Fix problem with constant modulus

[Richard Kenner]

     This failure does not predate the expmed.c patch.  It is definitely
    introduced by the expmed.c patch.  Whether it is caused directly by
    the change or is a secondary effect hasn't been determined.

    I don't know of any issues with respect to register renaming on this
    port.

I was talking about Eric's report, which was a SIGSEGV.  You got an
assertion failure.  I'm not sure that these are the same.