SUBTARGET_OPTIONS / SUBTARGET_SWITCHES with .opt

[Aldy Hernandez]

Hi Richard.

I've been converting the ppc options to use the .opt machinery, and
am confused as to how to approach subtargets.

What's the deal with these?

I need options only for certain subtargets.  For example, aix.h has
some options that should not be available by other targets.

I don't see anything relevant in options.texi, and I don't see any
converted backend that has this problem.

Should we just include the options for all subtargets, or should we
add generic functionality (I volunteer if so).

Or...am I missing something completely obvious?

Aldy