Linker: Copy metadata when linking declarations.

[pcc]

Summary

Split out from D21053.

[pcc]

Increase stack allocation to 8

[dexonsmith]

LGTM.

include/llvm/IR/GlobalObject.h

public:
   /// Appends all attachments for the global to \c MDs, sorting by attachment
   /// ID. Attachments with the same ID appear in insertion order.
   void
   getAllMetadata(SmallVectorImpl<std::pair<unsigned, MDNode *>> &MDs) const;
 
   /// Erase all metadata attachments with the given kind.
   void eraseMetadata(unsigned KindID);
 
+  /// Copy metadata from Src.
+  void copyMetadata(const GlobalObject *Src);
+
   void copyAttributesFrom(const GlobalValue *Src) override;
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const Value *V) {
     return V->getValueID() == Value::FunctionVal ||
            V->getValueID() == Value::GlobalVariableVal;
   }
 

lib/IR/Metadata.cpp

if (MDs.empty())
     return nullptr;
   return MDs[0];
 }
 
 MDNode *GlobalObject::getMetadata(StringRef Kind) const {
   return getMetadata(getContext().getMDKindID(Kind));
 }
 
+void GlobalObject::copyMetadata(const GlobalObject *Other) {
+  SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
+  Other->getAllMetadata(MDs);
+  for (auto &MD : MDs)
+    addMetadata(MD.first, *MD.second);
+}
+
 void Function::setSubprogram(DISubprogram *SP) {
   setMetadata(LLVMContext::MD_dbg, SP);
 }
 
 DISubprogram *Function::getSubprogram() const {
   return cast_or_null<DISubprogram>(getMetadata(LLVMContext::MD_dbg));
 }

lib/Linker/IRMover.cpp

GlobalValue *IRLinker::copyGlobalValueProto(const GlobalValue *SGV,
 
   if (ForDefinition)
     NewGV->setLinkage(SGV->getLinkage());
   else if (SGV->hasExternalWeakLinkage())
     NewGV->setLinkage(GlobalValue::ExternalWeakLinkage);
 
   NewGV->copyAttributesFrom(SGV);
 
+  if (auto *NewGO = dyn_cast<GlobalObject>(NewGV)) {
+    // Metadata for global variables and function declarations is copied eagerly.
+    if (isa<GlobalVariable>(SGV) || SGV->isDeclaration())
+      NewGO->copyMetadata(cast<GlobalObject>(SGV));
+  }
+
   // Remove these copied constants in case this stays a declaration, since
   // they point to the source module. If the def is linked the values will
   // be mapped in during linkFunctionBody.
   if (auto *NewF = dyn_cast<Function>(NewGV)) {
     NewF->setPersonalityFn(nullptr);
     NewF->setPrefixData(nullptr);
     NewF->setPrologueData(nullptr);
   }
Error IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
   if (Src.hasPrefixData())
     Dst.setPrefixData(Src.getPrefixData());
   if (Src.hasPrologueData())
     Dst.setPrologueData(Src.getPrologueData());
   if (Src.hasPersonalityFn())
     Dst.setPersonalityFn(Src.getPersonalityFn());
 
   // Copy over the metadata attachments without remapping.
-  SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
-  Src.getAllMetadata(MDs);
-  for (const auto &I : MDs)
-    Dst.setMetadata(I.first, I.second);
+  Dst.copyMetadata(&Src);
 
   // Steal arguments and splice the body of Src into Dst.
   Dst.stealArgumentListFrom(Src);
   Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
 
   // Everything has been moved over.  Remap it.
   Mapper.scheduleRemapFunction(Dst);
   return Error::success();

test/Linker/metadata-attach.ll

+; RUN: llvm-link %s -S -o - | FileCheck %s
+
+; CHECK: @g1 = global i32 0, !attach !0
+@g1 = global i32 0, !attach !0
+
+; CHECK: @g2 = external global i32, !attach !0
+@g2 = external global i32, !attach !0
+
+; CHECK: define void @f1() !attach !0
+define void @f1() !attach !0 {
+  call void @f2()
+  store i32 0, i32* @g2
+  ret void
+}
+
+; CHECK: declare !attach !0 void @f2()
+declare !attach !0 void @f2()
+
+!0 = !{}