[OpenMP 5.0] Parsing/sema support for "omp declare mapper" directive.

This patch implements parsing and sema for "omp declare mapper"
directive. User defined mapper, i.e., declare mapper directive, is a new
feature in OpenMP 5.0. It is introduced to extend existing map clauses
for the purpose of simplifying the copy of complex data structures
between host and device (i.e., deep copy). An example is shown below:

    struct S {  int len;  int *d; };
    #pragma omp declare mapper(struct S s) map(s, s.d[0:s.len]) // Memory region that d points to is also mapped using this mapper.

Contributed-by: Lingda Li <lildmh@gmail.com>

Differential Revision: https://reviews.llvm.org/D56326

llvm-svn: 352906

23 files changed, 602 insertions, 10 deletions

diff --git a/clang/lib/AST/ASTDumper.cpp b/clang/lib/AST/ASTDumper.cpp
index 7cb61c8affe..e539290fccf 100644
--- a/clang/lib/AST/ASTDumper.cpp
+++ b/clang/lib/AST/ASTDumper.cpp
@@ -381,6 +381,11 @@ namespace  {
         Visit(Initializer);
     }
 
+    void VisitOMPDeclareMapperDecl(const OMPDeclareMapperDecl *D) {
+      for (const auto *C : D->clauselists())
+        Visit(C);
+    }
+
     void VisitOMPCapturedExprDecl(const OMPCapturedExprDecl *D) {
       Visit(D->getInit());
     }
diff --git a/clang/lib/AST/CXXInheritance.cpp b/clang/lib/AST/CXXInheritance.cpp
index 1c0649a769b..150b5982152 100644
--- a/clang/lib/AST/CXXInheritance.cpp
+++ b/clang/lib/AST/CXXInheritance.cpp
@@ -486,6 +486,21 @@ bool CXXRecordDecl::FindOMPReductionMember(const CXXBaseSpecifier *Specifier,
   return false;
 }
 
+bool CXXRecordDecl::FindOMPMapperMember(const CXXBaseSpecifier *Specifier,
+                                        CXXBasePath &Path,
+                                        DeclarationName Name) {
+  RecordDecl *BaseRecord =
+      Specifier->getType()->castAs<RecordType>()->getDecl();
+
+  for (Path.Decls = BaseRecord->lookup(Name); !Path.Decls.empty();
+       Path.Decls = Path.Decls.slice(1)) {
+    if (Path.Decls.front()->isInIdentifierNamespace(IDNS_OMPMapper))
+      return true;
+  }
+
+  return false;
+}
+
 bool CXXRecordDecl::
 FindNestedNameSpecifierMember(const CXXBaseSpecifier *Specifier,
                               CXXBasePath &Path,
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 2d6fbddd0d3..a44c8398158 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -780,6 +780,9 @@ unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
     case OMPDeclareReduction:
       return IDNS_OMPReduction;
 
+    case OMPDeclareMapper:
+      return IDNS_OMPMapper;
+
     // Never have names.
     case Friend:
     case FriendTemplate:
@@ -1163,6 +1166,7 @@ DeclContext *DeclContext::getPrimaryContext() {
   case Decl::Block:
   case Decl::Captured:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPDeclareMapper:
     // There is only one DeclContext for these entities.
     return this;
 
diff --git a/clang/lib/AST/DeclOpenMP.cpp b/clang/lib/AST/DeclOpenMP.cpp
index f709013ba9d..5a1b0363137 100644
--- a/clang/lib/AST/DeclOpenMP.cpp
+++ b/clang/lib/AST/DeclOpenMP.cpp
@@ -123,6 +123,56 @@ OMPDeclareReductionDecl::getPrevDeclInScope() const {
 }
 
 //===----------------------------------------------------------------------===//
+// OMPDeclareMapperDecl Implementation.
+//===----------------------------------------------------------------------===//
+
+void OMPDeclareMapperDecl::anchor() {}
+
+OMPDeclareMapperDecl *
+OMPDeclareMapperDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
+                             DeclarationName Name, QualType T,
+                             DeclarationName VarName,
+                             OMPDeclareMapperDecl *PrevDeclInScope) {
+  return new (C, DC) OMPDeclareMapperDecl(OMPDeclareMapper, DC, L, Name, T,
+                                          VarName, PrevDeclInScope);
+}
+
+OMPDeclareMapperDecl *OMPDeclareMapperDecl::CreateDeserialized(ASTContext &C,
+                                                               unsigned ID,
+                                                               unsigned N) {
+  auto *D = new (C, ID)
+      OMPDeclareMapperDecl(OMPDeclareMapper, /*DC=*/nullptr, SourceLocation(),
+                           DeclarationName(), QualType(), DeclarationName(),
+                           /*PrevDeclInScope=*/nullptr);
+  if (N) {
+    auto **ClauseStorage = C.Allocate<OMPClause *>(N);
+    D->Clauses = llvm::makeMutableArrayRef<OMPClause *>(ClauseStorage, N);
+  }
+  return D;
+}
+
+/// Creates an array of clauses to this mapper declaration and intializes
+/// them. The space used to store clause pointers is dynamically allocated,
+/// because we do not know the number of clauses when creating
+/// OMPDeclareMapperDecl
+void OMPDeclareMapperDecl::CreateClauses(ASTContext &C,
+                                         ArrayRef<OMPClause *> CL) {
+  assert(Clauses.empty() && "Number of clauses should be 0 on initialization");
+  size_t NumClauses = CL.size();
+  if (NumClauses) {
+    auto **ClauseStorage = C.Allocate<OMPClause *>(NumClauses);
+    Clauses = llvm::makeMutableArrayRef<OMPClause *>(ClauseStorage, NumClauses);
+    setClauses(CL);
+  }
+}
+
+void OMPDeclareMapperDecl::setClauses(ArrayRef<OMPClause *> CL) {
+  assert(CL.size() == Clauses.size() &&
+         "Number of clauses is not the same as the preallocated buffer");
+  std::uninitialized_copy(CL.begin(), CL.end(), Clauses.data());
+}
+
+//===----------------------------------------------------------------------===//
 // OMPCapturedExprDecl Implementation.
 //===----------------------------------------------------------------------===//
 
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
index a3e8475a1e7..46069898cc0 100644
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -101,6 +101,7 @@ namespace {
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
+    void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
     void printTemplateParameters(const TemplateParameterList *Params);
@@ -423,7 +424,7 @@ void DeclPrinter::VisitDeclContext(DeclContext *DC, bool Indent) {
     // FIXME: Need to be able to tell the DeclPrinter when
     const char *Terminator = nullptr;
     if (isa<OMPThreadPrivateDecl>(*D) || isa<OMPDeclareReductionDecl>(*D) ||
-        isa<OMPRequiresDecl>(*D))
+        isa<OMPDeclareMapperDecl>(*D) || isa<OMPRequiresDecl>(*D))
       Terminator = nullptr;
     else if (isa<ObjCMethodDecl>(*D) && cast<ObjCMethodDecl>(*D)->hasBody())
       Terminator = nullptr;
@@ -1597,6 +1598,25 @@ void DeclPrinter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   }
 }
 
+void DeclPrinter::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
+  if (!D->isInvalidDecl()) {
+    Out << "#pragma omp declare mapper (";
+    D->printName(Out);
+    Out << " : ";
+    D->getType().print(Out, Policy);
+    Out << " ";
+    Out << D->getVarName();
+    Out << ")";
+    if (!D->clauselist_empty()) {
+      OMPClausePrinter Printer(Out, Policy);
+      for (auto *C : D->clauselists()) {
+        Out << " ";
+        Printer.Visit(C);
+      }
+    }
+  }
+}
+
 void DeclPrinter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   D->getInit()->printPretty(Out, nullptr, Policy, Indentation);
 }
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 34a6181bd4f..5d5d857c44f 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -60,7 +60,8 @@ static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   }
 
   const DeclContext *DC = D->getDeclContext();
-  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC)) {
+  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC) ||
+      isa<OMPDeclareMapperDecl>(DC)) {
     return getEffectiveDeclContext(cast<Decl>(DC));
   }
 
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 471e738bbbb..b2d961a4396 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -96,7 +96,8 @@ static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   }
 
   const DeclContext *DC = D->getDeclContext();
-  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC)) {
+  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC) ||
+      isa<OMPDeclareMapperDecl>(DC)) {
     return getEffectiveDeclContext(cast<Decl>(DC));
   }
 
diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
index c4215170063..ea8a46b4953 100644
--- a/clang/lib/Basic/OpenMPKinds.cpp
+++ b/clang/lib/Basic/OpenMPKinds.cpp
@@ -766,6 +766,16 @@ bool clang::isAllowedClauseForDirective(OpenMPDirectiveKind DKind,
       break;
     }
     break;
+  case OMPD_declare_mapper:
+    switch (CKind) {
+#define OPENMP_DECLARE_MAPPER_CLAUSE(Name)                                     \
+  case OMPC_##Name:                                                            \
+    return true;
+#include "clang/Basic/OpenMPKinds.def"
+    default:
+      break;
+    }
+    break;
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_unknown:
@@ -1000,6 +1010,7 @@ void clang::getOpenMPCaptureRegions(
   case OMPD_cancel:
   case OMPD_flush:
   case OMPD_declare_reduction:
+  case OMPD_declare_mapper:
   case OMPD_declare_simd:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 6e8f85430a4..72fd902ecee 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -141,6 +141,9 @@ void CodeGenFunction::EmitDecl(const Decl &D) {
   case Decl::OMPDeclareReduction:
     return CGM.EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(&D), this);
 
+  case Decl::OMPDeclareMapper:
+    return CGM.EmitOMPDeclareMapper(cast<OMPDeclareMapperDecl>(&D), this);
+
   case Decl::Typedef:      // typedef int X;
   case Decl::TypeAlias: {  // using X = int; [C++0x]
     const TypedefNameDecl &TD = cast<TypedefNameDecl>(D);
@@ -2416,6 +2419,13 @@ void CodeGenModule::EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
   getOpenMPRuntime().emitUserDefinedReduction(CGF, D);
 }
 
+void CodeGenModule::EmitOMPDeclareMapper(const OMPDeclareMapperDecl *D,
+                                            CodeGenFunction *CGF) {
+  if (!LangOpts.OpenMP || (!LangOpts.EmitAllDecls && !D->isUsed()))
+    return;
+  // FIXME: need to implement mapper code generation
+}
+
 void CodeGenModule::EmitOMPRequiresDecl(const OMPRequiresDecl *D) {
   getOpenMPRuntime().checkArchForUnifiedAddressing(*this, D);
 }
diff --git a/clang/lib/CodeGen/CGOpenMPRuntime.cpp b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
index ad02ee6e21e..f650bd98e61 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntime.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntime.cpp
@@ -8230,6 +8230,7 @@ getNestedDistributeDirective(ASTContext &Ctx, const OMPExecutableDirective &D) {
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
     case OMPD_requires:
@@ -8652,6 +8653,7 @@ void CGOpenMPRuntime::scanForTargetRegionsFunctions(const Stmt *S,
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
     case OMPD_requires:
@@ -9132,6 +9134,7 @@ void CGOpenMPRuntime::emitTargetDataStandAloneCall(
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
     case OMPD_target:
diff --git a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
index 788fa83ea05..ca9673096ec 100644
--- a/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
+++ b/clang/lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp
@@ -858,6 +858,7 @@ static bool hasNestedSPMDDirective(ASTContext &Ctx,
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
     case OMPD_requires:
@@ -926,6 +927,7 @@ static bool supportsSPMDExecutionMode(ASTContext &Ctx,
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction:
+  case OMPD_declare_mapper:
   case OMPD_taskloop:
   case OMPD_taskloop_simd:
   case OMPD_requires:
@@ -1076,6 +1078,7 @@ static bool hasNestedLightweightDirective(ASTContext &Ctx,
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_taskloop:
     case OMPD_taskloop_simd:
     case OMPD_requires:
@@ -1149,6 +1152,7 @@ static bool supportsLightweightRuntime(ASTContext &Ctx,
   case OMPD_declare_target:
   case OMPD_end_declare_target:
   case OMPD_declare_reduction:
+  case OMPD_declare_mapper:
   case OMPD_taskloop:
   case OMPD_taskloop_simd:
   case OMPD_requires:
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index b8004452f83..199ec598351 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2191,6 +2191,10 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) {
       if (MustBeEmitted(Global))
         EmitOMPDeclareReduction(DRD);
       return;
+    } else if (auto *DMD = dyn_cast<OMPDeclareMapperDecl>(Global)) {
+      if (MustBeEmitted(Global))
+        EmitOMPDeclareMapper(DMD);
+      return;
     }
   }
 
@@ -5053,6 +5057,10 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(D));
     break;
 
+  case Decl::OMPDeclareMapper:
+    EmitOMPDeclareMapper(cast<OMPDeclareMapperDecl>(D));
+    break;
+
   case Decl::OMPRequires:
     EmitOMPRequiresDecl(cast<OMPRequiresDecl>(D));
     break;
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 35e94d7bb04..5d146daee85 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1243,6 +1243,10 @@ public:
   void EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
                                CodeGenFunction *CGF = nullptr);
 
+  /// Emit a code for declare mapper construct.
+  void EmitOMPDeclareMapper(const OMPDeclareMapperDecl *D,
+                            CodeGenFunction *CGF = nullptr);
+
   /// Emit a code for requires directive.
   /// \param D Requires declaration
   void EmitOMPRequiresDecl(const OMPRequiresDecl *D);
diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
index 2308e6e3da9..5b8670e928b 100644
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -40,7 +40,8 @@ enum OpenMPDirectiveKindEx {
   OMPD_update,
   OMPD_distribute_parallel,
   OMPD_teams_distribute_parallel,
-  OMPD_target_teams_distribute_parallel
+  OMPD_target_teams_distribute_parallel,
+  OMPD_mapper,
 };
 
 class ThreadprivateListParserHelper final {
@@ -76,6 +77,7 @@ static unsigned getOpenMPDirectiveKindEx(StringRef S) {
       .Case("point", OMPD_point)
       .Case("reduction", OMPD_reduction)
       .Case("update", OMPD_update)
+      .Case("mapper", OMPD_mapper)
       .Default(OMPD_unknown);
 }
 
@@ -86,6 +88,7 @@ static OpenMPDirectiveKind parseOpenMPDirectiveKind(Parser &P) {
   static const unsigned F[][3] = {
       {OMPD_cancellation, OMPD_point, OMPD_cancellation_point},
       {OMPD_declare, OMPD_reduction, OMPD_declare_reduction},
+      {OMPD_declare, OMPD_mapper, OMPD_declare_mapper},
       {OMPD_declare, OMPD_simd, OMPD_declare_simd},
       {OMPD_declare, OMPD_target, OMPD_declare_target},
       {OMPD_distribute, OMPD_parallel, OMPD_distribute_parallel},
@@ -469,6 +472,141 @@ void Parser::ParseOpenMPReductionInitializerForDecl(VarDecl *OmpPrivParm) {
   }
 }
 
+/// Parses 'omp declare mapper' directive.
+///
+///       declare-mapper-directive:
+///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifier> ':']
+///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
+///         annot_pragma_openmp_end
+/// <mapper-identifier> and <var> are base language identifiers.
+///
+Parser::DeclGroupPtrTy
+Parser::ParseOpenMPDeclareMapperDirective(AccessSpecifier AS) {
+  bool IsCorrect = true;
+  // Parse '('
+  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
+  if (T.expectAndConsume(diag::err_expected_lparen_after,
+                         getOpenMPDirectiveName(OMPD_declare_mapper))) {
+    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
+    return DeclGroupPtrTy();
+  }
+
+  // Parse <mapper-identifier>
+  auto &DeclNames = Actions.getASTContext().DeclarationNames;
+  DeclarationName MapperId;
+  if (PP.LookAhead(0).is(tok::colon)) {
+    if (Tok.isNot(tok::identifier) && Tok.isNot(tok::kw_default)) {
+      Diag(Tok.getLocation(), diag::err_omp_mapper_illegal_identifier);
+      IsCorrect = false;
+    } else {
+      MapperId = DeclNames.getIdentifier(Tok.getIdentifierInfo());
+    }
+    ConsumeToken();
+    // Consume ':'.
+    ExpectAndConsume(tok::colon);
+  } else {
+    // If no mapper identifier is provided, its name is "default" by default
+    MapperId =
+        DeclNames.getIdentifier(&Actions.getASTContext().Idents.get("default"));
+  }
+
+  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
+    return DeclGroupPtrTy();
+
+  // Parse <type> <var>
+  DeclarationName VName;
+  QualType MapperType;
+  SourceRange Range;
+  TypeResult ParsedType = parseOpenMPDeclareMapperVarDecl(Range, VName, AS);
+  if (ParsedType.isUsable())
+    MapperType =
+        Actions.ActOnOpenMPDeclareMapperType(Range.getBegin(), ParsedType);
+  if (MapperType.isNull())
+    IsCorrect = false;
+  if (!IsCorrect) {
+    SkipUntil(tok::annot_pragma_openmp_end, Parser::StopBeforeMatch);
+    return DeclGroupPtrTy();
+  }
+
+  // Consume ')'.
+  IsCorrect &= !T.consumeClose();
+  if (!IsCorrect) {
+    SkipUntil(tok::annot_pragma_openmp_end, Parser::StopBeforeMatch);
+    return DeclGroupPtrTy();
+  }
+
+  // Enter scope.
+  OMPDeclareMapperDecl *DMD = Actions.ActOnOpenMPDeclareMapperDirectiveStart(
+      getCurScope(), Actions.getCurLexicalContext(), MapperId, MapperType,
+      Range.getBegin(), VName, AS);
+  DeclarationNameInfo DirName;
+  SourceLocation Loc = Tok.getLocation();
+  unsigned ScopeFlags = Scope::FnScope | Scope::DeclScope |
+                        Scope::CompoundStmtScope | Scope::OpenMPDirectiveScope;
+  ParseScope OMPDirectiveScope(this, ScopeFlags);
+  Actions.StartOpenMPDSABlock(OMPD_declare_mapper, DirName, getCurScope(), Loc);
+
+  // Add the mapper variable declaration.
+  Actions.ActOnOpenMPDeclareMapperDirectiveVarDecl(
+      DMD, getCurScope(), MapperType, Range.getBegin(), VName);
+
+  // Parse map clauses.
+  SmallVector<OMPClause *, 6> Clauses;
+  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_declare_mapper, CKind, Clauses.size() == 0);
+    if (Clause)
+      Clauses.push_back(Clause);
+    else
+      IsCorrect = false;
+    // Skip ',' if any.
+    if (Tok.is(tok::comma))
+      ConsumeToken();
+    Actions.EndOpenMPClause();
+  }
+  if (Clauses.empty()) {
+    Diag(Tok, diag::err_omp_expected_clause)
+        << getOpenMPDirectiveName(OMPD_declare_mapper);
+    IsCorrect = false;
+  }
+
+  // Exit scope.
+  Actions.EndOpenMPDSABlock(nullptr);
+  OMPDirectiveScope.Exit();
+
+  DeclGroupPtrTy DGP =
+      Actions.ActOnOpenMPDeclareMapperDirectiveEnd(DMD, getCurScope(), Clauses);
+  if (!IsCorrect)
+    return DeclGroupPtrTy();
+  return DGP;
+}
+
+TypeResult Parser::parseOpenMPDeclareMapperVarDecl(SourceRange &Range,
+                                                   DeclarationName &Name,
+                                                   AccessSpecifier AS) {
+  // Parse the common declaration-specifiers piece.
+  Parser::DeclSpecContext DSC = Parser::DeclSpecContext::DSC_type_specifier;
+  DeclSpec DS(AttrFactory);
+  ParseSpecifierQualifierList(DS, AS, DSC);
+
+  // Parse the declarator.
+  DeclaratorContext Context = DeclaratorContext::PrototypeContext;
+  Declarator DeclaratorInfo(DS, Context);
+  ParseDeclarator(DeclaratorInfo);
+  Range = DeclaratorInfo.getSourceRange();
+  if (DeclaratorInfo.getIdentifier() == nullptr) {
+    Diag(Tok.getLocation(), diag::err_omp_mapper_expected_declarator);
+    return true;
+  }
+  Name = Actions.GetNameForDeclarator(DeclaratorInfo).getName();
+
+  return Actions.ActOnOpenMPDeclareMapperVarDecl(getCurScope(), DeclaratorInfo);
+}
+
 namespace {
 /// RAII that recreates function context for correct parsing of clauses of
 /// 'declare simd' construct.
@@ -707,6 +845,11 @@ void Parser::ParseOMPEndDeclareTargetDirective(OpenMPDirectiveKind DKind,
 ///        annot_pragma_openmp 'declare' 'reduction' [...]
 ///        annot_pragma_openmp_end
 ///
+///       declare-mapper-directive:
+///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifer> ':']
+///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
+///         annot_pragma_openmp_end
+///
 ///       declare-simd-directive:
 ///         annot_pragma_openmp 'declare simd' {<clause> [,]}
 ///         annot_pragma_openmp_end
@@ -800,6 +943,15 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
       return Res;
     }
     break;
+  case OMPD_declare_mapper: {
+    ConsumeToken();
+    if (DeclGroupPtrTy Res = ParseOpenMPDeclareMapperDirective(AS)) {
+      // Skip the last annot_pragma_openmp_end.
+      ConsumeAnnotationToken();
+      return Res;
+    }
+    break;
+  }
   case OMPD_declare_simd: {
     // The syntax is:
     // { #pragma omp declare simd }
@@ -954,6 +1106,11 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
 ///         ('omp_priv' '=' <expression>|<function_call>) ')']
 ///         annot_pragma_openmp_end
 ///
+///       declare-mapper-directive:
+///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifer> ':']
+///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
+///         annot_pragma_openmp_end
+///
 ///       executable-directive:
 ///         annot_pragma_openmp 'parallel' | 'simd' | 'for' | 'sections' |
 ///         'section' | 'single' | 'master' | 'critical' [ '(' <name> ')' ] |
@@ -1034,6 +1191,18 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
       SkipUntil(tok::annot_pragma_openmp_end);
     }
     break;
+  case OMPD_declare_mapper: {
+    ConsumeToken();
+    if (DeclGroupPtrTy Res =
+            ParseOpenMPDeclareMapperDirective(/*AS=*/AS_none)) {
+      // Skip the last annot_pragma_openmp_end.
+      ConsumeAnnotationToken();
+      Directive = Actions.ActOnDeclStmt(Res, Loc, Tok.getLocation());
+    } else {
+      SkipUntil(tok::annot_pragma_openmp_end);
+    }
+    break;
+  }
   case OMPD_flush:
     if (PP.LookAhead(0).is(tok::l_paren)) {
       FlushHasClause = true;
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 136162ad0fa..5b6fd880ca8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -6192,7 +6192,8 @@ static bool isIncompleteDeclExternC(Sema &S, const T *D) {
 
 static bool shouldConsiderLinkage(const VarDecl *VD) {
   const DeclContext *DC = VD->getDeclContext()->getRedeclContext();
-  if (DC->isFunctionOrMethod() || isa<OMPDeclareReductionDecl>(DC))
+  if (DC->isFunctionOrMethod() || isa<OMPDeclareReductionDecl>(DC) ||
+      isa<OMPDeclareMapperDecl>(DC))
     return VD->hasExternalStorage();
   if (DC->isFileContext())
     return true;
@@ -6204,7 +6205,7 @@ static bool shouldConsiderLinkage(const VarDecl *VD) {
 static bool shouldConsiderLinkage(const FunctionDecl *FD) {
   const DeclContext *DC = FD->getDeclContext()->getRedeclContext();
   if (DC->isFileContext() || DC->isFunctionOrMethod() ||
-      isa<OMPDeclareReductionDecl>(DC))
+      isa<OMPDeclareReductionDecl>(DC) || isa<OMPDeclareMapperDecl>(DC))
     return true;
   if (DC->isRecord())
     return false;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 15957ae49d3..b675986f56b 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -310,6 +310,19 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
     return true;
   }
 
+  // [OpenMP 5.0], 2.19.7.3. declare mapper Directive, Restrictions
+  //  List-items in map clauses on this construct may only refer to the declared
+  //  variable var and entities that could be referenced by a procedure defined
+  //  at the same location
+  auto *DMD = dyn_cast<OMPDeclareMapperDecl>(CurContext);
+  if (LangOpts.OpenMP && DMD && !CurContext->containsDecl(D) &&
+      isa<VarDecl>(D)) {
+    Diag(Loc, diag::err_omp_declare_mapper_wrong_var)
+        << DMD->getVarName().getAsString();
+    Diag(D->getLocation(), diag::note_entity_declared_at) << D;
+    return true;
+  }
+
   DiagnoseAvailabilityOfDecl(D, Locs, UnknownObjCClass, ObjCPropertyAccess,
                              AvoidPartialAvailabilityChecks, ClassReceiver);
 
@@ -2988,6 +3001,7 @@ ExprResult Sema::BuildDeclarationNameExpr(
     case Decl::EnumConstant:
     case Decl::UnresolvedUsingValue:
     case Decl::OMPDeclareReduction:
+    case Decl::OMPDeclareMapper:
       valueKind = VK_RValue;
       break;
 
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 653fc133b2a..249be780985 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -278,6 +278,10 @@ static inline unsigned getIDNS(Sema::LookupNameKind NameKind,
     IDNS = Decl::IDNS_OMPReduction;
     break;
 
+  case Sema::LookupOMPMapperName:
+    IDNS = Decl::IDNS_OMPMapper;
+    break;
+
   case Sema::LookupAnyName:
     IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member
       | Decl::IDNS_Using | Decl::IDNS_Namespace | Decl::IDNS_ObjCProtocol
@@ -2103,6 +2107,10 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
       BaseCallback = &CXXRecordDecl::FindOMPReductionMember;
       break;
 
+    case LookupOMPMapperName:
+      BaseCallback = &CXXRecordDecl::FindOMPMapperMember;
+      break;
+
     case LookupUsingDeclName:
       // This lookup is for redeclarations only.
 
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 59a40ec41c7..6b345bfd239 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -2808,6 +2808,7 @@ void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
   case OMPD_cancel:
   case OMPD_flush:
   case OMPD_declare_reduction:
+  case OMPD_declare_mapper:
   case OMPD_declare_simd:
   case OMPD_declare_target:
   case OMPD_end_declare_target:
@@ -3656,6 +3657,7 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   case OMPD_end_declare_target:
   case OMPD_threadprivate:
   case OMPD_declare_reduction:
+  case OMPD_declare_mapper:
   case OMPD_declare_simd:
   case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
@@ -8435,6 +8437,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8501,6 +8504,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8568,6 +8572,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8632,6 +8637,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8697,6 +8703,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8761,6 +8768,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -8824,6 +8832,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_cancellation_point:
     case OMPD_flush:
     case OMPD_declare_reduction:
+    case OMPD_declare_mapper:
     case OMPD_declare_simd:
     case OMPD_declare_target:
     case OMPD_end_declare_target:
@@ -13464,6 +13473,143 @@ Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareReductionDirectiveEnd(
   return DeclReductions;
 }
 
+TypeResult Sema::ActOnOpenMPDeclareMapperVarDecl(Scope *S, Declarator &D) {
+  TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
+  QualType T = TInfo->getType();
+  if (D.isInvalidType())
+    return true;
+
+  if (getLangOpts().CPlusPlus) {
+    // Check that there are no default arguments (C++ only).
+    CheckExtraCXXDefaultArguments(D);
+  }
+
+  return CreateParsedType(T, TInfo);
+}
+
+QualType Sema::ActOnOpenMPDeclareMapperType(SourceLocation TyLoc,
+                                            TypeResult ParsedType) {
+  assert(ParsedType.isUsable() && "Expect usable parsed mapper type");
+
+  QualType MapperType = GetTypeFromParser(ParsedType.get());
+  assert(!MapperType.isNull() && "Expect valid mapper type");
+
+  // [OpenMP 5.0], 2.19.7.3 declare mapper Directive, Restrictions
+  //  The type must be of struct, union or class type in C and C++
+  if (!MapperType->isStructureOrClassType() && !MapperType->isUnionType()) {
+    Diag(TyLoc, diag::err_omp_mapper_wrong_type);
+    return QualType();
+  }
+  return MapperType;
+}
+
+OMPDeclareMapperDecl *Sema::ActOnOpenMPDeclareMapperDirectiveStart(
+    Scope *S, DeclContext *DC, DeclarationName Name, QualType MapperType,
+    SourceLocation StartLoc, DeclarationName VN, AccessSpecifier AS,
+    Decl *PrevDeclInScope) {
+  LookupResult Lookup(*this, Name, SourceLocation(), LookupOMPMapperName,
+                      forRedeclarationInCurContext());
+  // [OpenMP 5.0], 2.19.7.3 declare mapper Directive, Restrictions
+  //  A mapper-identifier may not be redeclared in the current scope for the
+  //  same type or for a type that is compatible according to the base language
+  //  rules.
+  llvm::DenseMap<QualType, SourceLocation> PreviousRedeclTypes;
+  OMPDeclareMapperDecl *PrevDMD = nullptr;
+  bool InCompoundScope = true;
+  if (S != nullptr) {
+    // Find previous declaration with the same name not referenced in other
+    // declarations.
+    FunctionScopeInfo *ParentFn = getEnclosingFunction();
+    InCompoundScope =
+        (ParentFn != nullptr) && !ParentFn->CompoundScopes.empty();
+    LookupName(Lookup, S);
+    FilterLookupForScope(Lookup, DC, S, /*ConsiderLinkage=*/false,
+                         /*AllowInlineNamespace=*/false);
+    llvm::DenseMap<OMPDeclareMapperDecl *, bool> UsedAsPrevious;
+    LookupResult::Filter Filter = Lookup.makeFilter();
+    while (Filter.hasNext()) {
+      auto *PrevDecl = cast<OMPDeclareMapperDecl>(Filter.next());
+      if (InCompoundScope) {
+        auto I = UsedAsPrevious.find(PrevDecl);
+        if (I == UsedAsPrevious.end())
+          UsedAsPrevious[PrevDecl] = false;
+        if (OMPDeclareMapperDecl *D = PrevDecl->getPrevDeclInScope())
+          UsedAsPrevious[D] = true;
+      }
+      PreviousRedeclTypes[PrevDecl->getType().getCanonicalType()] =
+          PrevDecl->getLocation();
+    }
+    Filter.done();
+    if (InCompoundScope) {
+      for (const auto &PrevData : UsedAsPrevious) {
+        if (!PrevData.second) {
+          PrevDMD = PrevData.first;
+          break;
+        }
+      }
+    }
+  } else if (PrevDeclInScope) {
+    auto *PrevDMDInScope = PrevDMD =
+        cast<OMPDeclareMapperDecl>(PrevDeclInScope);
+    do {
+      PreviousRedeclTypes[PrevDMDInScope->getType().getCanonicalType()] =
+          PrevDMDInScope->getLocation();
+      PrevDMDInScope = PrevDMDInScope->getPrevDeclInScope();
+    } while (PrevDMDInScope != nullptr);
+  }
+  const auto I = PreviousRedeclTypes.find(MapperType.getCanonicalType());
+  bool Invalid = false;
+  if (I != PreviousRedeclTypes.end()) {
+    Diag(StartLoc, diag::err_omp_declare_mapper_redefinition)
+        << MapperType << Name;
+    Diag(I->second, diag::note_previous_definition);
+    Invalid = true;
+  }
+  auto *DMD = OMPDeclareMapperDecl::Create(Context, DC, StartLoc, Name,
+                                           MapperType, VN, PrevDMD);
+  DC->addDecl(DMD);
+  DMD->setAccess(AS);
+  if (Invalid)
+    DMD->setInvalidDecl();
+
+  // Enter new function scope.
+  PushFunctionScope();
+  setFunctionHasBranchProtectedScope();
+
+  CurContext = DMD;
+
+  return DMD;
+}
+
+void Sema::ActOnOpenMPDeclareMapperDirectiveVarDecl(OMPDeclareMapperDecl *DMD,
+                                                    Scope *S,
+                                                    QualType MapperType,
+                                                    SourceLocation StartLoc,
+                                                    DeclarationName VN) {
+  VarDecl *VD = buildVarDecl(*this, StartLoc, MapperType, VN.getAsString());
+  if (S)
+    PushOnScopeChains(VD, S);
+  else
+    DMD->addDecl(VD);
+  Expr *MapperVarRefExpr = buildDeclRefExpr(*this, VD, MapperType, StartLoc);
+  DMD->setMapperVarRef(MapperVarRefExpr);
+}
+
+Sema::DeclGroupPtrTy
+Sema::ActOnOpenMPDeclareMapperDirectiveEnd(OMPDeclareMapperDecl *D, Scope *S,
+                                           ArrayRef<OMPClause *> ClauseList) {
+  PopDeclContext();
+  PopFunctionScopeInfo();
+
+  if (D) {
+    if (S)
+      PushOnScopeChains(D, S, /*AddToContext=*/false);
+    D->CreateClauses(Context, ClauseList);
+  }
+
+  return DeclGroupPtrTy::make(DeclGroupRef(D));
+}
+
 OMPClause *Sema::ActOnOpenMPNumTeamsClause(Expr *NumTeams,
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 883a73f2266..e3f57e00381 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2924,6 +2924,87 @@ Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
   return NewDRD;
 }
 
+Decl *
+TemplateDeclInstantiator::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
+  // Instantiate type and check if it is allowed.
+  const bool RequiresInstantiation =
+      D->getType()->isDependentType() ||
+      D->getType()->isInstantiationDependentType() ||
+      D->getType()->containsUnexpandedParameterPack();
+  QualType SubstMapperTy;
+  DeclarationName VN = D->getVarName();
+  if (RequiresInstantiation) {
+    SubstMapperTy = SemaRef.ActOnOpenMPDeclareMapperType(
+        D->getLocation(),
+        ParsedType::make(SemaRef.SubstType(D->getType(), TemplateArgs,
+                                           D->getLocation(), VN)));
+  } else {
+    SubstMapperTy = D->getType();
+  }
+  if (SubstMapperTy.isNull())
+    return nullptr;
+  // Create an instantiated copy of mapper.
+  auto *PrevDeclInScope = D->getPrevDeclInScope();
+  if (PrevDeclInScope && !PrevDeclInScope->isInvalidDecl()) {
+    PrevDeclInScope = cast<OMPDeclareMapperDecl>(
+        SemaRef.CurrentInstantiationScope->findInstantiationOf(PrevDeclInScope)
+            ->get<Decl *>());
+  }
+  OMPDeclareMapperDecl *NewDMD = SemaRef.ActOnOpenMPDeclareMapperDirectiveStart(
+      /*S=*/nullptr, Owner, D->getDeclName(), SubstMapperTy, D->getLocation(),
+      VN, D->getAccess(), PrevDeclInScope);
+  SemaRef.CurrentInstantiationScope->InstantiatedLocal(D, NewDMD);
+  SmallVector<OMPClause *, 6> Clauses;
+  bool IsCorrect = true;
+  if (!RequiresInstantiation) {
+    // Copy the mapper variable.
+    NewDMD->setMapperVarRef(D->getMapperVarRef());
+    // Copy map clauses from the original mapper.
+    for (OMPClause *C : D->clauselists())
+      Clauses.push_back(C);
+  } else {
+    // Instantiate the mapper variable.
+    DeclarationNameInfo DirName;
+    SemaRef.StartOpenMPDSABlock(OMPD_declare_mapper, DirName, /*S=*/nullptr,
+                                (*D->clauselist_begin())->getBeginLoc());
+    SemaRef.ActOnOpenMPDeclareMapperDirectiveVarDecl(
+        NewDMD, /*S=*/nullptr, SubstMapperTy, D->getLocation(), VN);
+    SemaRef.CurrentInstantiationScope->InstantiatedLocal(
+        cast<DeclRefExpr>(D->getMapperVarRef())->getDecl(),
+        cast<DeclRefExpr>(NewDMD->getMapperVarRef())->getDecl());
+    auto *ThisContext = dyn_cast_or_null<CXXRecordDecl>(Owner);
+    Sema::CXXThisScopeRAII ThisScope(SemaRef, ThisContext, Qualifiers(),
+                                     ThisContext);
+    // Instantiate map clauses.
+    for (OMPClause *C : D->clauselists()) {
+      auto *OldC = cast<OMPMapClause>(C);
+      SmallVector<Expr *, 4> NewVars;
+      for (Expr *OE : OldC->varlists()) {
+        Expr *NE = SemaRef.SubstExpr(OE, TemplateArgs).get();
+        if (!NE) {
+          IsCorrect = false;
+          break;
+        }
+        NewVars.push_back(NE);
+      }
+      if (!IsCorrect)
+        break;
+      OMPClause *NewC = SemaRef.ActOnOpenMPMapClause(
+          OldC->getMapTypeModifiers(), OldC->getMapTypeModifiersLoc(),
+          OldC->getMapType(), OldC->isImplicitMapType(), OldC->getMapLoc(),
+          OldC->getColonLoc(), NewVars, OldC->getBeginLoc(),
+          OldC->getLParenLoc(), OldC->getEndLoc());
+      Clauses.push_back(NewC);
+    }
+    SemaRef.EndOpenMPDSABlock(nullptr);
+  }
+  (void)SemaRef.ActOnOpenMPDeclareMapperDirectiveEnd(NewDMD, /*S=*/nullptr,
+                                                     Clauses);
+  if (!IsCorrect)
+    return nullptr;
+  return NewDMD;
+}
+
 Decl *TemplateDeclInstantiator::VisitOMPCapturedExprDecl(
     OMPCapturedExprDecl * /*D*/) {
   llvm_unreachable("Should not be met in templates");
@@ -5005,7 +5086,8 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
   if (isa<ParmVarDecl>(D) || isa<NonTypeTemplateParmDecl>(D) ||
       isa<TemplateTypeParmDecl>(D) || isa<TemplateTemplateParmDecl>(D) ||
       ((ParentDC->isFunctionOrMethod() ||
-        isa<OMPDeclareReductionDecl>(ParentDC)) &&
+        isa<OMPDeclareReductionDecl>(ParentDC) ||
+        isa<OMPDeclareMapperDecl>(ParentDC)) &&
        ParentDC->isDependentContext()) ||
       (isa<CXXRecordDecl>(D) && cast<CXXRecordDecl>(D)->isLambda())) {
     // D is a local of some kind. Look into the map of local
diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index a54ba5fabf3..1e15cb4afdd 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -390,6 +390,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::OMPRequires:
   case Decl::OMPCapturedExpr:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPDeclareMapper:
   case Decl::BuiltinTemplate:
   case Decl::Decomposition:
   case Decl::Binding:
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index def42ac7203..aaf40b93f19 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -12300,7 +12300,7 @@ void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
   SmallVector<Expr *, 16> Vars;
   Vars.reserve(NumVars);
   for (unsigned i = 0; i != NumVars; ++i)
-    Vars.push_back(Record.readSubExpr());
+    Vars.push_back(Record.readExpr());
   C->setVarRefs(Vars);
 
   SmallVector<ValueDecl *, 16> Decls;
@@ -12324,7 +12324,7 @@ void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
   SmallVector<OMPClauseMappableExprCommon::MappableComponent, 32> Components;
   Components.reserve(TotalComponents);
   for (unsigned i = 0; i < TotalComponents; ++i) {
-    Expr *AssociatedExpr = Record.readSubExpr();
+    Expr *AssociatedExpr = Record.readExpr();
     auto *AssociatedDecl = Record.readDeclAs<ValueDecl>();
     Components.push_back(OMPClauseMappableExprCommon::MappableComponent(
         AssociatedExpr, AssociatedDecl));
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 8b40dc853ba..1c56cdbf948 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -445,6 +445,7 @@ namespace clang {
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
+    void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
   };
@@ -2659,6 +2660,22 @@ void ASTDeclReader::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   D->PrevDeclInScope = ReadDeclID();
 }
 
+void ASTDeclReader::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
+  VisitValueDecl(D);
+  D->setLocation(ReadSourceLocation());
+  Expr *MapperVarRefE = Record.readExpr();
+  D->setMapperVarRef(MapperVarRefE);
+  D->VarName = Record.readDeclarationName();
+  D->PrevDeclInScope = ReadDeclID();
+  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::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   VisitVarDecl(D);
 }
@@ -2776,7 +2793,8 @@ static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
       isa<PragmaCommentDecl>(D) ||
       isa<PragmaDetectMismatchDecl>(D))
     return true;
-  if (isa<OMPThreadPrivateDecl>(D) || isa<OMPDeclareReductionDecl>(D))
+  if (isa<OMPThreadPrivateDecl>(D) || isa<OMPDeclareReductionDecl>(D) ||
+      isa<OMPDeclareMapperDecl>(D))
     return !D->getDeclContext()->isFunctionOrMethod();
   if (const auto *Var = dyn_cast<VarDecl>(D))
     return Var->isFileVarDecl() &&
@@ -3853,6 +3871,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_OMP_DECLARE_REDUCTION:
     D = OMPDeclareReductionDecl::CreateDeserialized(Context, ID);
     break;
+  case DECL_OMP_DECLARE_MAPPER:
+    D = OMPDeclareMapperDecl::CreateDeserialized(Context, ID, Record.readInt());
+    break;
   case DECL_OMP_CAPTUREDEXPR:
     D = OMPCapturedExprDecl::CreateDeserialized(Context, ID);
     break;
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 16fdb54ee9b..bd5191dcb91 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -146,6 +146,7 @@ namespace clang {
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
+    void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
     /// Add an Objective-C type parameter list to the given record.
@@ -1765,6 +1766,19 @@ void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   Code = serialization::DECL_OMP_DECLARE_REDUCTION;
 }
 
+void ASTDeclWriter::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
+  Record.push_back(D->clauselist_size());
+  VisitValueDecl(D);
+  Record.AddSourceLocation(D->getBeginLoc());
+  Record.AddStmt(D->getMapperVarRef());
+  Record.AddDeclarationName(D->getVarName());
+  Record.AddDeclRef(D->getPrevDeclInScope());
+  OMPClauseWriter ClauseWriter(Record);
+  for (OMPClause *C : D->clauselists())
+    ClauseWriter.writeClause(C);
+  Code = serialization::DECL_OMP_DECLARE_MAPPER;
+}
+
 void ASTDeclWriter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   VisitVarDecl(D);
   Code = serialization::DECL_OMP_CAPTUREDEXPR;