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Re: Baby's First AldyVec/AltiVec patch


On Dec 29, 2003, at 12:20 PM, Segher Boessenkool wrote:

On 23-dec-03, at 19:56, Matt Austern wrote:
And remember the downside if we don't introduce the Motorola syntax:
Altivec code won't be portable between the various compilers that all
claim to support Altivec. That's a very serious problem, and it's exactly
what standards are supposed to prevent.

Hey, the Motorola AltiVec PIM does not support 64-bit PowerPC at all; in fact, it requires incompatible changes to sanely support it.

There is a real need for a new, better, C binding for VMX; I for sure
don't care for compatibility with the Motorola AltiVec PIM at all,
as it is very very awkward to use (in fact, the _only_ thing that
it buys over writing real assembly is register allocation, and for
that you have to write casts almost everywhere -- I prefer to stay
with handwriting assembly (or having the compiler auto-vectorize
stuff of course)).

All in all, I think we would do better to learn from the mistakes
in the Motorola AltiVec PIM and start over.

"Start over" really isn't practical given that the existing syntax in the Motorola Altivec PIM is widely used. Moving to a new syntax might be a good idea, but it'll need a transition strategy and it'll have to be something that gets buy-in from *all* compilers that target this architecture.

--Matt


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