[clang] [serialization] no transitive decl change (PR #92083)

[Chuanqi Xu via cfe-commits]

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@@ -124,6 +130,15 @@ class DeclIDBase {
 
   bool isInvalid() const { return ID == PREDEF_DECL_NULL_ID; }
 
+  unsigned getModuleFileIndex() const { return ID >> 32; }
+
+  unsigned getLocalDeclIndex() const {
+    // Implement it directly instead of calling `llvm::maskTrailingOnes` since
+    // we don't want `MathExtras.h` to be inclued here.
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ChuanqiXu9 wrote:

Maybe I just didn't want to create an implementation file for such a single simple function. But I just realized I can append it in `DeclBase.cpp` just like many other classes did. So done.

https://github.com/llvm/llvm-project/pull/92083