[PATCH] D122077: [InstCombine] Fold (ctpop(X) == 1) | (X == 0) into ctpop(X) < 2

[Dávid Bolvanský via Phabricator via cfe-commits]

xbolva00 added a comment.

In D122077#3413550 <https://reviews.llvm.org/D122077#3413550>, @joerg wrote:

> Why is this fold preferable to `(X & (X-1)) == 0`? At least on all architectures without native population count, the binary-and based test is preferable and it might even be better with it.

Less IR instructions. I think SDAG already expands some ctpop patterns to logic (backends should decide about optimal form)


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