[lldb] [llvm] Add support for using foreign type units in .debug_names. (PR #87740)

[Pavel Labath via llvm-commits]

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@@ -64,6 +64,32 @@ class DWARFAcceleratorTable {
       return std::nullopt;
     }
 
+    /// Returns the type signature of the Type Unit associated with this
+    /// Accelerator Entry or std::nullopt if the Type Unit offset is not
+    /// recorded in this Accelerator Entry.
+    virtual std::optional<uint64_t> getForeignTUTypeSignature() const {
+      // Default return for accelerator tables that don't support type units.
+      return std::nullopt;
+    }
+
+    // Returns the the CU offset for a foreign TU.
+    //
+    // Entries that represent foreign type units can have both a
+    // DW_IDX_compile_unit and a DW_IDX_type_unit. In this case the
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labath wrote:

Reading about DW_IDX_compile_unit in a supposedly-generic interface feels a bit out of place. Do these even need to be defined on the interface? AFAICT, the only callers are in DebugNamesDWARFIndex, which already know they are dealing with a debug_names table, and the debug_names entry class already has a bunch of non-virtual methods (`hasParentInformation` and friends) for debug_names-specific functionality.

https://github.com/llvm/llvm-project/pull/87740