Make SymbolFileDWARF::ParseLineTable use std::sort instead of insertion sort

Summary:
Motivation: When setting breakpoints in certain projects line sequences are frequently being inserted out of order.

Rather than inserting sequences one at a time into a sorted line table, store all the line sequences as we're building them up and sort and flatten afterwards.

Reviewers: jdoerfert, labath

Reviewed By: labath

Subscribers: teemperor, labath, mgrang, JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D72909

Author: Unnar Freyr Erlendsson

lldb/include/lldb/Symbol/LineTable.h

@@ -42,6 +42,12 @@ class LineTable {
   ///     The compile unit to which this line table belongs.
   LineTable(CompileUnit *comp_unit);
 
+  /// Construct with entries found in \a sequences.
+  ///
+  /// \param[in] sequences
+  ///     Unsorted list of line sequences.
+  LineTable(CompileUnit *comp_unit, std::vector<LineSequence *> &sequences);
+
   /// Destructor.
   ~LineTable();
 
@@ -64,11 +70,11 @@ class LineTable {
                        bool is_epilogue_begin, bool is_terminal_entry);
 
   // Used to instantiate the LineSequence helper class
-  LineSequence *CreateLineSequenceContainer();
+  static LineSequence *CreateLineSequenceContainer();
 
   // Append an entry to a caller-provided collection that will later be
   // inserted in this line table.
-  void AppendLineEntryToSequence(LineSequence *sequence, lldb::addr_t file_addr,
+  static void AppendLineEntryToSequence(LineSequence *sequence, lldb::addr_t file_addr,
                                  uint32_t line, uint16_t column,
                                  uint16_t file_idx, bool is_start_of_statement,
                                  bool is_start_of_basic_block,
@@ -259,6 +265,7 @@ class LineTable {
     public:
       LessThanBinaryPredicate(LineTable *line_table);
       bool operator()(const LineTable::Entry &, const LineTable::Entry &) const;
+      bool operator()(const LineSequence*, const LineSequence*) const;
 
     protected:
       LineTable *m_line_table;

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

@@ -1007,20 +1007,22 @@ bool SymbolFileDWARF::ParseLineTable(CompileUnit &comp_unit) {
   // FIXME: Rather than parsing the whole line table and then copying it over
   // into LLDB, we should explore using a callback to populate the line table
   // while we parse to reduce memory usage.
-  std::unique_ptr<LineTable> line_table_up =
-      std::make_unique<LineTable>(&comp_unit);
-  LineSequence *sequence = line_table_up->CreateLineSequenceContainer();
+  LineSequence *sequence = LineTable::CreateLineSequenceContainer();
+  std::vector<LineSequence *> sequences;
   for (auto &row : line_table->Rows) {
-    line_table_up->AppendLineEntryToSequence(
+    LineTable::AppendLineEntryToSequence(
         sequence, row.Address.Address, row.Line, row.Column, row.File,
         row.IsStmt, row.BasicBlock, row.PrologueEnd, row.EpilogueBegin,
         row.EndSequence);
     if (row.EndSequence) {
-      line_table_up->InsertSequence(sequence);
-      sequence = line_table_up->CreateLineSequenceContainer();
+      sequences.push_back(sequence);
+      sequence = LineTable::CreateLineSequenceContainer();
     }
   }
 
+  std::unique_ptr<LineTable> line_table_up =
+      std::make_unique<LineTable>(&comp_unit, sequences);
+
   if (SymbolFileDWARFDebugMap *debug_map_symfile = GetDebugMapSymfile()) {
     // We have an object file that has a line table with addresses that are not
     // linked. We need to link the line table and convert the addresses that

lldb/source/Symbol/LineTable.cpp

@@ -21,6 +21,17 @@ using namespace lldb_private;
 LineTable::LineTable(CompileUnit *comp_unit)
     : m_comp_unit(comp_unit), m_entries() {}
 
+LineTable::LineTable(CompileUnit *comp_unit, std::vector<LineSequence *> &sequences)
+    : m_comp_unit(comp_unit), m_entries() {
+  LineTable::Entry::LessThanBinaryPredicate less_than_bp(this);
+  std::sort(sequences.begin(), sequences.end(), less_than_bp);
+  for (auto *sequence : sequences) {
+    LineSequenceImpl *seq = reinterpret_cast<LineSequenceImpl *>(sequence);
+    m_entries.insert(m_entries.end(), seq->m_entries.begin(),
+      seq->m_entries.end());
+  }
+}
+
 // Destructor
 LineTable::~LineTable() {}
 
@@ -154,6 +165,13 @@ operator()(const LineTable::Entry &a, const LineTable::Entry &b) const {
 #undef LT_COMPARE
 }
 
+bool LineTable::Entry::LessThanBinaryPredicate::
+operator()(const LineSequence *sequence_a, const LineSequence *sequence_b) const {
+  auto *seq_a = static_cast<const LineSequenceImpl *>(sequence_a);
+  auto *seq_b = static_cast<const LineSequenceImpl *>(sequence_b);
+  return (*this)(seq_a->m_entries.front(), seq_b->m_entries.front());
+}
+
 uint32_t LineTable::GetSize() const { return m_entries.size(); }
 
 bool LineTable::GetLineEntryAtIndex(uint32_t idx, LineEntry &line_entry) {