llvm dev - Sep 2016 - Auto-vectorization optimization passes cost

Hi,

I see that the BBVectorize optimization pass is awfully slow in the kind of LLVM
IR code that we generate and JIT (tested with LLVM 3.8).  I also activate
LoopVectorize and SLPVectorize which are much faster. Since AFAIR BBVectorize
was developed first in the history of auto-vectorization passes, what is the
status of these different passes? Can we safely only use LoopVectorize and
SLPVectorize ? Do they cover the same use cases that BBVectorize was solving?

Thanks.

Stéphane Letz

Hi Stéphane,

Yes, you should be using only LoopVectorize and SLPVectorize in production. If
you find something that BBVectorize usefully vectorizes, and SLPVectorize does
not, please file a bug. SLPVectorize should cover all of the use cases that
BBVectorize covers, but it uses a stricter set of heuristics to find candidates,
and sometimes misses things that BBVectorize gets.

 -Hal

----- Original Message -----
> From: "Stéphane Letz via llvm-dev" <llvm-dev at
lists.llvm.org>
> To: "via llvm-dev" <llvm-dev at lists.llvm.org>
> Sent: Monday, September 26, 2016 4:22:22 AM
> Subject: [llvm-dev] Auto-vectorization optimization passes cost
> 
> Hi,
> 
> I see that the BBVectorize optimization pass is awfully slow in the
> kind of LLVM IR code that we generate and JIT (tested with LLVM
> 3.8).  I also activate LoopVectorize and SLPVectorize which are much
> faster. Since AFAIR BBVectorize was developed first in the history
> of auto-vectorization passes, what is the status of these different
> passes? Can we safely only use LoopVectorize and SLPVectorize ? Do
> they cover the same use cases that BBVectorize was solving?
> 
> Thanks.
> 
> Stéphane Letz
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory