[PATCH] D44683: [SelectionDAG] Removing FABS folding from DAGCombiner

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D44683#1044354, @arsenm wrote:

> There is supposed to be redundancy between instcombine and dagcombiner. Patterns can appear during lowering that won’t appear in instcombine


I agree that there should be partial redundancy between these passes, but if we are confident that a pattern should not be created, then trying to match it is just overhead.

In this case, we have ISD::FABS, so if there's some existing code that is creating compare and select when it could be creating FABS directly, then I think it should be fixed to not do that.


https://reviews.llvm.org/D44683