[llvm-dev] Enable vectorizer-maximize-bandwidth by default?

[Nema, Ashutosh via llvm-dev]

Hi,

We enabled “vectorizer-maximize-bandwidth” and ran SPEC CPU2006 (base,rate) on Ryzen 8 core, 16 copies with below config:

Base: -m64 -O3 -march=znver1 -mavx2
Base + VMB: -m64 -O3 -march=znver1 -mavx2  -mllvm -vectorizer-maximize-bandwidth

There’s a small uplift for gcc and some small regression for sjeng. Others are within noise levels.

CPU2006 Results:
Benchmark

Base/(Base + VMB)

400.perlbench

1

401.bzip2

1

403.gcc

1.01517

429.mcf

1.00222

445.gobmk

1

456.hmmer

1

458.sjeng

0.98641

462.libquantum

1

464.h264ref

1.01005

471.omnetpp

1.00187

473.astar

1

483.xalancbmk

1.00149

433.milc

1

444.namd

1

447.dealII

1

450.soplex

1

453.povray

1.00515

470.lbm

1

482.sphinx3

1


*  Ratio more than 1 indicates vectorizer-maximize-bandwidth is improving the performance
*  Ratio less than 1 indicates vectorizer-maximize-bandwidth is regressing the performance.
*  Ratio 1 indicates no change.

Regards,
Ashutosh

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Adam Nemet via llvm-dev
Sent: Tuesday, May 30, 2017 9:47 PM
To: Chandler Carruth <chandlerc at gmail.com>
Cc: llvm-dev <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] Enable vectorizer-maximize-bandwidth by default?


On May 30, 2017, at 12:58 AM, Chandler Carruth <chandlerc at gmail.com<mailto:chandlerc at gmail.com>> wrote:

On Fri, May 19, 2017 at 4:01 PM Adam Nemet via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
I will run it on Cyclone/AArch64 next week.

FYI, we're still waiting on these Adam…

I was going to test spec but this does not seem to trigger on spec according to Dehao, so there is really no reason for me to test this.  We have some spec perf bots that test trunk; if there is some unexpected regression we should pick it up.  Sorry for not being explicit about this.

Adam

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