[PATCH] D45862: [InstCombine] Relax restriction in foldSelectInstWithICmp for sake of smaller code size

[Sanjay Patel via Phabricator via llvm-commits]

spatel added reviewers: majnemer, efriedma, hfinkel, sanjoy.
spatel added a comment.

I don't think we should be doing any of these select-of-constant transforms in instcombine.

It's worse for code analysis, more IR instructions, and may be detrimental to perf. Think about the cases where a conditional move executes at the same speed as a simple add (Ryzen?) or we have profile data for the compare, so branch prediction is perfect.

There's lots of code that does this kind of thing in the DAG, and that's where I think it belongs (using target hooks as needed). There was some discussion about this on llvm-dev here:
https://groups.google.com/forum/#!topic/llvm-dev/pid_thv2X-A

So I think we should be removing some of these transforms from instcombine rather than adding to them.


https://reviews.llvm.org/D45862