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

[Bin Meng]

Hi Stefan,

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?

Regards,
Bin