[U-Boot] [PATCH v2] x86: lib: Implement standalone __udivdi3 etc instead of libgcc ones

[Stefan Roese]

Hi Bin,

On 29.11.2017 10:23, Bin Meng wrote:
> On Wed, Nov 29, 2017 at 4:42 PM, Stefan Roese <sr at denx.de> wrote:
>> Hi Bin,
>>
>> On 29.11.2017 09:30, Bin Meng wrote:
>>
>> <snip>
>>
>>>>> I wrote some codes soemthing like:
>>>>>
>>>>> s64 a, b, c;
>>>>> c = a/b;
>>>>>
>>>>> The compiler will generate codes to call __divdi3. This works before
>>>>> your
>>>>> patch.
>>>>
>>>>
>>>>
>>>> Yes, I understand this. But right now, we don't have any code
>>>> generating this error. And if this will happen at some time, I would
>>>> prefer to investigate this code sequence introducing this division, to
>>>> use the division functions / macros available in U-Boot (as mentioned
>>>> above) and in the kernel instead.
>>>>
>>>> Here a short explanation, why this new version is preferred to the
>>>> currently available functions pulled from libgcc: We are fixing an
>>>> "ugly" Yocto build problem with this patch, related to 32bit binaries
>>>> with 64bit toolchains (multilib) building by not relying on anything
>>>> from libgcc. Please see this thread for some more details:
>>>>
>>>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36721.html
>>>>
>>>> I hope this helps a bit to understand the motivation behind this patch.
>>>>
>>>
>>> Thanks for the background. I am not familiar with yocto project, but
>>> is the build broken due to the gcc on the build host does not ship
>>> with multilib?
>>
>>
>> Please take a look at the email thread mentioned above for a detailed
>> explanation. Especially this post should answer your questions:
>>
>> https://www.mail-archive.com/yocto@yoctoproject.org/msg36748.html
> 
> Now I see. Thank you.
> 
>>
>>> I am using a 64-bit host with gcc multilib, and there is no such build
>>> error observed.
>>
>>
>> Right. This issue is only seen on Yocto builds (AFAIK). But again,
>> I would really like to see U-Boot x86 being self-contained without
>> any host libgcc dependencies as on other architectures as well.
> 
> So to completely resolve such issue to make U-Boot self-contained, we
> should remove the reference to the host libgcc.a in
> arch/x86/lib/Makefile, and use CONFIG_USE_PRIVATE_GCC to include the
> build for div64.o. Thoughts?

I was under the impression, that I already removed the host libgcc
reference completely for x86 with my patch. But you are correct - there
still is a reference in this Makefile which is used by the standalone
code, AFAICT.

Any quick idea on how to rid of this one as well?

Thanks,
Stefan