[PATCH] D80175: [PowerPC][MachineCombiner] reassociate fma to expose more ILP

[Aaron H Liu via Phabricator via llvm-commits]

AaronLiu added a comment.

In D80175#2085326 <https://reviews.llvm.org/D80175#2085326>, @nemanjai wrote:

> In D80175#2081483 <https://reviews.llvm.org/D80175#2081483>, @AaronLiu wrote:
>
> > Can you add a hidden option with init false?  You can turn it true later on.
> >  So that people can try with your option off and on? Thanks!
>
>
> This is not adding a new optimization but is increasing the scope of an existing optimization. So I don't think it is appropriate to add an option to control only this aspect of this. If there is a use case for allowing the user to have fine grained control over which combiner patterns to use, then we can add an `enum` option. But we need to have justification for why that is needed.
>
> OTOH, I am not opposed to adding an option to turn off the machine combiner (i.e. change the value returned by `PPCInstrInfo::useMachineCombiner()`) - but that is orthogonal to this patch and can be done separately.


Thanks for the explanation!


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