[llvm] DynamicAPInt: optimize size of structure (PR #97831)

[Ramkumar Ramachandra via llvm-commits]

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@@ -1895,6 +1896,9 @@ class [[nodiscard]] APInt {
   friend struct DenseMapInfo<APInt, void>;
   friend class APSInt;
 
+  // Make DynamicAPInt a friend so it can access BitWidth directly.
+  friend DynamicAPInt;
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artagnon wrote:

`friend class` doesn't seem to work, either with or without the forward declaration. Please see the difference between elaborated class specifiers and type specifiers: https://en.cppreference.com/w/cpp/language/friend.

https://github.com/llvm/llvm-project/pull/97831