[clang] [Clang] Reduce the size of Decl and classes derived from it (PR #87361)

[Nikolas Klauser via cfe-commits]

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@@ -268,17 +268,34 @@ class alignas(8) Decl {
   ///   }
   ///   void A::f(); // SemanticDC == namespace 'A'
   ///                // LexicalDC == global namespace
-  llvm::PointerUnion<DeclContext*, MultipleDC*> DeclCtx;
+  llvm::PointerIntPair<
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philnik777 wrote:

IDK. I'm personally not a huge fan of manual bit twiddling, since it's way to easy to get things wrong. I much rather let the compiler do it.

https://github.com/llvm/llvm-project/pull/87361