?
Possibly not. Which then begs the question as to whether we need an A8
variant at all.
>> 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.