[llvm-dev] Recent -Os code size regressions

Steve King via llvm-dev
Sat, 21 Nov 2015 00:00:42 -0000

On Thu, Nov 19, 2015 at 1:10 PM, Renato Golin <renato.golin at linaro.org>
wrote:
> On 19 November 2015 at 19:08, Steve King via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> Does the community have bots or humans tracking code size for -Os
>> builds?
>
> Hi Steve,
>
> I still haven't got around doing a CI for EEMBC or SPEC on ARM. I do
> track performance every release, but not code size at -Os.
>
>>  I've noticed troubling regressions lately.  Sometime near Nov
>> 5, the EEMBC bitmnp01 benchmark grew by 25% for ARMv7m and 35% for
>> i586.  That's ghastly.  This week, the EEMBC matrix01 workload grew
by
>> 5% for ARMv7m and 3% for i586.
>
> Hum, v7M is even lower priority for me at the moment. :)
>
> Though, I have to say, 25% is really bad. Can you bisect to see which
> commit was that?

Hi Renato, Thanks for advising.  The commit is:

[llvm] r252152 - [SimplifyCFG] Tweak heuristic for merging conditional stores

Can this be reverted until the surprising code size impact is
understood?  I'm about to leave for the week, so I can't delve further
anytime soon.

Regards,
-steve