llvm dev - Feb 2013 - [LLVMdev] Pointer Context Metadata (was: Parallel Loop Metadata)

On 02/18/2013 07:42 PM, Hal Finkel wrote:
> Why don't we just add an optional iteration id to
> !llvm.mem.parallel_loop_access?
Sounds like a good idea to me.

-- 
--Pekka

----- Original Message -----
> From: "Pekka Jääskeläinen" <pekka.jaaskelainen at tut.fi>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "Andrew Trick" <atrick at apple.com>, "Tobias
Grosser" <tobias at grosser.es>, "llvmdev at cs.uiuc.edu
Dev"
> <llvmdev at cs.uiuc.edu>
> Sent: Monday, February 18, 2013 1:34:49 PM
> Subject: Re: [LLVMdev] Pointer Context Metadata (was: Parallel Loop
Metadata)
> 
> On 02/18/2013 07:42 PM, Hal Finkel wrote:
> > Why don't we just add an optional iteration id to
> > !llvm.mem.parallel_loop_access?
> 
> Sounds like a good idea to me.
Okay. If you'll update your local BBVectorize patches, then we can pull them
upstream. Then we'll just need to update the unroller.

 -Hal
> 
> --
> --Pekka
> 
>

> 
> Okay. If you'll update your local BBVectorize patches, then we can pull
them upstream. Then we'll just need to update the unroller.

If I understand this thread correctly, you want to enable vecorization by
telling the BB vectorizer that different operations are independent. I
understand your motivation and I agree that this is indeed one way to do
vectorization.  However, I don't completely understand something.  If we
already have the information that consecutive iterations of the loops are
independent, then the loop vectorizer should already vectorize the loop.  Also,
at the moment we unroll loops before BB Vectorization. Can you think of cases
where the unrolling can help BB-vecoriation ? I think that it can only help in
cases that are easily detected by the loop vectorizer.

Thanks,
Nadav