rs6000 fused multiply-add patch [+ patchlet]

[Segher Boessenkool]

Richard Kenner wrote:
> 
>     Reducing the amount of rtl isn't the same as improving performance.
> 
> No, but unless the MD file has a serious problem, it is *one way* of
> improving performance.

I don't dispute that.

> There's no question that we don't current have a pass which is good at
> finding the simplest form of the RTL.  The idea is to move as much of
> combine as possible into simplify-rtx.c.

It's on my todo list (it's in the beginner projects list).

> Then combine is very small and other passes will do what you are
> trying to do.

Part of it, maybe.  But certainly not all, unless we run simplify
and combine over and over again until nothing changes anymore.


Segher