Commit c65f9346 authored by Duncan P. N. Exon Smith's avatar Duncan P. N. Exon Smith
Browse files

Merging r226044: 

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r226044 | dexonsmith | 2015-01-14 13:58:17 -0800 (Wed, 14 Jan 2015) | 15 lines

IR: Drop metadata references more aggressively during teardown

Sometimes teardown happens before the debug info graph is complete
(e.g., when clang throws an error).  In that case, `MDNode`s will still
have RAUW, so deleting constants that the `MDNode`s point at will be
relatively expensive -- it'll cause re-uniquing all up the chain (what
I've been referring to as "teardown madness").

So, drop references *before* deleting constants.  We need to drop a few
more references now: the metadata side of the metadata/value bridges
needs to be dropped off the cliff along with the rest of it (previously,
the bridges were cleaned before we did anything with the `MDNode`s).

There's no real functionality change here -- state before and after
`LLVMContextImpl::~LLVMContextImpl()` is unchanged -- so no testcase.
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llvm-svn: 226091
parent aa90c32d

llvm/include/llvm/IR/Metadata.h

+8 −0
Original line number Diff line number Diff line
@@ -115,6 +115,9 @@ class MetadataAsValue : public Value { 
  MetadataAsValue(Type *Ty, Metadata *MD);

  ~MetadataAsValue();



  /// \brief Drop use of metadata (during teardown).

  void dropUse() { MD = nullptr; }



public:

  static MetadataAsValue *get(LLVMContext &Context, Metadata *MD);

  static MetadataAsValue *getIfExists(LLVMContext &Context, Metadata *MD);
@@ -185,6 +188,11 @@ class ValueAsMetadata : public Metadata, ReplaceableMetadataImpl { 


  Value *V;



  /// \brief Drop users without RAUW (during teardown).

  void dropUsers() {

    ReplaceableMetadataImpl::resolveAllUses(/* ResolveUsers */ false);

  }



protected:

  ValueAsMetadata(unsigned ID, Value *V)

      : Metadata(ID), V(V) {

llvm/lib/IR/LLVMContextImpl.cpp

+24 −16
Original line number Diff line number Diff line
@@ -73,6 +73,29 @@ LLVMContextImpl::~LLVMContextImpl() { 
  while (!OwnedModules.empty())

    delete *OwnedModules.begin();



  // Drop references for MDNodes.  Do this before Values get deleted to avoid

  // unnecessary RAUW when nodes are still unresolved.

  for (auto *I : DistinctMDNodes)

    I->dropAllReferences();

  for (auto *I : MDTuples)

    I->dropAllReferences();

  for (auto *I : MDLocations)

    I->dropAllReferences();



  // Also drop references that come from the Value bridges.

  for (auto &Pair : ValuesAsMetadata)

    Pair.second->dropUsers();

  for (auto &Pair : MetadataAsValues)

    Pair.second->dropUse();



  // Destroy MDNodes.

  for (UniquableMDNode *I : DistinctMDNodes)

    I->deleteAsSubclass();

  for (MDTuple *I : MDTuples)

    delete I;

  for (MDLocation *I : MDLocations)

    delete I;



  // Free the constants.  This is important to do here to ensure that they are

  // freed before the LeakDetector is torn down.

  std::for_each(ExprConstants.map_begin(), ExprConstants.map_end(),
@@ -135,21 +158,6 @@ LLVMContextImpl::~LLVMContextImpl() { 
  for (auto &Pair : ValuesAsMetadata)

    delete Pair.second;



  // Destroy MDNodes.

  for (auto *I : DistinctMDNodes)

    I->dropAllReferences();

  for (auto *I : MDTuples)

    I->dropAllReferences();

  for (auto *I : MDLocations)

    I->dropAllReferences();



  for (UniquableMDNode *I : DistinctMDNodes)

    I->deleteAsSubclass();

  for (MDTuple *I : MDTuples)

    delete I;

  for (MDLocation *I : MDLocations)

    delete I;



  // Destroy MDStrings.

  MDStringCache.clear();

}