[Lldb-commits] [lldb] [lldb] Speed up SymbolContextList::AppendIfUnique (PR #181952)

[Michael Buch via lldb-commits]

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@@ -453,13 +456,20 @@ class SymbolContextList {
   ///     The zero based index into the symbol context list.
   ///
   /// \return
-  ///     A const reference to the symbol context to fill in.
-  SymbolContext &operator[](size_t idx) { return m_symbol_contexts[idx]; }
-
+  ///     A const reference to the symbol context.
   const SymbolContext &operator[](size_t idx) const {
     return m_symbol_contexts[idx];
   }
 
+  /// Replace the symbol in the symbol context at index \a idx.
+  ///
+  /// The symbol field is excluded from the hash and equality used by the
+  /// internal set, so this is the only mutation that is safe to perform on
+  /// an element that is already in the list.
+  void SetSymbolAtIndex(size_t idx, Symbol *symbol) {
+    const_cast<SymbolContext &>(m_symbol_contexts[idx]).symbol = symbol;
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Michael137 wrote:

Hmm what we'd want is an `insert_or_assign` method. Maybe that'd be not too difficult to contribute?

I don't think it's technically UB, but if we can avoid doing it that'd be great.

https://github.com/llvm/llvm-project/pull/181952