[llvm] [LoopIdiom] Fix a DL-related crash in optimizeCRCLoop (PR #161509)

[Piotr Fusik via llvm-commits]

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@@ -1654,7 +1654,7 @@ bool LoopIdiomRecognize::optimizeCRCLoop(const PolynomialInfo &Info) {
                                     : LoByte(Builder, Indexer, "indexer.lo");
 
     // Always index into a GEP using the index type.
-    Indexer = Builder.CreateZExt(
+    Indexer = Builder.CreateZExtOrTrunc(
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pfusik wrote:

Let's just fix the problem that is reported. I would be suprised to see that LLVM targets 8-bit address space.

I now see that `CreateZExt` returns identity if the sizes match. Is the reported case starting with 32-bit indices for a 16-bit address space?

https://github.com/llvm/llvm-project/pull/161509