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

[Hal Finkel]

On Tue, 6 Dec 2011 09:19:43 +0200
"Rotem, Nadav" <nadav.rotem at intel.com> wrote:

> Hi, 
> 
> I just wanted to let you know that I committed the pointer-vector
> patch. 

Nadav,

I just committed a change to BBVectorizer to allow it to generate these
(and also vector selects) [>= r154735]. If you have cases where you
think these should be generated, and they're now not generated by the
vectorizer, please let me know.

Thanks again,
Hal

> 
> Thanks,
> Nadav 
> 
> -----Original Message-----
> From: David A. Greene [mailto:greened at obbligato.org] 
> Sent: Tuesday, December 06, 2011 00:10
> To: Jose Fonseca
> Cc: David A. Greene; Rotem, Nadav; LLVM Developers Mailing List
> Subject: Re: [LLVMdev] [llvm-commits] Vectors of Pointers and
> Vector-GEP
> 
> Jose Fonseca <jfonseca at vmware.com> writes:
> 
> > I was referring to gathering a vector of sparse 32bit words, all
> > relative from a base scalar pointer in a 64bit address space, where
> > the offsets are in a 32bit integer vector.  My other reply gave a
> > more detailed and concrete example.
> 
> Yep, I saw that.  I think LLVM IR should support it directly.
> 
> > Anyway, from Nadav's and your other replies on this thread it is now
> > clear to me that even if the IR doesn't express base scalar pointers
> > w/ vector indices directly, the backend can always match and emit
> > the most efficient machine instruction. This addresses my main
> > concern.
> 
> It can, but it would have to go through varying amounts of pain to do
> so.  This is such a common operation that the IR should really support
> it directly.
> 
>                            -Dave
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-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory