[BOLT][DWARF] Output DWO files as they are being processed

Changed how we handle writing out .dwo and .dwp files. We now write out DWO
sections sooner and destroy DIEBuilder. This should decrease memory footprint.

Ran on clang-17 build in debug mode with split-dwarf.
before
8:07.49 real,   664.62 user,    69.00 sys,      0 amem, 41601612 mmem
8:07.06 real,   669.60 user,    68.75 sys,      0 amem, 41822588 mmem
8:00.36 real,   664.14 user,    66.36 sys,      0 amem, 41561548 mmem

after
8:21.85 real,   682.23 user,    69.64 sys,      0 amem, 39379880 mmem
8:04.58 real,   671.62 user,    66.50 sys,      0 amem, 39735800 mmem
8:10.02 real,   680.67 user,    67.24 sys,       0 amem, 39662888 mmem

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D151908

Author: Alexander Yermolovich

bolt/include/bolt/Rewrite/DWARFRewriter.h

@@ -13,7 +13,10 @@
 #include "bolt/Core/DebugData.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/CodeGen/DIE.h"
+#include "llvm/DWP/DWP.h"
 #include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/Support/ToolOutputFile.h"
 #include <cstdint>
 #include <memory>
 #include <mutex>
@@ -45,6 +48,7 @@ class DWARFRewriter {
     uint64_t Length;
     uint64_t TUHash;
   };
+  using UnitMetaVectorType = std::vector<UnitMeta>;
 
 private:
   BinaryContext &BC;
@@ -88,15 +92,6 @@ class DWARFRewriter {
 
   std::mutex LocListDebugInfoPatchesMutex;
 
-  /// Dwo id specific its .debug_info.dwo section content.
-  std::unordered_map<uint64_t, std::string> DwoDebugInfoMap;
-
-  /// Dwo id specific its .debug_abbrev.dwo section content.
-  std::unordered_map<uint64_t, std::string> DwoDebugAbbrevMap;
-
-  /// Dwo id specific its .debug_types.dwo section content.
-  std::unordered_map<uint64_t, std::string> DwoDebugTypeMap;
-
   /// Dwo id specific its RangesBase.
   std::unordered_map<uint64_t, uint64_t> DwoRangesBase;
 
@@ -107,12 +102,6 @@ class DWARFRewriter {
   using GDBIndexTUEntryType = std::vector<GDBIndexTUEntry>;
   GDBIndexTUEntryType GDBIndexTUEntryVector;
 
-  using UnitMetaVectorType = std::vector<UnitMeta>;
-  using TUnitMetaDwoMapType = std::unordered_map<uint64_t, UnitMetaVectorType>;
-  using CUnitMetaDwoMapType = std::unordered_map<uint64_t, UnitMeta>;
-  CUnitMetaDwoMapType CUnitMetaDwoMap;
-  TUnitMetaDwoMapType TUnitMetaDwoMap;
-
   /// DWARFLegacy is all DWARF versions before DWARF 5.
   enum class DWARFVersion { DWARFLegacy, DWARF5 };
 
@@ -149,12 +138,6 @@ class DWARFRewriter {
   /// Rewrite .gdb_index section if present.
   void updateGdbIndexSection(CUOffsetMap &CUMap, uint32_t NumCUs);
 
-  /// Output .dwo files.
-  void writeDWOFiles(std::unordered_map<uint64_t, std::string> &DWOIdToName);
-
-  /// Output .dwp files.
-  void writeDWP(std::unordered_map<uint64_t, std::string> &DWOIdToName);
-
   /// DWARFDie contains a pointer to a DIE and hence gets invalidated once the
   /// embedded DIE is destroyed. This wrapper class stores a DIE internally and
   /// could be cast to a DWARFDie that is valid even after the initial DIE is
@@ -197,39 +180,8 @@ class DWARFRewriter {
   /// Update stmt_list for CUs based on the new .debug_line \p Layout.
   void updateLineTableOffsets(const MCAsmLayout &Layout);
 
-  /// Given a \p DWOId, return its DebugLocWriter if it exists.
-  DebugLocWriter *getDebugLocWriter(uint64_t DWOId) {
-    auto Iter = LocListWritersByCU.find(DWOId);
-    return Iter == LocListWritersByCU.end() ? nullptr
-                                            : LocListWritersByCU[DWOId].get();
-  }
-
-  StringRef getDwoDebugInfoStr(uint64_t DWOId) {
-    return DwoDebugInfoMap[DWOId];
-  }
-
-  StringRef getDwoDebugAbbrevStr(uint64_t DWOId) {
-    return DwoDebugAbbrevMap[DWOId];
-  }
-
-  StringRef getDwoDebugTypeStr(uint64_t DWOId) {
-    return DwoDebugTypeMap[DWOId];
-  }
-
   uint64_t getDwoRangesBase(uint64_t DWOId) { return DwoRangesBase[DWOId]; }
 
-  void setDwoDebugInfoStr(uint64_t DWOId, StringRef Str) {
-    DwoDebugInfoMap[DWOId] = Str.str();
-  }
-
-  void setDwoDebugAbbrevStr(uint64_t DWOId, StringRef Str) {
-    DwoDebugAbbrevMap[DWOId] = Str.str();
-  }
-
-  void setDwoDebugTypeStr(uint64_t DWOId, StringRef Str) {
-    DwoDebugTypeMap[DWOId] = Str.str();
-  }
-
   void setDwoRangesBase(uint64_t DWOId, uint64_t RangesBase) {
     DwoRangesBase[DWOId] = RangesBase;
   }
@@ -242,30 +194,37 @@ class DWARFRewriter {
     return GDBIndexTUEntryVector;
   }
 
-  /// Stores meta data for each CU per DWO ID. It's used to create cu-index for
-  /// DWARF5.
-  void addCUnitMetaEntry(const uint64_t DWOId, const UnitMeta &Entry) {
-    auto RetVal = CUnitMetaDwoMap.insert({DWOId, Entry});
-    if (!RetVal.second)
-      errs() << "BOLT-WARNING: [internal-dwarf-error]: Trying to set CU meta "
-                "data twice for DWOID: "
-             << Twine::utohexstr(DWOId) << ".\n";
-  }
+  using OverriddenSectionsMap = std::unordered_map<DWARFSectionKind, StringRef>;
+  /// Output .dwo files.
+  void writeDWOFiles(DWARFUnit &, const OverriddenSectionsMap &,
+                     const std::string &, DebugLocWriter &);
+  using KnownSectionsEntry = std::pair<MCSection *, DWARFSectionKind>;
+  struct DWPState {
+    std::unique_ptr<ToolOutputFile> Out;
+    std::unique_ptr<BinaryContext> TmpBC;
+    std::unique_ptr<MCStreamer> Streamer;
+    std::unique_ptr<DWPStringPool> Strings;
+    const MCObjectFileInfo *MCOFI = nullptr;
+    const DWARFUnitIndex *CUIndex = nullptr;
+    std::deque<SmallString<32>> UncompressedSections;
+    MapVector<uint64_t, UnitIndexEntry> IndexEntries;
+    MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
+    StringMap<KnownSectionsEntry> KnownSections;
+    uint32_t ContributionOffsets[8] = {};
+    uint32_t IndexVersion = 2;
+    uint64_t DebugInfoSize = 0;
+    uint16_t Version = 0;
+    bool IsDWP = false;
+  };
+  /// Init .dwp file
+  void initDWPState(DWPState &);
 
-  /// Stores meta data for each TU per DWO ID. It's used to create cu-index for
-  /// DWARF5.
-  void addTUnitMetaEntry(const uint64_t DWOId, const UnitMeta &Entry) {
-    TUnitMetaDwoMap[DWOId].emplace_back(Entry);
-  }
+  /// Write out .dwp File
+  void finalizeDWP(DWPState &);
 
-  /// Returns Meta data for TUs in offset increasing order.
-  UnitMetaVectorType &getTUnitMetaEntries(const uint64_t DWOId) {
-    return TUnitMetaDwoMap[DWOId];
-  }
-  /// Returns Meta data for TUs in offset increasing order.
-  const UnitMeta &getCUnitMetaEntry(const uint64_t DWOId) {
-    return CUnitMetaDwoMap[DWOId];
-  }
+  /// add content of dwo to .dwp file.
+  void updateDWP(DWARFUnit &, const OverriddenSectionsMap &, const UnitMeta &,
+                 UnitMetaVectorType &, DWPState &, DebugLocWriter &);
 };
 
 } // namespace bolt