CodeGen: Introduce CodeGenModule::CreateMetadataIdentifierForType.

[pcc]

Summary

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.

[Prazek]

lib/CodeGen/CodeGenModule.cpp

3677

question: so You are storing distinct and normal mdnodes here. Is it faster to grap normal node from this map than to just create new one using get?

[pcc]

lib/CodeGen/CodeGenModule.cpp

3677

Quite possibly (the latter involves string comparisons and possibly memory allocation) but they should both have the same complexity so it doesn't matter much.

[pcc]

@rsmith: Ping.

[rsmith]

This seems fine to me.

lib/CodeGen/CodeGenModule.h

private:
 
   std::unique_ptr<SanitizerMetadata> SanitizerMD;
 
   /// @}
 
   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,
                 const CodeGenOptions &CodeGenOpts, llvm::Module &M,
                 DiagnosticsEngine &Diags,
                 CoverageSourceInfo *CoverageInfo = nullptr);
 
   ~CodeGenModule();
public:
   /// integrity checks.
   bool IsCFIBlacklistedRecord(const CXXRecordDecl *RD);
 
   /// Emit bit set entries for the given vtable using the given layout if
   /// vptr CFI is enabled.
   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,
                                          const CXXRecordDecl *RD);
 
   /// \breif Get the declaration of std::terminate for the platform.
   llvm::Constant *getTerminateFn();
 

lib/CodeGen/CodeGenModule.cpp

bool PerformInit =
         !VD->getAnyInitializer()->isConstantInitializer(getContext(),
                                                         /*ForRef=*/false);
     if (auto InitFunction = getOpenMPRuntime().emitThreadPrivateVarDefinition(
             VD, GetAddrOfGlobalVar(VD), RefExpr->getLocStart(), PerformInit))
       CXXGlobalInits.push_back(InitFunction);
   }
 }
 
+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;
   llvm::raw_string_ostream Out(OutName);
   getCXXABI().getMangleContext().mangleCXXVTableBitSet(RD, Out);
 
   llvm::Metadata *BitsetOps[] = {
       llvm::MDString::get(getLLVMContext(), Out.str()),
       llvm::ConstantAsMetadata::get(VTable),
       llvm::ConstantAsMetadata::get(
           llvm::ConstantInt::get(Int64Ty, Offset.getQuantity()))};
   return llvm::MDTuple::get(getLLVMContext(), BitsetOps);
 }