[clang] [CIR] Fix getNewInitValue on string-literal arrays (PR #206538)

[Erich Keane via cfe-commits]

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@@ -1063,8 +1063,13 @@ static mlir::Attribute getNewInitValue(CIRGenModule &cgm, cir::GlobalOp newGlob,
   };
 
   if (auto oldArray = mlir::dyn_cast<cir::ConstArrayAttr>(oldInit)) {
-    mlir::Attribute newElements =
-        getNewInitElements(mlir::cast<mlir::ArrayAttr>(oldArray.getElts()));
+    // A ConstArrayAttr backed by a StringAttr (a string-literal initializer)
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erichkeane wrote:

This comment seems very incomplete, and this fix does as well.  Why would any non-array-attr be fine here?  Are there any other cases we need to consider?  

In fact, the example seems to be cir::ArrayAttr (vs an mlir::ArrayAttr) which could contain basically anything, and could very well contain global references, right?  So I think we actually DO need to handle those as well.

https://github.com/llvm/llvm-project/pull/206538