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

> 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

> 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 ?
Yeah, sounds great to me. I had merely got as far as looking at the AArch64 code
to see how easy it would be to copy, without any honest expectation of being
able to look into it properly any time soon. I imagine there are plenty of
pitfalls on Arm/Thumb that could make this difficult to get correct.

Thanks for working on it! Let us know how it goes and if we can do anything to
help.
Dave

On 26 April 2018 at 23:27, David Green <David.Green at arm.com>
wrote:
>> 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 ?
>
> Yeah, sounds great to me. I had merely got as far as looking at the AArch64
code to see how easy it would be to copy, without any honest expectation of
being able to look into it properly any time soon. I imagine there are plenty of
pitfalls on Arm/Thumb that could make this difficult to get correct.
yes I have the same feeling.
> Thanks for working on it! Let us know how it goes and if we can do anything
to help.
Ok great, sure I'll let you know.

Thanks
Yvan