[PATCH] D29295: Move core RDF files from lib/Target/Hexagon to CodeGen

Hal Finkel via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Jan 30 21:04:24 PST 2017

hfinkel added a comment.

In https://reviews.llvm.org/D29295#660902, @MatzeB wrote:

> My intuition would be that needing/computing a full dataflow graph that late in the compilation process is a bad sign. Having said that this probably won't go away for Hexagon and sharing code between targets is a good idea. Do you know of any plans to use this in other targets?

I'm certainly interested in testing this for PowerPC, and I'm happy to see this as target independent code. There are certainly cases where we want to do transformations post-RA where this kind of information is helpful (e.g. where we do register scavenging, shrink wrapping, etc.), and I'm definitely open to the possibility that this is the right way to get it.

We should definitely address the question of "Why is this needed currently?". If you're using this for copy propagation and DCE, why do you have dead code post-RA that was not eliminated by our pre-RA DCE? Why do you have copy-propagation opportunities that present themselves only after RA? Does this mean that you/we're missing opportunities to make better RA decisions?

> Some random nitpicks following but I didn't really read the whole patch yet.



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