pa8000 fmpyfadd instruction help?

[Jerry Quinn]

Hi all.  Having put in place a minimal pa8000 schedule option (see
egcs-patches), I thought I'd try my hand at adding the fused multiply
accumulate instructions.  The first step is geting gas to recognize and
assemble them.

So far, I've added recognition of the .LEVEL 2.0 directive (although I
don't know how to tell if the obj file is correct), and I've added the
instruction to the list of hppa opcodes.  The problem I have at the
moment is that I can't tell how the bits for the addend are supposed to
be placed.  Unlike any other instruction, the addend register is split
into two sets of 3 bits, which makes it non-obvious where the L/R
selector is supposed to go.  I have the pa-risc 2.0 architecture book,
but it seems to be missing this little tidbit.

I'd guess that it goes in the lsb, similar to the other input operands,
but it's only a guess.

I may be in over my head, but I think the extrapolation approach will
work for this stuff.

If I get this working, I'll also add the FNEG and FNEGABS instructions.

-- 
Jerry Quinn                             Tel: (514) 761-8737
jquinn@nortelnetworks.com               Fax: (514) 761-8505
Speech Recognition Research