[llvm] [InstCombine] Generalize `icmp (shl nuw C2, Y), C -> icmp Y, C3` (PR #104696)

[via llvm-commits]

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@@ -2251,9 +2257,9 @@ static Instruction *foldICmpShlOne(ICmpInst &Cmp, Instruction *Shl,
         Pred = ICmpInst::ICMP_UGT;
     }
 
-    unsigned CLog2 = C.logBase2();
+    unsigned CLog2 = Div.logBase2();
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goldsteinn wrote:

Can you add a test where `C` and `C2` are not a power of two and we need to roundup the log? I.e
`(48 << X) u>= 144`?

I don't see the ceil logic for that case.

https://github.com/llvm/llvm-project/pull/104696