[clang] [CIR] Add undef handling to enable global lambdas (PR #169721)

[Andy Kaylor via cfe-commits]

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@@ -591,6 +592,13 @@ mlir::Value CIRAttrToValue::visitCirAttr(cir::TypeInfoAttr typeInfoAttr) {
   return result;
 }
 
+/// UndefAttr visitor.
+mlir::Value CIRAttrToValue::visitCirAttr(cir::UndefAttr undefAttr) {
+  mlir::Location loc = parentOp->getLoc();
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andykaylor wrote:

Attributes are an uncommon thing in MLIR in that they don't have a location.

https://github.com/llvm/llvm-project/pull/169721