(really Fortran patches)

[Joe Buck]

> The USE variant didn't use fmpysub because it couldn't find an independent 
> fmpy and fsub to issue together -- fmpyadd/fmpysub was a poor man's
> way to increase FP performance back in 1991.  It's still useful on
> most PAs, except the PA8000 based machines.

Well, in digital logic you can convert a multiplier into a multiply-add or
multiply-subtract unit almost for free (almost no timing or area penalty),
and they are common operations, so it does make sense even in a RISC view
of the world.  It's common for very small DSP cores to have such
instruction for this reason.