Reorder/combine insns on superscalar arch

[Bernd Schmidt]

On 01/15/2016 07:05 AM, Jeff Law wrote:

> Well, you have to write the pattern and a splitter.  But these days
> there's define_insn_and_split to help with that.  Reusing Bernd's work
> may ultimately be easier though.

Maybe, but maybe also not in the way you think. I've always wanted the 
ability to combine 2->2 insns, for cases like this. The parallel would 
be split into two separate insns if it doesn't match. This would allow 
more complicated forms to be used if they are equally cheap, and can 
lead to elimination of instructions if it triggers more combinations.

I had a patch for this... 20 years ago. It was in pgcc for a while but 
apparently it had some bookkeeping problems. It would be nice to solve 
this at some point.


Bernd