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

Alexander Holler
2011-01-01T18:47:51Z

Am 01.01.2011 19:25, schrieb Dirk Behme:
> 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?

No, sorry, I don't have a test case for consequent write* and I will
have to write one. I will do such, when testing gcc 4.5.2 (sometimes in
the next days).

Regards,

Alexander