[llvm] [LLVM][DWARF] Change .debug_names abbrev to be an index (PR #81200)

[Alexander Yermolovich via llvm-commits]

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@@ -467,26 +427,43 @@ getFormForIdxParent(const DenseSet<OffsetAndUnitID> &IndexedOffsets,
   return dwarf::Form::DW_FORM_flag_present;
 }
 
+void DebugNamesAbbrev::Profile(FoldingSetNodeID &ID) const {
+  ID.AddInteger(DieTag);
+  for (const DebugNamesAbbrev::AttributeEncoding &Enc : AttrVect) {
+    ID.AddInteger(Enc.Index);
+    if (Enc.Index == dwarf::DW_IDX_parent)
+      ID.AddInteger(Enc.Form);
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ayermolo wrote:

For DW_IDX_parent it can be DW_FORM_flag_present or DW_FORM_ref4. It depends on a DIE. For all others form is unique per module.
For DW_IDX_die_offset it's always DW_IDX_die_offset.
For DW_IDX_compile_unit/DW_IDX_type_unit it can change based on size of CU/TU lists in the module. So DW_FORM_data{1,2,4}.

https://github.com/llvm/llvm-project/pull/81200