On 01/07/11 15:40, Paolo Bonzini wrote: > On 07/01/2011 03:30 PM, Stubbs, Andrew wrote: >>> > However, perhaps there is a catch. We can do the following thought >>> > experiment. What would happen if you had multiple widening multiplies? >>> > Like 8-bit signed to 64-bit unsigned and then 64-bit unsigned to >>> 128-bit >>> > unsigned? I believe in this case you couldn't optimize 8-bit signed to >>> > 128-bit unsigned. Would your code do it? >> My code does not attempt to combine multiple multiplies. In any case, if >> you have two multiplications, surely you have at least three input >> values, so they can't be combined? > > What about (u128)c + (u64)((s8)a * (s8)b)? You cannot convert this to > (u128)c + (u128)((s8)a * (s8)b).
Oh I see, sorry. Yes, that's exactly what I'm trying to do here. No, wait, I don't see. Where are these multiple widening multiplies you're talking about? I only see one multiply? Andrew
