[llvm] [PowerPC] Add flag to DAG combiner to improve compile time. (PR #86884)

[Stefan Pintilie via llvm-commits]

stefanp-ibm wrote:

> Can you give any more information on what nodes you are adding that causes such a problem? Are you adding a large number of TokenFactors or something?
> 
> I should also mention #83422 which will/would/maybe help with compile times in the DAG :)

Yes, there are quite a few TokenFactors in the test case. Also, we have noticed that reducing the `GatherAllAliasesMaxDepth` from 18 down to 9 seems to help. However, I'm not sure what kind of performance impact that would have. We are investigating in that direction at the moment.

https://github.com/llvm/llvm-project/pull/86884