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

[Ramkumar Ramachandra 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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artagnon wrote:

That unfortunately doesn't work: LLVM automatically inserts an sext of i8 to the indextype for indexing into the GEP.

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