[llvm-commits] Vectors of Pointers and Vector-GEP

[Hal Finkel]

On Wed, 2011-11-23 at 10:35 +0100, Duncan Sands wrote:
> Hi Nadav,
> 
> > Following the discussion in last week’s LLVM developers conference I started
> > working on support for vectors-of-pointers. Vectors of pointers are needed for
> > supporting scatter/gather operations and are the first step in the direction of
> > supporting predicated architectures. In the attached patch, I change the LLVM-IR
> > in order to support vectors-of-pointers and added basic support for vector-gep.
> > In following patches I plan to extend the vector-gep support to more indices and
> > add scatter/gather intrinsics.
> 
> one of the issues with vectors-of-pointers is then you can no longer say what
> the size of a vector is without target data, since you don't know what the size
> of a pointer is without target data.  Methods like VectorType::getBitWidth will
> have to be deleted.  Methods like VectorType::getTruncatedElementVectorType,
> VectorType::getExtendedElementVectorType and VectorType::getInteger will need to
> either be removed, or changed to take a target data parameter (which is probably
> a layering violation, so they would need to be moved elsewhere).  The PtrToInt
> and IntToPtr operations will need to be enhanced to work on vectors, and a
> bunch of places that bitcast vectors will need to become more careful, in case
> they are trying to bitcast between a vector of pointers and a vector of
> integers.

getExtendedElementVectorType, etc. don't "work" for floating-point
vectors currently, so there is some precedent for this kind of thing.

Another option would be to make another derived type for pointer
vectors.

 -Hal

> 
> Ciao, Duncan.
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-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory