[Bug driver/37551] New: gcc help should provide subarchitecture details

["martinrb at google dot com" <gcc-bugzilla at gcc dot gnu dot org>]

How do I find out whether a particular gcc supports a
particular subarchitecture, e.g. MMX instructions, by default?
If the gcc has been configured --with-arch=XXXX,
I can get that value using:
gcc -v --help 2>&1 | grep 'Configured with'

but if the arch has defaulted based on the target triplet,
it is less obvious.  Is it documented that
configure i486-xxxxxx
is equivalent to 
configure .... --with-arch=i486
?

Even better, it would be nice if gcc -v --help
said something like:
mmx support is enabled (use -mno-mmx to disable it)
sse support is disabled (use -msse to enable it)

I would have guessed gcc -dumpspecs would give me
this kind of information, but it appears not to.


-- 
           Summary: gcc help should provide subarchitecture details
           Product: gcc
           Version: 4.2.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: driver
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: martinrb at google dot com
  GCC host triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37551