[llvm] [InstCombine] Infer zext nneg flag directly (PR #71906)

[Yingwei Zheng via llvm-commits]

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@@ -543,6 +543,8 @@ static Instruction *foldCttzCtlz(IntrinsicInst &II, InstCombinerImpl &IC) {
       auto *Cttz = IC.Builder.CreateBinaryIntrinsic(Intrinsic::cttz, X,
                                                     IC.Builder.getTrue());
       auto *ZextCttz = IC.Builder.CreateZExt(Cttz, II.getType());
+      if (auto *ZextInst = dyn_cast<PossiblyNonNegInst>(ZextCttz))
+        ZextInst->setNonNeg();
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dtcxzyw wrote:

It is correct for i1.
Alive2: https://alive2.llvm.org/ce/z/CvSF2z

https://github.com/llvm/llvm-project/pull/71906