[OpenMP 5.0] Parsing/sema support for map clause with mapper modifier.

This patch implements the parsing and sema support for OpenMP map
clauses with potential user-defined mapper attached. User defined mapper
is a new feature in OpenMP 5.0. A map clause can have an explicit or
implicit associated mapper, which instructs the compiler to generate
extra data mapping. An example is shown below:

    struct S { int len; int *d; };
    #pragma omp declare mapper(id: struct S s) map(s, s.d[0:s.len])
    struct S ss;
    #pragma omp target map(mapper(id) tofrom: ss) // use the mapper with name 'id' to map ss

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

Differential Revision: https://reviews.llvm.org/D58074

llvm-svn: 354347

7 files changed, 535 insertions, 293 deletions

diff --git a/clang/lib/AST/OpenMPClause.cpp b/clang/lib/AST/OpenMPClause.cpp
index 1640995cea0..549b869849d 100644
--- a/clang/lib/AST/OpenMPClause.cpp
+++ b/clang/lib/AST/OpenMPClause.cpp
@@ -791,24 +791,23 @@ unsigned OMPClauseMappableExprCommon::getUniqueDeclarationsTotalNumber(
   return TotalNum;
 }
 
-OMPMapClause *
-OMPMapClause::Create(const ASTContext &C, SourceLocation StartLoc,
-                     SourceLocation LParenLoc, SourceLocation EndLoc,
-                     ArrayRef<Expr *> Vars, ArrayRef<ValueDecl *> Declarations,
-                     MappableExprComponentListsRef ComponentLists,
-                     ArrayRef<OpenMPMapModifierKind> MapModifiers,
-                     ArrayRef<SourceLocation> MapModifiersLoc,
-                     OpenMPMapClauseKind Type, bool TypeIsImplicit,
-                     SourceLocation TypeLoc) {
-  unsigned NumVars = Vars.size();
-  unsigned NumUniqueDeclarations =
-      getUniqueDeclarationsTotalNumber(Declarations);
-  unsigned NumComponentLists = ComponentLists.size();
-  unsigned NumComponents = getComponentsTotalNumber(ComponentLists);
+OMPMapClause *OMPMapClause::Create(
+    const ASTContext &C, const OMPVarListLocTy &Locs, ArrayRef<Expr *> Vars,
+    ArrayRef<ValueDecl *> Declarations,
+    MappableExprComponentListsRef ComponentLists, ArrayRef<Expr *> UDMapperRefs,
+    ArrayRef<OpenMPMapModifierKind> MapModifiers,
+    ArrayRef<SourceLocation> MapModifiersLoc,
+    NestedNameSpecifierLoc UDMQualifierLoc, DeclarationNameInfo MapperId,
+    OpenMPMapClauseKind Type, bool TypeIsImplicit, SourceLocation TypeLoc) {
+  OMPMappableExprListSizeTy Sizes;
+  Sizes.NumVars = Vars.size();
+  Sizes.NumUniqueDeclarations = getUniqueDeclarationsTotalNumber(Declarations);
+  Sizes.NumComponentLists = ComponentLists.size();
+  Sizes.NumComponents = getComponentsTotalNumber(ComponentLists);
 
   // We need to allocate:
-  // NumVars x Expr* - we have an original list expression for each clause list
-  // entry.
+  // 2 x NumVars x Expr* - we have an original list expression and an associated
+  // user-defined mapper for each clause list entry.
   // NumUniqueDeclarations x ValueDecl* - unique base declarations associated
   // with each component list.
   // (NumUniqueDeclarations + NumComponentLists) x unsigned - we specify the
@@ -819,43 +818,43 @@ OMPMapClause::Create(const ASTContext &C, SourceLocation StartLoc,
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  OMPMapClause *Clause = new (Mem) OMPMapClause(
-      MapModifiers, MapModifiersLoc, Type, TypeIsImplicit, TypeLoc, StartLoc,
-      LParenLoc, EndLoc, NumVars, NumUniqueDeclarations, NumComponentLists,
-      NumComponents);
+          2 * Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  OMPMapClause *Clause = new (Mem)
+      OMPMapClause(MapModifiers, MapModifiersLoc, UDMQualifierLoc, MapperId,
+                   Type, TypeIsImplicit, TypeLoc, Locs, Sizes);
 
   Clause->setVarRefs(Vars);
+  Clause->setUDMapperRefs(UDMapperRefs);
   Clause->setClauseInfo(Declarations, ComponentLists);
   Clause->setMapType(Type);
   Clause->setMapLoc(TypeLoc);
   return Clause;
 }
 
-OMPMapClause *OMPMapClause::CreateEmpty(const ASTContext &C, unsigned NumVars,
-                                        unsigned NumUniqueDeclarations,
-                                        unsigned NumComponentLists,
-                                        unsigned NumComponents) {
+OMPMapClause *
+OMPMapClause::CreateEmpty(const ASTContext &C,
+                          const OMPMappableExprListSizeTy &Sizes) {
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  return new (Mem) OMPMapClause(NumVars, NumUniqueDeclarations,
-                                NumComponentLists, NumComponents);
+          2 * Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  return new (Mem) OMPMapClause(Sizes);
 }
 
-OMPToClause *OMPToClause::Create(const ASTContext &C, SourceLocation StartLoc,
-                                 SourceLocation LParenLoc,
-                                 SourceLocation EndLoc, ArrayRef<Expr *> Vars,
+OMPToClause *OMPToClause::Create(const ASTContext &C,
+                                 const OMPVarListLocTy &Locs,
+                                 ArrayRef<Expr *> Vars,
                                  ArrayRef<ValueDecl *> Declarations,
                                  MappableExprComponentListsRef ComponentLists) {
-  unsigned NumVars = Vars.size();
-  unsigned NumUniqueDeclarations =
-      getUniqueDeclarationsTotalNumber(Declarations);
-  unsigned NumComponentLists = ComponentLists.size();
-  unsigned NumComponents = getComponentsTotalNumber(ComponentLists);
+  OMPMappableExprListSizeTy Sizes;
+  Sizes.NumVars = Vars.size();
+  Sizes.NumUniqueDeclarations = getUniqueDeclarationsTotalNumber(Declarations);
+  Sizes.NumComponentLists = ComponentLists.size();
+  Sizes.NumComponents = getComponentsTotalNumber(ComponentLists);
 
   // We need to allocate:
   // NumVars x Expr* - we have an original list expression for each clause list
@@ -870,41 +869,37 @@ OMPToClause *OMPToClause::Create(const ASTContext &C, SourceLocation StartLoc,
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
 
-  OMPToClause *Clause = new (Mem)
-      OMPToClause(StartLoc, LParenLoc, EndLoc, NumVars, NumUniqueDeclarations,
-                  NumComponentLists, NumComponents);
+  OMPToClause *Clause = new (Mem) OMPToClause(Locs, Sizes);
 
   Clause->setVarRefs(Vars);
   Clause->setClauseInfo(Declarations, ComponentLists);
   return Clause;
 }
 
-OMPToClause *OMPToClause::CreateEmpty(const ASTContext &C, unsigned NumVars,
-                                      unsigned NumUniqueDeclarations,
-                                      unsigned NumComponentLists,
-                                      unsigned NumComponents) {
+OMPToClause *OMPToClause::CreateEmpty(const ASTContext &C,
+                                      const OMPMappableExprListSizeTy &Sizes) {
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  return new (Mem) OMPToClause(NumVars, NumUniqueDeclarations,
-                               NumComponentLists, NumComponents);
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  return new (Mem) OMPToClause(Sizes);
 }
 
 OMPFromClause *
-OMPFromClause::Create(const ASTContext &C, SourceLocation StartLoc,
-                      SourceLocation LParenLoc, SourceLocation EndLoc,
+OMPFromClause::Create(const ASTContext &C, const OMPVarListLocTy &Locs,
                       ArrayRef<Expr *> Vars, ArrayRef<ValueDecl *> Declarations,
                       MappableExprComponentListsRef ComponentLists) {
-  unsigned NumVars = Vars.size();
-  unsigned NumUniqueDeclarations =
-      getUniqueDeclarationsTotalNumber(Declarations);
-  unsigned NumComponentLists = ComponentLists.size();
-  unsigned NumComponents = getComponentsTotalNumber(ComponentLists);
+  OMPMappableExprListSizeTy Sizes;
+  Sizes.NumVars = Vars.size();
+  Sizes.NumUniqueDeclarations = getUniqueDeclarationsTotalNumber(Declarations);
+  Sizes.NumComponentLists = ComponentLists.size();
+  Sizes.NumComponents = getComponentsTotalNumber(ComponentLists);
 
   // We need to allocate:
   // NumVars x Expr* - we have an original list expression for each clause list
@@ -919,29 +914,27 @@ OMPFromClause::Create(const ASTContext &C, SourceLocation StartLoc,
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
 
-  OMPFromClause *Clause = new (Mem)
-      OMPFromClause(StartLoc, LParenLoc, EndLoc, NumVars, NumUniqueDeclarations,
-                    NumComponentLists, NumComponents);
+  OMPFromClause *Clause = new (Mem) OMPFromClause(Locs, Sizes);
 
   Clause->setVarRefs(Vars);
   Clause->setClauseInfo(Declarations, ComponentLists);
   return Clause;
 }
 
-OMPFromClause *OMPFromClause::CreateEmpty(const ASTContext &C, unsigned NumVars,
-                                          unsigned NumUniqueDeclarations,
-                                          unsigned NumComponentLists,
-                                          unsigned NumComponents) {
+OMPFromClause *
+OMPFromClause::CreateEmpty(const ASTContext &C,
+                           const OMPMappableExprListSizeTy &Sizes) {
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  return new (Mem) OMPFromClause(NumVars, NumUniqueDeclarations,
-                                 NumComponentLists, NumComponents);
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  return new (Mem) OMPFromClause(Sizes);
 }
 
 void OMPUseDevicePtrClause::setPrivateCopies(ArrayRef<Expr *> VL) {
@@ -957,15 +950,15 @@ void OMPUseDevicePtrClause::setInits(ArrayRef<Expr *> VL) {
 }
 
 OMPUseDevicePtrClause *OMPUseDevicePtrClause::Create(
-    const ASTContext &C, SourceLocation StartLoc, SourceLocation LParenLoc,
-    SourceLocation EndLoc, ArrayRef<Expr *> Vars, ArrayRef<Expr *> PrivateVars,
-    ArrayRef<Expr *> Inits, ArrayRef<ValueDecl *> Declarations,
+    const ASTContext &C, const OMPVarListLocTy &Locs, ArrayRef<Expr *> Vars,
+    ArrayRef<Expr *> PrivateVars, ArrayRef<Expr *> Inits,
+    ArrayRef<ValueDecl *> Declarations,
     MappableExprComponentListsRef ComponentLists) {
-  unsigned NumVars = Vars.size();
-  unsigned NumUniqueDeclarations =
-      getUniqueDeclarationsTotalNumber(Declarations);
-  unsigned NumComponentLists = ComponentLists.size();
-  unsigned NumComponents = getComponentsTotalNumber(ComponentLists);
+  OMPMappableExprListSizeTy Sizes;
+  Sizes.NumVars = Vars.size();
+  Sizes.NumUniqueDeclarations = getUniqueDeclarationsTotalNumber(Declarations);
+  Sizes.NumComponentLists = ComponentLists.size();
+  Sizes.NumComponents = getComponentsTotalNumber(ComponentLists);
 
   // We need to allocate:
   // 3 x NumVars x Expr* - we have an original list expression for each clause
@@ -980,12 +973,11 @@ OMPUseDevicePtrClause *OMPUseDevicePtrClause::Create(
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          3 * NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
+          3 * Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
 
-  OMPUseDevicePtrClause *Clause = new (Mem) OMPUseDevicePtrClause(
-      StartLoc, LParenLoc, EndLoc, NumVars, NumUniqueDeclarations,
-      NumComponentLists, NumComponents);
+  OMPUseDevicePtrClause *Clause = new (Mem) OMPUseDevicePtrClause(Locs, Sizes);
 
   Clause->setVarRefs(Vars);
   Clause->setPrivateCopies(PrivateVars);
@@ -994,29 +986,28 @@ OMPUseDevicePtrClause *OMPUseDevicePtrClause::Create(
   return Clause;
 }
 
-OMPUseDevicePtrClause *OMPUseDevicePtrClause::CreateEmpty(
-    const ASTContext &C, unsigned NumVars, unsigned NumUniqueDeclarations,
-    unsigned NumComponentLists, unsigned NumComponents) {
+OMPUseDevicePtrClause *
+OMPUseDevicePtrClause::CreateEmpty(const ASTContext &C,
+                                   const OMPMappableExprListSizeTy &Sizes) {
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          3 * NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  return new (Mem) OMPUseDevicePtrClause(NumVars, NumUniqueDeclarations,
-                                         NumComponentLists, NumComponents);
+          3 * Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  return new (Mem) OMPUseDevicePtrClause(Sizes);
 }
 
 OMPIsDevicePtrClause *
-OMPIsDevicePtrClause::Create(const ASTContext &C, SourceLocation StartLoc,
-                             SourceLocation LParenLoc, SourceLocation EndLoc,
+OMPIsDevicePtrClause::Create(const ASTContext &C, const OMPVarListLocTy &Locs,
                              ArrayRef<Expr *> Vars,
                              ArrayRef<ValueDecl *> Declarations,
                              MappableExprComponentListsRef ComponentLists) {
-  unsigned NumVars = Vars.size();
-  unsigned NumUniqueDeclarations =
-      getUniqueDeclarationsTotalNumber(Declarations);
-  unsigned NumComponentLists = ComponentLists.size();
-  unsigned NumComponents = getComponentsTotalNumber(ComponentLists);
+  OMPMappableExprListSizeTy Sizes;
+  Sizes.NumVars = Vars.size();
+  Sizes.NumUniqueDeclarations = getUniqueDeclarationsTotalNumber(Declarations);
+  Sizes.NumComponentLists = ComponentLists.size();
+  Sizes.NumComponents = getComponentsTotalNumber(ComponentLists);
 
   // We need to allocate:
   // NumVars x Expr* - we have an original list expression for each clause list
@@ -1031,28 +1022,27 @@ OMPIsDevicePtrClause::Create(const ASTContext &C, SourceLocation StartLoc,
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
 
-  OMPIsDevicePtrClause *Clause = new (Mem) OMPIsDevicePtrClause(
-      StartLoc, LParenLoc, EndLoc, NumVars, NumUniqueDeclarations,
-      NumComponentLists, NumComponents);
+  OMPIsDevicePtrClause *Clause = new (Mem) OMPIsDevicePtrClause(Locs, Sizes);
 
   Clause->setVarRefs(Vars);
   Clause->setClauseInfo(Declarations, ComponentLists);
   return Clause;
 }
 
-OMPIsDevicePtrClause *OMPIsDevicePtrClause::CreateEmpty(
-    const ASTContext &C, unsigned NumVars, unsigned NumUniqueDeclarations,
-    unsigned NumComponentLists, unsigned NumComponents) {
+OMPIsDevicePtrClause *
+OMPIsDevicePtrClause::CreateEmpty(const ASTContext &C,
+                                  const OMPMappableExprListSizeTy &Sizes) {
   void *Mem = C.Allocate(
       totalSizeToAlloc<Expr *, ValueDecl *, unsigned,
                        OMPClauseMappableExprCommon::MappableComponent>(
-          NumVars, NumUniqueDeclarations,
-          NumUniqueDeclarations + NumComponentLists, NumComponents));
-  return new (Mem) OMPIsDevicePtrClause(NumVars, NumUniqueDeclarations,
-                                        NumComponentLists, NumComponents);
+          Sizes.NumVars, Sizes.NumUniqueDeclarations,
+          Sizes.NumUniqueDeclarations + Sizes.NumComponentLists,
+          Sizes.NumComponents));
+  return new (Mem) OMPIsDevicePtrClause(Sizes);
 }
 
 //===----------------------------------------------------------------------===//
@@ -1432,6 +1422,14 @@ void OMPClausePrinter::VisitOMPMapClause(OMPMapClause *Node) {
         if (Node->getMapTypeModifier(I) != OMPC_MAP_MODIFIER_unknown) {
           OS << getOpenMPSimpleClauseTypeName(OMPC_map,
                                               Node->getMapTypeModifier(I));
+          if (Node->getMapTypeModifier(I) == OMPC_MAP_MODIFIER_mapper) {
+            OS << '(';
+            NestedNameSpecifier *MapperNNS =
+                Node->getMapperQualifierLoc().getNestedNameSpecifier();
+            if (MapperNNS)
+              MapperNNS->print(OS, Policy);
+            OS << Node->getMapperIdInfo() << ')';
+          }
           OS << ',';
         }
       }
diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
index d0463416f54..fafc34c9602 100644
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -1961,36 +1961,62 @@ static OpenMPMapModifierKind isMapModifier(Parser &P) {
 
 /// Parse map-type-modifiers in map clause.
 /// map([ [map-type-modifier[,] [map-type-modifier[,] ...] map-type : ] list)
-/// where, map-type-modifier ::= always | close 
-static void parseMapTypeModifiers(Parser &P,
-                                  Parser::OpenMPVarListDataTy &Data) {
-  Preprocessor &PP = P.getPreprocessor();
-  while (P.getCurToken().isNot(tok::colon)) {
-    Token Tok = P.getCurToken();
-    OpenMPMapModifierKind TypeModifier = isMapModifier(P);
+/// where, map-type-modifier ::= always | close | mapper(mapper-identifier)
+bool Parser::parseMapTypeModifiers(OpenMPVarListDataTy &Data) {
+  while (getCurToken().isNot(tok::colon)) {
+    OpenMPMapModifierKind TypeModifier = isMapModifier(*this);
     if (TypeModifier == OMPC_MAP_MODIFIER_always ||
         TypeModifier == OMPC_MAP_MODIFIER_close) {
       Data.MapTypeModifiers.push_back(TypeModifier);
       Data.MapTypeModifiersLoc.push_back(Tok.getLocation());
-      P.ConsumeToken();
+      ConsumeToken();
+    } else if (TypeModifier == OMPC_MAP_MODIFIER_mapper) {
+      Data.MapTypeModifiers.push_back(TypeModifier);
+      Data.MapTypeModifiersLoc.push_back(Tok.getLocation());
+      ConsumeToken();
+      // Parse '('.
+      BalancedDelimiterTracker T(*this, tok::l_paren, tok::colon);
+      if (T.expectAndConsume(diag::err_expected_lparen_after,
+                             getOpenMPSimpleClauseTypeName(
+                                 OMPC_map, OMPC_MAP_MODIFIER_mapper))) {
+        SkipUntil(tok::colon, tok::annot_pragma_openmp_end, StopBeforeMatch);
+        return true;
+      }
+      // Parse mapper-identifier
+      if (getLangOpts().CPlusPlus)
+        ParseOptionalCXXScopeSpecifier(Data.ReductionOrMapperIdScopeSpec,
+                                       /*ObjectType=*/nullptr,
+                                       /*EnteringContext=*/false);
+      if (Tok.isNot(tok::identifier) && Tok.isNot(tok::kw_default)) {
+        Diag(Tok.getLocation(), diag::err_omp_mapper_illegal_identifier);
+        SkipUntil(tok::colon, tok::annot_pragma_openmp_end, StopBeforeMatch);
+        return true;
+      }
+      auto &DeclNames = Actions.getASTContext().DeclarationNames;
+      Data.ReductionOrMapperId = DeclarationNameInfo(
+          DeclNames.getIdentifier(Tok.getIdentifierInfo()), Tok.getLocation());
+      ConsumeToken();
+      // Parse ')'.
+      T.consumeClose();
     } else {
       // For the case of unknown map-type-modifier or a map-type.
       // Map-type is followed by a colon; the function returns when it
       // encounters a token followed by a colon.
       if (Tok.is(tok::comma)) {
-        P.Diag(Tok, diag::err_omp_map_type_modifier_missing);
-        P.ConsumeToken();
+        Diag(Tok, diag::err_omp_map_type_modifier_missing);
+        ConsumeToken();
         continue;
       }
       // Potential map-type token as it is followed by a colon.
       if (PP.LookAhead(0).is(tok::colon))
-        return;
-      P.Diag(Tok, diag::err_omp_unknown_map_type_modifier);
-      P.ConsumeToken();
+        return false;
+      Diag(Tok, diag::err_omp_unknown_map_type_modifier);
+      ConsumeToken();
     }
-    if (P.getCurToken().is(tok::comma))
-      P.ConsumeToken();
+    if (getCurToken().is(tok::comma))
+      ConsumeToken();
   }
+  return false;
 }
 
 /// Checks if the token is a valid map-type.
@@ -2027,6 +2053,7 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
                                 OpenMPVarListDataTy &Data) {
   UnqualifiedId UnqualifiedReductionId;
   bool InvalidReductionId = false;
+  bool IsInvalidMapModifier = false;
 
   // Parse '('.
   BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
@@ -2042,11 +2069,11 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
       Kind == OMPC_in_reduction) {
     ColonProtectionRAIIObject ColonRAII(*this);
     if (getLangOpts().CPlusPlus)
-      ParseOptionalCXXScopeSpecifier(Data.ReductionIdScopeSpec,
+      ParseOptionalCXXScopeSpecifier(Data.ReductionOrMapperIdScopeSpec,
                                      /*ObjectType=*/nullptr,
                                      /*EnteringContext=*/false);
-    InvalidReductionId = ParseReductionId(*this, Data.ReductionIdScopeSpec,
-                                          UnqualifiedReductionId);
+    InvalidReductionId = ParseReductionId(
+        *this, Data.ReductionOrMapperIdScopeSpec, UnqualifiedReductionId);
     if (InvalidReductionId) {
       SkipUntil(tok::colon, tok::r_paren, tok::annot_pragma_openmp_end,
                 StopBeforeMatch);
@@ -2056,7 +2083,7 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
     else
       Diag(Tok, diag::warn_pragma_expected_colon) << "reduction identifier";
     if (!InvalidReductionId)
-      Data.ReductionId =
+      Data.ReductionOrMapperId =
           Actions.GetNameFromUnqualifiedId(UnqualifiedReductionId);
   } else if (Kind == OMPC_depend) {
   // Handle dependency type for depend clause.
@@ -2115,8 +2142,9 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
     // Only parse map-type-modifier[s] and map-type if a colon is present in
     // the map clause.
     if (ColonPresent) {
-      parseMapTypeModifiers(*this, Data);
-      parseMapType(*this, Data);
+      IsInvalidMapModifier = parseMapTypeModifiers(Data);
+      if (!IsInvalidMapModifier)
+        parseMapType(*this, Data);
     }
     if (Data.MapType == OMPC_MAP_unknown) {
       Data.MapType = OMPC_MAP_tofrom;
@@ -2185,7 +2213,8 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
   return (Kind == OMPC_depend && Data.DepKind != OMPC_DEPEND_unknown &&
           Vars.empty()) ||
          (Kind != OMPC_depend && Kind != OMPC_map && Vars.empty()) ||
-         (MustHaveTail && !Data.TailExpr) || InvalidReductionId;
+         (MustHaveTail && !Data.TailExpr) || InvalidReductionId ||
+         IsInvalidMapModifier;
 }
 
 /// Parsing of OpenMP clause 'private', 'firstprivate', 'lastprivate',
@@ -2218,6 +2247,7 @@ bool Parser::ParseOpenMPVarList(OpenMPDirectiveKind DKind,
 ///       'depend' '(' in | out | inout : list | source ')'
 ///    map-clause:
 ///       'map' '(' [ [ always [,] ] [ close [,] ]
+///          [ mapper(mapper-identifier) [,] ]
 ///          to | from | tofrom | alloc | release | delete ':' ] list ')';
 ///    to-clause:
 ///       'to' '(' list ')'
@@ -2245,10 +2275,11 @@ OMPClause *Parser::ParseOpenMPVarListClause(OpenMPDirectiveKind DKind,
 
   if (ParseOnly)
     return nullptr;
+  OMPVarListLocTy Locs(Loc, LOpen, Data.RLoc);
   return Actions.ActOnOpenMPVarListClause(
-      Kind, Vars, Data.TailExpr, Loc, LOpen, Data.ColonLoc, Data.RLoc,
-      Data.ReductionIdScopeSpec, Data.ReductionId, Data.DepKind, Data.LinKind,
-      Data.MapTypeModifiers, Data.MapTypeModifiersLoc, Data.MapType,
-      Data.IsMapTypeImplicit, Data.DepLinMapLoc);
+      Kind, Vars, Data.TailExpr, Locs, Data.ColonLoc,
+      Data.ReductionOrMapperIdScopeSpec, Data.ReductionOrMapperId, Data.DepKind,
+      Data.LinKind, Data.MapTypeModifiers, Data.MapTypeModifiersLoc,
+      Data.MapType, Data.IsMapTypeImplicit, Data.DepLinMapLoc);
 }
 
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 203de2a57a4..04be5b56e36 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -3451,11 +3451,12 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
       }
     }
     if (!ImplicitMaps.empty()) {
+      CXXScopeSpec MapperIdScopeSpec;
+      DeclarationNameInfo MapperId;
       if (OMPClause *Implicit = ActOnOpenMPMapClause(
-              llvm::None, llvm::None, OMPC_MAP_tofrom,
-              /*IsMapTypeImplicit=*/true, SourceLocation(), SourceLocation(),
-              ImplicitMaps, SourceLocation(), SourceLocation(),
-              SourceLocation())) {
+              llvm::None, llvm::None, MapperIdScopeSpec, MapperId,
+              OMPC_MAP_tofrom, /*IsMapTypeImplicit=*/true, SourceLocation(),
+              SourceLocation(), ImplicitMaps, OMPVarListLocTy())) {
         ClausesWithImplicit.emplace_back(Implicit);
         ErrorFound |=
             cast<OMPMapClause>(Implicit)->varlist_size() != ImplicitMaps.size();
@@ -9734,14 +9735,16 @@ OMPClause *Sema::ActOnOpenMPDynamicAllocatorsClause(SourceLocation StartLoc,
 
 OMPClause *Sema::ActOnOpenMPVarListClause(
     OpenMPClauseKind Kind, ArrayRef<Expr *> VarList, Expr *TailExpr,
-    SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation ColonLoc,
-    SourceLocation EndLoc, CXXScopeSpec &ReductionIdScopeSpec,
-    const DeclarationNameInfo &ReductionId, OpenMPDependClauseKind DepKind,
+    const OMPVarListLocTy &Locs, SourceLocation ColonLoc,
+    CXXScopeSpec &ReductionOrMapperIdScopeSpec,
+    DeclarationNameInfo &ReductionOrMapperId, OpenMPDependClauseKind DepKind,
     OpenMPLinearClauseKind LinKind,
     ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
-    ArrayRef<SourceLocation> MapTypeModifiersLoc,
-    OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
-    SourceLocation DepLinMapLoc) {
+    ArrayRef<SourceLocation> MapTypeModifiersLoc, OpenMPMapClauseKind MapType,
+    bool IsMapTypeImplicit, SourceLocation DepLinMapLoc) {
+  SourceLocation StartLoc = Locs.StartLoc;
+  SourceLocation LParenLoc = Locs.LParenLoc;
+  SourceLocation EndLoc = Locs.EndLoc;
   OMPClause *Res = nullptr;
   switch (Kind) {
   case OMPC_private:
@@ -9758,17 +9761,18 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
     break;
   case OMPC_reduction:
     Res = ActOnOpenMPReductionClause(VarList, StartLoc, LParenLoc, ColonLoc,
-                                     EndLoc, ReductionIdScopeSpec, ReductionId);
+                                     EndLoc, ReductionOrMapperIdScopeSpec,
+                                     ReductionOrMapperId);
     break;
   case OMPC_task_reduction:
     Res = ActOnOpenMPTaskReductionClause(VarList, StartLoc, LParenLoc, ColonLoc,
-                                         EndLoc, ReductionIdScopeSpec,
-                                         ReductionId);
+                                         EndLoc, ReductionOrMapperIdScopeSpec,
+                                         ReductionOrMapperId);
     break;
   case OMPC_in_reduction:
-    Res =
-        ActOnOpenMPInReductionClause(VarList, StartLoc, LParenLoc, ColonLoc,
-                                     EndLoc, ReductionIdScopeSpec, ReductionId);
+    Res = ActOnOpenMPInReductionClause(VarList, StartLoc, LParenLoc, ColonLoc,
+                                       EndLoc, ReductionOrMapperIdScopeSpec,
+                                       ReductionOrMapperId);
     break;
   case OMPC_linear:
     Res = ActOnOpenMPLinearClause(VarList, TailExpr, StartLoc, LParenLoc,
@@ -9792,21 +9796,22 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
                                   StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_map:
-    Res = ActOnOpenMPMapClause(MapTypeModifiers, MapTypeModifiersLoc, MapType,
-                               IsMapTypeImplicit, DepLinMapLoc, ColonLoc,
-                               VarList, StartLoc, LParenLoc, EndLoc);
+    Res = ActOnOpenMPMapClause(MapTypeModifiers, MapTypeModifiersLoc,
+                               ReductionOrMapperIdScopeSpec,
+                               ReductionOrMapperId, MapType, IsMapTypeImplicit,
+                               DepLinMapLoc, ColonLoc, VarList, Locs);
     break;
   case OMPC_to:
-    Res = ActOnOpenMPToClause(VarList, StartLoc, LParenLoc, EndLoc);
+    Res = ActOnOpenMPToClause(VarList, Locs);
     break;
   case OMPC_from:
-    Res = ActOnOpenMPFromClause(VarList, StartLoc, LParenLoc, EndLoc);
+    Res = ActOnOpenMPFromClause(VarList, Locs);
     break;
   case OMPC_use_device_ptr:
-    Res = ActOnOpenMPUseDevicePtrClause(VarList, StartLoc, LParenLoc, EndLoc);
+    Res = ActOnOpenMPUseDevicePtrClause(VarList, Locs);
     break;
   case OMPC_is_device_ptr:
-    Res = ActOnOpenMPIsDevicePtrClause(VarList, StartLoc, LParenLoc, EndLoc);
+    Res = ActOnOpenMPIsDevicePtrClause(VarList, Locs);
     break;
   case OMPC_if:
   case OMPC_final:
@@ -10622,8 +10627,8 @@ public:
 } // namespace
 
 template <typename T, typename U>
-static T filterLookupForUDR(SmallVectorImpl<U> &Lookups,
-                            const llvm::function_ref<T(ValueDecl *)> Gen) {
+static T filterLookupForUDReductionAndMapper(
+    SmallVectorImpl<U> &Lookups, const llvm::function_ref<T(ValueDecl *)> Gen) {
   for (U &Set : Lookups) {
     for (auto *D : Set) {
       if (T Res = Gen(cast<ValueDecl>(D)))
@@ -10650,7 +10655,7 @@ static NamedDecl *findAcceptableDecl(Sema &SemaRef, NamedDecl *D) {
 }
 
 static void
-argumentDependentLookup(Sema &SemaRef, const DeclarationNameInfo &ReductionId,
+argumentDependentLookup(Sema &SemaRef, const DeclarationNameInfo &Id,
                         SourceLocation Loc, QualType Ty,
                         SmallVectorImpl<UnresolvedSet<8>> &Lookups) {
   // Find all of the associated namespaces and classes based on the
@@ -10684,13 +10689,14 @@ argumentDependentLookup(Sema &SemaRef, const DeclarationNameInfo &ReductionId,
     //        associated classes are visible within their respective
     //        namespaces even if they are not visible during an ordinary
     //        lookup (11.4).
-    DeclContext::lookup_result R = NS->lookup(ReductionId.getName());
+    DeclContext::lookup_result R = NS->lookup(Id.getName());
     for (auto *D : R) {
       auto *Underlying = D;
       if (auto *USD = dyn_cast<UsingShadowDecl>(D))
         Underlying = USD->getTargetDecl();
 
-      if (!isa<OMPDeclareReductionDecl>(Underlying))
+      if (!isa<OMPDeclareReductionDecl>(Underlying) &&
+          !isa<OMPDeclareMapperDecl>(Underlying))
         continue;
 
       if (!SemaRef.isVisible(D)) {
@@ -10743,7 +10749,7 @@ buildDeclareReductionRef(Sema &SemaRef, SourceLocation Loc, SourceRange Range,
   if (SemaRef.CurContext->isDependentContext() || Ty->isDependentType() ||
       Ty->isInstantiationDependentType() ||
       Ty->containsUnexpandedParameterPack() ||
-      filterLookupForUDR<bool>(Lookups, [](ValueDecl *D) {
+      filterLookupForUDReductionAndMapper<bool>(Lookups, [](ValueDecl *D) {
         return !D->isInvalidDecl() &&
                (D->getType()->isDependentType() ||
                 D->getType()->isInstantiationDependentType() ||
@@ -10792,7 +10798,7 @@ buildDeclareReductionRef(Sema &SemaRef, SourceLocation Loc, SourceRange Range,
   }
   // Perform ADL.
   argumentDependentLookup(SemaRef, ReductionId, Loc, Ty, Lookups);
-  if (auto *VD = filterLookupForUDR<ValueDecl *>(
+  if (auto *VD = filterLookupForUDReductionAndMapper<ValueDecl *>(
           Lookups, [&SemaRef, Ty](ValueDecl *D) -> ValueDecl * {
             if (!D->isInvalidDecl() &&
                 SemaRef.Context.hasSameType(D->getType(), Ty))
@@ -10801,7 +10807,7 @@ buildDeclareReductionRef(Sema &SemaRef, SourceLocation Loc, SourceRange Range,
           }))
     return SemaRef.BuildDeclRefExpr(VD, VD->getType().getNonReferenceType(),
                                     VK_LValue, Loc);
-  if (auto *VD = filterLookupForUDR<ValueDecl *>(
+  if (auto *VD = filterLookupForUDReductionAndMapper<ValueDecl *>(
           Lookups, [&SemaRef, Ty, Loc](ValueDecl *D) -> ValueDecl * {
             if (!D->isInvalidDecl() &&
                 SemaRef.IsDerivedFrom(Loc, Ty, D->getType()) &&
@@ -12998,6 +13004,109 @@ static bool checkMapConflicts(
   return FoundError;
 }
 
+// Look up the user-defined mapper given the mapper name and mapped type, and
+// build a reference to it.
+ExprResult buildUserDefinedMapperRef(Sema &SemaRef, Scope *S,
+                                     CXXScopeSpec &MapperIdScopeSpec,
+                                     const DeclarationNameInfo &MapperId,
+                                     QualType Type, Expr *UnresolvedMapper) {
+  if (MapperIdScopeSpec.isInvalid())
+    return ExprError();
+  // Find all user-defined mappers with the given MapperId.
+  SmallVector<UnresolvedSet<8>, 4> Lookups;
+  LookupResult Lookup(SemaRef, MapperId, Sema::LookupOMPMapperName);
+  Lookup.suppressDiagnostics();
+  if (S) {
+    while (S && SemaRef.LookupParsedName(Lookup, S, &MapperIdScopeSpec)) {
+      NamedDecl *D = Lookup.getRepresentativeDecl();
+      while (S && !S->isDeclScope(D))
+        S = S->getParent();
+      if (S)
+        S = S->getParent();
+      Lookups.emplace_back();
+      Lookups.back().append(Lookup.begin(), Lookup.end());
+      Lookup.clear();
+    }
+  } else if (auto *ULE = cast_or_null<UnresolvedLookupExpr>(UnresolvedMapper)) {
+    // Extract the user-defined mappers with the given MapperId.
+    Lookups.push_back(UnresolvedSet<8>());
+    for (NamedDecl *D : ULE->decls()) {
+      auto *DMD = cast<OMPDeclareMapperDecl>(D);
+      assert(DMD && "Expect valid OMPDeclareMapperDecl during instantiation.");
+      Lookups.back().addDecl(DMD);
+    }
+  }
+  // Defer the lookup for dependent types. The results will be passed through
+  // UnresolvedMapper on instantiation.
+  if (SemaRef.CurContext->isDependentContext() || Type->isDependentType() ||
+      Type->isInstantiationDependentType() ||
+      Type->containsUnexpandedParameterPack() ||
+      filterLookupForUDReductionAndMapper<bool>(Lookups, [](ValueDecl *D) {
+        return !D->isInvalidDecl() &&
+               (D->getType()->isDependentType() ||
+                D->getType()->isInstantiationDependentType() ||
+                D->getType()->containsUnexpandedParameterPack());
+      })) {
+    UnresolvedSet<8> URS;
+    for (const UnresolvedSet<8> &Set : Lookups) {
+      if (Set.empty())
+        continue;
+      URS.append(Set.begin(), Set.end());
+    }
+    return UnresolvedLookupExpr::Create(
+        SemaRef.Context, /*NamingClass=*/nullptr,
+        MapperIdScopeSpec.getWithLocInContext(SemaRef.Context), MapperId,
+        /*ADL=*/false, /*Overloaded=*/true, URS.begin(), URS.end());
+  }
+  // [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 (!Type->isStructureOrClassType() && !Type->isUnionType())
+    return ExprEmpty();
+  SourceLocation Loc = MapperId.getLoc();
+  // Perform argument dependent lookup.
+  if (SemaRef.getLangOpts().CPlusPlus && !MapperIdScopeSpec.isSet())
+    argumentDependentLookup(SemaRef, MapperId, Loc, Type, Lookups);
+  // Return the first user-defined mapper with the desired type.
+  if (auto *VD = filterLookupForUDReductionAndMapper<ValueDecl *>(
+          Lookups, [&SemaRef, Type](ValueDecl *D) -> ValueDecl * {
+            if (!D->isInvalidDecl() &&
+                SemaRef.Context.hasSameType(D->getType(), Type))
+              return D;
+            return nullptr;
+          }))
+    return SemaRef.BuildDeclRefExpr(VD, Type, VK_LValue, Loc);
+  // Find the first user-defined mapper with a type derived from the desired
+  // type.
+  if (auto *VD = filterLookupForUDReductionAndMapper<ValueDecl *>(
+          Lookups, [&SemaRef, Type, Loc](ValueDecl *D) -> ValueDecl * {
+            if (!D->isInvalidDecl() &&
+                SemaRef.IsDerivedFrom(Loc, Type, D->getType()) &&
+                !Type.isMoreQualifiedThan(D->getType()))
+              return D;
+            return nullptr;
+          })) {
+    CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
+                       /*DetectVirtual=*/false);
+    if (SemaRef.IsDerivedFrom(Loc, Type, VD->getType(), Paths)) {
+      if (!Paths.isAmbiguous(SemaRef.Context.getCanonicalType(
+              VD->getType().getUnqualifiedType()))) {
+        if (SemaRef.CheckBaseClassAccess(
+                Loc, VD->getType(), Type, Paths.front(),
+                /*DiagID=*/0) != Sema::AR_inaccessible) {
+          return SemaRef.BuildDeclRefExpr(VD, Type, VK_LValue, Loc);
+        }
+      }
+    }
+  }
+  // Report error if a mapper is specified, but cannot be found.
+  if (MapperIdScopeSpec.isSet() || MapperId.getAsString() != "default") {
+    SemaRef.Diag(Loc, diag::err_omp_invalid_mapper)
+        << Type << MapperId.getName();
+    return ExprError();
+  }
+  return ExprEmpty();
+}
+
 namespace {
 // Utility struct that gathers all the related lists associated with a mappable
 // expression.
@@ -13010,6 +13119,8 @@ struct MappableVarListInfo {
   OMPClauseMappableExprCommon::MappableExprComponentLists VarComponents;
   // The base declaration of the variable.
   SmallVector<ValueDecl *, 16> VarBaseDeclarations;
+  // The reference to the user-defined mapper associated with every expression.
+  SmallVector<Expr *, 16> UDMapperList;
 
   MappableVarListInfo(ArrayRef<Expr *> VarList) : VarList(VarList) {
     // We have a list of components and base declarations for each entry in the
@@ -13021,19 +13132,30 @@ struct MappableVarListInfo {
 }
 
 // Check the validity of the provided variable list for the provided clause kind
-// \a CKind. In the check process the valid expressions, and mappable expression
-// components and variables are extracted and used to fill \a Vars,
-// \a ClauseComponents, and \a ClauseBaseDeclarations. \a MapType and
-// \a IsMapTypeImplicit are expected to be valid if the clause kind is 'map'.
-static void
-checkMappableExpressionList(Sema &SemaRef, DSAStackTy *DSAS,
-                            OpenMPClauseKind CKind, MappableVarListInfo &MVLI,
-                            SourceLocation StartLoc,
-                            OpenMPMapClauseKind MapType = OMPC_MAP_unknown,
-                            bool IsMapTypeImplicit = false) {
+// \a CKind. In the check process the valid expressions, mappable expression
+// components, variables, and user-defined mappers are extracted and used to
+// fill \a ProcessedVarList, \a VarComponents, \a VarBaseDeclarations, and \a
+// UDMapperList in MVLI. \a MapType, \a IsMapTypeImplicit, \a MapperIdScopeSpec,
+// and \a MapperId are expected to be valid if the clause kind is 'map'.
+static void checkMappableExpressionList(
+    Sema &SemaRef, DSAStackTy *DSAS, OpenMPClauseKind CKind,
+    MappableVarListInfo &MVLI, SourceLocation StartLoc,
+    OpenMPMapClauseKind MapType = OMPC_MAP_unknown,
+    bool IsMapTypeImplicit = false, CXXScopeSpec *MapperIdScopeSpec = nullptr,
+    const DeclarationNameInfo *MapperId = nullptr,
+    ArrayRef<Expr *> UnresolvedMappers = llvm::None) {
   // We only expect mappable expressions in 'to', 'from', and 'map' clauses.
   assert((CKind == OMPC_map || CKind == OMPC_to || CKind == OMPC_from) &&
          "Unexpected clause kind with mappable expressions!");
+  assert(
+      ((CKind == OMPC_map && MapperIdScopeSpec && MapperId) ||
+       (CKind != OMPC_map && !MapperIdScopeSpec && !MapperId)) &&
+      "Map clauses and only map clauses have user-defined mapper identifiers.");
+
+  // Iterators to find the current unresolved mapper expression.
+  auto UMIt = UnresolvedMappers.begin(), UMEnd = UnresolvedMappers.end();
+  bool UpdateUMIt = false;
+  Expr *UnresolvedMapper = nullptr;
 
   // Keep track of the mappable components and base declarations in this clause.
   // Each entry in the list is going to have a list of components associated. We
@@ -13045,11 +13167,33 @@ checkMappableExpressionList(Sema &SemaRef, DSAStackTy *DSAS,
     assert(RE && "Null expr in omp to/from/map clause");
     SourceLocation ELoc = RE->getExprLoc();
 
+    // Find the current unresolved mapper expression.
+    if (UpdateUMIt && UMIt != UMEnd) {
+      UMIt++;
+      assert(
+          UMIt != UMEnd &&
+          "Expect the size of UnresolvedMappers to match with that of VarList");
+    }
+    UpdateUMIt = true;
+    if (UMIt != UMEnd)
+      UnresolvedMapper = *UMIt;
+
     const Expr *VE = RE->IgnoreParenLValueCasts();
 
     if (VE->isValueDependent() || VE->isTypeDependent() ||
         VE->isInstantiationDependent() ||
         VE->containsUnexpandedParameterPack()) {
+      if (CKind == OMPC_map) {
+        // Try to find the associated user-defined mapper.
+        ExprResult ER = buildUserDefinedMapperRef(
+            SemaRef, DSAS->getCurScope(), *MapperIdScopeSpec, *MapperId,
+            VE->getType().getCanonicalType(), UnresolvedMapper);
+        if (ER.isInvalid())
+          continue;
+        MVLI.UDMapperList.push_back(ER.get());
+      } else {
+        MVLI.UDMapperList.push_back(nullptr);
+      }
       // We can only analyze this information once the missing information is
       // resolved.
       MVLI.ProcessedVarList.push_back(RE);
@@ -13081,6 +13225,17 @@ checkMappableExpressionList(Sema &SemaRef, DSAStackTy *DSAS,
     if (const auto *TE = dyn_cast<CXXThisExpr>(BE)) {
       // Add store "this" pointer to class in DSAStackTy for future checking
       DSAS->addMappedClassesQualTypes(TE->getType());
+      if (CKind == OMPC_map) {
+        // Try to find the associated user-defined mapper.
+        ExprResult ER = buildUserDefinedMapperRef(
+            SemaRef, DSAS->getCurScope(), *MapperIdScopeSpec, *MapperId,
+            VE->getType().getCanonicalType(), UnresolvedMapper);
+        if (ER.isInvalid())
+          continue;
+        MVLI.UDMapperList.push_back(ER.get());
+      } else {
+        MVLI.UDMapperList.push_back(nullptr);
+      }
       // Skip restriction checking for variable or field declarations
       MVLI.ProcessedVarList.push_back(RE);
       MVLI.VarComponents.resize(MVLI.VarComponents.size() + 1);
@@ -13197,6 +13352,16 @@ checkMappableExpressionList(Sema &SemaRef, DSAStackTy *DSAS,
           continue;
         }
       }
+
+      // Try to find the associated user-defined mapper.
+      ExprResult ER = buildUserDefinedMapperRef(
+          SemaRef, DSAS->getCurScope(), *MapperIdScopeSpec, *MapperId,
+          Type.getCanonicalType(), UnresolvedMapper);
+      if (ER.isInvalid())
+        continue;
+      MVLI.UDMapperList.push_back(ER.get());
+    } else {
+      MVLI.UDMapperList.push_back(nullptr);
     }
 
     // Save the current expression.
@@ -13218,19 +13383,16 @@ checkMappableExpressionList(Sema &SemaRef, DSAStackTy *DSAS,
   }
 }
 
-OMPClause *
-Sema::ActOnOpenMPMapClause(ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
-                           ArrayRef<SourceLocation> MapTypeModifiersLoc,
-                           OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
-                           SourceLocation MapLoc, SourceLocation ColonLoc,
-                           ArrayRef<Expr *> VarList, SourceLocation StartLoc,
-                           SourceLocation LParenLoc, SourceLocation EndLoc) {
-  MappableVarListInfo MVLI(VarList);
-  checkMappableExpressionList(*this, DSAStack, OMPC_map, MVLI, StartLoc,
-                              MapType, IsMapTypeImplicit);
-
-  OpenMPMapModifierKind Modifiers[] = { OMPC_MAP_MODIFIER_unknown,
-                                        OMPC_MAP_MODIFIER_unknown };
+OMPClause *Sema::ActOnOpenMPMapClause(
+    ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
+    ArrayRef<SourceLocation> MapTypeModifiersLoc,
+    CXXScopeSpec &MapperIdScopeSpec, DeclarationNameInfo &MapperId,
+    OpenMPMapClauseKind MapType, bool IsMapTypeImplicit, SourceLocation MapLoc,
+    SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
+    const OMPVarListLocTy &Locs, ArrayRef<Expr *> UnresolvedMappers) {
+  OpenMPMapModifierKind Modifiers[] = {OMPC_MAP_MODIFIER_unknown,
+                                       OMPC_MAP_MODIFIER_unknown,
+                                       OMPC_MAP_MODIFIER_unknown};
   SourceLocation ModifiersLoc[OMPMapClause::NumberOfModifiers];
 
   // Process map-type-modifiers, flag errors for duplicate modifiers.
@@ -13248,12 +13410,25 @@ Sema::ActOnOpenMPMapClause(ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
     ++Count;
   }
 
+  // If the identifier of user-defined mapper is not specified, it is "default".
+  if (!MapperId.getName() || MapperId.getName().isEmpty()) {
+    auto &DeclNames = getASTContext().DeclarationNames;
+    MapperId.setName(
+        DeclNames.getIdentifier(&getASTContext().Idents.get("default")));
+  }
+
+  MappableVarListInfo MVLI(VarList);
+  checkMappableExpressionList(*this, DSAStack, OMPC_map, MVLI, Locs.StartLoc,
+                              MapType, IsMapTypeImplicit, &MapperIdScopeSpec,
+                              &MapperId, UnresolvedMappers);
+
   // We need to produce a map clause even if we don't have variables so that
   // other diagnostics related with non-existing map clauses are accurate.
-  return OMPMapClause::Create(Context, StartLoc, LParenLoc, EndLoc,
-                              MVLI.ProcessedVarList, MVLI.VarBaseDeclarations,
-                              MVLI.VarComponents, Modifiers, ModifiersLoc,
-                              MapType, IsMapTypeImplicit, MapLoc);
+  return OMPMapClause::Create(Context, Locs, MVLI.ProcessedVarList,
+                              MVLI.VarBaseDeclarations, MVLI.VarComponents,
+                              MVLI.UDMapperList, Modifiers, ModifiersLoc,
+                              MapperIdScopeSpec.getWithLocInContext(Context),
+                              MapperId, MapType, IsMapTypeImplicit, MapLoc);
 }
 
 QualType Sema::ActOnOpenMPDeclareReductionType(SourceLocation TyLoc,
@@ -13994,37 +14169,29 @@ void Sema::checkDeclIsAllowedInOpenMPTarget(Expr *E, Decl *D,
 }
 
 OMPClause *Sema::ActOnOpenMPToClause(ArrayRef<Expr *> VarList,
-                                     SourceLocation StartLoc,
-                                     SourceLocation LParenLoc,
-                                     SourceLocation EndLoc) {
+                                     const OMPVarListLocTy &Locs) {
   MappableVarListInfo MVLI(VarList);
-  checkMappableExpressionList(*this, DSAStack, OMPC_to, MVLI, StartLoc);
+  checkMappableExpressionList(*this, DSAStack, OMPC_to, MVLI, Locs.StartLoc);
   if (MVLI.ProcessedVarList.empty())
     return nullptr;
 
-  return OMPToClause::Create(Context, StartLoc, LParenLoc, EndLoc,
-                             MVLI.ProcessedVarList, MVLI.VarBaseDeclarations,
-                             MVLI.VarComponents);
+  return OMPToClause::Create(Context, Locs, MVLI.ProcessedVarList,
+                             MVLI.VarBaseDeclarations, MVLI.VarComponents);
 }
 
 OMPClause *Sema::ActOnOpenMPFromClause(ArrayRef<Expr *> VarList,
-                                       SourceLocation StartLoc,
-                                       SourceLocation LParenLoc,
-                                       SourceLocation EndLoc) {
+                                       const OMPVarListLocTy &Locs) {
   MappableVarListInfo MVLI(VarList);
-  checkMappableExpressionList(*this, DSAStack, OMPC_from, MVLI, StartLoc);
+  checkMappableExpressionList(*this, DSAStack, OMPC_from, MVLI, Locs.StartLoc);
   if (MVLI.ProcessedVarList.empty())
     return nullptr;
 
-  return OMPFromClause::Create(Context, StartLoc, LParenLoc, EndLoc,
-                               MVLI.ProcessedVarList, MVLI.VarBaseDeclarations,
-                               MVLI.VarComponents);
+  return OMPFromClause::Create(Context, Locs, MVLI.ProcessedVarList,
+                               MVLI.VarBaseDeclarations, MVLI.VarComponents);
 }
 
 OMPClause *Sema::ActOnOpenMPUseDevicePtrClause(ArrayRef<Expr *> VarList,
-                                               SourceLocation StartLoc,
-                                               SourceLocation LParenLoc,
-                                               SourceLocation EndLoc) {
+                                               const OMPVarListLocTy &Locs) {
   MappableVarListInfo MVLI(VarList);
   SmallVector<Expr *, 8> PrivateCopies;
   SmallVector<Expr *, 8> Inits;
@@ -14104,14 +14271,12 @@ OMPClause *Sema::ActOnOpenMPUseDevicePtrClause(ArrayRef<Expr *> VarList,
     return nullptr;
 
   return OMPUseDevicePtrClause::Create(
-      Context, StartLoc, LParenLoc, EndLoc, MVLI.ProcessedVarList,
-      PrivateCopies, Inits, MVLI.VarBaseDeclarations, MVLI.VarComponents);
+      Context, Locs, MVLI.ProcessedVarList, PrivateCopies, Inits,
+      MVLI.VarBaseDeclarations, MVLI.VarComponents);
 }
 
 OMPClause *Sema::ActOnOpenMPIsDevicePtrClause(ArrayRef<Expr *> VarList,
-                                              SourceLocation StartLoc,
-                                              SourceLocation LParenLoc,
-                                              SourceLocation EndLoc) {
+                                              const OMPVarListLocTy &Locs) {
   MappableVarListInfo MVLI(VarList);
   for (Expr *RefExpr : VarList) {
     assert(RefExpr && "NULL expr in OpenMP is_device_ptr clause.");
@@ -14187,7 +14352,7 @@ OMPClause *Sema::ActOnOpenMPIsDevicePtrClause(ArrayRef<Expr *> VarList,
   if (MVLI.ProcessedVarList.empty())
     return nullptr;
 
-  return OMPIsDevicePtrClause::Create(
-      Context, StartLoc, LParenLoc, EndLoc, MVLI.ProcessedVarList,
-      MVLI.VarBaseDeclarations, MVLI.VarComponents);
+  return OMPIsDevicePtrClause::Create(Context, Locs, MVLI.ProcessedVarList,
+                                      MVLI.VarBaseDeclarations,
+                                      MVLI.VarComponents);
 }
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index e3f57e00381..91a402d6d8d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2989,11 +2989,19 @@ TemplateDeclInstantiator::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
       }
       if (!IsCorrect)
         break;
+      NestedNameSpecifierLoc NewQualifierLoc =
+          SemaRef.SubstNestedNameSpecifierLoc(OldC->getMapperQualifierLoc(),
+                                              TemplateArgs);
+      CXXScopeSpec SS;
+      SS.Adopt(NewQualifierLoc);
+      DeclarationNameInfo NewNameInfo = SemaRef.SubstDeclarationNameInfo(
+          OldC->getMapperIdInfo(), TemplateArgs);
+      OMPVarListLocTy Locs(OldC->getBeginLoc(), OldC->getLParenLoc(),
+                           OldC->getEndLoc());
       OMPClause *NewC = SemaRef.ActOnOpenMPMapClause(
-          OldC->getMapTypeModifiers(), OldC->getMapTypeModifiersLoc(),
-          OldC->getMapType(), OldC->isImplicitMapType(), OldC->getMapLoc(),
-          OldC->getColonLoc(), NewVars, OldC->getBeginLoc(),
-          OldC->getLParenLoc(), OldC->getEndLoc());
+          OldC->getMapTypeModifiers(), OldC->getMapTypeModifiersLoc(), SS,
+          NewNameInfo, OldC->getMapType(), OldC->isImplicitMapType(),
+          OldC->getMapLoc(), OldC->getColonLoc(), NewVars, Locs);
       Clauses.push_back(NewC);
     }
     SemaRef.EndOpenMPDSABlock(nullptr);
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index ff33028ebbc..870a9604b43 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -1805,17 +1805,17 @@ public:
   ///
   /// By default, performs semantic analysis to build the new OpenMP clause.
   /// Subclasses may override this routine to provide different behavior.
-  OMPClause *
-  RebuildOMPMapClause(ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
-                      ArrayRef<SourceLocation> MapTypeModifiersLoc,
-                      OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
-                      SourceLocation MapLoc, SourceLocation ColonLoc,
-                      ArrayRef<Expr *> VarList, SourceLocation StartLoc,
-                      SourceLocation LParenLoc, SourceLocation EndLoc) {
+  OMPClause *RebuildOMPMapClause(
+      ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
+      ArrayRef<SourceLocation> MapTypeModifiersLoc,
+      CXXScopeSpec MapperIdScopeSpec, DeclarationNameInfo MapperId,
+      OpenMPMapClauseKind MapType, bool IsMapTypeImplicit,
+      SourceLocation MapLoc, SourceLocation ColonLoc, ArrayRef<Expr *> VarList,
+      const OMPVarListLocTy &Locs, ArrayRef<Expr *> UnresolvedMappers) {
     return getSema().ActOnOpenMPMapClause(MapTypeModifiers, MapTypeModifiersLoc,
-                                          MapType, IsMapTypeImplicit, MapLoc,
-                                          ColonLoc, VarList, StartLoc,
-                                          LParenLoc, EndLoc);
+                                          MapperIdScopeSpec, MapperId, MapType,
+                                          IsMapTypeImplicit, MapLoc, ColonLoc,
+                                          VarList, Locs, UnresolvedMappers);
   }
 
   /// Build a new OpenMP 'num_teams' clause.
@@ -1902,10 +1902,8 @@ public:
   /// By default, performs semantic analysis to build the new statement.
   /// Subclasses may override this routine to provide different behavior.
   OMPClause *RebuildOMPToClause(ArrayRef<Expr *> VarList,
-                                SourceLocation StartLoc,
-                                SourceLocation LParenLoc,
-                                SourceLocation EndLoc) {
-    return getSema().ActOnOpenMPToClause(VarList, StartLoc, LParenLoc, EndLoc);
+                                const OMPVarListLocTy &Locs) {
+    return getSema().ActOnOpenMPToClause(VarList, Locs);
   }
 
   /// Build a new OpenMP 'from' clause.
@@ -1913,11 +1911,8 @@ public:
   /// By default, performs semantic analysis to build the new statement.
   /// Subclasses may override this routine to provide different behavior.
   OMPClause *RebuildOMPFromClause(ArrayRef<Expr *> VarList,
-                                  SourceLocation StartLoc,
-                                  SourceLocation LParenLoc,
-                                  SourceLocation EndLoc) {
-    return getSema().ActOnOpenMPFromClause(VarList, StartLoc, LParenLoc,
-                                           EndLoc);
+                                  const OMPVarListLocTy &Locs) {
+    return getSema().ActOnOpenMPFromClause(VarList, Locs);
   }
 
   /// Build a new OpenMP 'use_device_ptr' clause.
@@ -1925,11 +1920,8 @@ public:
   /// By default, performs semantic analysis to build the new OpenMP clause.
   /// Subclasses may override this routine to provide different behavior.
   OMPClause *RebuildOMPUseDevicePtrClause(ArrayRef<Expr *> VarList,
-                                          SourceLocation StartLoc,
-                                          SourceLocation LParenLoc,
-                                          SourceLocation EndLoc) {
-    return getSema().ActOnOpenMPUseDevicePtrClause(VarList, StartLoc, LParenLoc,
-                                                   EndLoc);
+                                          const OMPVarListLocTy &Locs) {
+    return getSema().ActOnOpenMPUseDevicePtrClause(VarList, Locs);
   }
 
   /// Build a new OpenMP 'is_device_ptr' clause.
@@ -1937,11 +1929,8 @@ public:
   /// By default, performs semantic analysis to build the new OpenMP clause.
   /// Subclasses may override this routine to provide different behavior.
   OMPClause *RebuildOMPIsDevicePtrClause(ArrayRef<Expr *> VarList,
-                                         SourceLocation StartLoc,
-                                         SourceLocation LParenLoc,
-                                         SourceLocation EndLoc) {
-    return getSema().ActOnOpenMPIsDevicePtrClause(VarList, StartLoc, LParenLoc,
-                                                  EndLoc);
+                                         const OMPVarListLocTy &Locs) {
+    return getSema().ActOnOpenMPIsDevicePtrClause(VarList, Locs);
   }
 
   /// Rebuild the operand to an Objective-C \@synchronized statement.
@@ -8832,10 +8821,47 @@ OMPClause *TreeTransform<Derived>::TransformOMPMapClause(OMPMapClause *C) {
       return nullptr;
     Vars.push_back(EVar.get());
   }
+  NestedNameSpecifierLoc QualifierLoc;
+  if (C->getMapperQualifierLoc()) {
+    QualifierLoc = getDerived().TransformNestedNameSpecifierLoc(
+        C->getMapperQualifierLoc());
+    if (!QualifierLoc)
+      return nullptr;
+  }
+  CXXScopeSpec MapperIdScopeSpec;
+  MapperIdScopeSpec.Adopt(QualifierLoc);
+  DeclarationNameInfo MapperIdInfo = C->getMapperIdInfo();
+  if (MapperIdInfo.getName()) {
+    MapperIdInfo = getDerived().TransformDeclarationNameInfo(MapperIdInfo);
+    if (!MapperIdInfo.getName())
+      return nullptr;
+  }
+  // Build a list of all candidate OMPDeclareMapperDecls, which is provided by
+  // the previous user-defined mapper lookup in dependent environment.
+  llvm::SmallVector<Expr *, 16> UnresolvedMappers;
+  for (auto *E : C->mapperlists()) {
+    // Transform all the decls.
+    if (E) {
+      auto *ULE = cast<UnresolvedLookupExpr>(E);
+      UnresolvedSet<8> Decls;
+      for (auto *D : ULE->decls()) {
+        NamedDecl *InstD =
+            cast<NamedDecl>(getDerived().TransformDecl(E->getExprLoc(), D));
+        Decls.addDecl(InstD, InstD->getAccess());
+      }
+      UnresolvedMappers.push_back(UnresolvedLookupExpr::Create(
+          SemaRef.Context, /*NamingClass=*/nullptr,
+          MapperIdScopeSpec.getWithLocInContext(SemaRef.Context), MapperIdInfo,
+          /*ADL=*/false, ULE->isOverloaded(), Decls.begin(), Decls.end()));
+    } else {
+      UnresolvedMappers.push_back(nullptr);
+    }
+  }
+  OMPVarListLocTy Locs(C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
   return getDerived().RebuildOMPMapClause(
-      C->getMapTypeModifiers(), C->getMapTypeModifiersLoc(), C->getMapType(),
-      C->isImplicitMapType(), C->getMapLoc(), C->getColonLoc(), Vars,
-      C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+      C->getMapTypeModifiers(), C->getMapTypeModifiersLoc(), MapperIdScopeSpec,
+      MapperIdInfo, C->getMapType(), C->isImplicitMapType(), C->getMapLoc(),
+      C->getColonLoc(), Vars, Locs, UnresolvedMappers);
 }
 
 template <typename Derived>
@@ -8924,8 +8950,8 @@ OMPClause *TreeTransform<Derived>::TransformOMPToClause(OMPToClause *C) {
       return 0;
     Vars.push_back(EVar.get());
   }
-  return getDerived().RebuildOMPToClause(Vars, C->getBeginLoc(),
-                                         C->getLParenLoc(), C->getEndLoc());
+  OMPVarListLocTy Locs(C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  return getDerived().RebuildOMPToClause(Vars, Locs);
 }
 
 template <typename Derived>
@@ -8938,8 +8964,8 @@ OMPClause *TreeTransform<Derived>::TransformOMPFromClause(OMPFromClause *C) {
       return 0;
     Vars.push_back(EVar.get());
   }
-  return getDerived().RebuildOMPFromClause(Vars, C->getBeginLoc(),
-                                           C->getLParenLoc(), C->getEndLoc());
+  OMPVarListLocTy Locs(C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  return getDerived().RebuildOMPFromClause(Vars, Locs);
 }
 
 template <typename Derived>
@@ -8953,8 +8979,8 @@ OMPClause *TreeTransform<Derived>::TransformOMPUseDevicePtrClause(
       return nullptr;
     Vars.push_back(EVar.get());
   }
-  return getDerived().RebuildOMPUseDevicePtrClause(
-      Vars, C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  OMPVarListLocTy Locs(C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  return getDerived().RebuildOMPUseDevicePtrClause(Vars, Locs);
 }
 
 template <typename Derived>
@@ -8968,8 +8994,8 @@ TreeTransform<Derived>::TransformOMPIsDevicePtrClause(OMPIsDevicePtrClause *C) {
       return nullptr;
     Vars.push_back(EVar.get());
   }
-  return getDerived().RebuildOMPIsDevicePtrClause(
-      Vars, C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  OMPVarListLocTy Locs(C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+  return getDerived().RebuildOMPIsDevicePtrClause(Vars, Locs);
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index aaf40b93f19..39dc808c7f4 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11784,12 +11784,12 @@ OMPClause *OMPClauseReader::readClause() {
     C = new (Context) OMPDeviceClause();
     break;
   case OMPC_map: {
-    unsigned NumVars = Record.readInt();
-    unsigned NumDeclarations = Record.readInt();
-    unsigned NumLists = Record.readInt();
-    unsigned NumComponents = Record.readInt();
-    C = OMPMapClause::CreateEmpty(Context, NumVars, NumDeclarations, NumLists,
-                                  NumComponents);
+    OMPMappableExprListSizeTy Sizes;
+    Sizes.NumVars = Record.readInt();
+    Sizes.NumUniqueDeclarations = Record.readInt();
+    Sizes.NumComponentLists = Record.readInt();
+    Sizes.NumComponents = Record.readInt();
+    C = OMPMapClause::CreateEmpty(Context, Sizes);
     break;
   }
   case OMPC_num_teams:
@@ -11817,39 +11817,39 @@ OMPClause *OMPClauseReader::readClause() {
     C = new (Context) OMPDefaultmapClause();
     break;
   case OMPC_to: {
-    unsigned NumVars = Record.readInt();
-    unsigned NumDeclarations = Record.readInt();
-    unsigned NumLists = Record.readInt();
-    unsigned NumComponents = Record.readInt();
-    C = OMPToClause::CreateEmpty(Context, NumVars, NumDeclarations, NumLists,
-                                 NumComponents);
+    OMPMappableExprListSizeTy Sizes;
+    Sizes.NumVars = Record.readInt();
+    Sizes.NumUniqueDeclarations = Record.readInt();
+    Sizes.NumComponentLists = Record.readInt();
+    Sizes.NumComponents = Record.readInt();
+    C = OMPToClause::CreateEmpty(Context, Sizes);
     break;
   }
   case OMPC_from: {
-    unsigned NumVars = Record.readInt();
-    unsigned NumDeclarations = Record.readInt();
-    unsigned NumLists = Record.readInt();
-    unsigned NumComponents = Record.readInt();
-    C = OMPFromClause::CreateEmpty(Context, NumVars, NumDeclarations, NumLists,
-                                   NumComponents);
+    OMPMappableExprListSizeTy Sizes;
+    Sizes.NumVars = Record.readInt();
+    Sizes.NumUniqueDeclarations = Record.readInt();
+    Sizes.NumComponentLists = Record.readInt();
+    Sizes.NumComponents = Record.readInt();
+    C = OMPFromClause::CreateEmpty(Context, Sizes);
     break;
   }
   case OMPC_use_device_ptr: {
-    unsigned NumVars = Record.readInt();
-    unsigned NumDeclarations = Record.readInt();
-    unsigned NumLists = Record.readInt();
-    unsigned NumComponents = Record.readInt();
-    C = OMPUseDevicePtrClause::CreateEmpty(Context, NumVars, NumDeclarations,
-                                           NumLists, NumComponents);
+    OMPMappableExprListSizeTy Sizes;
+    Sizes.NumVars = Record.readInt();
+    Sizes.NumUniqueDeclarations = Record.readInt();
+    Sizes.NumComponentLists = Record.readInt();
+    Sizes.NumComponents = Record.readInt();
+    C = OMPUseDevicePtrClause::CreateEmpty(Context, Sizes);
     break;
   }
   case OMPC_is_device_ptr: {
-    unsigned NumVars = Record.readInt();
-    unsigned NumDeclarations = Record.readInt();
-    unsigned NumLists = Record.readInt();
-    unsigned NumComponents = Record.readInt();
-    C = OMPIsDevicePtrClause::CreateEmpty(Context, NumVars, NumDeclarations,
-                                          NumLists, NumComponents);
+    OMPMappableExprListSizeTy Sizes;
+    Sizes.NumVars = Record.readInt();
+    Sizes.NumUniqueDeclarations = Record.readInt();
+    Sizes.NumComponentLists = Record.readInt();
+    Sizes.NumComponents = Record.readInt();
+    C = OMPIsDevicePtrClause::CreateEmpty(Context, Sizes);
     break;
   }
   }
@@ -12288,6 +12288,10 @@ void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
         I, static_cast<OpenMPMapModifierKind>(Record.readInt()));
     C->setMapTypeModifierLoc(I, Record.readSourceLocation());
   }
+  C->setMapperQualifierLoc(Record.readNestedNameSpecifierLoc());
+  DeclarationNameInfo DNI;
+  Record.readDeclarationNameInfo(DNI);
+  C->setMapperIdInfo(DNI);
   C->setMapType(
      static_cast<OpenMPMapClauseKind>(Record.readInt()));
   C->setMapLoc(Record.readSourceLocation());
@@ -12303,6 +12307,12 @@ void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
     Vars.push_back(Record.readExpr());
   C->setVarRefs(Vars);
 
+  SmallVector<Expr *, 16> UDMappers;
+  UDMappers.reserve(NumVars);
+  for (unsigned I = 0; I < NumVars; ++I)
+    UDMappers.push_back(Record.readExpr());
+  C->setUDMapperRefs(UDMappers);
+
   SmallVector<ValueDecl *, 16> Decls;
   Decls.reserve(UniqueDecls);
   for (unsigned i = 0; i < UniqueDecls; ++i)
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index ff01155d820..e52d4ce564d 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6785,11 +6785,15 @@ void OMPClauseWriter::VisitOMPMapClause(OMPMapClause *C) {
     Record.push_back(C->getMapTypeModifier(I));
     Record.AddSourceLocation(C->getMapTypeModifierLoc(I));
   }
+  Record.AddNestedNameSpecifierLoc(C->getMapperQualifierLoc());
+  Record.AddDeclarationNameInfo(C->getMapperIdInfo());
   Record.push_back(C->getMapType());
   Record.AddSourceLocation(C->getMapLoc());
   Record.AddSourceLocation(C->getColonLoc());
   for (auto *E : C->varlists())
     Record.AddStmt(E);
+  for (auto *E : C->mapperlists())
+    Record.AddStmt(E);
   for (auto *D : C->all_decls())
     Record.AddDeclRef(D);
   for (auto N : C->all_num_lists())