Compilation for ARM

[Stepan Dyatkovskiy]

Modern compilers forbid to use nested .fnstart constructions (actually 
nested ENTRY uses). But FreeBSD code has them in few places. For 
example, in arm/exception.S file (see swi_entry). I saw the comment 
nearby swi_exit definition, but now quite understand how it relates with 
nested ENTRY uses...
It looks like several entries were intruduced just because of 
alternative names for the same function. But I'm not sure...

Thanks!

-Stepan

Why we need them
Ian Lepore wrote:
> On Fri, 2014-06-13 at 22:20 +0600, Stepan Dyatkovskiy wrote:
>> Hi Ian,
>> Yup. I have done it with default options. That works fine. Thanks!
>>
>> But, currently we need to compare launch times for kernel that was
>> compiled with cortex-a9 options and for kernel that was compiled with
>> cortex-a15 options.
>>
>> The reason of doing that is some improvements in clang backend that
>> promises faster execution for (-mcpu=cortex-a15). So we would like to
>> check it on FreeBSD kernel, since we going to use this OS as base for
>> our applications.
>>
>> -Stepan
>
> I wonder if it is upset that the nesting is backwards, like
>
>    NP_ENTRY(btext)
>    ASENTRY_NP(_start)
>    ...
>    END(btext)
>    END(_start)
>
> Maybe try switching the order of the END macros?  If that doesn't help,
> try removing the btext macros completely, I don't think they're needed
> by anything these days.
>
> -- Ian
>
>