[LLVMdev] Enabling the SLP vectorizer by default for -O3

[Chandler Carruth]

Cool!

What changes have you seen to generated code size?

I'll take it for a spin on our benchmarks.


On Sat, Jul 13, 2013 at 11:30 PM, Nadav Rotem <nrotem at apple.com> wrote:

> Hi,
>
> LLVM’s SLP-vectorizer is a new pass that combines similar independent
> instructions in a straight-line code.  It is currently not enabled by
> default, and people who want to experiment with it can use the clang
> command line flag “-fslp-vectorize”.  I ran LLVM’s test suite with and
> without the SLP vectorizer on a Sandybridge mac (using SSE4, w/o AVX).
>  Based on my performance measurements (below) I would like to enable the
> SLP-vectorizer by default on -O3.  I would like to hear what others in the
> community think about this and give other people the opportunity to perform
> their own performance measurements.
>
> — Performance Gains —
> SingleSource/Benchmarks/Misc/matmul_f64_4x4 -53.68%
> MultiSource/Benchmarks/Olden/power/power  -18.55%
> MultiSource/Benchmarks/TSVC/LoopRerolling-flt/LoopRerolling-flt -14.71%
> SingleSource/Benchmarks/Misc/flops-6  -11.02%
> SingleSource/Benchmarks/Misc/flops-5  -10.03%
> MultiSource/Benchmarks/TSVC/LinearDependence-flt/LinearDependence-flt
> -8.37%
> External/Nurbs/nurbs  -7.98%
> SingleSource/Benchmarks/Misc/pi -7.29%
> External/SPEC/CINT2000/252_eon/252_eon  -5.78%
> External/SPEC/CFP2006/444_namd/444_namd -4.52%
> External/SPEC/CFP2000/188_ammp/188_ammp -4.45%
> MultiSource/Applications/SIBsim4/SIBsim4  -3.58%
> MultiSource/Benchmarks/TSVC/LoopRerolling-dbl/LoopRerolling-dbl -3.52%
> SingleSource/Benchmarks/Misc-C++/Large/sphereflake  -2.96%
> MultiSource/Benchmarks/TSVC/LinearDependence-dbl/LinearDependence-dbl
> -2.75%
> MultiSource/Benchmarks/VersaBench/beamformer/beamformer -2.70%
> MultiSource/Benchmarks/TSVC/NodeSplitting-dbl/NodeSplitting-dbl -1.95%
> SingleSource/Benchmarks/Misc/flops  -1.89%
> SingleSource/Benchmarks/Misc/oourafft -1.71%
> MultiSource/Benchmarks/mafft/pairlocalalign -1.16%
> External/SPEC/CFP2006/447_dealII/447_dealII -1.06%
>
> — Regressions —
> MultiSource/Benchmarks/Olden/bh/bh  22.47%
> MultiSource/Benchmarks/Bullet/bullet  7.31%
> SingleSource/Benchmarks/Misc-C++-EH/spirit  5.68%
> SingleSource/Benchmarks/SmallPT/smallpt 3.91%
>
> Thanks,
> Nadav
>
>
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