[Buildroot] [PATCH] package/kmsxx: work around gcc bug 85180

[Giulio Benetti]

Il 08/06/2019 14:46, Giulio Benetti ha scritto:
> Il 08/06/2019 13:51, Giulio Benetti ha scritto:
>> Hi Arnout, Thomas H.,
>>
>> Il 08/06/2019 12:56, Arnout Vandecappelle ha scritto:
>>>
>>>
>>> On 07/06/2019 09:19, Thomas Huth wrote:
>>>> Am Fri, 7 Jun 2019 08:39:07 +0200
>>>> schrieb Giulio Benetti <giulio.benetti at micronovasrl.com>:
>>>>
>>>>> Hello Thomas H.,
>>>>>
>>>>> adding Thomas P.+
>>>>>
>>>>> Il 07/06/2019 08:08, Thomas Huth ha scritto:
>>>>>> Am Thu,  6 Jun 2019 15:10:35 +0200
>>>>>> schrieb Giulio Benetti <giulio.benetti at micronovasrl.com>:
>>>>>>      
>>>>>>> With Microblaze Gcc version < 8.x the build hangs due to gcc bug
>>>>>>> 85180: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180. The bug
>>>>>>> shows up when building kmsxx with optimization but not when
>>>>>>> building with -O0. To work around this, if
>>>>>>> BR2_TOOLCHAIN_HAS_GCC_BUG_85180=y we force using -O0.
>>>>>>
>>>>>> According to the description in the bugzilla, the bug should also go
>>>>>> away when compiling with -fno-dse ... so wouldn't it be better to
>>>>>> use "-fno-dse" here instead of disabling the optimizations
>>>>>> completely?
>>>>>
>>>>> Honestly I've completely missed that possible solution and didn't
>>>>> even tested.
>>>>>
>>>>> Anyway it's been discussed on IRC channel to keep a common work
>>>>> around for every different GCC_BUG_*, so since many packages are
>>>>> affected by Bug 85180 and -O0 seemed to work every time Thomas P.
>>>>> suggested to always keep that flag as solution.
>>>
>>>     It's not the same solution for every GCC_BUG_* that we want, it is the same
>>> solution for every package. So we don't want to use -O2 -g0 in one package and
>>> -O0 in another package.
>>
>> Yes you'r right.
>>
>>>     If the -fno-dse also works, that would be an even better solution.
>>
>> Yes, I was thinking about it and you've beaten me on time :)
> 
> I've given a try with kmsxx using -fno-dse, unfortunately it's a NOK.
> -fno-dse still hangs while -O0 is ok.
> 
> Thomas H.:
> Can you please double check with this defconfig substituting '-O0' with
> '-fno-dse'?
> R2_microblazeel=y
> BR2_ENABLE_DEBUG=y
> BR2_TOOLCHAIN_BUILDROOT_LOCALE=y
> BR2_GCC_VERSION_4_9_X=y
> BR2_TOOLCHAIN_BUILDROOT_CXX=y
> BR2_PACKAGE_KMSXX=y
> 
> Thanks!
> 

Hmm, now it works...

I will check for every toolchain and every package affected by Gcc Bug 
85180 and if it's ok I proceed creating new patches.

-- 
Giulio Benetti
CTO

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