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.
> Andrew

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