[PATCH] D123408: [InstCombine] Limit folding of cast into PHI

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

In D123408#3570605 <https://reviews.llvm.org/D123408#3570605>, @syzaara wrote:

> @spatel Could you please provide some feedback about this change to InstCombine.

In general, making exceptions to transforms will not solve the general problem. I'm not sure if this is enough, but instcombine seems to miss a narrowing transform like this:
https://alive2.llvm.org/ce/z/hRy3rE

We do already have a variation of that fold, so it should be a small enhancement. I can take a shot at that.
A demanded bits solution within instcombine might be better, but I'm not seeing how to make that work in general since we have to create 3 instructions from the pattern.


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  https://reviews.llvm.org/D123408/new/

https://reviews.llvm.org/D123408