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

Yvan Roux via llvm-dev llvm-dev at lists.llvm.org
Thu Apr 26 02:17:35 PDT 2018


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
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