[llvm] [InstCombine] Canonicalize `icmp ult (add X, C2), C` expressions (PR #95649)

[Nikita Popov via llvm-commits]

================
@@ -3130,6 +3130,13 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp,
     return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C),
                         ConstantExpr::getNeg(cast<Constant>(Y)));
 
+  // X+C2 <u C -> (X & C) == 2C
+  //   iff C == -(C2)
+  //       C2 is a power of 2
+  if (Pred == ICmpInst::ICMP_ULT && C2->isPowerOf2() && (C == -(*C2)))
----------------
nikic wrote:

```suggestion
  if (Pred == ICmpInst::ICMP_ULT && C2->isPowerOf2() && C == -*C2)
```

https://github.com/llvm/llvm-project/pull/95649