libDebugInfo: Avoid independently parsing the same .dwo file for two separate CUs residing there

NFC, just an optimization. Will be building on this for DWP support
shortly.

llvm-svn: 303591

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

@@ -71,6 +71,12 @@ class DWARFContext : public DIContext {
   std::unique_ptr<DWARFDebugAbbrev> AbbrevDWO;
   std::unique_ptr<DWARFDebugLocDWO> LocDWO;
 
+  struct DWOFile {
+    object::OwningBinary<object::ObjectFile> File;
+    std::unique_ptr<DWARFContext> Context;
+  };
+  StringMap<std::weak_ptr<DWOFile>> DWOFiles;
+
   /// Read compile units from the debug_info section (if necessary)
   /// and store them in CUs.
   void parseCompileUnits();
@@ -248,6 +254,8 @@ public:
     return version == 2 || version == 3 || version == 4 || version == 5;
   }
 
+  std::shared_ptr<DWARFContext> getDWOContext(StringRef AbsolutePath);
+
 private:
   /// Return the compile unit that includes an offset (relative to .debug_info).
   DWARFCompileUnit *getCompileUnitForOffset(uint32_t Offset);

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

@@ -143,17 +143,7 @@ class DWARFUnit {
   typedef iterator_range<std::vector<DWARFDebugInfoEntry>::iterator>
       die_iterator_range;
 
-  class DWOHolder {
-    object::OwningBinary<object::ObjectFile> DWOFile;
-    std::unique_ptr<DWARFContext> DWOContext;
-    DWARFUnit *DWOU = nullptr;
-
-  public:
-    DWOHolder(StringRef DWOPath, uint64_t DWOId);
-
-    DWARFUnit *getUnit() const { return DWOU; }
-  };
-  std::unique_ptr<DWOHolder> DWO;
+  std::shared_ptr<DWARFUnit> DWO;
 
   const DWARFUnitIndex::Entry *IndexEntry;
 

llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

@@ -897,6 +897,28 @@ DWARFContext::getInliningInfoForAddress(uint64_t Address,
   return InliningInfo;
 }
 
+std::shared_ptr<DWARFContext>
+DWARFContext::getDWOContext(StringRef AbsolutePath) {
+  auto &Entry = DWOFiles[AbsolutePath];
+  if (auto S = Entry.lock()) {
+    DWARFContext *Ctxt = S->Context.get();
+    return std::shared_ptr<DWARFContext>(std::move(S), Ctxt);
+  }
+
+  auto S = std::make_shared<DWOFile>();
+  auto Obj = object::ObjectFile::createObjectFile(AbsolutePath);
+  if (!Obj) {
+    // TODO: Actually report errors helpfully.
+    consumeError(Obj.takeError());
+    return nullptr;
+  }
+  S->File = std::move(Obj.get());
+  S->Context = llvm::make_unique<DWARFContextInMemory>(*S->File.getBinary());
+  Entry = S;
+  auto *Ctxt = S->Context.get();
+  return std::shared_ptr<DWARFContext>(std::move(S), Ctxt);
+}
+
 static Error createError(const Twine &Reason, llvm::Error E) {
   return make_error<StringError>(Reason + toString(std::move(E)),
                                  inconvertibleErrorCode());

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

@@ -249,23 +249,6 @@ size_t DWARFUnit::extractDIEsIfNeeded(bool CUDieOnly) {
   return DieArray.size();
 }
 
-DWARFUnit::DWOHolder::DWOHolder(StringRef DWOPath, uint64_t DWOId) {
-  auto Obj = object::ObjectFile::createObjectFile(DWOPath);
-  if (!Obj) {
-    // TODO: Actually report errors helpfully.
-    consumeError(Obj.takeError());
-    return;
-  }
-  DWOFile = std::move(Obj.get());
-  DWOContext.reset(
-      cast<DWARFContext>(new DWARFContextInMemory(*DWOFile.getBinary())));
-  for (const auto &DWOCU : DWOContext->dwo_compile_units())
-    if (DWOCU->getDWOId() == DWOId) {
-      DWOU = DWOCU.get();
-      return;
-    }
-}
-
 bool DWARFUnit::parseDWO() {
   if (isDWO)
     return false;
@@ -287,16 +270,21 @@ bool DWARFUnit::parseDWO() {
   auto DWOId = getDWOId();
   if (!DWOId)
     return false;
-  DWO = llvm::make_unique<DWOHolder>(AbsolutePath, *DWOId);
-  DWARFUnit *DWOCU = DWO->getUnit();
-  if (!DWOCU) {
-    DWO.reset();
+  auto DWOContext = Context.getDWOContext(AbsolutePath);
+  if (!DWOContext)
+    return false;
+
+  for (const auto &DWOCU : DWOContext->dwo_compile_units())
+    if (DWOCU->getDWOId() == DWOId) {
+      DWO = std::shared_ptr<DWARFUnit>(std::move(DWOContext), DWOCU.get());
+      break;
+    }
+  if (!DWO)
     return false;
-  }
   // Share .debug_addr and .debug_ranges section with compile unit in .dwo
-  DWOCU->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
+  DWO->setAddrOffsetSection(AddrOffsetSection, AddrOffsetSectionBase);
   auto DWORangesBase = UnitDie.getRangesBaseAttribute();
-  DWOCU->setRangesSection(RangeSection, DWORangesBase ? *DWORangesBase : 0);
+  DWO->setRangesSection(RangeSection, DWORangesBase ? *DWORangesBase : 0);
   return true;
 }
 
@@ -339,8 +327,9 @@ void DWARFUnit::collectAddressRanges(DWARFAddressRangesVector &CURanges) {
 
   // Collect address ranges from DIEs in .dwo if necessary.
   bool DWOCreated = parseDWO();
-  if (DWO.get())
-    DWO->getUnit()->collectAddressRanges(CURanges);
+  assert(!DWOCreated);
+  if (DWO)
+    DWO->collectAddressRanges(CURanges);
   if (DWOCreated)
     DWO.reset();
 
@@ -400,7 +389,7 @@ DWARFUnit::getInlinedChainForAddress(uint64_t Address,
   // First, find the subroutine that contains the given address (the leaf
   // of inlined chain).
   DWARFDie SubroutineDIE =
-      (DWO ? DWO->getUnit() : this)->getSubroutineForAddress(Address);
+      (DWO ? DWO.get() : this)->getSubroutineForAddress(Address);
 
   while (SubroutineDIE) {
     if (SubroutineDIE.isSubroutineDIE())