powerpc/ppc64: Allow allmodconfig to build (finally !)

[Alan Modra]

On Wed, May 14, 2014 at 08:34:30AM -0700, Guenter Roeck wrote:
> Bummer. Confirmed, if I replace "@h" with "@high" in just one place,
> the builds pass with binutils 2.24. Unfortunately the same builds then
> fails with binutils 2.23.
> 
> Any idea how to get it to compile with both old and new versions ?

The standard way with GNU software would be to write a configure test,
that checks for @high support in the assembler, and defines a macro
if the assembler passes the check.  I'm not that familiar with the
linux kernel these days, but a little grepping around says that
something like

ashigh := $(call as-instr,lis 9$(comma)foo at high,-DHAVE_AS_ATHIGH=1)
KBUILD_AFLAGS += $(ashigh)

might work.

> Is there some predefined constant which I could possibly use for
> something like
> 
> .if as_version_below_2.24_
> 	oris    reg,reg,(expr)@h;
> .else
> 	oris    reg,reg,(expr)@high;
> .endif
> 
> Thanks,
> Guenter

-- 
Alan Modra
Australia Development Lab, IBM