[DebugInfo] Construct DW_TAG_label DIEs from DbgLabels.

lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

class DwarfCompileUnit final : public DwarfUnit {
 
   DenseMap<const MDNode *, DIE *> AbstractSPDies;
   DenseMap<const MDNode *, std::unique_ptr<DbgVariable>> AbstractVariables;
 
   /// \brief Construct a DIE for the given DbgVariable without initializing the
   /// DbgVariable's DIE reference.
   DIE *constructVariableDIEImpl(const DbgVariable &DV, bool Abstract);
 
+  /// \brief Construct a DIE for the given DbgLabel without initializing the
+  /// DbgLabel's DIE reference.
+  DIE *constructLabelDIEImpl(const DbgLabel &DL);
+
   bool isDwoUnit() const override;
 
   DenseMap<const MDNode *, DIE *> &getAbstractSPDies() {
     if (isDwoUnit() && !DD->shareAcrossDWOCUs())
       return AbstractSPDies;
     return DU->getAbstractSPDies();
   }
 
public:
   DIE *constructLexicalScopeDIE(LexicalScope *Scope);
 
   /// constructVariableDIE - Construct a DIE for the given DbgVariable.
   DIE *constructVariableDIE(DbgVariable &DV, bool Abstract = false);
 
   DIE *constructVariableDIE(DbgVariable &DV, const LexicalScope &Scope,
                             DIE *&ObjectPointer);
 
+  /// constructLabelDIE - Construct a DIE for the given DbgLabel.
+  DIE *constructLabelDIE(DbgLabel &DL);
+
   /// A helper function to create children of a Scope DIE.
   DIE *createScopeChildrenDIE(LexicalScope *Scope,
                               SmallVectorImpl<DIE *> &Children,
                               bool *HasNonScopeChildren = nullptr);
 
   /// \brief Construct a DIE for this subprogram scope.
   void constructSubprogramScopeDIE(const DISubprogram *Sub, LexicalScope *Scope);
 

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

 
 /// constructVariableDIE - Construct a DIE for the given DbgVariable.
 DIE *DwarfCompileUnit::constructVariableDIE(DbgVariable &DV, bool Abstract) {
   auto D = constructVariableDIEImpl(DV, Abstract);
   DV.setDIE(*D);
   return D;
 }
 
+/// constructLabelDIE - Construct a DIE for the given DbgLabel.
+DIE *DwarfCompileUnit::constructLabelDIE(DbgLabel &DL) {
+  auto D = constructLabelDIEImpl(DL);
+  DL.setDIE(*D);
+  return D;
+}
+
 DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
                                                 bool Abstract) {
   // Define variable debug information entry.
   auto VariableDie = DIE::get(DIEValueAllocator, DV.getTag());
   insertDIE(DV.getVariable(), VariableDie);
 
   if (Abstract) {
     applyVariableAttributes(DV, *VariableDie);
DwarfExpr.addMachineRegExpression(
         *Asm->MF->getSubtarget().getRegisterInfo(), Cursor, FrameReg);
     DwarfExpr.addExpression(std::move(Cursor));
   }
   addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
 
   return VariableDie;
 }
 
+DIE *DwarfCompileUnit::constructLabelDIEImpl(const DbgLabel &DL) {
+  // Define label debug information entry.
+  auto LabelDie = DIE::get(DIEValueAllocator, DL.getTag());
+  return LabelDie;
+}
+
 DIE *DwarfCompileUnit::constructVariableDIE(DbgVariable &DV,
                                             const LexicalScope &Scope,
                                             DIE *&ObjectPointer) {
   auto Var = constructVariableDIE(DV, Scope.isAbstractScope());
   if (DV.isObjectPointer())
     ObjectPointer = Var;
   return Var;
 }
if (!includeMinimalInlineScopes()) {
     for (const auto *IE : ImportedEntities[Scope->getScopeNode()])
       Children.push_back(
           constructImportedEntityDIE(cast<DIImportedEntity>(IE)));
   }
 
   if (HasNonScopeChildren)
     *HasNonScopeChildren = !Children.empty();
 
+  for (DbgLabel *DL : DU->getScopeLabels().lookup(Scope))
+    Children.push_back(constructLabelDIE(*DL));
+
   for (LexicalScope *LS : Scope->getChildren())
     constructScopeDIE(LS, Children);
 
   return ObjectPointer;
 }
 
 void DwarfCompileUnit::constructSubprogramScopeDIE(const DISubprogram *Sub, LexicalScope *Scope) {
   DIE &ScopeDIE = updateSubprogramScopeDIE(Sub);