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

[Greg Clayton via llvm-commits]

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@@ -496,13 +496,29 @@ void DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
 }
 
 Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
-  if ((CUDieOnly && !DieArray.empty()) ||
-      DieArray.size() > 1)
-    return Error::success(); // Already parsed.
-
-  bool HasCUDie = !DieArray.empty();
-  extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
-
+  {
+    llvm::sys::ScopedReader Lock(m_cu_die_array_mutex);
+    if ((CUDieOnly && !DieArray.empty()) || DieArray.size() > 1)
+      return Error::success(); // Already parsed.
+  }
+  bool HasCUDie = false;
+  {
+    llvm::sys::ScopedWriter Lock(m_cu_die_array_mutex);
+    if ((CUDieOnly && !DieArray.empty()) || DieArray.size() > 1)
+      return Error::success(); // Already parsed.
+    HasCUDie = !DieArray.empty();
+    extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
+  }
+  {
+    llvm::sys::ScopedReader Lock(m_all_die_array_mutex);
+    if (DieArray.empty())
+      return Error::success();
+
+    // If CU DIE was just parsed, copy several attribute values from it.
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clayborg wrote:

This comment doesn't match what is happening. Is this from a copy/paste?

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