[cryptodev:master 130/134] aes_generic.c:undefined reference to `_restgpr_31_x'

[Arnd Bergmann]

On Fri, Jan 12, 2018 at 9:41 PM, Segher Boessenkool
<segher at kernel.crashing.org> wrote:
> On Fri, Jan 12, 2018 at 08:43:21PM +0100, Arnd Bergmann wrote:
>> On Fri, Jan 12, 2018 at 5:39 PM, Segher Boessenkool

>> We could theoretically work around it by turning that into
>> "#if defined(CONFIG_CC_OPTIMIZE_FOR_SIZE) ||
>> defined(CONFIG_CRYPTO_AES)", but that seems rather ugly.
>>
>> My earlier patch already tried to be more specific, turning very
>> specific optimizations off rather than moving from -O2 to -Os,
>> but that turned out to lead to significantly worse performance,
>> where -Os improved performance slightly. Is there a way
>> to ask powerpc compilers to use mostly -Os but not the
>> specific thing that makes it link to _restgpr_31_x?
>
> There is no such thing, sorry.  Would be very hard to implement, and
> older compilers will never get it, so it won't help you anyway :-(

We use -Os only for gcc-7.1 and higher, where it produces faster
code for AES and avoids running into
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356

> Maybe for now just enable it in crtsavres.S always, with a comment?
> That -Os workaround is hopefully not going to live long either...

It depends on whether or how soon someone comes up with a
better fix for PR83356.
gcc-8.0.0 is currently not affected by it, so we could limit the
workaround (and the hack in crtsavres.S) to gcc-7-only.

     Arnd