[llvm] [MachineCopyPropagation] Detect and fix suboptimal instruction order to enable optimizations (PR #98087)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> So basically this dependency breaker already implements exactly what I have wrote here, but it isn't yet used?

I'm not quite sure in either part of the statement. We did use the dependency breaker with the new machine scheduler a few years ago in a downstream target, and it did eliminate some copies.

> Or it is rather that, there is this generic dependency breaking stuff that has to be extended to also find and resolve copy propagation related dependencies?

>From my recollection, it wasn't too difficult to attach the dependency breaker to the new scheduler, so it may worth a try, it might already be powerful enough.


https://github.com/llvm/llvm-project/pull/98087