[U-Boot] [PATCH v3] ARM: Avoid compiler optimization for usages of readb, writeb and friends.

Dirk Behme
2011-01-01T18:25:27Z

On 01.01.2011 18:52, Alexander Holler wrote:
> Hello,
>
> Am 01.01.2011 13:04, schrieb Dirk Behme:
>> On 22.12.2010 12:04, Alexander Holler wrote:
>>> gcc 4.5.1 seems to ignore (at least some) volatile definitions,
>>> avoid that as done in the kernel.
>>>
>>> Reading C99 6.7.3 8 and the comment 114) there, I think it is a bug of
>>> that
>>> gcc version to ignore the volatile type qualifier used e.g. in
>>> __arch_getl().
>>> Anyway, using a definition as in the kernel headers avoids such
>>> optimizations when
>>> gcc 4.5.1 is used.
>>>
>>> Maybe the headers as used in the current linux-kernel should be used,
>>> but to avoid large changes, I've just added a small change to the
>>> current headers.
>
>> Do you like to test the patch in the attachment? I named it 'v4'.
>>
>> After some thinking and testing, it seems to me that the volatile
>> optimization issue this patch shall fix is only with the readx()
>> macros.
>> So the idea is to drop all writex() changes done in the v3 version of
>> this patch. With dropping the writex() changes, we would drop all
>> issues
>> we discussed with e.g. the GCC statement-expression and the do while
>> workaround, too.
>
> I've come across a bug which reads as the problem might be fixed in
> gcc 4.5.2:
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45052
>
> I will test gcc 4.5.2 in the next days.

Have you been able to test v4 of the patch I sent with gcc 4.5.1?

Thanks

Dirk