Reduce llvm-gsymutil memory usage

Author: Arslan Khabutdinov

llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h

@@ -103,6 +103,7 @@ class DWARFContext : public DIContext {
     std::unique_ptr<DWARFDebugMacro>
     parseMacroOrMacinfo(MacroSecType SectionType);
 
+    virtual void doWorkThreadSafely(function_ref<void()> Work) = 0;
   };
   friend class DWARFContextState;
 
@@ -491,6 +492,10 @@ class DWARFContext : public DIContext {
   /// manually only for DWARF5.
   void setParseCUTUIndexManually(bool PCUTU) { ParseCUTUIndexManually = PCUTU; }
 
+  void doWorkThreadSafely(function_ref<void()> Work) {
+    State->doWorkThreadSafely(Work);
+  }
+
 private:
   void addLocalsForDie(DWARFCompileUnit *CU, DWARFDie Subprogram, DWARFDie Die,
                        std::vector<DILocal> &Result);

llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h

@@ -566,6 +566,9 @@ class DWARFUnit {
 
   Error tryExtractDIEsIfNeeded(bool CUDieOnly);
 
+  /// clearDIEs - Clear parsed DIEs to keep memory usage low.
+  void clearDIEs(bool KeepCUDie, bool KeepDWODies = false);
+
 private:
   /// Size in bytes of the .debug_info data associated with this compile unit.
   size_t getDebugInfoSize() const {
@@ -581,9 +584,6 @@ class DWARFUnit {
   void extractDIEsToVector(bool AppendCUDie, bool AppendNonCUDIEs,
                            std::vector<DWARFDebugInfoEntry> &DIEs) const;
 
-  /// clearDIEs - Clear parsed DIEs to keep memory usage low.
-  void clearDIEs(bool KeepCUDie);
-
   /// parseDWO - Parses .dwo file for current compile unit. Returns true if
   /// it was actually constructed.
   /// The \p AlternativeLocation specifies an alternative location to get

llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

@@ -622,7 +622,7 @@ class ThreadUnsafeDWARFContextState : public DWARFContext::DWARFContextState {
       return getNormalTypeUnitMap();
   }
 
-
+  void doWorkThreadSafely(function_ref<void()> Work) override { Work(); }
 };
 
 class ThreadSafeState : public ThreadUnsafeDWARFContextState {
@@ -738,6 +738,11 @@ class ThreadSafeState : public ThreadUnsafeDWARFContextState {
     std::unique_lock<std::recursive_mutex> LockGuard(Mutex);
     return ThreadUnsafeDWARFContextState::getTypeUnitMap(IsDWO);
   }
+
+  void doWorkThreadSafely(function_ref<void()> Work) override {
+    std::unique_lock<std::recursive_mutex> LockGuard(Mutex);
+    ThreadUnsafeDWARFContextState::doWorkThreadSafely(Work);
+  }
 };
 } // namespace
 

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -496,108 +496,114 @@ void DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
 }
 
 Error DWARFUnit::tryExtractDIEsIfNeeded(bool CUDieOnly) {
-  if ((CUDieOnly && !DieArray.empty()) ||
-      DieArray.size() > 1)
-    return Error::success(); // Already parsed.
-
-  bool HasCUDie = !DieArray.empty();
-  extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
-
-  if (DieArray.empty())
-    return Error::success();
-
-  // If CU DIE was just parsed, copy several attribute values from it.
-  if (HasCUDie)
-    return Error::success();
-
-  DWARFDie UnitDie(this, &DieArray[0]);
-  if (std::optional<uint64_t> DWOId =
-          toUnsigned(UnitDie.find(DW_AT_GNU_dwo_id)))
-    Header.setDWOId(*DWOId);
-  if (!IsDWO) {
-    assert(AddrOffsetSectionBase == std::nullopt);
-    assert(RangeSectionBase == 0);
-    assert(LocSectionBase == 0);
-    AddrOffsetSectionBase = toSectionOffset(UnitDie.find(DW_AT_addr_base));
-    if (!AddrOffsetSectionBase)
-      AddrOffsetSectionBase =
-          toSectionOffset(UnitDie.find(DW_AT_GNU_addr_base));
-    RangeSectionBase = toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0);
-    LocSectionBase = toSectionOffset(UnitDie.find(DW_AT_loclists_base), 0);
-  }
+  Error e = Error::success();
+  Context.doWorkThreadSafely([&] {
+    if ((CUDieOnly && !DieArray.empty()) ||
+        DieArray.size() > 1)
+      return; // Already parsed.
 
-  // In general, in DWARF v5 and beyond we derive the start of the unit's
-  // contribution to the string offsets table from the unit DIE's
-  // DW_AT_str_offsets_base attribute. Split DWARF units do not use this
-  // attribute, so we assume that there is a contribution to the string
-  // offsets table starting at offset 0 of the debug_str_offsets.dwo section.
-  // In both cases we need to determine the format of the contribution,
-  // which may differ from the unit's format.
-  DWARFDataExtractor DA(Context.getDWARFObj(), StringOffsetSection,
-                        IsLittleEndian, 0);
-  if (IsDWO || getVersion() >= 5) {
-    auto StringOffsetOrError =
-        IsDWO ? determineStringOffsetsTableContributionDWO(DA)
-              : determineStringOffsetsTableContribution(DA);
-    if (!StringOffsetOrError)
-      return createStringError(errc::invalid_argument,
-                               "invalid reference to or invalid content in "
-                               ".debug_str_offsets[.dwo]: " +
-                                   toString(StringOffsetOrError.takeError()));
-
-    StringOffsetsTableContribution = *StringOffsetOrError;
-  }
+    bool HasCUDie = !DieArray.empty();
+    extractDIEsToVector(!HasCUDie, !CUDieOnly, DieArray);
+
+    if (DieArray.empty())
+      return;
+
+    // If CU DIE was just parsed, copy several attribute values from it.
+    if (HasCUDie)
+      return;
+
+    DWARFDie UnitDie(this, &DieArray[0]);
+    if (std::optional<uint64_t> DWOId =
+            toUnsigned(UnitDie.find(DW_AT_GNU_dwo_id)))
+      Header.setDWOId(*DWOId);
+    if (!IsDWO) {
+      assert(AddrOffsetSectionBase == std::nullopt);
+      assert(RangeSectionBase == 0);
+      assert(LocSectionBase == 0);
+      AddrOffsetSectionBase = toSectionOffset(UnitDie.find(DW_AT_addr_base));
+      if (!AddrOffsetSectionBase)
+        AddrOffsetSectionBase =
+            toSectionOffset(UnitDie.find(DW_AT_GNU_addr_base));
+      RangeSectionBase = toSectionOffset(UnitDie.find(DW_AT_rnglists_base), 0);
+      LocSectionBase = toSectionOffset(UnitDie.find(DW_AT_loclists_base), 0);
+    }
+
+    // In general, in DWARF v5 and beyond we derive the start of the unit's
+    // contribution to the string offsets table from the unit DIE's
+    // DW_AT_str_offsets_base attribute. Split DWARF units do not use this
+    // attribute, so we assume that there is a contribution to the string
+    // offsets table starting at offset 0 of the debug_str_offsets.dwo section.
+    // In both cases we need to determine the format of the contribution,
+    // which may differ from the unit's format.
+    DWARFDataExtractor DA(Context.getDWARFObj(), StringOffsetSection,
+                          IsLittleEndian, 0);
+    if (IsDWO || getVersion() >= 5) {
+      auto StringOffsetOrError =
+          IsDWO ? determineStringOffsetsTableContributionDWO(DA)
+                : determineStringOffsetsTableContribution(DA);
+      if (!StringOffsetOrError) {
+        e = createStringError(errc::invalid_argument,
+                                "invalid reference to or invalid content in "
+                                ".debug_str_offsets[.dwo]: " +
+                                    toString(StringOffsetOrError.takeError()));
+        return;
+      }
+
+      StringOffsetsTableContribution = *StringOffsetOrError;
+    }
+
+    // DWARF v5 uses the .debug_rnglists and .debug_rnglists.dwo sections to
+    // describe address ranges.
+    if (getVersion() >= 5) {
+      // In case of DWP, the base offset from the index has to be added.
+      if (IsDWO) {
+        uint64_t ContributionBaseOffset = 0;
+        if (auto *IndexEntry = Header.getIndexEntry())
+          if (auto *Contrib = IndexEntry->getContribution(DW_SECT_RNGLISTS))
+            ContributionBaseOffset = Contrib->getOffset();
+        setRangesSection(
+            &Context.getDWARFObj().getRnglistsDWOSection(),
+            ContributionBaseOffset +
+                DWARFListTableHeader::getHeaderSize(Header.getFormat()));
+      } else
+        setRangesSection(&Context.getDWARFObj().getRnglistsSection(),
+                        toSectionOffset(UnitDie.find(DW_AT_rnglists_base),
+                                        DWARFListTableHeader::getHeaderSize(
+                                            Header.getFormat())));
+    }
 
-  // DWARF v5 uses the .debug_rnglists and .debug_rnglists.dwo sections to
-  // describe address ranges.
-  if (getVersion() >= 5) {
-    // In case of DWP, the base offset from the index has to be added.
     if (IsDWO) {
-      uint64_t ContributionBaseOffset = 0;
+      // If we are reading a package file, we need to adjust the location list
+      // data based on the index entries.
+      StringRef Data = Header.getVersion() >= 5
+                          ? Context.getDWARFObj().getLoclistsDWOSection().Data
+                          : Context.getDWARFObj().getLocDWOSection().Data;
       if (auto *IndexEntry = Header.getIndexEntry())
-        if (auto *Contrib = IndexEntry->getContribution(DW_SECT_RNGLISTS))
-          ContributionBaseOffset = Contrib->getOffset();
-      setRangesSection(
-          &Context.getDWARFObj().getRnglistsDWOSection(),
-          ContributionBaseOffset +
-              DWARFListTableHeader::getHeaderSize(Header.getFormat()));
-    } else
-      setRangesSection(&Context.getDWARFObj().getRnglistsSection(),
-                       toSectionOffset(UnitDie.find(DW_AT_rnglists_base),
-                                       DWARFListTableHeader::getHeaderSize(
-                                           Header.getFormat())));
-  }
+        if (const auto *C = IndexEntry->getContribution(
+                Header.getVersion() >= 5 ? DW_SECT_LOCLISTS : DW_SECT_EXT_LOC))
+          Data = Data.substr(C->getOffset(), C->getLength());
+
+      DWARFDataExtractor DWARFData(Data, IsLittleEndian, getAddressByteSize());
+      LocTable =
+          std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
+      LocSectionBase = DWARFListTableHeader::getHeaderSize(Header.getFormat());
+    } else if (getVersion() >= 5) {
+      LocTable = std::make_unique<DWARFDebugLoclists>(
+          DWARFDataExtractor(Context.getDWARFObj(),
+                            Context.getDWARFObj().getLoclistsSection(),
+                            IsLittleEndian, getAddressByteSize()),
+          getVersion());
+    } else {
+      LocTable = std::make_unique<DWARFDebugLoc>(DWARFDataExtractor(
+          Context.getDWARFObj(), Context.getDWARFObj().getLocSection(),
+          IsLittleEndian, getAddressByteSize()));
+    }
 
-  if (IsDWO) {
-    // If we are reading a package file, we need to adjust the location list
-    // data based on the index entries.
-    StringRef Data = Header.getVersion() >= 5
-                         ? Context.getDWARFObj().getLoclistsDWOSection().Data
-                         : Context.getDWARFObj().getLocDWOSection().Data;
-    if (auto *IndexEntry = Header.getIndexEntry())
-      if (const auto *C = IndexEntry->getContribution(
-              Header.getVersion() >= 5 ? DW_SECT_LOCLISTS : DW_SECT_EXT_LOC))
-        Data = Data.substr(C->getOffset(), C->getLength());
-
-    DWARFDataExtractor DWARFData(Data, IsLittleEndian, getAddressByteSize());
-    LocTable =
-        std::make_unique<DWARFDebugLoclists>(DWARFData, Header.getVersion());
-    LocSectionBase = DWARFListTableHeader::getHeaderSize(Header.getFormat());
-  } else if (getVersion() >= 5) {
-    LocTable = std::make_unique<DWARFDebugLoclists>(
-        DWARFDataExtractor(Context.getDWARFObj(),
-                           Context.getDWARFObj().getLoclistsSection(),
-                           IsLittleEndian, getAddressByteSize()),
-        getVersion());
-  } else {
-    LocTable = std::make_unique<DWARFDebugLoc>(DWARFDataExtractor(
-        Context.getDWARFObj(), Context.getDWARFObj().getLocSection(),
-        IsLittleEndian, getAddressByteSize()));
-  }
+    // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
+    // skeleton CU DIE, so that DWARF users not aware of it are not broken.
+  });
 
-  // Don't fall back to DW_AT_GNU_ranges_base: it should be ignored for
-  // skeleton CU DIE, so that DWARF users not aware of it are not broken.
-  return Error::success();
+  return e;
 }
 
 bool DWARFUnit::parseDWO(StringRef DWOAlternativeLocation) {
@@ -652,15 +658,20 @@ bool DWARFUnit::parseDWO(StringRef DWOAlternativeLocation) {
   return true;
 }
 
-void DWARFUnit::clearDIEs(bool KeepCUDie) {
-  // Do not use resize() + shrink_to_fit() to free memory occupied by dies.
-  // shrink_to_fit() is a *non-binding* request to reduce capacity() to size().
-  // It depends on the implementation whether the request is fulfilled.
-  // Create a new vector with a small capacity and assign it to the DieArray to
-  // have previous contents freed.
-  DieArray = (KeepCUDie && !DieArray.empty())
-                 ? std::vector<DWARFDebugInfoEntry>({DieArray[0]})
-                 : std::vector<DWARFDebugInfoEntry>();
+void DWARFUnit::clearDIEs(bool KeepCUDie, bool KeepDWODies) {
+  Context.doWorkThreadSafely([&] {
+    if (!KeepDWODies && DWO) {
+      DWO->clearDIEs(KeepCUDie, KeepDWODies);
+    }
+    // Do not use resize() + shrink_to_fit() to free memory occupied by dies.
+    // shrink_to_fit() is a *non-binding* request to reduce capacity() to size().
+    // It depends on the implementation whether the request is fulfilled.
+    // Create a new vector with a small capacity and assign it to the DieArray to
+    // have previous contents freed.
+    DieArray = (KeepCUDie && !DieArray.empty())
+                  ? std::vector<DWARFDebugInfoEntry>({DieArray[0]})
+                  : std::vector<DWARFDebugInfoEntry>();
+  });
 }
 
 Expected<DWARFAddressRangesVector>

llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp

@@ -656,6 +656,11 @@ Error DwarfTransformer::convert(uint32_t NumThreads, OutputAggregator &Out) {
       DWARFDie Die = getDie(*CU);
       CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
       handleDie(Out, CUI, Die);
+      // Release the line table, once we're done.
+      DICtx.clearLineTableForUnit(CU.get());
+      // Free any DIEs that were allocated by the DWARF parser.
+      // If/when they're needed by other CU's, they'll be recreated.
+      CU->clearDIEs(/*KeepCUDie=*/false, /*KeepDWODIEs=*/false);
     }
   } else {
     // LLVM Dwarf parser is not thread-safe and we need to parse all DWARF up
@@ -668,24 +673,23 @@ Error DwarfTransformer::convert(uint32_t NumThreads, OutputAggregator &Out) {
     for (const auto &CU : DICtx.compile_units())
       CU->getAbbreviations();
 
-    // Now parse all DIEs in case we have cross compile unit references in a
-    // thread pool.
     DefaultThreadPool pool(hardware_concurrency(NumThreads));
-    for (const auto &CU : DICtx.compile_units())
-      pool.async([&CU]() { CU->getUnitDIE(false /*CUDieOnly*/); });
-    pool.wait();
 
     // Now convert all DWARF to GSYM in a thread pool.
     std::mutex LogMutex;
     for (const auto &CU : DICtx.compile_units()) {
       DWARFDie Die = getDie(*CU);
       if (Die) {
         CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
-        pool.async([this, CUI, &LogMutex, &Out, Die]() mutable {
+        pool.async([this, CUI, &CU, &LogMutex, &Out, Die]() mutable {
           std::string storage;
           raw_string_ostream StrStream(storage);
           OutputAggregator ThreadOut(Out.GetOS() ? &StrStream : nullptr);
           handleDie(ThreadOut, CUI, Die);
+          DICtx.clearLineTableForUnit(CU.get());
+          // Free any DIEs that were allocated by the DWARF parser.
+          // If/when they're needed by other CU's, they'll be recreated.
+          CU->clearDIEs(/*KeepCUDie=*/false, /*KeepDWODIEs=*/false);
           // Print ThreadLogStorage lines into an actual stream under a lock
           std::lock_guard<std::mutex> guard(LogMutex);
           if (Out.GetOS()) {
@@ -697,6 +701,9 @@ Error DwarfTransformer::convert(uint32_t NumThreads, OutputAggregator &Out) {
     }
     pool.wait();
   }
+  // Now get rid of all the DIEs that may have been recreated
+  for (const auto &CU : DICtx.compile_units())
+    CU->clearDIEs(/*KeepCUDie=*/false, /*KeepDWODIEs=*/false);
   size_t FunctionsAddedCount = Gsym.getNumFunctionInfos() - NumBefore;
   Out << "Loaded " << FunctionsAddedCount << " functions from DWARF.\n";
   return Error::success();