[llvm] Add the 'initialized' attribute langref and support (PR #84803)

[Jan Voung via llvm-commits]

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@@ -226,6 +236,10 @@ class Attribute {
   /// attribute to be a ConstantRange attribute.
   ConstantRange getValueAsConstantRange() const;
 
+  /// Return the attribute's value as a const range list. This requires the
+  /// attribute to be a const range list attribute.
+  SmallVector<std::pair<int64_t, int64_t>, 16> getValueAsRanges() const;
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jvoung wrote:

Is it possible to return an ArrayRef instead of a copy? Will the underlying storage lifetime work out?

https://github.com/llvm/llvm-project/pull/84803