MIPS bootstrap fix (Was":SUBREG related reload fix)

[Jan Hubicka]

> May we have the patches causing the problems reversed until the
> problems are solved?  I'd like to have a successful mips-sgi-irix6.5
> gcc 3.1 nightly build to make sure other code changes are not causing
> problems.  (I cannot do this myself because I cannot figure out which
> of your recent patches affect SUBREGs.)
Majority of them. Thats the problem with reverting, as you would need
to revert many of them.

I will try to build mips native and try to figure out the bootstrap problem
today. Still believe that it is better to have bugs fixed, than keeping latent
problem by reverting patch.
Again, the problem is not in simplify_subreg code, rather it is bug in
gen_lowpart and operand_subword callers.

Honza
> 
> Thanks for your consideration,
> Jeffrey D. Oldham
> oldham@codesourcery.com