Rebased and addressed comments

Author: grigorypas

bolt/include/bolt/Core/DebugData.h

@@ -858,14 +858,23 @@ class ClusteredRows {
   ArrayRef<DebugLineTableRowRef> getRows() const {
     return ArrayRef<DebugLineTableRowRef>(beginPtrConst(), Size);
   }
+
+  /// Returns the number of elements in the array.
   uint64_t size() const { return Size; }
+
+  /// We re-purpose SMLoc inside MCInst to store the pointer
+  /// to ClusteredRows. fromSMLoc() and toSMLoc() are helper
+  /// functions to convert between SMLoc and ClusteredRows.
+
   static const ClusteredRows *fromSMLoc(const SMLoc &Loc) {
     return reinterpret_cast<const ClusteredRows *>(Loc.getPointer());
   }
   SMLoc toSMLoc() const {
     return SMLoc::getFromPointer(reinterpret_cast<const char *>(this));
   }
 
+  /// Given a vector of DebugLineTableRowRef, this method
+  /// copies the elements into pre-allocated memory.
   template <typename T> void populate(const T Vec) {
     assert(Vec.size() == Size && "Sizes must match");
     DebugLineTableRowRef *CurRawPtr = beginPtr();
@@ -880,6 +889,8 @@ class ClusteredRows {
   DebugLineTableRowRef Rows;
 
   ClusteredRows(uint64_t Size) : Size(Size) {}
+
+  /// Total size of the object including the array.
   static uint64_t getTotalSize(uint64_t Size) {
     assert(Size > 0 && "Size must be greater than 0");
     return sizeof(ClusteredRows) + (Size - 1) * sizeof(DebugLineTableRowRef);

bolt/lib/Core/BinaryContext.cpp

@@ -1698,7 +1698,7 @@ void BinaryContext::preprocessDebugInfo() {
     }
     Function.addDWARFUnit(It->Unit);
 
-    // Go forward and add all units from ranges that cover the function
+    // Go forward and add all units from ranges that cover the function.
     while (++It != AllRanges.end()) {
       if (It->LowPC > FunctionAddress || FunctionAddress >= It->HighPC)
         break;

bolt/lib/Core/BinaryEmitter.cpp

@@ -178,7 +178,7 @@ class BinaryEmitter {
   /// marker in the line table program, but provides one to the DWARF generator
   /// when it needs it.
   void emitLineInfoEnd(const BinaryFunction &BF, MCSymbol *FunctionEndSymbol,
-                       DWARFUnit *Unit);
+                       const DWARFUnit &Unit);
 
   /// Emit debug line info for unprocessed functions from CUs that include
   /// emitted functions.
@@ -439,7 +439,7 @@ bool BinaryEmitter::emitFunction(BinaryFunction &Function,
 
   if (opts::UpdateDebugSections && !Function.getDWARFUnits().empty())
     for (const auto &[_, Unit] : Function.getDWARFUnits())
-      emitLineInfoEnd(Function, EndSymbol, Unit);
+      emitLineInfoEnd(Function, EndSymbol, *Unit);
 
   // Exception handling info for the function.
   emitLSDA(Function, FF);
@@ -707,13 +707,14 @@ SMLoc BinaryEmitter::emitLineInfo(const BinaryFunction &BF, SMLoc NewLoc,
                                CurrentRow.Discriminator);
     const MCDwarfLoc &DwarfLoc = BC.Ctx->getCurrentDwarfLoc();
     BC.Ctx->clearDwarfLocSeen();
-    auto &MapLineEntries = BC.getDwarfLineTable(TargetUnitIndex)
-                               .getMCLineSections()
-                               .getMCLineEntries();
+    const MCLineSection::MCLineDivisionMap &MapLineEntries =
+        BC.getDwarfLineTable(TargetUnitIndex)
+            .getMCLineSections()
+            .getMCLineEntries();
     const auto *It = MapLineEntries.find(Streamer.getCurrentSectionOnly());
-    auto NewLineEntry = MCDwarfLineEntry(&InstrLabel, DwarfLoc);
+    MCDwarfLineEntry NewLineEntry = MCDwarfLineEntry(&InstrLabel, DwarfLoc);
 
-    // Check if line table exists and has entries before doing comparison
+    // Check if line table exists and has entries before doing comparison.
     if (It != MapLineEntries.end() && !It->second.empty()) {
       // Check if the new line entry has the same debug info as the last one
       // to avoid duplicates. We don't compare labels since different
@@ -769,12 +770,11 @@ SMLoc BinaryEmitter::emitLineInfo(const BinaryFunction &BF, SMLoc NewLoc,
 
 void BinaryEmitter::emitLineInfoEnd(const BinaryFunction &BF,
                                     MCSymbol *FunctionEndLabel,
-                                    DWARFUnit *Unit) {
-  assert(Unit && "DWARF unit expected");
+                                    const DWARFUnit &Unit) {
   BC.Ctx->setCurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_END_SEQUENCE, 0, 0);
   const MCDwarfLoc &DwarfLoc = BC.Ctx->getCurrentDwarfLoc();
   BC.Ctx->clearDwarfLocSeen();
-  BC.getDwarfLineTable(Unit->getOffset())
+  BC.getDwarfLineTable(Unit.getOffset())
       .getMCLineSections()
       .addLineEntry(MCDwarfLineEntry(FunctionEndLabel, DwarfLoc),
                     Streamer.getCurrentSectionOnly());

bolt/test/perf2bolt/Inputs/perf_test.lds

@@ -1,12 +1,13 @@
 SECTIONS {
-  . = 0x400000 + SIZEOF_HEADERS;
+  . = SIZEOF_HEADERS;
   .interp : { *(.interp) }
   .note.gnu.build-id : { *(.note.gnu.build-id) }
+  . = 0x212e8;
   .dynsym         : { *(.dynsym) }
-  . = 0x801000;
+  . = 0x31860;
   .text : { *(.text*) }
-  . = 0x803000;
+  . = 0x41c20;
   .fini_array : { *(.fini_array) }
-  . = 0x805000;
+  . = 0x54e18;
   .data : { *(.data) }
-}
+}