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Re: conversions between vectors

On 22 Dec 2001, Aldy Hernandez wrote:

> > Does Dan's patch include docs?  Let's first get in docs for vectors
> > corresponding to valarrays (effectively explaining those parts of
> > valarrays for C programmers), stating what is and is not currently
> ok, i don't understand c++ (or valarrays) sufficiently to be able to
> write those docs.  for that matter, i don't agree we should be
> patterning vectors after valarrays just because it's a well known
> interface.  but if this is the route agreed by everyone, then i suggest
> someone knowledgeable with valarrays document the corresponding C
> extensions.
> would you be willing to write the docs?

I'm not familiar enough with valarrays.  Someone else should do those

> this is something i want to do for 3.2.  for that matter i want to
> implement the whole shebang of sythesizeable vector operations.  if you
> define vector size to be 16, and you only have vectors of 8bytes, then
> the optab code should be able to use a pair of V2SIs to do V4SI
> operations.  this should provide a basis for auto-vectorization work.

Yes, the operations should in general be synthesised if the CPU doesn't
have operations for the particular sort of vector.  (Including converting
to loops over scalars if necessary.)

Joseph S. Myers

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