[llvm] Reduce llvm-gsymutil memory usage (PR #91023)

[via llvm-commits]

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@@ -257,6 +258,9 @@ class DWARFUnit {
 
   std::shared_ptr<DWARFUnit> DWO;
 
+  mutable llvm::sys::RWMutex m_cu_die_array_mutex;
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jeffreytan81 wrote:

These two do not align with the naming convention of other fields in this class.

https://github.com/llvm/llvm-project/pull/91023