[BOLT][DWARF] Fix race conditions for debug fission in non-deterministic mode

Summary: Adding mutexes to avoid runtime race conditions.

(cherry picked from FBD33439854)

bolt/include/bolt/Core/DebugData.h

@@ -259,6 +259,8 @@ private:
   std::unordered_map<uint64_t, AddressForDWOCU> AddressMaps;
   /// Maps DWOID to offset within .debug_addr section.
   std::unordered_map<uint64_t, uint64_t> DWOIdToOffsetMap;
+  /// Mutex used for parallel processing of debug info.
+  std::mutex WriterMutex;
 };
 
 using DebugStrBufferVector = SmallVector<char, 16>;
@@ -278,6 +280,8 @@ public:
   bool isInitialized() const { return !StrBuffer->empty(); }
 
 private:
+  /// Mutex used for parallel processing of debug info.
+  std::mutex WriterMutex;
   /// Initializes Buffer and Stream.
   void initialize();
   /// Creats internal data stractures.

bolt/include/bolt/Rewrite/DWARFRewriter.h

@@ -69,9 +69,10 @@ class DWARFRewriter {
   std::mutex LocListDebugInfoPatchesMutex;
 
   /// Update debug info for all DIEs in \p Unit.
-  void updateUnitDebugInfo(uint64_t CUIndex, DWARFUnit &Unit,
+  void updateUnitDebugInfo(DWARFUnit &Unit,
                            DebugInfoBinaryPatcher &DebugInfoPatcher,
                            DebugAbbrevWriter &AbbrevWriter,
+                           DebugLocWriter &DebugLocWriter,
                            Optional<uint64_t> RangesBase = None);
 
   /// Patches the binary for an object's address ranges to be updated.
@@ -179,6 +180,7 @@ class DWARFRewriter {
   /// Helper function for creating and returning per-DWO patchers/writers.
   template <class T, class Patcher>
   Patcher *getBinaryDWOPatcherHelper(T &BinaryPatchers, uint64_t DwoId) {
+    std::lock_guard<std::mutex> Lock(DebugInfoPatcherMutex);
     auto Iter = BinaryPatchers.find(DwoId);
     if (Iter == BinaryPatchers.end()) {
       // Using make_pair instead of {} to work around bug in older version of
@@ -211,6 +213,7 @@ public:
   /// Creates abbrev writer for DWO unit with \p DWOId.
   DebugAbbrevWriter *createBinaryDWOAbbrevWriter(DWARFContext &Context,
                                                  uint64_t DWOId) {
+    std::lock_guard<std::mutex> Lock(DebugInfoPatcherMutex);
     auto &Entry = BinaryDWOAbbrevWriters[DWOId];
     Entry = std::make_unique<DebugAbbrevWriter>(Context, DWOId);
     return Entry.get();

bolt/lib/Core/DebugData.cpp

@@ -181,6 +181,7 @@ void DebugAddrWriter::AddressForDWOCU::dump() {
 }
 uint32_t DebugAddrWriter::getIndexFromAddress(uint64_t Address,
                                               uint64_t DWOId) {
+  std::lock_guard<std::mutex> Lock(WriterMutex);
   if (!AddressMaps.count(DWOId))
     AddressMaps[DWOId] = AddressForDWOCU();
 
@@ -199,6 +200,7 @@ uint32_t DebugAddrWriter::getIndexFromAddress(uint64_t Address,
 // update AddressToIndex and IndexToAddress
 void DebugAddrWriter::addIndexAddress(uint64_t Address, uint32_t Index,
                                       uint64_t DWOId) {
+  std::lock_guard<std::mutex> Lock(WriterMutex);
   AddressForDWOCU &Map = AddressMaps[DWOId];
   auto Entry = Map.find(Address);
   if (Entry != Map.end()) {
@@ -666,6 +668,7 @@ void DebugStrWriter::initialize() {
 }
 
 uint32_t DebugStrWriter::addString(StringRef Str) {
+  std::lock_guard<std::mutex> Lock(WriterMutex);
   if (StrBuffer->empty())
     initialize();
   auto Offset = StrBuffer->size();

bolt/lib/Rewrite/DWARFRewriter.cpp

@@ -223,6 +223,7 @@ void DWARFRewriter::updateDebugInfo() {
   // specified.
   std::unordered_map<std::string, uint32_t> NameToIndexMap;
   std::unordered_map<uint64_t, std::string> DWOIdToName;
+  std::mutex AccessMutex;
 
   auto updateDWONameCompDir = [&](DWARFUnit &Unit) -> void {
     const DWARFDie &DIE = Unit.getUnitDIE();
@@ -231,7 +232,13 @@ void DWARFRewriter::updateDebugInfo() {
     (void)AttrInfoVal;
     assert(AttrInfoVal && "Skeleton CU doesn't have dwo_name.");
 
-    std::string ObjectName = getDWOName(Unit, &NameToIndexMap, DWOIdToName);
+    std::string ObjectName = "";
+
+    {
+      std::lock_guard<std::mutex> Lock(AccessMutex);
+      ObjectName = getDWOName(Unit, &NameToIndexMap, DWOIdToName);
+    }
+
     uint32_t NewOffset = StrWriter->addString(ObjectName.c_str());
     DebugInfoPatcher->addLE32Patch(AttrInfoVal->Offset, NewOffset,
                                    AttrInfoVal->Size);
@@ -256,6 +263,7 @@ void DWARFRewriter::updateDebugInfo() {
     if (DWOId)
       SplitCU = BC.getDWOCU(*DWOId);
 
+    DebugLocWriter *DebugLocWriter = nullptr;
     // Skipping CUs that failed to load.
     if (SplitCU) {
       updateDWONameCompDir(*Unit);
@@ -264,8 +272,14 @@ void DWARFRewriter::updateDebugInfo() {
       // have same DWO ID.
       assert(LocListWritersByCU.count(*DWOId) == 0 &&
              "LocList writer for DWO unit already exists.");
-      LocListWritersByCU[*DWOId] =
-          std::make_unique<DebugLoclistWriter>(&BC, *DWOId);
+      {
+        std::lock_guard<std::mutex> Lock(AccessMutex);
+        DebugLocWriter =
+            LocListWritersByCU
+                .insert(
+                    {*DWOId, std::make_unique<DebugLoclistWriter>(&BC, *DWOId)})
+                .first->second.get();
+      }
       DebugInfoBinaryPatcher *DwoDebugInfoPatcher =
           llvm::cast<DebugInfoBinaryPatcher>(
               getBinaryDWODebugInfoPatcher(*DWOId));
@@ -278,16 +292,20 @@ void DWARFRewriter::updateDebugInfo() {
       DwoDebugInfoPatcher->addUnitBaseOffsetLabel((*SplitCU)->getOffset());
       DebugAbbrevWriter *DWOAbbrevWriter =
           createBinaryDWOAbbrevWriter((*SplitCU)->getContext(), *DWOId);
-      updateUnitDebugInfo(*DWOId, *(*SplitCU), *DwoDebugInfoPatcher,
-                          *DWOAbbrevWriter);
+      updateUnitDebugInfo(*(*SplitCU), *DwoDebugInfoPatcher, *DWOAbbrevWriter,
+                          *DebugLocWriter);
       DwoDebugInfoPatcher->clearDestinationLabels();
       if (!DwoDebugInfoPatcher->getWasRangBasedUsed())
         RangesBase = None;
     }
 
+    {
+      std::lock_guard<std::mutex> Lock(AccessMutex);
+      DebugLocWriter = LocListWritersByCU[CUIndex].get();
+    }
     DebugInfoPatcher->addUnitBaseOffsetLabel(Unit->getOffset());
-    updateUnitDebugInfo(CUIndex, *Unit, *DebugInfoPatcher, *AbbrevWriter,
-                        RangesBase);
+    updateUnitDebugInfo(*Unit, *DebugInfoPatcher, *AbbrevWriter,
+                        *DebugLocWriter, RangesBase);
   };
 
   if (opts::NoThreads || opts::DeterministicDebugInfo) {
@@ -318,13 +336,12 @@ void DWARFRewriter::updateDebugInfo() {
 }
 
 void DWARFRewriter::updateUnitDebugInfo(
-    uint64_t CUIndex, DWARFUnit &Unit, DebugInfoBinaryPatcher &DebugInfoPatcher,
-    DebugAbbrevWriter &AbbrevWriter, Optional<uint64_t> RangesBase) {
+    DWARFUnit &Unit, DebugInfoBinaryPatcher &DebugInfoPatcher,
+    DebugAbbrevWriter &AbbrevWriter, DebugLocWriter &DebugLocWriter,
+    Optional<uint64_t> RangesBase) {
   // Cache debug ranges so that the offset for identical ranges could be reused.
   std::map<DebugAddressRangesVector, uint64_t> CachedRanges;
 
-  auto &DebugLocWriter = *LocListWritersByCU[CUIndex].get();
-
   uint64_t DIEOffset = Unit.getOffset() + Unit.getHeaderSize();
   uint64_t NextCUOffset = Unit.getNextUnitOffset();
   DWARFDebugInfoEntry Die;