[PATCH] D86468: [WIP][GlobalISel] CSE copies

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D86468#2234000 <https://reviews.llvm.org/D86468#2234000>, @paquette wrote:

> Shouldn't running the copy_prop combine post-legalization do the same thing as this?
>
> (AArch64 does this as of 7006bb69efb04f32e0a666e8a74f85d7fa745981 <https://reviews.llvm.org/rG7006bb69efb04f32e0a666e8a74f85d7fa745981>)

I thought the argument for having a CSEMIRBuilder is as a compile time improvement to avoid creating the instructions in the first place. I do think we are missing optimization combines during legalization though, copy propagation being among them.


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