[PATCH] Reorganize rs6000_rtx_costs

[Geoffrey Keating]

Roger Sayle <roger@eyesopen.com> writes:

At the moment, however, such optimization is premature;
> the rs6000 backend still thinks that "nand" and "nor" require
> two instructions, ...

Here's a thought.  The .md file already contains all the information
needed to get a nearly-perfect RTX_COSTS macro in the -Os case.  So
does the .md file for most other ports.  Would it be possible to use
that information?