How to describe a FMAC insn

[Richard Kenner]

> Could someone give some hints of how to describe a FMAC (float mult and
> add) insn in machine description, it matches d = b*c+a, which is a four
> operands float instrution. With a glimp through the array optabs[] in
> genopinit.c, it seems no OP handler could match FMAC operation? 

Correct.  It isn't generated directly during RTL generation, but instead
created by the optimizer (combine) from add and multiply insns.