[llvm] [TableGen] Add a !listflatten operator to TableGen (PR #109346)

[Rahul Joshi via llvm-commits]

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@@ -987,6 +987,29 @@ Init *UnOpInit::Fold(Record *CurRec, bool IsFinal) const {
       }
     }
     break;
+
+  case LISTFLATTEN:
+    if (ListInit *LHSList = dyn_cast<ListInit>(LHS)) {
+      ListRecTy *InnerListTy = dyn_cast<ListRecTy>(LHSList->getElementType());
+      // list of non-lists, !listflatten() is a NOP.
+      if (!InnerListTy)
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jurahul wrote:

The nop case is handled here.

https://github.com/llvm/llvm-project/pull/109346