CodeGen: Introduce CodeGenModule::CreateMetadataIdentifierForType.

This function can be used to create a metadata identifier for a specific
type. No functionality change, but this will be used by D11857 and D12026.

Differential Revision: http://reviews.llvm.org/D12038

llvm-svn: 247098

2 files changed, 30 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index e76ee12512e..a2d554bde54 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -3803,6 +3803,25 @@ void CodeGenModule::EmitOMPThreadPrivateDecl(const OMPThreadPrivateDecl *D) {
   }
 }
 
+llvm::Metadata *CodeGenModule::CreateMetadataIdentifierForType(QualType T) {
+  llvm::Metadata *&InternalId = MetadataIdMap[T.getCanonicalType()];
+  if (InternalId)
+    return InternalId;
+
+  if (isExternallyVisible(T->getLinkage())) {
+    std::string OutName;
+    llvm::raw_string_ostream Out(OutName);
+    getCXXABI().getMangleContext().mangleTypeName(T, Out);
+
+    InternalId = llvm::MDString::get(getLLVMContext(), Out.str());
+  } else {
+    InternalId = llvm::MDNode::getDistinct(getLLVMContext(),
+                                           llvm::ArrayRef<llvm::Metadata *>());
+  }
+
+  return InternalId;
+}
+
 llvm::MDTuple *CodeGenModule::CreateVTableBitSetEntry(
     llvm::GlobalVariable *VTable, CharUnits Offset, const CXXRecordDecl *RD) {
   std::string OutName;
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 4bb50a35f40..754e3d1d29f 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -483,6 +483,12 @@ private:
   llvm::DenseMap<const Decl *, bool> DeferredEmptyCoverageMappingDecls;
 
   std::unique_ptr<CoverageMappingModuleGen> CoverageMapping;
+
+  /// Mapping from canonical types to their metadata identifiers. We need to
+  /// maintain this mapping because identifiers may be formed from distinct
+  /// MDNodes.
+  llvm::DenseMap<QualType, llvm::Metadata *> MetadataIdMap;
+
 public:
   CodeGenModule(ASTContext &C, const HeaderSearchOptions &headersearchopts,
                 const PreprocessorOptions &ppopts,
@@ -1112,6 +1118,11 @@ public:
   void EmitVTableBitSetEntries(llvm::GlobalVariable *VTable,
                                const VTableLayout &VTLayout);
 
+  /// Create a metadata identifier for the given type. This may either be an
+  /// MDString (for external identifiers) or a distinct unnamed MDNode (for
+  /// internal identifiers).
+  llvm::Metadata *CreateMetadataIdentifierForType(QualType T);
+
   /// Create a bitset entry for the given vtable.
   llvm::MDTuple *CreateVTableBitSetEntry(llvm::GlobalVariable *VTable,
                                          CharUnits Offset,