[llvm-dev] [RFC] Enable Partial Inliner by default

Tue Nov 14 13:40:28 PST 2017

Hi Evgeny,

I agree that we probably need to tweak when the partial inliner should run
when using LTO/thinLTO.  The easiest thing to do is likely to just disable
partial inlining in the pre-LTO pass during compilation, so we don't
outline things that the LTO inliner will eventually inline again.

As for the code size increases you're seeing, it's not too surprising,
though it would've been nice to see some performance speed-ups.  Do you
know if we just happen to increase the size of functions that are
infrequently executed?

Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077      C2-707/8200/Markham
Email: gyiu at ca.ibm.com

From:	Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
To:	Graham Yiu <gyiu at ca.ibm.com>
Cc:	"junbuml at codeaurora.org" <junbuml at codeaurora.org>,
            "llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, Tobias
            Grosser <tobias.grosser at inf.ethz.ch>, nd <nd at arm.com>
Date:	11/13/2017 09:47 AM
Subject:	Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Graham,

I created a bug report with a reproducer for the failures I’ve got:
https://bugs.llvm.org/show_bug.cgi?id=35288
I have also found that LTO reverts everything the partial inliner has done.
Maybe the partial inliner should not be used at the first LTO phase
(compilation).

I hope I’ll have a chance to look at the code size regressions this week.

Thanks,
Evgeny Astigeevich

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Evgeny
Astigeevich via llvm-dev <llvm-dev at lists.llvm.org>
Reply-To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Date: Saturday, 11 November 2017 at 17:21
To: Graham Yiu <gyiu at ca.ibm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, Tobias Grosser
<tobias.grosser at inf.ethz.ch>, nd <nd at arm.com>
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Graham,

I’ve got results of benchmarking. Armv7m and armv6m are not affected. No
changes in scores nor code sizes.
I did some additional benchmarks runs for AArch64 and AArch32.

LNT test suite, AArch32, Cortex-A57, -O3 -mcpu=cortex-a57 -mthumb
-fomit-frame-pointer
-------------------------------------------------------------------------------------------------------------------------
MultiSource/Applications/aha/aha                          6.73% execution
time regression
MultiSource/Applications/sqlite3/sqlite3              2.61% execution time
improvement

Code size regressions greater than 5%:
MultiSource/Benchmarks/MiBench/automotive-susan/automotive-susan
27.07%
MultiSource/Benchmarks/Fhourstones-3.1/fhourstones3.1
16.54%
MultiSource/Benchmarks/Olden/bh/bh
10.11%
MultiSource/Benchmarks/McCat/18-imp/imp
8.38%
SingleSource/Benchmarks/Misc-C++/Large/ray
6.54%
MultiSource/Benchmarks/Prolangs-C/bison/mybison
5.92%
MultiSource/Benchmarks/MallocBench/espresso/espresso
5.09%
-------------------------------------------------------------------------------------------------------------------------

LNT test suite, AArch64, Cortex-A57, -O3 -mcpu=cortex-a57
-fomit-frame-pointer
-------------------------------------------------------------------------------------------------------------------------
No significant performance improvements/regressions.

Code size regressions greater than 5%:
MultiSource/Benchmarks/MiBench/automotive-susan/automotive-susan
24.51%
MultiSource/Benchmarks/McCat/18-imp/imp
12.99%
MultiSource/Benchmarks/McCat/08-main/main Profile
8.63%
MultiSource/Benchmarks/Olden/bh/bh
8.30%
SingleSource/Benchmarks/Shootout-C++/Shootout-C++-hash
7.43%
SingleSource/Benchmarks/Misc-C++/bigfib
6.24%
MultiSource/Benchmarks/Fhourstones-3.1/fhourstones3.1
6.10%
MultiSource/Benchmarks/Prolangs-C/agrep/agrep
5.65%
MultiSource/Benchmarks/Ptrdist/yacr2/yacr2
5.01%
-------------------------------------------------------------------------------------------------------------------------

It can be seen there are the same benchmarks have code size regressed. Are
they known?
I am still trying to figure out what is wrong with the debug info.

Thanks,
Evgeny Astigeevich

From: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Date: Friday, 10 November 2017 at 21:28
To: Graham Yiu <gyiu at ca.ibm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
Tobias Grosser <tobias.grosser at inf.ethz.ch>
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Graham,

Thank you for offering help. I am trying to create a reproducer. The
problem is that the crashes happen whilst LTO is used. One thing I am sure
about IR is broken at compile time.

Thanks,
Evgeny

From: Graham Yiu <gyiu at ca.ibm.com>
Date: Friday, 10 November 2017 at 16:09
To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
Tobias Grosser <tobias.grosser at inf.ethz.ch>
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Evgeny,

I just realized that if these are compile-time errors I can help
investigate on my end. Do you have something I can use to reproduce?

Cheers,

Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com

Inactive hide details for Graham Yiu---11/08/2017 06:00:05 PM---Thanks,
Evgeny. Let me know if there's something in the partialGraham
Yiu---11/08/2017 06:00:05 PM---Thanks, Evgeny. Let me know if there's
something in the partial inlining code that is causing the is

From: Graham Yiu/Toronto/IBM
To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
"Tobias Grosser" <tobias.grosser at inf.ethz.ch>
Date: 11/08/2017 06:00 PM
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Thanks, Evgeny.

Let me know if there's something in the partial inlining code that is
causing the issue(s) you're seeing.

Cheers,

Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com

Inactive hide details for Evgeny Astigeevich ---11/08/2017 05:13:09 PM---Hi
Graham, I’ve almost finished my runs. However I’vEvgeny Astigeevich
---11/08/2017 05:13:09 PM---Hi Graham, I’ve almost finished my runs.
However I’ve got couple compiler crashes:

From: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
To: Graham Yiu <gyiu at ca.ibm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
"Tobias Grosser" <tobias.grosser at inf.ethz.ch>, nd <nd at arm.com>
Date: 11/08/2017 05:13 PM
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Graham,

I’ve almost finished my runs. However I’ve got couple compiler crashes:

!dbg attachment points at wrong subprogram for function
…
LLVM ERROR: Broken module found, compilation aborted!

This will take some time to investigate.

Thanks,
Evgeny Astigeevich

From: Graham Yiu <gyiu at ca.ibm.com>
Date: Tuesday, 7 November 2017 at 16:19
To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
Tobias Grosser <tobias.grosser at inf.ethz.ch>
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Evgeny,

When you think the experiments on armv7m and armv6m targets will be
complete? We're looking to turn this on sooner rather than later, if there
aren't objections from folks running on other platforms.

Cheers,

Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com

Inactive hide details for Graham Yiu---11/03/2017 12:40:10 PM---Hi Evgeny,
Yes, please do.  It was our hope that folks would veGraham Yiu---11/03/2017
12:40:10 PM---Hi Evgeny, Yes, please do. It was our hope that folks would
verify the impact of the partial inline

From: Graham Yiu/Toronto/IBM
To: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>,
Tobias Grosser <tobias.grosser at inf.ethz.ch>
Date: 11/03/2017 12:40 PM
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Evgeny,

Yes, please do. It was our hope that folks would verify the impact of the
partial inliner on the platforms they're currently working on.

Cheers,

Graham Yiu
LLVM Compiler Development
IBM Toronto Software Lab
Office: (905) 413-4077 C2-707/8200/Markham
Email: gyiu at ca.ibm.com

Inactive hide details for Evgeny Astigeevich ---11/03/2017 12:18:05
PM---Hi, We'd like to check impact on armv7m and armv6m tarEvgeny
Astigeevich ---11/03/2017 12:18:05 PM---Hi, We'd like to check impact on
armv7m and armv6m targets, especially code size. We have not tried

From: Evgeny Astigeevich <Evgeny.Astigeevich at arm.com>
To: Tobias Grosser <tobias.grosser at inf.ethz.ch>, Graham Yiu
<gyiu at ca.ibm.com>
Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>,
"llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>, nd <nd at arm.com>
Date: 11/03/2017 12:18 PM
Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi,

We'd like to check impact on armv7m and armv6m targets, especially code
size. We have not tried the partial inliner on them.

Could a decision to turn it on by default wait for results?

Thanks,

Evgeny Astigeevich

The Arm Compiler Optimization team

-----Original Message-----

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Tobias
Grosser via llvm-dev <llvm-dev at lists.llvm.org>

Reply-To: Tobias Grosser <tobias.grosser at inf.ethz.ch>

Date: Thursday, 2 November 2017 at 23:32

To: Graham Yiu <gyiu at ca.ibm.com>, "llvm-dev at lists.llvm.org"
<llvm-dev at lists.llvm.org>

Cc: "junbuml at codeaurora.org" <junbuml at codeaurora.org>

Subject: Re: [llvm-dev] [RFC] Enable Partial Inliner by default

Hi Graham,

I think this is a good idea. It is also useful for libquantum, where

together with some other changes, it enables Polly to perform libfusion.

The ARM people also played with the partial inliner and might have

feedback.

Best,

Tobias

On Thu, Nov 2, 2017, at 23:05, Graham Yiu via llvm-dev wrote:

>

> Forgot to add that all experiments were done with '-O3 -m64

> -fexperimental-new-pass-manager'.

>

> Graham Yiu

> LLVM Compiler Development

> IBM Toronto Software Lab

> Office: (905) 413-4077 C2-707/8200/Markham

> Email: gyiu at ca.ibm.com

>

>

>

> From: Graham Yiu/Toronto/IBM

> To: llvm-dev at lists.llvm.org

> Cc: junbuml at codeaurora.org, xinliangli at gmail.com

> Date: 11/02/2017 05:26 PM

> Subject: [RFC] Enable Partial Inliner by default

>

>

> Hello,

>

> I'd like to propose turning on the partial inliner

> (-enable-partial-inlining) by default.

>

> We've seen small gains on SPEC2006/2017 runtimes as well as lnt

> compile-times with a 2nd stage bootstrap of LLVM. We also saw positive

> gains on our internal workloads.

>

> -------------------------------------

> Brief description of Partial Inlining

> -------------------------------------

> A pass in opt that runs after the normal inlining pass. Looks for

> branches

> to a return block in the entry and immediate successor blocks of a

> function. If found, it outlines the rest of the function using the

> CodeExtractor. It then attempts to inline the leftover entry block (and

> possibly one or more of its successors) to all its callers. This

> effectively peels the early return block(s) into the caller, which could

> be

> executed without incurring the call overhead of the function just to

> return

> immediately. Inlining and call overhead cost, as well as branch

> probabilities of the return block(s) are taken into account before

> inlining

> is done. If inlining is not successful, then the changes are discarded.

>

> eg.

>

> void foo() {

> bar();

> // rest of the code in foo

> }

>

> void bar() {

> if (X)

> return;

> // rest of code (to be outlined)

> }

>

> After Partial Inlining:

>

> void foo() {

> if (!X)

> bar.outlined();

> // rest of the code in foo

> }

>

> void bar.outlined() {

> // rest of the code in bar

> }

>

>

> Here are the numbers on a Power8 PPCLE running Ubuntu 15.04 in ST-mode

>

> ----------------------------------------------

> Runtime performance (speed)

> ----------------------------------------------

> Workload Improvement

> -------- -----------

> SPEC2006(C/C++) 0.06% (geomean)

> SPEC2017(C/C++) 0.10% (geomean)

> ----------------------------------------------

> Compile time performance for Bootstrapped LLVM

> ----------------------------------------------

> Workload Improvement

> -------- -----------

> SPEC2006(C/C++) 0.41% (cumulative)

> SPEC2017(C/C++) -0.16% (cumulative)

> lnt 0.61% (geomean)

> ----------------------------------------------

> Compile time performance

> ----------------------------------------------

> Workload Increase

> -------- --------

> SPEC2006(C/C++) 1.31% (cumulative)

> SPEC2017(C/C++) 0.25% (cumulative)

> ----------------------------------------------

> Code size

> ----------------------------------------------

> Workload Increase

> -------- --------

> SPEC2006(C/C++) 3.90% (geomean)

> SPEC2017(C/C++) 1.05% (geomean)

>

> NOTE1: Code size increase in SPEC2006 was mainly attributed to benchmark

> "astar", which increased by 86%. Removing this outlier, we get a more

> reasonable increase of 0.58%.

>

> NOTE2: There is a patch up for review on Phabricator to enhance the

> partial

> inliner with the presence of profiling information (

>
https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D38190&d=DwIGaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=4ST7e3kMd0GTi3w9ByK5Cw&m=sY89ox2ivgmox5Vg311rAsEr4WFT-o-LRopDU9e7rl0&s=6o17wydYZM0l4kPAb3l3cJ95JRPoYb-3l4sHv-R0GaA&e=
).

>

>

> Graham Yiu

> LLVM Compiler Development

> IBM Toronto Software Lab

> Office: (905) 413-4077 C2-707/8200/Markham

> Email: gyiu at ca.ibm.com

>

> _______________________________________________

> LLVM Developers mailing list

> llvm-dev at lists.llvm.org

>
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