[llvm] [InstCombine] Added optimisation for trunc (Pow2 >> x) to i1 (PR #157030)

[Yingwei Zheng via llvm-commits]

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@@ -969,6 +971,27 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst &Trunc) {
     Changed = true;
   }
 
+  const APInt *C1;
+  Value *V1;
+  // trunc (lshr i8 C1, V1) to i1 -> icmp eq V1, sqrt(C1) iff C1 is power of 2
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dtcxzyw wrote:

It should be log2.

https://github.com/llvm/llvm-project/pull/157030