[PATCH] D47831: [DAGCombiner] Recognize more patterns for ABS

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D47831#1123943, @kparzysz wrote:

> I see what you mean...  Adding the sub variant to instcombine, not dagcombine, and deleting all abs from dagcombine.  Yes, that should work.


Great - I'll add that (simple translation of https://reviews.llvm.org/D40984) if you're not already doing it.

I think nobody is ever quite sure when the IR improvements allow us to remove DAG folds, so we end up with largely dead code in the backend.

But Simon raises a point that has come up before - we should be producing ABS nodes in SelectionDAGBuilder similar to how we already produce MIN/MAX. We'll want to do that before deleting any DAGCombiner code.


Repository:
  rL LLVM

https://reviews.llvm.org/D47831