Revert "[DWARFLinker] Fix matching logic to remove type 1 missing off… (#151424)

…sets (#149618)"

This reverts commit ed940d7.

Author: DataCorrupted

llvm/lib/DWARFLinker/Classic/DWARFLinker.cpp

@@ -413,116 +413,6 @@ static bool isTlsAddressCode(uint8_t DW_OP_Code) {
          DW_OP_Code == dwarf::DW_OP_GNU_push_tls_address;
 }
 
-static void constructSeqOffsettoOrigRowMapping(
-    CompileUnit &Unit, const DWARFDebugLine::LineTable &LT,
-    DenseMap<size_t, unsigned> &SeqOffToOrigRow) {
-
-  // Use std::map for ordered iteration.
-  std::map<uint64_t, unsigned> LineTableMapping;
-
-  // First, trust the sequences that the DWARF parser did identify.
-  for (const DWARFDebugLine::Sequence &Seq : LT.Sequences)
-    LineTableMapping[Seq.StmtSeqOffset] = Seq.FirstRowIndex;
-
-  // Second, manually find sequence boundaries and match them to the
-  // sorted attributes to handle sequences the parser might have missed.
-  auto StmtAttrs = Unit.getStmtSeqListAttributes();
-  llvm::sort(StmtAttrs, [](const PatchLocation &A, const PatchLocation &B) {
-    return A.get() < B.get();
-  });
-
-  std::vector<size_t> SeqStartRows;
-  SeqStartRows.push_back(0);
-  for (auto [I, Row] : llvm::enumerate(ArrayRef(LT.Rows).drop_back()))
-    if (Row.EndSequence)
-      SeqStartRows.push_back(I + 1);
-
-  // While SeqOffToOrigRow parsed from CU could be the ground truth,
-  // e.g.
-  //
-  // SeqOff     Row
-  // 0x08        9
-  // 0x14       15
-  //
-  // The StmtAttrs and SeqStartRows may not match perfectly, e.g.
-  //
-  // StmtAttrs  SeqStartRows
-  // 0x04        3
-  // 0x08        5
-  // 0x10        9
-  // 0x12       11
-  // 0x14       15
-  //
-  // In this case, we don't want to assign 5 to 0x08, since we know 0x08
-  // maps to 9. If we do a dummy 1:1 mapping 0x10 will be mapped to 9
-  // which is incorrect. The expected behavior is ignore 5, realign the
-  // table based on the result from the line table:
-  //
-  // StmtAttrs  SeqStartRows
-  // 0x04        3
-  //   --        5
-  // 0x08        9 <- LineTableMapping ground truth
-  // 0x10       11
-  // 0x12       --
-  // 0x14       15 <- LineTableMapping ground truth
-
-  ArrayRef StmtAttrsRef(StmtAttrs);
-  ArrayRef SeqStartRowsRef(SeqStartRows);
-
-  // Dummy last element to make sure StmtAttrsRef and SeqStartRowsRef always
-  // run out first.
-  constexpr size_t DummyKey = UINT64_MAX;
-  constexpr unsigned DummyVal = UINT32_MAX;
-  LineTableMapping[DummyKey] = DummyVal;
-
-  for (auto [NextSeqOff, NextRow] : LineTableMapping) {
-    auto StmtAttrSmallerThanNext = [NextSeqOff](const PatchLocation &SA) {
-      return SA.get() < NextSeqOff;
-    };
-    auto SeqStartSmallerThanNext = [NextRow](const size_t &Row) {
-      return Row < NextRow;
-    };
-
-    // If both StmtAttrs and SeqStartRows points to value not in
-    // the LineTableMapping yet, we do a dummy one to one mapping and
-    // move the pointer.
-    while (!StmtAttrsRef.empty() && !SeqStartRowsRef.empty() &&
-           StmtAttrSmallerThanNext(StmtAttrsRef.front()) &&
-           SeqStartSmallerThanNext(SeqStartRowsRef.front())) {
-      SeqOffToOrigRow[StmtAttrsRef.consume_front().get()] =
-          SeqStartRowsRef.consume_front();
-    }
-    // One of the pointer points to the value at or past Next in the
-    // LineTableMapping, We move the pointer to re-align with the
-    // LineTableMapping
-    StmtAttrsRef = StmtAttrsRef.drop_while(StmtAttrSmallerThanNext);
-    SeqStartRowsRef = SeqStartRowsRef.drop_while(SeqStartSmallerThanNext);
-    // Use the LineTableMapping's result as the ground truth and move
-    // on.
-    if (NextSeqOff != DummyKey) {
-      SeqOffToOrigRow[NextSeqOff] = NextRow;
-    }
-    // Move the pointers if they are pointed at Next.
-    // It is possible that they point to later entries in LineTableMapping.
-    // Therefore we only increment the pointers after we validate they are
-    // pointing to the `Next` entry. e.g.
-    //
-    // LineTableMapping
-    // SeqOff      Row
-    // 0x08         9    <- NextSeqOff/NextRow
-    // 0x14        15
-    //
-    // StmtAttrs  SeqStartRows
-    // 0x14       13    <- StmtAttrsRef.front() / SeqStartRowsRef.front()
-    // 0x16       15
-    //  --        17
-    if (!StmtAttrsRef.empty() && StmtAttrsRef.front().get() == NextSeqOff)
-      StmtAttrsRef.consume_front();
-    if (!SeqStartRowsRef.empty() && SeqStartRowsRef.front() == NextRow)
-      SeqStartRowsRef.consume_front();
-  }
-}
-
 std::pair<bool, std::optional<int64_t>>
 DWARFLinker::getVariableRelocAdjustment(AddressesMap &RelocMgr,
                                         const DWARFDie &DIE) {
@@ -2407,12 +2297,8 @@ void DWARFLinker::DIECloner::generateLineTableForUnit(CompileUnit &Unit) {
 
         // Create a map of stmt sequence offsets to original row indices.
         DenseMap<uint64_t, unsigned> SeqOffToOrigRow;
-        // The DWARF parser's discovery of sequences can be incomplete. To
-        // ensure all DW_AT_LLVM_stmt_sequence attributes can be patched, we
-        // build a map from both the parser's results and a manual
-        // reconstruction.
-        if (!LT->Rows.empty())
-          constructSeqOffsettoOrigRowMapping(Unit, *LT, SeqOffToOrigRow);
+        for (const DWARFDebugLine::Sequence &Seq : LT->Sequences)
+          SeqOffToOrigRow[Seq.StmtSeqOffset] = Seq.FirstRowIndex;
 
         // Create a map of original row indices to new row indices.
         DenseMap<size_t, size_t> OrigRowToNewRow;