[llvm-dev] RFC: Switching to the new pass manager by default
Hal Finkel via llvm-dev
llvm-dev at lists.llvm.org
Wed Oct 25 10:38:15 PDT 2017
On 10/25/2017 12:32 PM, Evgeny Astigeevich wrote:
>
> Hi Hal,
>
> I quickly checked the execution profile. It is real. The code changed
> significantly. A number of the hottest regions changed. I’ll compare IRs.
>
Thanks. Obviously a 1000% execution performance regression seems
problematic.
-Hal
> JFYI FreeBench/fourinarow time graph:
> http://lnt.llvm.org/db_default/v4/nts/graph?highlight_run=76922&plot.1604615=1349.1604615.3
>
>
> Its graph in our LNT is more stable.
>
> Thanks,
>
> Evgeny
>
> *From: *Hal Finkel <hfinkel at anl.gov>
> *Organization: *Argonne National Laboratory
> *Date: *Wednesday, 25 October 2017 at 18:14
> *To: *Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>, Chandler
> Carruth <chandlerc at gmail.com>
> *Cc: *llvm-dev <llvm-dev at lists.llvm.org>, nd <nd at arm.com>
> *Subject: *Re: [llvm-dev] RFC: Switching to the new pass manager by
> default
>
> On 10/25/2017 12:10 PM, Evgeny Astigeevich via llvm-dev wrote:
>
> Hi Chandler,
>
> I ran the LNT benchmarks and SPEC2k6.train on AArch64 Cortex-A57.
> I used revisions: Clang 316561, LLVM 316563.
>
> Options: -O3 -mcpu=cortex-a57 -fomit-frame-pointer
> -fexperimental-new-pass-manager
>
> Regressions: execution time increase
>
> LNT
>
> MultiSource/Benchmarks/FreeBench/fourinarow/fourinarow 1018.58%
>
>
> How real is this?
>
> -Hal
>
>
> MultiSource/Benchmarks/Fhourstones/fhourstones
> 9.06%
>
> MultiSource/Benchmarks/Ptrdist/yacr2/yacr2
> 7.23%
>
> MultiSource/Benchmarks/Olden/perimeter/perimeter
> 6.87%
>
> MultiSource/Benchmarks/MiBench/consumer-typeset/consumer-typeset 6.02%
>
> MultiSource/Benchmarks/Trimaran/enc-pc1/enc-pc1
> 5.59%
>
> MultiSource/Benchmarks/ASC_Sequoia/AMGmk/AMGmk
> 5.03%
>
> SPEC2k6
>
> 453.povray 17.11%
>
> 482.sphinx3 3.44%
>
> 444.namd 2.89%
>
> Improvements: execution time decrease
>
> LNT
>
> MultiSource/Benchmarks/BitBench/uudecode/uudecode
> -50.90%
>
> SingleSource/Benchmarks/Adobe-C++/loop_unroll
> -27.75%
>
> SingleSource/Benchmarks/Misc/perlin
> -21.35%
>
> MultiSource/Benchmarks/Olden/em3d/em3d
> -19.12%
>
> MultiSource/Benchmarks/tramp3d-v4/tramp3d-v4
> -8.58%
>
> SingleSource/Benchmarks/McGill/chomp
> -6.33%
>
> MultiSource/Benchmarks/sim/sim
> -5.41%
>
> MultiSource/Applications/ClamAV/clamscan
> -3.11%
>
> MultiSource/Benchmarks/TSVC/Symbolics-dbl/Symbolics-dbl
> -2.81%
>
> SPEC2k6
>
> 429.mcf -5.18%
>
> 473.astar -2.65%
>
> 400.perlbench -1.90%
>
> There are also code sizes increases/decreases. The maximum
> increase is 18.98%. The maximum decrease is 25.65%.
>
> Thanks,
>
> Evgeny Astigeevich
>
> *From: *llvm-dev <llvm-dev-bounces at lists.llvm.org>
> <mailto:llvm-dev-bounces at lists.llvm.org> on behalf of Chandler
> Carruth via llvm-dev <llvm-dev at lists.llvm.org>
> <mailto:llvm-dev at lists.llvm.org>
> *Reply-To: *Chandler Carruth <chandlerc at gmail.com>
> <mailto:chandlerc at gmail.com>
> *Date: *Wednesday, 18 October 2017 at 07:51
> *To: *llvm-dev <llvm-dev at lists.llvm.org>
> <mailto:llvm-dev at lists.llvm.org>
> *Subject: *[llvm-dev] RFC: Switching to the new pass manager by
> default
>
> Greetings everyone!
>
> The new pass manager is getting extremely close to the point where
> I'm not aware of any significant outstanding work needed, and I'd
> like to see what else would be needed to enable it by default.
> Here are the current functionality I'm aware of outstanding:
>
> 1) Does not do non-trivial loop unswitching. Majority of this is
> in https://reviews.llvm.org/D34200 but will need one or two small
> follow-ups.
>
> 2) Currently, sanitizers don't work correctly with it. Thanks to
> the work of others, the missing infrastructure has been added and
> I'll send a patch to wire this up this week.
>
> 3) Missing support for 'optnone'. I've been working on this, but
> the existing testing wasn't as thorough as I wanted, so it is
> going slowly. I've got about 1/4 of this implemented and should
> have patches this week or next.
>
> 4) Missing opt-bisect (or similar) facility. This looks pretty
> trivial to add, but I've not even started. If anyone is interested
> in it, go for it. We might even be able to do something simpler
> using the generic debug counters and get equivalent functionality.
>
> ... that's it?
>
> Optimization quality / run-time performance:
>
> - We've been using it at Google extensively and are very happy
> with the optimization quality. Benchmarks look *very* good here.
>
> - More data from other users would be important.
>
> - You can try it out with `-fexperimental-new-pass-manager` to Clang
>
> Compile-time performance:
>
> - Sometimes *much* better due to cached analyses.
>
> - Sometimes worse, typically due to more / different inlining in
> turn running main pipeline (GVN + InstCombine) more times or over
> more code.
>
> - Overall somewhat a wash, but the increased compile times
> typically due to the optimizer "trying" harder, so not too
> concerning on our end.
>
> - Again, more feedback from other users good:
> `-fexperimental-new-pass-manager` to Clang
>
> Once the four missing things land, I'll also happily work on
> collecting some of the basics on the test-suite and CTMark. But I
> suspect more "in the wild" data would really be useful here given
> the significance of the change.
>
> Thoughts? What else (beyond the four items above and feedback on
> run-time and compile-time) would folks like to see?
>
> Once this happens, I'll also be preparing some batch, mechanical
> updates to the test suite to primarily use the new pass manager.
> Also there is lots of documentation updates that will be needed here.
>
> -Chandler
>
> PS: I'll be sending a note to cfe-dev as a "heads up" about this
> discussion as in some ways, the default flip is mostly a Clang
> default flip. But hopefully our doc updates will trigger this
> being "perceived" as the default for other frontends, and I'll try
> to reach out to other major frontends as well (Swift and Rust are
> on my radar, and I've already started talking with Philip Reames
> about their Falcon JIT).
>
>
>
>
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>
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>
>
> --
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory
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