Index: lldb/include/lldb/Core/ModuleList.h
===================================================================
--- lldb/include/lldb/Core/ModuleList.h
+++ lldb/include/lldb/Core/ModuleList.h
@@ -58,6 +58,7 @@
 
   FileSpec GetClangModulesCachePath() const;
   bool SetClangModulesCachePath(const FileSpec &path);
+  uint64_t GetDemanglingLimit() const;
   bool GetEnableExternalLookup() const;
   bool SetEnableExternalLookup(bool new_value);
   bool GetEnableLLDBIndexCache() const;
Index: lldb/source/Core/CoreProperties.td
===================================================================
--- lldb/source/Core/CoreProperties.td
+++ lldb/source/Core/CoreProperties.td
@@ -9,6 +9,10 @@
     Global,
     DefaultStringValue<"">,
     Desc<"The path to the clang modules cache directory (-fmodules-cache-path).">;
+  def DemanglingLimit: Property<"demangling-max-length", "UInt64">,
+    Global,
+    DefaultUnsignedValue<1000>,
+    Desc<"The maximum length of the mangled symbol name. Mangled symbols that exceed this threshold will not be demangled when indexing the symbol table. A value of 0 means no limit.">;
   def SymLinkPaths: Property<"debug-info-symlink-paths", "FileSpecList">,
     Global,
     DefaultStringValue<"">,
Index: lldb/source/Core/ModuleList.cpp
===================================================================
--- lldb/source/Core/ModuleList.cpp
+++ lldb/source/Core/ModuleList.cpp
@@ -125,6 +125,12 @@
       ->GetCurrentValue();
 }
 
+uint64_t ModuleListProperties::GetDemanglingLimit() const {
+  const uint32_t idx = ePropertyDemanglingLimit;
+  return m_collection_sp->GetPropertyAtIndexAsUInt64(
+      nullptr, idx, g_modulelist_properties[idx].default_uint_value);
+}
+
 bool ModuleListProperties::SetLLDBIndexCachePath(const FileSpec &path) {
   return m_collection_sp->SetPropertyAtIndexAsFileSpec(
       nullptr, ePropertyLLDBIndexCachePath, path);
Index: lldb/source/Symbol/Symtab.cpp
===================================================================
--- lldb/source/Symbol/Symtab.cpp
+++ lldb/source/Symbol/Symtab.cpp
@@ -297,11 +297,19 @@
     std::vector<std::pair<NameToIndexMap::Entry, const char *>> backlog;
     backlog.reserve(num_symbols / 2);
 
+    const uint64_t mangling_limit =
+        ModuleList::GetGlobalModuleListProperties().GetDemanglingLimit();
+
     // Instantiation of the demangler is expensive, so better use a single one
     // for all entries during batch processing.
     RichManglingContext rmc;
     for (uint32_t value = 0; value < num_symbols; ++value) {
       Symbol *symbol = &m_symbols[value];
+      Mangled &mangled = symbol->GetMangled();
+
+      if (mangling_limit)
+        if (mangled.GetMangledName().GetLength() > mangling_limit)
+          continue;
 
       // Don't let trampolines get into the lookup by name map If we ever need
       // the trampoline symbols to be searchable by name we can remove this and
@@ -314,7 +322,6 @@
 
       // If the symbol's name string matched a Mangled::ManglingScheme, it is
       // stored in the mangled field.
-      Mangled &mangled = symbol->GetMangled();
       if (ConstString name = mangled.GetMangledName()) {
         name_to_index.Append(name, value);