I completed re-testing everything.
It turns out I cannot reproduce the original error on gcc-4.4 (rev 173968)
So, I am submitting only the patch that I tested for gcc-4.5/4.6/4.7

Regression tested for e500mc target on:
4.5: Revision: 173928
4.6: Revision: 173936
trunk: Revision: 173966

The patch gcc.fix_rnreg4 applies directly to 4.6, 4.7 (1 line offset),
and 4.5 (-632 lines offset)

Thanks,
Edmar