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

[Alexander Yermolovich via llvm-commits]

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@@ -338,12 +339,42 @@ class DWARF5AccelTableData : public AccelTableData {
   std::variant<const DIE *, uint64_t> OffsetVal;
   std::optional<uint64_t> ParentOffset;
   uint32_t DieTag : 16;
-  uint32_t UnitID : 15;
+  uint32_t AbbrevID : 15;
   uint32_t IsTU : 1;
-
+  uint32_t UnitID;
   uint64_t order() const override { return getDieOffset(); }
 };
 
+class DebugNamesAbbrev : public FoldingSetNode {
+public:
+  uint32_t DieTag;
+  uint32_t Index;
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ayermolo wrote:

Not sure I follow. This is equivalent to DIEAbbrev, which also has a Number.
```
class DIEAbbrev : public FoldingSetNode {
  /// Unique number for node.
  unsigned Number = 0;

  /// Dwarf tag code.
  dwarf::Tag Tag;
  ```

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