Revert "[CLANG][DWARF] Handle DIE offset collision in DW_IDX_parent"

llvm/include/llvm/CodeGen/AccelTable.h

@@ -257,38 +257,18 @@ class AppleAccelTableData : public AccelTableData {
 
 /// Helper class to identify an entry in DWARF5AccelTable based on their DIE
 /// offset and UnitID.
-struct OffsetAndUnitID {
-  uint64_t Offset = 0;
-  uint32_t UnitID = 0;
-  bool IsTU = false;
-  OffsetAndUnitID() = default;
-  OffsetAndUnitID(uint64_t Offset, uint32_t UnitID, bool IsTU)
-      : Offset(Offset), UnitID(UnitID), IsTU(IsTU) {}
-  uint64_t offset() const { return Offset; };
-  uint32_t unitID() const { return UnitID; };
-  bool isTU() const { return IsTU; }
-};
+struct OffsetAndUnitID : std::pair<uint64_t, uint32_t> {
+  using Base = std::pair<uint64_t, uint32_t>;
+  OffsetAndUnitID(Base B) : Base(B) {}
 
-template <> struct DenseMapInfo<OffsetAndUnitID> {
-  static inline OffsetAndUnitID getEmptyKey() {
-    OffsetAndUnitID Entry;
-    Entry.Offset = uint64_t(-1);
-    return Entry;
-  }
-  static inline OffsetAndUnitID getTombstoneKey() {
-    OffsetAndUnitID Entry;
-    Entry.Offset = uint64_t(-2);
-    return Entry;
-  }
-  static unsigned getHashValue(const OffsetAndUnitID &Val) {
-    return (unsigned)llvm::hash_combine(Val.offset(), Val.unitID(), Val.IsTU);
-  }
-  static bool isEqual(const OffsetAndUnitID &LHS, const OffsetAndUnitID &RHS) {
-    return LHS.offset() == RHS.offset() && LHS.unitID() == RHS.unitID() &&
-           LHS.IsTU == RHS.isTU();
-  }
+  OffsetAndUnitID(uint64_t Offset, uint32_t UnitID) : Base(Offset, UnitID) {}
+  uint64_t offset() const { return first; };
+  uint32_t unitID() const { return second; };
 };
 
+template <>
+struct DenseMapInfo<OffsetAndUnitID> : DenseMapInfo<OffsetAndUnitID::Base> {};
+
 /// The Data class implementation for DWARF v5 accelerator table. Unlike the
 /// Apple Data classes, this class is just a DIE wrapper, and does not know to
 /// serialize itself. The complete serialization logic is in the
@@ -297,11 +277,12 @@ class DWARF5AccelTableData : public AccelTableData {
 public:
   static uint32_t hash(StringRef Name) { return caseFoldingDjbHash(Name); }
 
-  DWARF5AccelTableData(const DIE &Die, const uint32_t UnitID, const bool IsTU);
+  DWARF5AccelTableData(const DIE &Die, const uint32_t UnitID,
+                       const bool IsTU = false);
   DWARF5AccelTableData(const uint64_t DieOffset,
                        const std::optional<uint64_t> DefiningParentOffset,
                        const unsigned DieTag, const unsigned UnitID,
-                       const bool IsTU)
+                       const bool IsTU = false)
       : OffsetVal(DieOffset), ParentOffset(DefiningParentOffset),
         DieTag(DieTag), AbbrevNumber(0), IsTU(IsTU), UnitID(UnitID) {}
 
@@ -315,7 +296,7 @@ class DWARF5AccelTableData : public AccelTableData {
   }
 
   OffsetAndUnitID getDieOffsetAndUnitID() const {
-    return {getDieOffset(), getUnitID(), isTU()};
+    return {getDieOffset(), UnitID};
   }
 
   unsigned getDieTag() const { return DieTag; }
@@ -341,7 +322,7 @@ class DWARF5AccelTableData : public AccelTableData {
     assert(isNormalized() && "Accessing DIE Offset before normalizing.");
     if (!ParentOffset)
       return std::nullopt;
-    return OffsetAndUnitID(*ParentOffset, getUnitID(), isTU());
+    return OffsetAndUnitID(*ParentOffset, getUnitID());
   }
 
   /// Sets AbbrevIndex for an Entry.
@@ -435,7 +416,7 @@ class DWARF5AccelTable : public AccelTable<DWARF5AccelTableData> {
       for (auto *Data : Entry.second.getValues<DWARF5AccelTableData *>()) {
         addName(Entry.second.Name, Data->getDieOffset(),
                 Data->getParentDieOffset(), Data->getDieTag(),
-                Data->getUnitID(), Data->isTU());
+                Data->getUnitID(), true);
       }
     }
   }

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -3592,8 +3592,7 @@ void DwarfDebug::addAccelNameImpl(
                "Kind is TU but CU is being processed.");
     // The type unit can be discarded, so need to add references to final
     // acceleration table once we know it's complete and we emit it.
-    Current.addName(Ref, Die, Unit.getUniqueID(),
-                    Unit.getUnitDie().getTag() == dwarf::DW_TAG_type_unit);
+    Current.addName(Ref, Die, Unit.getUniqueID());
     break;
   }
   case AccelTableKind::Default:

llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp

@@ -2247,20 +2247,17 @@ void DWARFLinker::emitAcceleratorEntriesForUnit(CompileUnit &Unit) {
         DebugNames.addName(
             Namespace.Name, Namespace.Die->getOffset(),
             DWARF5AccelTableData::getDefiningParentDieOffset(*Namespace.Die),
-            Namespace.Die->getTag(), Unit.getUniqueID(),
-            Unit.getOutputUnitDIE()->getTag() == dwarf::DW_TAG_type_unit);
+            Namespace.Die->getTag(), Unit.getUniqueID());
       for (const auto &Pubname : Unit.getPubnames())
         DebugNames.addName(
             Pubname.Name, Pubname.Die->getOffset(),
             DWARF5AccelTableData::getDefiningParentDieOffset(*Pubname.Die),
-            Pubname.Die->getTag(), Unit.getUniqueID(),
-            Unit.getOutputUnitDIE()->getTag() == dwarf::DW_TAG_type_unit);
+            Pubname.Die->getTag(), Unit.getUniqueID());
       for (const auto &Pubtype : Unit.getPubtypes())
         DebugNames.addName(
             Pubtype.Name, Pubtype.Die->getOffset(),
             DWARF5AccelTableData::getDefiningParentDieOffset(*Pubtype.Die),
-            Pubtype.Die->getTag(), Unit.getUniqueID(),
-            Unit.getOutputUnitDIE()->getTag() == dwarf::DW_TAG_type_unit);
+            Pubtype.Die->getTag(), Unit.getUniqueID());
     } break;
     }
   }

llvm/lib/DWARFLinker/Parallel/DWARFLinkerImpl.cpp

@@ -1356,10 +1356,9 @@ void DWARFLinkerImpl::emitDWARFv5DebugNamesSection(const Triple &TargetTriple) {
       case DwarfUnit::AccelType::Name:
       case DwarfUnit::AccelType::Namespace:
       case DwarfUnit::AccelType::Type: {
-        DebugNames->addName(
-            *DebugStrStrings.getExistingEntry(Info.String), Info.OutOffset,
-            std::nullopt /*ParentDIEOffset*/, Info.Tag, CU->getUniqueID(),
-            CU->getOutUnitDIE()->getTag() == dwarf::DW_TAG_type_unit);
+        DebugNames->addName(*DebugStrStrings.getExistingEntry(Info.String),
+                            Info.OutOffset, std::nullopt /*ParentDIEOffset*/,
+                            Info.Tag, CU->getUniqueID());
       } break;
 
       default: