On 8 January 2012 02:54, Peter Alexander <peter.alexander...@gmail.com>wrote:
> I agree with Manu that we should just have a single type like __m128 in > MSVC. The other types and their conversions should be solvable in a library > with something like strong typedefs. > Walter put in a reasonable effort to sway me to his side of the fence last night. I'm still not entirely sold that implementation inside the language is necessary to achieve these details, but I don't have enough background into to argue, and I'm not the one that has to maintain the code :) Here are some points we discussed... how do we do these (efficiently) in a library? ** Literal syntax.. and constant folding: Constants and literals also need to be aligned. If we use array syntax to express literals, this will be a problem. int4 v = [ 1,2,3,4 ] + [ 5,6,7,8 ]; Any constant expressions need to be simplified at compile time: int4 vec = [ 6,8,10,12 ]; Perhaps this is possible with CTFE? Or will it be automatic if you express literals as if they were arrays? ** Expression interpretation/simplification: float4 v = -b + a; Obviously, this should be simplified to 'a - b'. float4 v = a*b + c; This should use a multiply-accumulate opcode on most architectures: FMADDPS v, a, b, c ** Typed debug info In a debugger it's nice to inspect variables in their supposed type. Can probably use unions to do this... probably wouldn't be as nice though. ** God knows what other optimisations float4 v = [ 0,0,0,0 ]; // XOR v etc... I don't know what amount of this is achievable with libraries, but Walter seems to think this will all work much better in the language... I'm inclined to trust his judgement.
