[llvm] [DWARFLinker] Fix matching logic to remove type 1 missing offsets (PR #149618)

[Ellis Hoag via llvm-commits]

================
@@ -2297,8 +2297,133 @@ void DWARFLinker::DIECloner::generateLineTableForUnit(CompileUnit &Unit) {
 
         // Create a map of stmt sequence offsets to original row indices.
         DenseMap<uint64_t, unsigned> SeqOffToOrigRow;
-        for (const DWARFDebugLine::Sequence &Seq : LT->Sequences)
-          SeqOffToOrigRow[Seq.StmtSeqOffset] = Seq.FirstRowIndex;
+        DenseMap<uint64_t, unsigned> LineTableMapping;
+        // 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()) {
+          // 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 (size_t i = 0; i < LT->Rows.size() - 1; ++i)
----------------
ellishg wrote:

Oh, forgot to add `llvm::enumerate(...)`, you might need the `&`, I' not sure.


```
for (auto &[Index, Row] : llvm::enumerate(ArrayRef(LT->Rows).drop_back()))
```

https://github.com/llvm/llvm-project/pull/149618