[PATCH] D45598: [DAGCombiner, PowerPC] allow X - (fpext(-Y) --> X + fpext(Y) with multiple uses

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In https://reviews.llvm.org/D45598#1067909, @nemanjai wrote:

> From the PPC perspective, this is fine since the sequences are equivalent. It also seems perfectly reasonable to look through a free operation here.


The sequence with fadd is better in theory because we've reduced the dependency chain (the fneg can execute in parallel now).

> However, I imagine that @escha might want to look at this as well and give the final approval.

There are follow-up comments in the post-commit thread for https://reviews.llvm.org/rL329821. The source of the problem for the original motivating case is unknown. But I think this change can't hurt that target, so I'll proceed with this one.


https://reviews.llvm.org/D45598