[PATCH] D140649: [AArch64][SelectionDAG] Eliminates redundant zero-extension for 32-bit popcount

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I don't think this is right.  The high bits do in fact have to be zero; otherwise they affect the result of the uaddlv.

If you add a pattern to optimize "insertelement <2 x i32> zeroinitializer, i32 %x, i32 0", you should be able to leverage that for ctpop lowering.


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  https://reviews.llvm.org/D140649/new/

https://reviews.llvm.org/D140649