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Re: rs6000 fused multiply-add patch [+ patchlet]
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: dje at watson dot ibm dot com
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 6 Jan 03 17:10:33 EST
- Subject: Re: rs6000 fused multiply-add patch [+ patchlet]
I don't think that anyone is objecting to the concept and the benefit.
If I understand correctly, the patch violates the semantics of the
combiner algorithm which requires a declining cost calculated as the
number of instructions. Allowing combinations that do not decrease
the cost would make the algorithm non-deterministic and possibly not
converge, right?
That's what I'm saying, yes. I'm out of the country right now with poor
email access and will have more to say on this when I et bck in a few days.