[rs6000] Fix compare debug failure on AIX

[Eric Botcazou]

> I'm sorry that XCOFF debugging changes the generated code (only in the
> sense of allocating a frame), but that is a system dependency.  It's
> been this way for over 20 years.  I see no reason to produce worse
> code at -O0 when not debugging simply to make testcases happier.

You apparently read my previous message too quickly, this was reported to 
AdaCore on real code, i.e. someone opened a ticket and complained that the 
compiler was generating different code with and without -g for XCOFF.

Note that someone a little perverse could easily use this obvious defect to 
prevent the compiler from bootstrapping on AIX. ;-)

-- 
Eric Botcazou