[PATCH] D123394: [CodeGen] Late cleanup of redundant address/immediate definitions.

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa added a comment.

In D123394#3595772 <https://reviews.llvm.org/D123394#3595772>, @asb wrote:

> @jonpa: From your perspective, what's the threshold on whether this should be added to the pass pipeline or not? A pass like this that always results in better code (as opposed to sometimes producing better, sometimes worse code) is attractive even if it triggers rarely. But obviously being too eager to add such code will hit compile time.

I think it should be enabled on targets where there is some kind of real performance improvement and compile time is not top-priority. If there are only static code-generation improvements that do not really make a difference in execution time, it seems better to leave it out. On SystemZ, there are just one or two slight performance improvements (~1%), enough to want to use it, I think.

Generally, loads of immediates and address anchors are easily done ahead of time on an OOO machine, so just because it is a nice cleanup doesn't mean it would be worth adding. I am hoping that the other targets would care to try it on benchmarks, and if there are then some more interest we could enable it for those targets.


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  https://reviews.llvm.org/D123394/new/

https://reviews.llvm.org/D123394