From: oliver <oohall@gmail.com>
To: "Martin Liška" <mliska@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>,
kbuild test robot <fengguang.wu@intel.com>,
kbuild-all@01.org, linux-mm@kvack.org,
Jason Baron <jbaron@akamai.com>,
Andrew Morton <akpm@linux-foundation.org>,
Balbir Singh <bsingharora@gmail.com>
Subject: Re: [memcg:auto-latest 238/243] include/linux/compiler-gcc.h:243:38: error: impossible constraint in 'asm'
Date: Mon, 1 Aug 2016 22:41:28 +1000 [thread overview]
Message-ID: <CAOSf1CG1OB+tQx=u5C5RSEFydPy4Rsa04L=Cwm4PfENWJa658A@mail.gmail.com> (raw)
In-Reply-To: <35a0878d-84bd-ad93-8810-23c861ed464e@suse.cz>
On Mon, Aug 1, 2016 at 9:27 PM, Martin Liška <mliska@suse.cz> wrote:
> On 08/01/2016 01:09 PM, Michal Hocko wrote:
>> [CC our gcc guy - I guess he has some theory for this]
>>
>> On Sun 31-07-16 14:11:25, Michal Hocko wrote:
>>> It seems that this has been already reported and Jason has noticed [1] that
>>> the problem is in the disabled optimizations:
>>>
>>> $ grep CRYPTO_DEV_UX500_DEBUG .config
>>> CONFIG_CRYPTO_DEV_UX500_DEBUG=y
>>>
>>> if I disable this particular option the code compiles just fine. I have
>>> no idea what is wrong about the code but it seems to depend on
>>> optimizations enabled which sounds a bit scrary...
>>>
>>> [1] http://www.spinics.net/lists/linux-mm/msg109590.html
>
> Hi.
>
> The difference is that w/o any optimization level, GCC doesn't make %c0 an
> intermediate integer operand [1] (see description of "i" constraint).
We recently hit a similar problem on ppc where the compiler couldn't
satisfy an "i" when it was wrapped in an function and optimisations
were disabled. The fix[1] was to change the function signature so that
it's arguments were explicitly const. I don't know enough about gcc to
tell if that behaviour is arch specific or not, but it's worth trying.
Oliver
[1] https://lists.ozlabs.org/pipermail/skiboot/2016-July/004061.html
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next prev parent reply other threads:[~2016-08-01 12:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-29 21:04 [memcg:auto-latest 238/243] include/linux/compiler-gcc.h:243:38: error: impossible constraint in 'asm' kbuild test robot
2016-07-31 12:11 ` Michal Hocko
2016-08-01 11:09 ` Michal Hocko
2016-08-01 11:27 ` Martin Liška
2016-08-01 12:41 ` oliver [this message]
2016-08-03 5:17 ` Balbir Singh
2016-08-02 15:18 ` Jason Baron
2016-08-01 15:00 ` Jason Baron
2016-08-01 15:29 ` Michal Hocko
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