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Re: (really Fortran patches)
- To: law at cygnus dot com
- Subject: Re: (really Fortran patches)
- From: Joe Buck <jbuck at synopsys dot com>
- Date: Thu, 23 Oct 97 12:18:16 PDT
- Cc: toon at moene dot indiv dot nluug dot nl, egcs at cygnus dot com
> 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.