Re: -march=native and build failures

On 08/25/2013 02:16 PM, Kinkie wrote:

> how about only enabling it on 32-bit builds and testing it out?
> If Large Rock needs it, then removing it altoghether is not a viable option.

To test out 64-bit atomics I was talking about, you may try to build the
Collapsed Forwarding branch on lp:

 https://code.launchpad.net/~measurement-factory/squid/collapsed-fwd

Building current trunk code would not test that aspect because the
current code does not use 64-bit atomics AFAIK. IIRC, they were removed
some time ago to avoid exactly these problems (it was possible to avoid
them by using smaller atomics back then).

HTH,

Alex.

> On Sun, Aug 25, 2013 at 10:04 PM, Alex Rousskov
> <rousskov_at_measurement-factory.com> wrote:
>> On 08/25/2013 01:08 PM, Kinkie wrote:
>>
>>> I've traced down at least some build failures to our use of -march=native.
>>> What apparently happens is that in some ocasions gcc emits some mmx
>>> instructions which fail with a SIGILL.
>>>
>>> We have a few choices:
>>> 1- leave the builds broken for now and try rework the code
>>> 2- add an --enable-extra-compiler-optimizations configure switch to
>>> optionally enable -march=native instead of unconditionally.
>>> 3- work around this on the broken nodes and on those only by using
>>> build trickery.
>>>
>>> Thoughts?
>>> I'd favor option 2'; we can then leave a specifically-broken build job
>>> so that when some change we make helps fix the build, we will know.
>>
>> IIRC, -march=native or similar was needed to build Squid on some 32-bit
>> systems. Without it, the build (linking) failed due to the lack of
>> 64-bit atomic operations if compiler assumes it needs to preserve
>> compatibility with much older 32 bit systems.
>>
>> Current trunk does not use such operations, but the pending Large Rock
>> and Collapsed Forward code do (because swap_file_sz that they need to
>> keep in sync across Squid kids is 64 bits).
>>
>> I hope this info helps you make the right decision but I do not know
>> enough about the related compiler options to pick the right choice among
>> the three offered.
>>
>>
>> Thank you,
>>
>> Alex.
>>
>
>
>
Received on Sun Aug 25 2013 - 20:43:31 MDT