diff --git a/clang/lib/AST/OpenMPClause.cpp b/clang/lib/AST/OpenMPClause.cpp
@@ -106,6 +106,7 @@ const OMPClauseWithPreInit *OMPClauseWithPreInit::get(const OMPClause *C) {
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     break;
   }
 
@@ -175,6 +176,7 @@ const OMPClauseWithPostUpdate *OMPClauseWithPostUpdate::get(const OMPClause *C)
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     break;
   }
 

diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
@@ -698,6 +698,10 @@ void OMPClausePrinter::VisitOMPProcBindClause(OMPProcBindClause *Node) {
      << ")";
 }
 
+void OMPClausePrinter::VisitOMPUnifiedAddressClause(OMPUnifiedAddressClause *) {
+  OS << "unified_address";
+}
+
 void OMPClausePrinter::VisitOMPScheduleClause(OMPScheduleClause *Node) {
   OS << "schedule(";
   if (Node->getFirstScheduleModifier() != OMPC_SCHEDULE_MODIFIER_unknown) {

diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
@@ -467,6 +467,9 @@ void OMPClauseProfiler::VisitOMPDefaultClause(const OMPDefaultClause *C) { }
 
 void OMPClauseProfiler::VisitOMPProcBindClause(const OMPProcBindClause *C) { }
 
+void OMPClauseProfiler::VisitOMPUnifiedAddressClause(
+    const OMPUnifiedAddressClause *C) {}
+
 void OMPClauseProfiler::VisitOMPScheduleClause(const OMPScheduleClause *C) {
   VistOMPClauseWithPreInit(C);
   if (auto *S = C->getChunkSize())

diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
@@ -168,6 +168,7 @@ unsigned clang::getOpenMPSimpleClauseType(OpenMPClauseKind Kind,
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     break;
   }
   llvm_unreachable("Invalid OpenMP simple clause kind");
@@ -309,6 +310,7 @@ const char *clang::getOpenMPSimpleClauseTypeName(OpenMPClauseKind Kind,
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     break;
   }
   llvm_unreachable("Invalid OpenMP simple clause kind");
@@ -437,6 +439,16 @@ bool clang::isAllowedClauseForDirective(OpenMPDirectiveKind DKind,
 #define OPENMP_TARGET_CLAUSE(Name)                                             \
   case OMPC_##Name:                                                            \
     return true;
+#include "clang/Basic/OpenMPKinds.def"
+    default:
+      break;
+    }
+    break;
+  case OMPD_requires:
+    switch (CKind) {
+#define OPENMP_REQUIRES_CLAUSE(Name)                                             \
+  case OMPC_##Name:                                                            \
+    return true;
 #include "clang/Basic/OpenMPKinds.def"
     default:
       break;
@@ -961,6 +973,7 @@ void clang::getOpenMPCaptureRegions(
   case OMPD_declare_simd:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
+  case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
@@ -105,6 +105,7 @@ void CodeGenFunction::EmitDecl(const Decl &D) {
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPCapturedExpr:
+  case Decl::OMPRequires:
   case Decl::Empty:
     // None of these decls require codegen support.
     return;
@@ -2146,3 +2147,7 @@ void CodeGenModule::EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
     return;
   getOpenMPRuntime().emitUserDefinedReduction(CGF, D);
 }
+
+void CodeGenModule::EmitOMPRequiresDecl(const OMPRequiresDecl *D) {
+  //Do nothing - here to avoid build errors
+}
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -8273,6 +8273,7 @@ void CGOpenMPRuntime::scanForTargetRegionsFunctions(const Stmt *S,
     case OMPD_declare_reduction:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
+    case OMPD_requires:
     case OMPD_unknown:
       llvm_unreachable("Unknown target directive for OpenMP device codegen.");
     }
@@ -8748,6 +8749,7 @@ void CGOpenMPRuntime::emitTargetDataStandAloneCall(
     case OMPD_target_parallel:
     case OMPD_target_parallel_for:
     case OMPD_target_parallel_for_simd:
+    case OMPD_requires:
     case OMPD_unknown:
       llvm_unreachable("Unexpected standalone target data directive.");
       break;

diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
@@ -762,6 +762,7 @@ static bool hasNestedSPMDDirective(ASTContext &Ctx,
     case OMPD_declare_reduction:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
+    case OMPD_requires:
     case OMPD_unknown:
       llvm_unreachable("Unexpected directive.");
     }
@@ -831,6 +832,7 @@ static bool supportsSPMDExecutionMode(ASTContext &Ctx,
   case OMPD_declare_reduction:
   case OMPD_taskloop:
   case OMPD_taskloop_simd:
+  case OMPD_requires:
   case OMPD_unknown:
     break;
   }
@@ -980,6 +982,7 @@ static bool hasNestedLightweightDirective(ASTContext &Ctx,
     case OMPD_declare_reduction:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
+    case OMPD_requires:
     case OMPD_unknown:
       llvm_unreachable("Unexpected directive.");
     }
@@ -1052,6 +1055,7 @@ static bool supportsLightweightRuntime(ASTContext &Ctx,
   case OMPD_declare_reduction:
   case OMPD_taskloop:
   case OMPD_taskloop_simd:
+  case OMPD_requires:
   case OMPD_unknown:
     break;
   }

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -3903,6 +3903,7 @@ static void emitOMPAtomicExpr(CodeGenFunction &CGF, OpenMPClauseKind Kind,
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     llvm_unreachable("Clause is not allowed in 'omp atomic'.");
   }
 }

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4879,6 +4879,10 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
   case Decl::OMPDeclareReduction:
     EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(D));
     break;
+
+  case Decl::OMPRequires:
+    EmitOMPRequiresDecl(cast<OMPRequiresDecl>(D));
+    break;
 
   default:
     // Make sure we handled everything we should, every other kind is a

diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
@@ -1224,6 +1224,10 @@ class CodeGenModule : public CodeGenTypeCache {
   void EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
                                CodeGenFunction *CGF = nullptr);
 
+  /// Emit a code for requires directive.
+  /// \param D Requires declaration
+  void EmitOMPRequiresDecl(const OMPRequiresDecl *D);
+
   /// Returns whether the given record has hidden LTO visibility and therefore
   /// may participate in (single-module) CFI and whole-program vtable
   /// optimization.

diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
@@ -659,6 +659,10 @@ Parser::ParseOMPDeclareSimdClauses(Parser::DeclGroupPtrTy Ptr,
 ///         annot_pragma_openmp_end
 ///         <function declaration/definition>
 ///
+///       requires directive:
+///         annot_pragma_openmp 'requires' <clause> [[[,] <clause>] ... ]
+///         annot_pragma_openmp_end
+///
 Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
     AccessSpecifier &AS, ParsedAttributesWithRange &Attrs,
     DeclSpec::TST TagType, Decl *Tag) {
@@ -687,6 +691,46 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
     }
     break;
   }
+  case OMPD_requires: {
+    SourceLocation StartLoc = ConsumeToken();
+    SmallVector<OMPClause *, 5> Clauses;
+    SmallVector<llvm::PointerIntPair<OMPClause *, 1, bool>, OMPC_unknown + 1>
+    FirstClauses(OMPC_unknown + 1);
+    if (Tok.is(tok::annot_pragma_openmp_end)) {
+      Diag(Tok, diag::err_omp_expected_clause) 
+          << getOpenMPDirectiveName(OMPD_requires);
+      break;
+    }
+    while (Tok.isNot(tok::annot_pragma_openmp_end)) {
+      OpenMPClauseKind CKind = Tok.isAnnotation()
+                                   ? OMPC_unknown
+                                   : getOpenMPClauseKind(PP.getSpelling(Tok));
+      Actions.StartOpenMPClause(CKind);
+      OMPClause *Clause =
+          ParseOpenMPClause(OMPD_requires, CKind, !FirstClauses[CKind].getInt());
+      SkipUntil(tok::comma, tok::identifier, tok::annot_pragma_openmp_end, StopBeforeMatch);
+      FirstClauses[CKind].setInt(true);
+      if (Clause != nullptr)
+        Clauses.push_back(Clause);
+      if (Tok.is(tok::annot_pragma_openmp_end)) {
+        Actions.EndOpenMPClause();
+        break;
+      }
+      // Skip ',' if any.
+      if (Tok.is(tok::comma))
+        ConsumeToken();
+      Actions.EndOpenMPClause();
+    }
+    // Consume final annot_pragma_openmp_end
+    if (Clauses.size() == 0) {
+      Diag(Tok, diag::err_omp_expected_clause)
+          << getOpenMPDirectiveName(OMPD_requires);
+      ConsumeAnnotationToken();
+      return nullptr;
+    }
+    ConsumeAnnotationToken();
+    return Actions.ActOnOpenMPRequiresDirective(StartLoc, Clauses);
+  }
   case OMPD_declare_reduction:
     ConsumeToken();
     if (DeclGroupPtrTy Res = ParseOpenMPDeclareReductionDirective(AS)) {
@@ -1141,6 +1185,7 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
   case OMPD_declare_simd:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
+  case OMPD_requires:
     Diag(Tok, diag::err_omp_unexpected_directive)
         << 1 << getOpenMPDirectiveName(DKind);
     SkipUntil(tok::annot_pragma_openmp_end);
@@ -1333,10 +1378,13 @@ OMPClause *Parser::ParseOpenMPClause(OpenMPDirectiveKind DKind,
   case OMPC_threads:
   case OMPC_simd:
   case OMPC_nogroup:
+  case OMPC_unified_address:
     // OpenMP [2.7.1, Restrictions, p. 9]
     //  Only one ordered clause can appear on a loop directive.
     // OpenMP [2.7.1, Restrictions, C/C++, p. 4]
     //  Only one nowait clause can appear on a for directive.
+    // OpenMP [5.0, Requires directive, Restrictions]
+    //   Each of the requires clauses can appear at most once on the directive.
     if (!FirstClause) {
       Diag(Tok, diag::err_omp_more_one_clause)
           << getOpenMPDirectiveName(DKind) << getOpenMPClauseName(CKind) << 0;

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
@@ -177,6 +177,9 @@ class DSAStackTy {
            Stack.back().first.empty();
   }
 
+  /// Vector of previously declared requires directives
+  SmallVector<const OMPRequiresDecl *, 2> RequiresDecls;
+
 public:
   explicit DSAStackTy(Sema &S) : SemaRef(S) {}
 
@@ -351,7 +354,34 @@ class DSAStackTy {
       return OMPD_unknown;
     return std::next(Stack.back().first.rbegin())->Directive;
   }
-
+
+  /// Add requires decl to internal vector
+  void addRequiresDecl(OMPRequiresDecl *RD) {
+    RequiresDecls.push_back(RD);
+  }
+
+  /// Checks for a duplicate clause amongst previously declared requires
+  /// directives
+  bool hasDuplicateRequiresClause(ArrayRef<OMPClause *> ClauseList) const {
+    bool IsDuplicate = false;
+    for (OMPClause *CNew : ClauseList) {
+      for (const OMPRequiresDecl *D : RequiresDecls) {
+        for (const OMPClause *CPrev : D->clauselists()) {
+          if (CNew->getClauseKind() == CPrev->getClauseKind()) {
+            SemaRef.Diag(CNew->getBeginLoc(),
+                         diag::err_omp_requires_clause_redeclaration)
+                << getOpenMPClauseName(CNew->getClauseKind());
+            SemaRef.Diag(CPrev->getBeginLoc(),
+                         diag::note_omp_requires_previous_clause)
+                << getOpenMPClauseName(CPrev->getClauseKind());
+            IsDuplicate = true;
+          }
+        }
+      }
+    }
+    return IsDuplicate;
+  }
+
   /// Set default data sharing attribute to none.
   void setDefaultDSANone(SourceLocation Loc) {
     assert(!isStackEmpty());
@@ -1899,6 +1929,30 @@ Sema::CheckOMPThreadPrivateDecl(SourceLocation Loc, ArrayRef<Expr *> VarList) {
   return D;
 }
 
+Sema::DeclGroupPtrTy
+Sema::ActOnOpenMPRequiresDirective(SourceLocation Loc,
+                                   ArrayRef<OMPClause *> ClauseList) {
+  OMPRequiresDecl *D = nullptr;
+  if (!CurContext->isFileContext()) {
+    Diag(Loc, diag::err_omp_invalid_scope) << "requires";
+  } else {
+    D = CheckOMPRequiresDecl(Loc, ClauseList);
+    if (D) {
+      CurContext->addDecl(D);
+      DSAStack->addRequiresDecl(D);
+    }
+  }
+  return DeclGroupPtrTy::make(DeclGroupRef(D));
+}
+
+OMPRequiresDecl *Sema::CheckOMPRequiresDecl(SourceLocation Loc,
+                                            ArrayRef<OMPClause *> ClauseList) {
+  if (!DSAStack->hasDuplicateRequiresClause(ClauseList))
+    return OMPRequiresDecl::Create(Context, getCurLexicalContext(), Loc,
+                                   ClauseList);
+  return nullptr;
+}
+
 static void reportOriginalDsa(Sema &SemaRef, const DSAStackTy *Stack,
                               const ValueDecl *D,
                               const DSAStackTy::DSAVarData &DVar,
@@ -2544,6 +2598,7 @@ void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
   case OMPD_declare_simd:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
+  case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
@@ -3385,6 +3440,7 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   case OMPD_threadprivate:
   case OMPD_declare_reduction:
   case OMPD_declare_simd:
+  case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
@@ -7954,6 +8010,7 @@ OMPClause *Sema::ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind, Expr *Expr,
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -8039,6 +8096,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_distribute_simd:
     case OMPD_teams_distribute:
     case OMPD_teams_distribute_simd:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with if-clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8104,6 +8162,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_distribute_simd:
     case OMPD_teams_distribute:
     case OMPD_teams_distribute_simd:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with num_threads-clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8167,6 +8226,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_ordered:
     case OMPD_atomic:
     case OMPD_distribute_simd:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with num_teams-clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8230,6 +8290,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_ordered:
     case OMPD_atomic:
     case OMPD_distribute_simd:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with thread_limit-clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8293,6 +8354,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_atomic:
     case OMPD_distribute_simd:
     case OMPD_target_teams:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with schedule clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8356,6 +8418,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_ordered:
     case OMPD_atomic:
     case OMPD_target_teams:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with schedule clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8419,6 +8482,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_ordered:
     case OMPD_atomic:
     case OMPD_distribute_simd:
+    case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with num_teams-clause");
     case OMPD_unknown:
       llvm_unreachable("Unknown OpenMP directive");
@@ -8468,6 +8532,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     llvm_unreachable("Unexpected OpenMP clause.");
   }
   return CaptureRegion;
@@ -8785,6 +8850,7 @@ OMPClause *Sema::ActOnOpenMPSimpleClause(
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -8941,6 +9007,7 @@ OMPClause *Sema::ActOnOpenMPSingleExprWithArgClause(
   case OMPC_from:
   case OMPC_use_device_ptr:
   case OMPC_is_device_ptr:
+  case OMPC_unified_address:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -9096,6 +9163,9 @@ OMPClause *Sema::ActOnOpenMPClause(OpenMPClauseKind Kind,
   case OMPC_nogroup:
     Res = ActOnOpenMPNogroupClause(StartLoc, EndLoc);
     break;
+  case OMPC_unified_address:
+    Res = ActOnOpenMPUnifiedAddressClause(StartLoc, EndLoc);
+    break;
   case OMPC_if:
   case OMPC_final:
   case OMPC_num_threads:
@@ -9196,6 +9266,11 @@ OMPClause *Sema::ActOnOpenMPNogroupClause(SourceLocation StartLoc,
   return new (Context) OMPNogroupClause(StartLoc, EndLoc);
 }
 
+OMPClause *Sema::ActOnOpenMPUnifiedAddressClause(SourceLocation StartLoc,
+                                                 SourceLocation EndLoc) {
+  return new (Context) OMPUnifiedAddressClause(StartLoc, EndLoc);
+}
+
 OMPClause *Sema::ActOnOpenMPVarListClause(
     OpenMPClauseKind Kind, ArrayRef<Expr *> VarList, Expr *TailExpr,
     SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation ColonLoc,
@@ -9303,6 +9378,7 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
   case OMPC_defaultmap:
   case OMPC_unknown:
   case OMPC_uniform:
+  case OMPC_unified_address:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2736,6 +2736,11 @@ Decl *TemplateDeclInstantiator::VisitOMPThreadPrivateDecl(
   return TD;
 }
 
+Decl *TemplateDeclInstantiator::VisitOMPRequiresDecl(OMPRequiresDecl *D) {
+  llvm_unreachable(
+      "Requires directive cannot be instantiated within a dependent context");
+}
+
 Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
     OMPDeclareReductionDecl *D) {
   // Instantiate type and check if it is allowed.

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
@@ -8413,6 +8413,12 @@ TreeTransform<Derived>::TransformOMPNogroupClause(OMPNogroupClause *C) {
   return C;
 }
 
+template <typename Derived>
+OMPClause *TreeTransform<Derived>::TransformOMPUnifiedAddressClause(
+    OMPUnifiedAddressClause *C) {
+  llvm_unreachable("unified address clause cannot appear in dependent context");
+}
+
 template <typename Derived>
 OMPClause *
 TreeTransform<Derived>::TransformOMPPrivateClause(OMPPrivateClause *C) {

diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
@@ -383,6 +383,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::ClassScopeFunctionSpecialization:
   case Decl::Import:
   case Decl::OMPThreadPrivate:
+  case Decl::OMPRequires:
   case Decl::OMPCapturedExpr:
   case Decl::OMPDeclareReduction:
   case Decl::BuiltinTemplate:

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
@@ -11721,6 +11721,9 @@ OMPClause *OMPClauseReader::readClause() {
   case OMPC_nogroup:
     C = new (Context) OMPNogroupClause();
     break;
+  case OMPC_unified_address:
+    C = new (Context) OMPUnifiedAddressClause();
+    break;
   case OMPC_private:
     C = OMPPrivateClause::CreateEmpty(Context, Record.readInt());
     break;
@@ -11949,6 +11952,8 @@ void OMPClauseReader::VisitOMPSIMDClause(OMPSIMDClause *) {}
 
 void OMPClauseReader::VisitOMPNogroupClause(OMPNogroupClause *) {}
 
+void OMPClauseReader::VisitOMPUnifiedAddressClause(OMPUnifiedAddressClause *) {}
+
 void OMPClauseReader::VisitOMPPrivateClause(OMPPrivateClause *C) {
   C->setLParenLoc(Record.readSourceLocation());
   unsigned NumVars = C->varlist_size();

diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -30,6 +30,7 @@
 #include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/LambdaCapture.h"
 #include "clang/AST/NestedNameSpecifier.h"
+#include "clang/AST/OpenMPClause.h"
 #include "clang/AST/Redeclarable.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/TemplateBase.h"
@@ -446,6 +447,7 @@ namespace clang {
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
+    void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
   };
 
@@ -2630,6 +2632,17 @@ void ASTDeclReader::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
   D->setVars(Vars);
 }
 
+void ASTDeclReader::VisitOMPRequiresDecl(OMPRequiresDecl * D) {
+  VisitDecl(D);
+  unsigned NumClauses = D->clauselist_size();
+  SmallVector<OMPClause *, 8> Clauses;
+  Clauses.reserve(NumClauses);
+  OMPClauseReader ClauseReader(Record);
+  for (unsigned I = 0; I != NumClauses; ++I)
+    Clauses.push_back(ClauseReader.readClause());
+  D->setClauses(Clauses);
+}
+
 void ASTDeclReader::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   VisitValueDecl(D);
   D->setLocation(ReadSourceLocation());
@@ -3830,6 +3843,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_OMP_THREADPRIVATE:
     D = OMPThreadPrivateDecl::CreateDeserialized(Context, ID, Record.readInt());
     break;
+  case DECL_OMP_REQUIRES:
+    D = OMPRequiresDecl::CreateDeserialized(Context, ID, Record.readInt());
+    break;
   case DECL_OMP_DECLARE_REDUCTION:
     D = OMPDeclareReductionDecl::CreateDeserialized(Context, ID);
     break;

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
@@ -6932,3 +6932,5 @@ void OMPClauseWriter::VisitOMPIsDevicePtrClause(OMPIsDevicePtrClause *C) {
     Record.AddDeclRef(M.getAssociatedDeclaration());
   }
 }
+
+void OMPClauseWriter::VisitOMPUnifiedAddressClause(OMPUnifiedAddressClause *) {}
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -17,6 +17,7 @@
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/DeclVisitor.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/OpenMPClause.h"
 #include "clang/AST/PrettyDeclStackTrace.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Serialization/ASTReader.h"
@@ -144,6 +145,7 @@ namespace clang {
     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
+    void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
@@ -1739,6 +1741,15 @@ void ASTDeclWriter::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
   Code = serialization::DECL_OMP_THREADPRIVATE;
 }
 
+void ASTDeclWriter::VisitOMPRequiresDecl(OMPRequiresDecl *D) {
+  Record.push_back(D->clauselist_size());
+  VisitDecl(D);
+  OMPClauseWriter ClauseWriter(Record); 
+  for (OMPClause *C : D->clauselists())
+    ClauseWriter.writeClause(C);
+  Code = serialization::DECL_OMP_REQUIRES;
+}
+
 void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   VisitValueDecl(D);
   Record.AddSourceLocation(D->getBeginLoc());

diff --git a/clang/test/OpenMP/requires_unified_address_ast_print.cpp b/clang/test/OpenMP/requires_unified_address_ast_print.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -verify -fopenmp -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp -x c++ -std=c++11 -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+
+// RUN: %clang_cc1 -verify -fopenmp-simd -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp-simd -x c++ -std=c++11 -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp-simd -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+#pragma omp requires unified_address 
+// CHECK:#pragma omp requires unified_address
+
+#endif
diff --git a/clang/test/OpenMP/requires_unified_address_messages.cpp b/clang/test/OpenMP/requires_unified_address_messages.cpp
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100  %s
+
+#pragma omp requires unified_address // expected-note {{unified_address clause previously used here}} expected-note {{unified_address clause previously used here}} expected-note {{unified_address clause previously used here}} expected-note {{unified_address clause previously used here}} expected-note {{unified_address clause previously used here}}
+
+#pragma omp requires unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}} 
+
+#pragma omp requires unified_address, unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}} expected-error {{directive '#pragma omp requires' cannot contain more than one 'unified_address' clause}}
+
+#pragma omp requires // expected-error {{expected at least one clause on '#pragma omp requires' directive}}
+
+#pragma omp requires invalid_clause // expected-warning {{extra tokens at the end of '#pragma omp requires' are ignored}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
+
+#pragma omp requires nowait // expected-error {{unexpected OpenMP clause 'nowait' in directive '#pragma omp requires'}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
+
+#pragma omp requires unified_address, invalid_clause // expected-warning {{extra tokens at the end of '#pragma omp requires' are ignored}} expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}}
+
+#pragma omp requires invalid_clause unified_address // expected-warning {{extra tokens at the end of '#pragma omp requires' are ignored}} expected-error {{expected at least one clause on '#pragma omp requires' directive}}
+
+namespace A {
+  #pragma omp requires unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}}
+  namespace B {
+    #pragma omp requires unified_address // expected-error {{Only one unified_address clause can appear on a requires directive in a single translation unit}}
+  }
+}
+
+template <typename T> T foo() {
+  #pragma omp requires unified_address // expected-error {{unexpected OpenMP directive '#pragma omp requires'}}
+}
+
+class C {
+  #pragma omp requires unified_address // expected-error {{'#pragma omp requires' directive must appear only in file scope}}
+};
+
+int main() {
+  #pragma omp requires unified_address // expected-error {{unexpected OpenMP directive '#pragma omp requires'}}
+}
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
@@ -2207,6 +2207,9 @@ void OMPClauseEnqueue::VisitOMPSIMDClause(const OMPSIMDClause *) {}
 
 void OMPClauseEnqueue::VisitOMPNogroupClause(const OMPNogroupClause *) {}
 
+void OMPClauseEnqueue::VisitOMPUnifiedAddressClause(
+    const OMPUnifiedAddressClause *) {}
+
 void OMPClauseEnqueue::VisitOMPDeviceClause(const OMPDeviceClause *C) {
   Visitor->AddStmt(C->getDevice());
 }
@@ -6220,6 +6223,7 @@ CXCursor clang_getCursorDefinition(CXCursor C) {
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPRequires:
   case Decl::ObjCTypeParam:
   case Decl::BuiltinTemplate:
   case Decl::PragmaComment:
-Original file line number
+Diff line change
@@ Expand Up @@
         Record.AddDeclRef(M.getAssociatedDeclaration());
       }
     }
+    void OMPClauseWriter::VisitOMPUnifiedAddressClause(OMPUnifiedAddressClause *) {}