[BOLT][DWARF] Add support for .debug_names

bolt/include/bolt/Core/BinaryContext.h

@@ -997,6 +997,10 @@ class BinaryContext {
     return getUniqueSectionByName(".gdb_index");
   }
 
+  ErrorOr<BinarySection &> getDebugNamesSection() const {
+    return getUniqueSectionByName(".debug_names");
+  }
+
   /// @}
 
   /// Register \p TargetFunction as a fragment of \p Function if checks pass:

bolt/include/bolt/Core/DIEBuilder.h

@@ -16,6 +16,7 @@
 #define BOLT_CORE_DIE_BUILDER_H
 
 #include "bolt/Core/BinaryContext.h"
+#include "bolt/Core/DebugNames.h"
 #include "llvm/CodeGen/DIE.h"
 #include "llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h"
 #include "llvm/DebugInfo/DWARF/DWARFDie.h"
@@ -127,6 +128,7 @@ class DIEBuilder {
   DWARFUnit *SkeletonCU{nullptr};
   uint64_t UnitSize{0};
   llvm::DenseSet<uint64_t> AllProcessed;
+  DWARF5AcceleratorTable &DebugNamesTable;
 
   /// Returns current state of the DIEBuilder
   State &getState() { return *BuilderState.get(); }
@@ -206,8 +208,8 @@ class DIEBuilder {
   /// Update references once the layout is finalized.
   void updateReferences();
 
-  /// Update the Offset and Size of DIE.
-  uint32_t computeDIEOffset(const DWARFUnit &CU, DIE &Die, uint32_t &CurOffset);
+  /// Update the Offset and Size of DIE, populate DebugNames table.
+  uint32_t finalizeDIEs(DWARFUnit &CU, DIE &Die, uint32_t &CurOffset);
 
   void registerUnit(DWARFUnit &DU, bool NeedSort);
 
@@ -269,6 +271,7 @@ class DIEBuilder {
 
 public:
   DIEBuilder(BinaryContext &BC, DWARFContext *DwarfContext,
+             DWARF5AcceleratorTable &DebugNamesTable,
              DWARFUnit *SkeletonCU = nullptr);
 
   /// Returns enum to what we are currently processing.

bolt/include/bolt/Core/DebugData.h

@@ -439,6 +439,8 @@ class DebugStrOffsetsWriter {
   /// Update Str offset in .debug_str in .debug_str_offsets.
   void updateAddressMap(uint32_t Index, uint32_t Address);
 
+  /// Get offset for given index in original .debug_str_offsets section.
+  uint64_t getOffset(uint32_t Index) const { return StrOffsets[Index]; }
   /// Writes out current sections entry into .debug_str_offsets.
   void finalizeSection(DWARFUnit &Unit, DIEBuilder &DIEBldr);
 
@@ -463,7 +465,7 @@ class DebugStrOffsetsWriter {
   std::unique_ptr<DebugStrOffsetsBufferVector> StrOffsetsBuffer;
   std::unique_ptr<raw_svector_ostream> StrOffsetsStream;
   std::map<uint32_t, uint32_t> IndexToAddressMap;
-  std::vector<uint32_t> StrOffsets;
+  SmallVector<uint32_t, 5> StrOffsets;
   std::unordered_map<uint64_t, uint64_t> ProcessedBaseOffsets;
   bool StrOffsetSectionWasModified = false;
 };
@@ -484,11 +486,12 @@ class DebugStrWriter {
   /// Returns False if no strings were added to .debug_str.
   bool isInitialized() const { return !StrBuffer->empty(); }
 
+  /// Initializes Buffer and Stream.
+  void initialize();
+
 private:
   /// Mutex used for parallel processing of debug info.
   std::mutex WriterMutex;
-  /// Initializes Buffer and Stream.
-  void initialize();
   /// Creates internal data structures.
   void create();
   std::unique_ptr<DebugStrBufferVector> StrBuffer;

bolt/include/bolt/Core/DebugNames.h

@@ -0,0 +1,172 @@
+//===- bolt/Core/DebugNames.h - Debug names support ---*- C++
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains declaration of classes required for generation of
+// .debug_names section.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef BOLT_CORE_DEBUG_NAMES_H
+#define BOLT_CORE_DEBUG_NAMES_H
+
+#include "DebugData.h"
+#include "llvm/CodeGen/AccelTable.h"
+
+namespace llvm {
+namespace bolt {
+class BOLTDWARF5AccelTableData : public DWARF5AccelTableData {
+public:
+  BOLTDWARF5AccelTableData(const uint64_t DieOffset,
+                           const std::optional<uint64_t> DefiningParentOffset,
+                           const unsigned DieTag, const unsigned UnitID,
+                           const bool IsTU,
+                           const std::optional<unsigned> SecondUnitID)
+      : DWARF5AccelTableData(DieOffset, DefiningParentOffset, DieTag, UnitID,
+                             IsTU),
+        SecondUnitID(SecondUnitID) {}
+
+  uint64_t getDieOffset() const { return DWARF5AccelTableData::getDieOffset(); }
+  unsigned getDieTag() const { return DWARF5AccelTableData::getDieTag(); }
+  unsigned getUnitID() const { return DWARF5AccelTableData::getUnitID(); }
+  bool isTU() const { return DWARF5AccelTableData::isTU(); }
+  std::optional<unsigned> getSecondUnitID() const { return SecondUnitID; }
+
+private:
+  std::optional<unsigned> SecondUnitID;
+};
+
+class DWARF5AcceleratorTable {
+public:
+  DWARF5AcceleratorTable(const bool CreateDebugNames, BinaryContext &BC,
+                         DebugStrWriter &MainBinaryStrWriter);
+  ~DWARF5AcceleratorTable() {
+    for (DebugNamesAbbrev *Abbrev : AbbreviationsVector)
+      Abbrev->~DebugNamesAbbrev();
+  }
+  /// Add DWARF5 Accelerator table entry.
+  /// Input is DWARFUnit being processed, DIE that belongs to it, and potential
+  /// SkeletonCU if the Unit comes from a DWO section.
+  void addAccelTableEntry(DWARFUnit &Unit, const DIE &Die,
+                          const std::optional<uint64_t> &DWOID);
+  /// Set current unit being processed.
+  void setCurrentUnit(DWARFUnit &Unit, const uint64_t UnitStartOffset);
+  /// Emit Accelerator table.
+  void emitAccelTable();
+  /// Returns true if the table was crated.
+  bool isCreated() const { return NeedToCreate; }
+  /// Returns buffer containing the accelerator table.
+  std::unique_ptr<DebugBufferVector> releaseBuffer() {
+    return std::move(FullTableBuffer);
+  }
+
+private:
+  BinaryContext &BC;
+  bool NeedToCreate = false;
+  BumpPtrAllocator Allocator;
+  DebugStrWriter &MainBinaryStrWriter;
+  StringRef StrSection;
+  uint64_t CurrentUnitOffset = 0;
+  const DWARFUnit *CurrentUnit = nullptr;
+  std::unordered_map<uint32_t, uint32_t> AbbrevTagToIndexMap;
+
+  /// Represents a group of entries with identical name (and hence, hash value).
+  struct HashData {
+    uint64_t StrOffset;
+    uint32_t HashValue;
+    uint32_t EntryOffset;
+    std::vector<BOLTDWARF5AccelTableData *> Values;
+  };
+  using HashList = std::vector<HashData *>;
+  using BucketList = std::vector<HashList>;
+  /// Contains all the offsets of CUs.
+  SmallVector<uint32_t, 1> CUList;
+  /// Contains all the offsets of local TUs.
+  SmallVector<uint32_t, 1> LocalTUList;
+  /// Contains all the type hashes for split dwarf TUs.
+  SmallVector<uint64_t, 1> ForeignTUList;
+  using StringEntries =
+      MapVector<std::string, HashData, llvm::StringMap<unsigned>>;
+  StringEntries Entries;
+  /// FoldingSet that uniques the abbreviations.
+  FoldingSet<DebugNamesAbbrev> AbbreviationsSet;
+  /// Vector containing DebugNames abbreviations for iteration in order.
+  SmallVector<DebugNamesAbbrev *, 5> AbbreviationsVector;
+  /// The bump allocator to use when creating DIEAbbrev objects in the uniqued
+  /// storage container.
+  BumpPtrAllocator Alloc;
+  uint32_t BucketCount = 0;
+  uint32_t UniqueHashCount = 0;
+  uint32_t AbbrevTableSize = 0;
+  uint32_t CUIndexEncodingSize = 4;
+  uint32_t TUIndexEncodingSize = 4;
+  uint32_t AugmentationStringSize = 0;
+  dwarf::Form CUIndexForm = dwarf::DW_FORM_data4;
+  dwarf::Form TUIndexForm = dwarf::DW_FORM_data4;
+
+  BucketList Buckets;
+
+  std::unique_ptr<DebugBufferVector> FullTableBuffer;
+  std::unique_ptr<raw_svector_ostream> FullTableStream;
+  std::unique_ptr<DebugBufferVector> StrBuffer;
+  std::unique_ptr<raw_svector_ostream> StrStream;
+  std::unique_ptr<DebugBufferVector> EntriesBuffer;
+  std::unique_ptr<raw_svector_ostream> Entriestream;
+  std::unique_ptr<DebugBufferVector> AugStringBuffer;
+  std::unique_ptr<raw_svector_ostream> AugStringtream;
+  llvm::DenseMap<llvm::hash_code, uint64_t> StrCacheToOffsetMap;
+  // Contains DWO ID to CUList Index.
+  llvm::DenseMap<uint64_t, uint32_t> CUOffsetsToPatch;
+  /// Adds Unit to either CUList, LocalTUList or ForeignTUList.
+  /// Input Unit being processed, and DWO ID if Unit is being processed comes
+  /// from a DWO section.
+  void addUnit(DWARFUnit &Unit, const std::optional<uint64_t> &DWOID);
+  /// Returns number of buckets in .debug_name table.
+  ArrayRef<HashList> getBuckets() const { return Buckets; }
+  /// Get encoding for a given attribute.
+  std::optional<DWARF5AccelTable::UnitIndexAndEncoding>
+  getIndexForEntry(const BOLTDWARF5AccelTableData &Value) const;
+  /// Get encoding for a given attribute for second index.
+  /// Returns nullopt if there is no second index.
+  std::optional<DWARF5AccelTable::UnitIndexAndEncoding>
+  getSecondIndexForEntry(const BOLTDWARF5AccelTableData &Value) const;
+  /// Uniquify Entries.
+  void finalize();
+  /// Computes bucket count.
+  void computeBucketCount();
+  /// Populate Abbreviations Map.
+  void populateAbbrevsMap();
+  /// Write Entries.
+  void writeEntries();
+  /// Write an Entry.
+  void writeEntry(const BOLTDWARF5AccelTableData &Entry);
+  /// Write augmentation_string for BOLT.
+  void writeAugmentationString();
+  /// Emit out Header for DWARF5 Accelerator table.
+  void emitHeader() const;
+  /// Emit out CU list.
+  void emitCUList() const;
+  /// Emit out TU List. Combination of LocalTUList and ForeignTUList.
+  void emitTUList() const;
+  /// Emit buckets.
+  void emitBuckets() const;
+  /// Emit hashes for hash table.
+  void emitHashes() const;
+  /// Emit string offsets for hash table.
+  void emitStringOffsets() const;
+  /// Emit Entry Offsets for hash table.
+  void emitOffsets() const;
+  /// Emit abbreviation table.
+  void emitAbbrevs();
+  /// Emit entries.
+  void emitData();
+  /// Emit augmentation string.
+  void emitAugmentationString() const;
+};
+} // namespace bolt
+} // namespace llvm
+#endif

bolt/include/bolt/Rewrite/DWARFRewriter.h

@@ -11,6 +11,7 @@
 
 #include "bolt/Core/DIEBuilder.h"
 #include "bolt/Core/DebugData.h"
+#include "bolt/Core/DebugNames.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/CodeGen/DIE.h"
 #include "llvm/DWP/DWP.h"
@@ -140,8 +141,10 @@ class DWARFRewriter {
                             const std::list<DWARFUnit *> &CUs);
 
   /// Finalize debug sections in the main binary.
-  void finalizeDebugSections(DIEBuilder &DIEBlder, DIEStreamer &Streamer,
-                             raw_svector_ostream &ObjOS, CUOffsetMap &CUMap);
+  void finalizeDebugSections(DIEBuilder &DIEBlder,
+                             DWARF5AcceleratorTable &DebugNamesTable,
+                             DIEStreamer &Streamer, raw_svector_ostream &ObjOS,
+                             CUOffsetMap &CUMap);
 
   /// Patches the binary for DWARF address ranges (e.g. in functions and lexical
   /// blocks) to be updated.

bolt/lib/Core/CMakeLists.txt

@@ -20,6 +20,7 @@ add_llvm_library(LLVMBOLTCore
   BinaryFunctionProfile.cpp
   BinarySection.cpp
   DebugData.cpp
+  DebugNames.cpp
   DIEBuilder.cpp
   DynoStats.cpp
   Exceptions.cpp

bolt/lib/Core/DIEBuilder.cpp

@@ -19,20 +19,17 @@
 #include "llvm/DebugInfo/DWARF/DWARFTypeUnit.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
-#include "llvm/ObjectYAML/DWARFYAML.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/LEB128.h"
-#include "llvm/Support/ThreadPool.h"
-#include "llvm/Support/YAMLTraits.h"
 
 #include <algorithm>
 #include <cstdint>
 #include <memory>
 #include <mutex>
-#include <string>
+#include <optional>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -179,8 +176,10 @@ void DIEBuilder::constructFromUnit(DWARFUnit &DU) {
 }
 
 DIEBuilder::DIEBuilder(BinaryContext &BC, DWARFContext *DwarfContext,
+                       DWARF5AcceleratorTable &DebugNamesTable,
                        DWARFUnit *SkeletonCU)
-    : BC(BC), DwarfContext(DwarfContext), SkeletonCU(SkeletonCU) {}
+    : BC(BC), DwarfContext(DwarfContext), SkeletonCU(SkeletonCU),
+      DebugNamesTable(DebugNamesTable) {}
 
 static unsigned int getCUNum(DWARFContext *DwarfContext, bool IsDWO) {
   unsigned int CUNum = IsDWO ? DwarfContext->getNumDWOCompileUnits()
@@ -378,18 +377,20 @@ getUnitForOffset(DIEBuilder &Builder, DWARFContext &DWCtx,
   return nullptr;
 }
 
-uint32_t DIEBuilder::computeDIEOffset(const DWARFUnit &CU, DIE &Die,
-                                      uint32_t &CurOffset) {
+uint32_t DIEBuilder::finalizeDIEs(DWARFUnit &CU, DIE &Die,
+                                  uint32_t &CurOffset) {
   getState().DWARFDieAddressesParsed.erase(Die.getOffset());
   uint32_t CurSize = 0;
   Die.setOffset(CurOffset);
+  DebugNamesTable.addAccelTableEntry(
+      CU, Die, SkeletonCU ? SkeletonCU->getDWOId() : std::nullopt);
   for (DIEValue &Val : Die.values())
     CurSize += Val.sizeOf(CU.getFormParams());
   CurSize += getULEB128Size(Die.getAbbrevNumber());
   CurOffset += CurSize;
 
   for (DIE &Child : Die.children()) {
-    uint32_t ChildSize = computeDIEOffset(CU, Child, CurOffset);
+    uint32_t ChildSize = finalizeDIEs(CU, Child, CurOffset);
     CurSize += ChildSize;
   }
   // for children end mark.
@@ -404,12 +405,12 @@ uint32_t DIEBuilder::computeDIEOffset(const DWARFUnit &CU, DIE &Die,
 }
 
 void DIEBuilder::finish() {
-  auto computeOffset = [&](const DWARFUnit &CU,
-                           uint64_t &UnitStartOffset) -> void {
+  auto finalizeCU = [&](DWARFUnit &CU, uint64_t &UnitStartOffset) -> void {
     DIE *UnitDIE = getUnitDIEbyUnit(CU);
     uint32_t HeaderSize = CU.getHeaderSize();
     uint32_t CurOffset = HeaderSize;
-    computeDIEOffset(CU, *UnitDIE, CurOffset);
+    DebugNamesTable.setCurrentUnit(CU, UnitStartOffset);
+    finalizeDIEs(CU, *UnitDIE, CurOffset);
 
     DWARFUnitInfo &CurUnitInfo = getUnitInfoByDwarfUnit(CU);
     CurUnitInfo.UnitOffset = UnitStartOffset;
@@ -420,18 +421,18 @@ void DIEBuilder::finish() {
   // It's processed first when CU is registered so will be at the begginnig of
   // the vector.
   uint64_t TypeUnitStartOffset = 0;
-  for (const DWARFUnit *CU : getState().DUList) {
+  for (DWARFUnit *CU : getState().DUList) {
     // We process DWARF$ types first.
     if (!(CU->getVersion() < 5 && CU->isTypeUnit()))
       break;
-    computeOffset(*CU, TypeUnitStartOffset);
+    finalizeCU(*CU, TypeUnitStartOffset);
   }
 
-  for (const DWARFUnit *CU : getState().DUList) {
+  for (DWARFUnit *CU : getState().DUList) {
     // Skipping DWARF4 types.
     if (CU->getVersion() < 5 && CU->isTypeUnit())
       continue;
-    computeOffset(*CU, UnitSize);
+    finalizeCU(*CU, UnitSize);
   }
   if (opts::Verbosity >= 1) {
     if (!getState().DWARFDieAddressesParsed.empty())