llvm dev - Apr 2018 - [RFC] Turn the MachineOutliner on by default in AArch64 under -Oz

Hello

A 4.4% geomean codesize improvement is really impressive. That stuff is hard to
come by, you usually have to nibble away at it bit at a time. I ran some
codesize benchmarks we have and they were in the same ballpark. Some of these
are quite small so had less opportunity for outlining, but the average was still
over 3% with some as high as 9-10%.

All the tests I ran were fine, although we don't have a lot of -Oz AArch64
testing.

Thanks for working on this, we'll have to see about getting it working for
Arm code too!
Dave

Hi,

On 25 April 2018 at 14:02, David Green via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hello
>
> A 4.4% geomean codesize improvement is really impressive. That stuff is
hard to come by, you usually have to nibble away at it bit at a time. I ran some
codesize benchmarks we have and they were in the same ballpark. Some of these
are quite small so had less opportunity for outlining, but the average was still
over 3% with some as high as 9-10%.
>
> All the tests I ran were fine, although we don't have a lot of -Oz
AArch64 testing.
I made the same experiments during the last weeks inside Linaro and
got the same kind of figures.
> Thanks for working on this, we'll have to see about getting it working
for Arm code too!
Porting the outliner on ARM is in my plans for this year (as discussed
with other ARM folks at EuroLLVM last week), to avoid duplication is
it ok for you if I work on it, David, Jessica ?

Cheers,
Yvan
> Dave
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

> Porting the outliner on ARM is in my plans for this year (as discussed
> with other ARM folks at EuroLLVM last week), to avoid duplication is
> it ok for you if I work on it, David, Jessica ?

Sounds good to me; an ARM target would be great!

- Jessica
> On Apr 26, 2018, at 2:17 AM, Yvan Roux <yvan.roux at linaro.org>
wrote:
> 
> Hi,
> 
> On 25 April 2018 at 14:02, David Green via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Hello
>> 
>> A 4.4% geomean codesize improvement is really impressive. That stuff is
hard to come by, you usually have to nibble away at it bit at a time. I ran some
codesize benchmarks we have and they were in the same ballpark. Some of these
are quite small so had less opportunity for outlining, but the average was still
over 3% with some as high as 9-10%.
>> 
>> All the tests I ran were fine, although we don't have a lot of -Oz
AArch64 testing.
> 
> I made the same experiments during the last weeks inside Linaro and
> got the same kind of figures.
> 
>> Thanks for working on this, we'll have to see about getting it
working for Arm code too!
> 
> Porting the outliner on ARM is in my plans for this year (as discussed
> with other ARM folks at EuroLLVM last week), to avoid duplication is
> it ok for you if I work on it, David, Jessica ?
> 
> Cheers,
> Yvan
> 
>> Dave
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Also realized that outlining is generating non-unique symbol names, which
don't work well with orderfiles. Filed
https://bugs.llvm.org/show_bug.cgi?id=39526.

On Mon, Oct 29, 2018 at 11:54 AM, Andrew Grieve <agrieve at chromium.org>
wrote:
> Yvan - wondering if you've made any inroads with outlining for arm32?
>
> On Thu, Apr 26, 2018 at 5:17 AM, Yvan Roux via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> On 25 April 2018 at 14:02, David Green via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> > Hello
>> >
>> > A 4.4% geomean codesize improvement is really impressive. That
stuff is
>> hard to come by, you usually have to nibble away at it bit at a time. I
ran
>> some codesize benchmarks we have and they were in the same ballpark.
Some
>> of these are quite small so had less opportunity for outlining, but the
>> average was still over 3% with some as high as 9-10%.
>> >
>> > All the tests I ran were fine, although we don't have a lot of
-Oz
>> AArch64 testing.
>>
>> I made the same experiments during the last weeks inside Linaro and
>> got the same kind of figures.
>>
>> > Thanks for working on this, we'll have to see about getting it
working
>> for Arm code too!
>>
>> Porting the outliner on ARM is in my plans for this year (as discussed
>> with other ARM folks at EuroLLVM last week), to avoid duplication is
>> it ok for you if I work on it, David, Jessica ?
>>
>> Cheers,
>> Yvan
>>
>> > Dave
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > llvm-dev at lists.llvm.org
>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
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Hi Andrew,

On Mon, 29 Oct 2018 at 16:54, Andrew Grieve <agrieve at chromium.org>
wrote:
>
> Yvan - wondering if you've made any inroads with outlining for arm32?
Yes, I'll submit an RFC soon, my prototype works fine but I still have
a couple issues to tackle (some Thumb1 corner cases, PIC code
generation, ...) and enhance the testsuite.

Cheers,
Yvan
> On Thu, Apr 26, 2018 at 5:17 AM, Yvan Roux via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hi,
>>
>> On 25 April 2018 at 14:02, David Green via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> > Hello
>> >
>> > A 4.4% geomean codesize improvement is really impressive. That
stuff is hard to come by, you usually have to nibble away at it bit at a time. I
ran some codesize benchmarks we have and they were in the same ballpark. Some of
these are quite small so had less opportunity for outlining, but the average was
still over 3% with some as high as 9-10%.
>> >
>> > All the tests I ran were fine, although we don't have a lot of
-Oz AArch64 testing.
>>
>> I made the same experiments during the last weeks inside Linaro and
>> got the same kind of figures.
>>
>> > Thanks for working on this, we'll have to see about getting it
working for Arm code too!
>>
>> Porting the outliner on ARM is in my plans for this year (as discussed
>> with other ARM folks at EuroLLVM last week), to avoid duplication is
>> it ok for you if I work on it, David, Jessica ?
>>
>> Cheers,
>> Yvan
>>
>> > Dave
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > llvm-dev at lists.llvm.org
>> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>

Hi Yvan,

On Mon, 5 Nov 2018 at 10:11, Yvan Roux via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Yes, I'll submit an RFC soon, my prototype works fine but I still have
> a couple issues to tackle (some Thumb1 corner cases, PIC code
> generation, ...) and enhance the testsuite.
Any news on this? I'm starting to look into 32-bit ARM outlining too
and could probably help out with some of those corner cases.

Cheers.

Tim.