llvm dev - Jul 2015 - [LLVMdev] [Shrink-Wrapping] Request For Benchmarking: X86 and AArch64

Hi,

Shrink-wrapping capabilities, i.e., better placement of prologue and epilogue
sequences, landed in r236507 but are not yet enabled by default.

Since r236507 AArch64 is shrink-wrapping ready, meaning we can turn the pass on
for this target.
I’ve done the same for X86 in r 238293.

Now, I need your help to test and benchmark how shrink-wrapping perform on those
targets.

The goal is to decide whether or not the support is good enough to be enabled by
default.


** How Can I Test/Benchmark It? **

Add (-mllvm) -enable-shrink-wrap on your command line or patch the XXXConfigPass
to set EnableShrinkWrap to true.
Note the -enable-shrink-wrap=<bool> takes precedence over whatever is set
for EnableShrinkWrap.

Please report any problem specific to this optimization turned on. A PR with a
small IR to reproduce are appreciated.

Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite + specs for
Os and O3.


Thanks in advance for your help,
-Quentin

I've run it across a wide variety of server benchmarks we care about. Looks
like all the changes are in the noise across sandybridge and ivybridge
architectures.

No interesting performance changes (in either direction sadly).

I saw some very minor size fluctuations and dug into it. Turns out there
was a missed easy size optimization in it that Quentin has already
implemented based on our conversation on IRC.

As far as I can see, this is pure goodness. Let's turn it on.

On Wed, May 27, 2015 at 3:17 PM Quentin Colombet <qcolombet at apple.com>
wrote:
> Hi,
>
> Shrink-wrapping capabilities, i.e., better placement of prologue and
> epilogue sequences, landed in r236507 but are not yet enabled by default.
>
> Since r236507 AArch64 is shrink-wrapping ready, meaning we can turn the
> pass on for this target.
> I’ve done the same for X86 in r 238293.
>
> Now, I need your help to test and benchmark how shrink-wrapping perform on
> those targets.
>
> The goal is to decide whether or not the support is good enough to be
> enabled by default.
>
>
> ** How Can I Test/Benchmark It? **
>
> Add (-mllvm) -enable-shrink-wrap on your command line or patch the
> XXXConfigPass to set EnableShrinkWrap to true.
> Note the -enable-shrink-wrap=<bool> takes precedence over whatever is
set
> for EnableShrinkWrap.
>
> Please report any problem specific to this optimization turned on. A PR
> with a small IR to reproduce are appreciated.
>
> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
> specs for Os and O3.
>
>
> Thanks in advance for your help,
> -Quentin
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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Hi Quentin,

This is interesting, I was meaning to look at that at some point. Glad
you did it. :)

On 27 May 2015 at 23:14, Quentin Colombet <qcolombet at apple.com>
wrote:
> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
specs for Os and O3.
Which target?

cheers,
--renato

On 27 May 2015 at 23:14, Quentin Colombet <qcolombet at apple.com>
wrote:
> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
specs for Os and O3.
I just did a quick test-suite run on AArch64 and I'm getting 1% worse
overall in the benchmark set. There were cases over 50% worse
(TSVC/Equivalencing-dbl, TSVC/Symbolics-dbl,
Polybench/medley/reg_detect) and the best case was only 30% better
(ASC_Sequoia/IRSmk).

Geomean difference of compile time is within noise range.

On an a57 device for Spec2000 with -O3 I'm seeing no significant performance
changes across the board.  With that being said, I think this is pretty cool
stuff.  Thanks for working on this Quentin.

 Chad

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Renato Golin
Sent: Wednesday, July 15, 2015 8:13 AM
To: Quentin Colombet
Cc: LLVM Developers Mailing List
Subject: Re: [LLVMdev] [Shrink-Wrapping] Request For Benchmarking: X86 and
AArch64

On 27 May 2015 at 23:14, Quentin Colombet <qcolombet at apple.com>
wrote:
> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
specs for Os and O3.
I just did a quick test-suite run on AArch64 and I'm getting 1% worse
overall in the benchmark set. There were cases over 50% worse
(TSVC/Equivalencing-dbl, TSVC/Symbolics-dbl,
Polybench/medley/reg_detect) and the best case was only 30% better
(ASC_Sequoia/IRSmk).

Geomean difference of compile time is within noise range.

_______________________________________________
LLVM Developers mailing list
LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Renato,
> On Jul 15, 2015, at 2:21 AM, Renato Golin <renato.golin at
linaro.org> wrote:
> 
> Hi Quentin,
> 
> This is interesting, I was meaning to look at that at some point. Glad
> you did it. :)
You’re welcome :).
> 
> On 27 May 2015 at 23:14, Quentin Colombet <qcolombet at apple.com>
wrote:
>> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
specs for Os and O3.
> 
> Which target?
That was AArch64.

Cheers,
Q.
> 
> cheers,
> --renato

> On Jul 15, 2015, at 5:12 AM, Renato Golin <renato.golin at
linaro.org> wrote:
> 
> On 27 May 2015 at 23:14, Quentin Colombet <qcolombet at apple.com>
wrote:
>> Note: I’ve seem up to 4% runtime improvements on the LLVM test-suite +
specs for Os and O3.
> 
> I just did a quick test-suite run on AArch64 and I'm getting 1% worse
> overall in the benchmark set. There were cases over 50% worse
> (TSVC/Equivalencing-dbl, TSVC/Symbolics-dbl,
> Polybench/medley/reg_detect) and the best case was only 30% better
> (ASC_Sequoia/IRSmk).
Strange.

I haven’t seen that big swings and the overall performance difference was in the
noise but better.
Would you mind looking closer to the diff and file a PR or gave me the command
line to reproduce?

Thanks,
-Quentin
> 
> Geomean difference of compile time is within noise range.