spatel added a comment. In D122077#3413565 <https://reviews.llvm.org/D122077#3413565>, @xbolva00 wrote:
> 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) Correct - we try to convert the setcc(ctpop) pattern here: https://github.com/llvm/llvm-project/blob/f1d8e46258c6a08ca1a375dc9670dd5581d6cf65/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp#L3772 That doesn't check whether the target has a popcount instruction for scalar types, so it is potentially too aggressive. For x86, we have a bonus optimization after that, so it should not show up there: https://godbolt.org/z/oc16Kdhcf Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D122077/new/ https://reviews.llvm.org/D122077 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
