On 03/07/17 14:23, Richard Earnshaw (lists) wrote:
> The existing code in arm/bpabi.h was quite fragile and relied on matching
> specific CPU and/or architecture names. The introduction of the option
> format for -mcpu and -march broke that in a way that would be non-trivial
> to fix by updating the list. The hook in that file was always a pain
> as it required every new CPU being added to be add an update here as well
> (easy to miss).
>
> I've fixed that problem once and for all by adding a new callback into
> the driver to select the correct BE8 behaviour. This uses features in
> the ISA capabilities list to select whether or not to use BE8 format
> during linking.
>
> I also noticed that if the user happened to pass both -mbig-endian and
> -mlittle-endian on the command line then the linker spec rules would
> get somewhat confused and potentially do the wrong thing. I've fixed that
> by marking these options as opposites in the option descriptions. The
> driver will now automatically suppress overridden options leading to the
> correct desired behavior.
>
> Whilst fixing this I noticed a couple of anomolus cases in the
> existing BE8 support: we were not generating BE8 format for ARMv6 or
> ARMv7-R targets. While the ARMv6 status was probably deliberate at
> the time, this is probably not a good idea in the long term as the
> alternative, BE32, has been deprecated by ARM. After discussion with
> a couple of colleagues I've decided to change this, but to then add an
> option to restore the existing behaviour at the user's option. So
> this patch introduces two new options (opposites) -mbe8 and -mbe32.
>
> This is a quiet behavior change, so I'll add a comment to the release
> notes shortly.
>
And this is the update to wwwdocs.
Index: htdocs/gcc-8/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-8/changes.html,v
retrieving revision 1.5
diff -p -r1.5 changes.html
*** htdocs/gcc-8/changes.html 20 Jun 2017 10:19:11 -0000 1.5
--- htdocs/gcc-8/changes.html 30 Jun 2017 15:25:58 -0000
*************** a work-in-progress.</h2>
*** 94,99 ****
--- 94,108 ----
setting unless the compiler has been configured with an explicit
<code>--with-fpu</code> option.
</li>
+ <li>
+ The default link behavior for ARMv6 and ARMv7-R targets has been
+ changed to produce BE8 format when generating big-endian images. A new
+ flag <code>-mbe32</code> can be used to force the linker to produce
+ legacy BE32 format images. There is no change of behavior for
+ ARMv6-m and other ARMv7 or later targets: these already defaulted
+ to BE8 format. This change brings GCC into alignment with other
+ compilers for the ARM architecture.
+ </li>
</ul>
<!-- <h3 id="avr">AVR</h3> -->
