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

[lildmh]

Summary

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.

[ABataev]

lib/AST/DeclOpenMP.cpp

163

No, bad idea. Use tail allocation for the clauses. Check the implementation of OMPRequiresDecl

lib/CodeGen/CodeGenModule.h

1248

Formatting.

lib/Parse/ParseOpenMP.cpp

502

Enclose substatement in braces.

588

Pass Range by reference rather than as a pointer

lib/Sema/SemaOpenMP.cpp

13719

Restore this comment.

13756

Restore original comment

14052

Restore al the comments that are not related to the patch itself.

lib/Sema/SemaTemplateInstantiateDecl.cpp

2929

Why?

lib/Serialization/ASTReader.cpp

12303

Restore original

12327

Restore original

[lildmh]

Hi Alexey,

Thanks a lot for the review! For 3 places I have doubt. Please see the comments inline. I tried to fix the rest of your comments.

lib/AST/DeclOpenMP.cpp

163

I think it is possible to use TrailingObjects for clause storage when the number of clauses are known before creating the directive (e.g., for OMPRequiresDecl and OMPExecutableDirective).

The reason that I had to create OMPDeclareMapperDecl before parsing map clauses, is the mapper variable (AA in the example below) needs to be declared within OMPDeclareMapperDecl, because the following map clauses will use it.

#pragma omp declare mapper(struct S AA) map(AA.field1)

A possible way to get around this is to count the number of map clauses before hand. But this solution is not trivial since the normal method for parsing map clauses cannot be used (e.g., it does not know AA when parsing map(AA.field1)). A customized and complex (because it needs to handle all possible situations) parsing method needs to be created, just for counting clause number. I think it's not worthy to do this compared with allocating map clause space later.

I checked the code for OMPDeclareReductionDecl that you wrote. It also has to be created before parsing the combiner and initializer. It does not have a variable number of clauses though.

Any suggestions?

lib/Sema/SemaTemplateInstantiateDecl.cpp

2929

Thanks! I was wrong about this. Has fixed it in the new patch. Please check

lib/Serialization/ASTReader.cpp

12303

I found using readSubExpr does not work with declare mapper. The reasons are as follows:

readSubExpr will call ASTReader::ReadSubExpr, which will call ReadSubStmt. ReadSubStmt only works with Stmt.

Before, this is correct because map clauses only come with OMPExecutableDirective, which is a Stmt.

Now, map clauses can come with OMPDeclareMapperDecl, which is a Decl. ReadSubStmt does not work with Decl. Instead, readExpr will call ASTReader::ReadExpr. ASTReader::ReadExpr calls ReadSubStmt if it is a Stmt, and it calls ReadStmtFromStream if it is a Decl. The map clause information is indeed in the stream for OMPDeclareMapperDecl. So I use readExpr instead.

This modification should not affect the behavior of map clause serialization for existing directives that are Stmts, since they will both call ReadSubStmt in the end. The regression test confirms that.

Any suggestions?

12327

The same as above.

[ABataev]

lib/AST/DeclOpenMP.cpp

163

Instead, you can introduce special DeclContext-based declaration and keep the reference to this declaration inside of the OMPDeclareMapperDecl.

lib/Serialization/ASTReader.cpp

12303

Ok, no problems. I thought it was an accidental change.

[lildmh]

lib/AST/DeclOpenMP.cpp

163

Hi Alexey,

Thanks a lot for your quick response! I don't think I understand your idea. Can you establish more on that?

In my current implementation, OMPDeclareMapperDecl is used as the DeclConext of the variable AA in the above example, and it already includes the reference to AA's declaration.

My problem is, I need to create OMPDeclareMapperDecl before parsing map clauses. But before parsing map clauses, I don't know the number of clauses. Using TrailingObject requires to know how many clauses there are when creating OMPDeclareMapperDecl. So I couldn't use TrailingObject.

My current solution is to create OMPDeclareMapperDecl before parsing map clauses, and to create the clause storage after parsing finishes.

[ABataev]

lib/AST/DeclOpenMP.cpp

163

What I meant, that you don't need to use OMPDeclareMapperDecl for this, instead you can add another (very simple) special declaration based on DeclContext to use it as the parent declaration for the variable. In the OMPDeclareMapperDecl you can keep the reference to this special declaration.

[lildmh]

lib/AST/DeclOpenMP.cpp

163

Thanks for your response! Please let me know if my understanding below is correct:

OMPDeclareMapperDecl no longer inherits from DeclContext. Instead, we create something like OMPDeclareMapperDeclContext which inherits from DeclContext, and OMPDeclareMapperDecl keeps a pointer that points to this OMPDeclareMapperDeclContext. AA and map clauses are parsed within OMPDeclareMapperDeclContext.

This sounds a bit more complex, but if you believe it's better, I can change the code. Please share your thoughts.

[ABataev]

lib/AST/DeclOpenMP.cpp

163

Yes, something like this.

[lildmh]

lib/AST/DeclOpenMP.cpp

163

Hi Alexey,

Sorry for the late response. I was working on something else last week.

When I tried to modify the code based on your suggestions, I found out that DeclContext is only meant to be used for a Decl (please see the comments before class DeclContext {...} in include/clang/AST/DeclBase.h).

It means, if I create a OMPDeclareMapperDeclContext which is a DeclContext but not a Decl, the code cannot work correctly. Therefore OMPDeclareMapperDeclContext must be a Decl itself. If I do it this way, a lot of useless information (all inherited from Decl) will exist within OMPDeclareMapperDeclContext, which is very inefficient.

An alternative way is to have something called OMPDeclareMapperClauses that inherits from TrailingObject to store clause information, and OMPDeclareMapperDecl keeps a pointer that points to OMPDeclareMapperClauses. But I don't think this is better than just having a OMPClause **Clauses, which is my current implementation.

What do you think?

[ABataev]

lib/AST/DeclOpenMP.cpp

163

I don't think the Decl requires a lot of memory. Seems to me, it requires ~32 bytes.

[lildmh]

lib/AST/DeclOpenMP.cpp

163

Hi Alexey,

Thanks for the quick response! In the case we discussed earlier, we'll have 2 entities for a mapper:

class OMPDeclareMapperDeclContext  : public Decl, public DeclContext {...};

class OMPDeclareMapperDecl : public ValueDecl, private TrailingObjects {
  OMPDeclareMapperDeclContext  *DC;
  ...
};

To me, the Decl within OMPDeclareMapperDeclContext is useless and confusing to people. If you insist to get rid of OMPClause **Clauses in the current implementation, I propose something below:

We still have 2 entities for a mapper:

class OMPDeclareMapperClauses :  private TrailingObjects {...}

class OMPDeclareMapperDecl : public ValueDecl, public DeclContext {
  OMPDeclareMapperClauses *Clauses;
  ...
};

This seems to be better than the above case. Do you like it?

[ABataev]

lib/AST/DeclOpenMP.cpp

163

Ok, let's keep the original implementation. But instead of the OMPClause** use MutableArrayRef<OMPClause*>

[lildmh]

lib/AST/DeclOpenMP.cpp

163

Sure. Will have it done soon. Thanks a lot!

[lildmh]

Change the type of mapper clause storage from OMPClause ** to MutableArrayRef<OMPClause *>, and rebase

[ABataev]

include/clang/AST/DeclBase.h

181

Add comma after 0x2000 to exclude this line from the next pactches

include/clang/AST/DeclOpenMP.h

220

Use /// style of comments in class interface

224

Better to call it MapperVarRef

279

Just Clauses.begin() does not work here?

282

Same here, the conversion looks ugly.

lib/AST/ASTDumper.cpp

659

const auto *

676

const auto *

lib/AST/DeclOpenMP.cpp

136

auto * or just return new ....

144

auto *

150

1. auto **
2. Use C.Allocate<OMPClause*>(N)

151

Use makeMutableArrayRef(ClauseStorage, N)

163

Do not use auto here

165

See previous comments for ClauseStorage

lib/AST/DeclPrinter.cpp

1612

Use range-based loop

lib/Parse/ParseOpenMP.cpp

44

Add comma after the new enum

571

Clauses.empty()

lib/Sema/SemaOpenMP.cpp

13492

Text message

13495

Add the text message for the assert

[lildmh]

Hi Alexey,

Thanks a lot for the review! Tried to address all of your comments in the new diff.

[lildmh]

Address review comments and rebase

[ABataev]

LG

[lildmh]

Rebase.

Hi Alexey,

Thanks a lot for the review! It seems no one else will review it. If you think it's ready to go, could you please accept this patch? I also need help to commit this patch since I don't have the privilege.

[ABataev]

Accepted, just was not marked as accepted for an unknown reason.

[lildmh]

Thanks a lot Alexey!

[Meinersbur]

@lildmh Thanks for the patch. I can commit this patch for you. The tests run fine on my machine. However, for committing on other's behalf, we were asked to make the contributor aware that the contribution will be published under a new license. Are you OK with the new license?

[lildmh]

In D56326#1381229, @Meinersbur wrote:

@lildmh Thanks for the patch. I can commit this patch for you. The tests run fine on my machine. However, for committing on other's behalf, we were asked to make the contributor aware that the contribution will be published under a new license. Are you OK with the new license?

Thanks a lot Michael! I'm fine with the license.

[dmajor]

While debugging something else, I noticed that with this patch, Decl now has 33 bits worth of bitfields, so it has gained an extra word. Is that ok? Just want to make sure it wasn't unintentional.

[lildmh]

Hi David,

An extra bit is needed to be added to IdentifierNamespace, and I could not find another field to shrink its width. As a result, it ends up larger than a word now. If you have a better solution, I'll be happy to know.

Thanks,
Lingda

include/clang/AST/DeclBase.h

enum IdentifierNamespace {
     /// This declaration is a function-local extern declaration of a
     /// variable or function. This may also be IDNS_Ordinary if it
     /// has been declared outside any function. These act mostly like
     /// invisible friend declarations, but are also visible to unqualified
     /// lookup within the scope of the declaring function.
     IDNS_LocalExtern         = 0x0800,
 
     /// This declaration is an OpenMP user defined reduction construction.
-    IDNS_OMPReduction        = 0x1000
+    IDNS_OMPReduction        = 0x1000,
+
+    /// This declaration is an OpenMP user defined mapper.
+    IDNS_OMPMapper           = 0x2000,
   };
 
   /// ObjCDeclQualifier - 'Qualifiers' written next to the return and
   /// parameter types in method declarations.  Other than remembering
   /// them and mangling them into the method's signature string, these
   /// are ignored by the compiler; they are consumed by certain
   /// remote-messaging frameworks.
   ///
protected:
   /// Access - Used by C++ decls for the access specifier.
   // NOTE: VC++ treats enums as signed, avoid using the AccessSpecifier enum
   unsigned Access : 2;
 
   /// Whether this declaration was loaded from an AST file.
   unsigned FromASTFile : 1;
 
   /// IdentifierNamespace - This specifies what IDNS_* namespace this lives in.
-  unsigned IdentifierNamespace : 13;
+  unsigned IdentifierNamespace : 14;
 
   /// If 0, we have not computed the linkage of this declaration.
   /// Otherwise, it is the linkage + 1.
   mutable unsigned CacheValidAndLinkage : 3;
 
   /// Allocate memory for a deserialized declaration.
   ///
   /// This routine must be used to allocate memory for any declaration that is

 /// can act as declaration contexts. These decls are (only the top classes
 /// that directly derive from DeclContext are mentioned, not their subclasses):
 ///
 ///   TranslationUnitDecl
 ///   ExternCContext
 ///   NamespaceDecl
 ///   TagDecl
 ///   OMPDeclareReductionDecl
+///   OMPDeclareMapperDecl
 ///   FunctionDecl
 ///   ObjCMethodDecl
 ///   ObjCContainerDecl
 ///   LinkageSpecDecl
 ///   ExportDecl
 ///   BlockDecl
 ///   CapturedDecl
 class DeclContext {

include/clang/AST/DeclCXX.h

   /// an OpenMP declare reduction member with the given name.
   ///
   /// This callback can be used with \c lookupInBases() to find members
   /// of the given name within a C++ class hierarchy.
   static bool FindOMPReductionMember(const CXXBaseSpecifier *Specifier,
                                      CXXBasePath &Path, DeclarationName Name);
 
   /// Base-class lookup callback that determines whether there exists
+  /// an OpenMP declare mapper member with the given name.
+  ///
+  /// This callback can be used with \c lookupInBases() to find members
+  /// of the given name within a C++ class hierarchy.
+  static bool FindOMPMapperMember(const CXXBaseSpecifier *Specifier,
+                                  CXXBasePath &Path, DeclarationName Name);
+
+  /// Base-class lookup callback that determines whether there exists
   /// a member with the given name that can be used in a nested-name-specifier.
   ///
   /// This callback can be used with \c lookupInBases() to find members of
   /// the given name within a C++ class hierarchy that can occur within
   /// nested-name-specifiers.
   static bool FindNestedNameSpecifierMember(const CXXBaseSpecifier *Specifier,
                                             CXXBasePath &Path,
                                             DeclarationName Name);

include/clang/AST/DeclOpenMP.h

static DeclContext *castToDeclContext(const OMPDeclareReductionDecl *D) {
     return static_cast<DeclContext *>(const_cast<OMPDeclareReductionDecl *>(D));
   }
   static OMPDeclareReductionDecl *castFromDeclContext(const DeclContext *DC) {
     return static_cast<OMPDeclareReductionDecl *>(
         const_cast<DeclContext *>(DC));
   }
 };
 
+/// This represents '#pragma omp declare mapper ...' directive. Map clauses are
+/// allowed to use with this directive. The following example declares a user
+/// defined mapper for the type 'struct vec'. This example instructs the fields
+/// 'len' and 'data' should be mapped when mapping instances of 'struct vec'.
+///
+/// \code
+/// #pragma omp declare mapper(mid: struct vec v) map(v.len, v.data[0:N])
+/// \endcode
+class OMPDeclareMapperDecl final : public ValueDecl, public DeclContext {
+  friend class ASTDeclReader;
+
+  /// Clauses assoicated with this mapper declaration
+  MutableArrayRef<OMPClause *> Clauses;
+
+  /// Mapper variable, which is 'v' in the example above
+  Expr *MapperVarRef = nullptr;
+
+  /// Name of the mapper variable
+  DeclarationName VarName;
+
+  LazyDeclPtr PrevDeclInScope;
+
+  virtual void anchor();
+
+  OMPDeclareMapperDecl(Kind DK, DeclContext *DC, SourceLocation L,
+                       DeclarationName Name, QualType Ty,
+                       DeclarationName VarName,
+                       OMPDeclareMapperDecl *PrevDeclInScope)
+      : ValueDecl(DK, DC, L, Name, Ty), DeclContext(DK), VarName(VarName),
+        PrevDeclInScope(PrevDeclInScope) {}
+
+  void setPrevDeclInScope(OMPDeclareMapperDecl *Prev) {
+    PrevDeclInScope = Prev;
+  }
+
+  /// Sets an array of clauses to this mapper declaration
+  void setClauses(ArrayRef<OMPClause *> CL);
+
+public:
+  /// Creates declare mapper node.
+  static OMPDeclareMapperDecl *Create(ASTContext &C, DeclContext *DC,
+                                      SourceLocation L, DeclarationName Name,
+                                      QualType T, DeclarationName VarName,
+                                      OMPDeclareMapperDecl *PrevDeclInScope);
+  /// Creates deserialized declare mapper node.
+  static OMPDeclareMapperDecl *CreateDeserialized(ASTContext &C, unsigned ID,
+                                                  unsigned N);
+
+  /// Creates an array of clauses to this mapper declaration and intializes
+  /// them.
+  void CreateClauses(ASTContext &C, ArrayRef<OMPClause *> CL);
+
+  using clauselist_iterator = MutableArrayRef<OMPClause *>::iterator;
+  using clauselist_const_iterator = ArrayRef<const OMPClause *>::iterator;
+  using clauselist_range = llvm::iterator_range<clauselist_iterator>;
+  using clauselist_const_range =
+      llvm::iterator_range<clauselist_const_iterator>;
+
+  unsigned clauselist_size() const { return Clauses.size(); }
+  bool clauselist_empty() const { return Clauses.empty(); }
+
+  clauselist_range clauselists() {
+    return clauselist_range(clauselist_begin(), clauselist_end());
+  }
+  clauselist_const_range clauselists() const {
+    return clauselist_const_range(clauselist_begin(), clauselist_end());
+  }
+  clauselist_iterator clauselist_begin() { return Clauses.begin(); }
+  clauselist_iterator clauselist_end() { return Clauses.end(); }
+  clauselist_const_iterator clauselist_begin() const { return Clauses.begin(); }
+  clauselist_const_iterator clauselist_end() const { return Clauses.end(); }
+
+  /// Get the variable declared in the mapper
+  Expr *getMapperVarRef() { return MapperVarRef; }
+  const Expr *getMapperVarRef() const { return MapperVarRef; }
+  /// Set the variable declared in the mapper
+  void setMapperVarRef(Expr *MapperVarRefE) { MapperVarRef = MapperVarRefE; }
+
+  /// Get the name of the variable declared in the mapper
+  DeclarationName getVarName() { return VarName; }
+
+  /// Get reference to previous declare mapper construct in the same
+  /// scope with the same name.
+  OMPDeclareMapperDecl *getPrevDeclInScope() {
+    return cast_or_null<OMPDeclareMapperDecl>(
+        PrevDeclInScope.get(getASTContext().getExternalSource()));
+  }
+  const OMPDeclareMapperDecl *getPrevDeclInScope() const {
+    return cast_or_null<OMPDeclareMapperDecl>(
+        PrevDeclInScope.get(getASTContext().getExternalSource()));
+  }
+
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) { return K == OMPDeclareMapper; }
+  static DeclContext *castToDeclContext(const OMPDeclareMapperDecl *D) {
+    return static_cast<DeclContext *>(const_cast<OMPDeclareMapperDecl *>(D));
+  }
+  static OMPDeclareMapperDecl *castFromDeclContext(const DeclContext *DC) {
+    return static_cast<OMPDeclareMapperDecl *>(const_cast<DeclContext *>(DC));
+  }
+};
+
 /// Pseudo declaration for capturing expressions. Also is used for capturing of
 /// non-static data members in non-static member functions.
 ///
 /// Clang supports capturing of variables only, but OpenMP 4.5 allows to
 /// privatize non-static members of current class in non-static member
 /// functions. This pseudo-declaration allows properly handle this kind of
 /// capture by wrapping captured expression into a variable-like declaration.
 class OMPCapturedExprDecl final : public VarDecl {

include/clang/AST/RecursiveASTVisitor.h

 
 DEF_TRAVERSE_DECL(ConstructorUsingShadowDecl, {})
 
 DEF_TRAVERSE_DECL(OMPThreadPrivateDecl, {
   for (auto *I : D->varlists()) {
     TRY_TO(TraverseStmt(I));
   }
  })
- 
 DEF_TRAVERSE_DECL(OMPRequiresDecl, {
   for (auto *C : D->clauselists()) {
     TRY_TO(TraverseOMPClause(C));
   }
 })
 
 DEF_TRAVERSE_DECL(OMPDeclareReductionDecl, {
   TRY_TO(TraverseStmt(D->getCombiner()));
   if (auto *Initializer = D->getInitializer())
     TRY_TO(TraverseStmt(Initializer));
   TRY_TO(TraverseType(D->getType()));
   return true;
 })
 
+DEF_TRAVERSE_DECL(OMPDeclareMapperDecl, {
+  for (auto *C : D->clauselists())
+    TRY_TO(TraverseOMPClause(C));
+  TRY_TO(TraverseType(D->getType()));
+  return true;
+})
+
 DEF_TRAVERSE_DECL(OMPCapturedExprDecl, { TRY_TO(TraverseVarHelper(D)); })
 
 // A helper method for TemplateDecl's children.
 template <typename Derived>
 bool RecursiveASTVisitor<Derived>::TraverseTemplateParameterListHelper(
     TemplateParameterList *TPL) {
   if (TPL) {
     for (TemplateParameterList::iterator I = TPL->begin(), E = TPL->end();

include/clang/Basic/DeclNodes.td

def Tag : DDecl<Type, "tag types", 1>, DeclContext;
               : DDecl<ClassTemplateSpecialization>;
     def TemplateTypeParm : DDecl<Type>;
   def Value : DDecl<Named, "value declarations", 1>;
     def EnumConstant : DDecl<Value, "enumerators">;
     def UnresolvedUsingValue : DDecl<Value>;
     def IndirectField : DDecl<Value>;
     def Binding : DDecl<Value>;
     def OMPDeclareReduction : DDecl<Value>, DeclContext;
+    def OMPDeclareMapper : DDecl<Value>, DeclContext;
     def Declarator : DDecl<Value, "declarators", 1>;
       def Field : DDecl<Declarator, "non-static data members">;
         def ObjCIvar : DDecl<Field>;
         def ObjCAtDefsField : DDecl<Field>;
       def MSProperty : DDecl<Declarator>;
       def Function : DDecl<Declarator, "functions">, DeclContext;
         def CXXDeductionGuide : DDecl<Function>;
         def CXXMethod : DDecl<Function>;

include/clang/Basic/DiagnosticParseKinds.td

 def err_omp_declare_simd_inbranch_notinbranch : Error<
   "unexpected '%0' clause, '%1' is specified already">;
 def err_expected_end_declare_target : Error<
   "expected '#pragma omp end declare target'">;
 def err_omp_declare_target_unexpected_clause: Error<
   "unexpected '%0' clause, only 'to' or 'link' clauses expected">;
 def err_omp_expected_clause: Error<
   "expected at least one clause on '#pragma omp %0' directive">;
+def err_omp_mapper_illegal_identifier : Error<
+  "illegal identifier on 'omp declare mapper' directive">;
+def err_omp_mapper_expected_declarator : Error<
+  "expected declarator on 'omp declare mapper' directive">;
 
 // Pragma loop support.
 def err_pragma_loop_missing_argument : Error<
   "missing argument; expected %select{an integer value|"
   "'enable'%select{|, 'full'}1%select{|, 'assume_safety'}2 or 'disable'}0">;
 def err_pragma_loop_invalid_option : Error<
   "%select{invalid|missing}0 option%select{ %1|}0; expected vectorize, "
   "vectorize_width, interleave, interleave_count, unroll, unroll_count, "

include/clang/Basic/DiagnosticSemaKinds.td

def err_omp_wrong_cancel_region : Error<
   "one of 'for', 'parallel', 'sections' or 'taskgroup' is expected">;
 def err_omp_parent_cancel_region_nowait : Error<
   "parent region for 'omp %select{cancellation point|cancel}0' construct cannot be nowait">;
 def err_omp_parent_cancel_region_ordered : Error<
   "parent region for 'omp %select{cancellation point|cancel}0' construct cannot be ordered">;
 def err_omp_reduction_wrong_type : Error<"reduction type cannot be %select{qualified with 'const', 'volatile' or 'restrict'|a function|a reference|an array}0 type">;
 def err_omp_wrong_var_in_declare_reduction : Error<"only %select{'omp_priv' or 'omp_orig'|'omp_in' or 'omp_out'}0 variables are allowed in %select{initializer|combiner}0 expression">;
 def err_omp_declare_reduction_redefinition : Error<"redefinition of user-defined reduction for type %0">;
+def err_omp_mapper_wrong_type : Error<
+  "mapper type must be of struct, union or class type">;
+def err_omp_declare_mapper_wrong_var : Error<
+  "only variable %0 is allowed in map clauses of this 'omp declare mapper' directive">;
+def err_omp_declare_mapper_redefinition : Error<
+  "redefinition of user-defined mapper for type %0 with name %1">;
 def err_omp_array_section_use : Error<"OpenMP array section is not allowed here">;
 def err_omp_typecheck_section_value : Error<
   "subscripted value is not an array or pointer">;
 def err_omp_typecheck_section_not_integer : Error<
   "array section %select{lower bound|length}0 is not an integer">;
 def err_omp_section_function_type : Error<
   "section of pointer to function type %0">;
 def warn_omp_section_is_char : Warning<"array section %select{lower bound|length}0 is of type 'char'">,

include/clang/Basic/OpenMPKinds.def

 #define OPENMP_TARGET_TEAMS_DISTRIBUTE_PARALLEL_FOR_SIMD_CLAUSE(Name)
 #endif
 #ifndef OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE
 #define OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE(Name)
 #endif
 #ifndef OPENMP_TASKGROUP_CLAUSE
 #define OPENMP_TASKGROUP_CLAUSE(Name)
 #endif
+#ifndef OPENMP_DECLARE_MAPPER_CLAUSE
+#define OPENMP_DECLARE_MAPPER_CLAUSE(Name)
+#endif
 
 // OpenMP directives.
 OPENMP_DIRECTIVE(threadprivate)
 OPENMP_DIRECTIVE(parallel)
 OPENMP_DIRECTIVE(task)
 OPENMP_DIRECTIVE(simd)
 OPENMP_DIRECTIVE(for)
 OPENMP_DIRECTIVE(sections)

 OPENMP_DIRECTIVE_EXT(target_parallel_for, "target parallel for")
 OPENMP_DIRECTIVE_EXT(target_update, "target update")
 OPENMP_DIRECTIVE_EXT(parallel_for, "parallel for")
 OPENMP_DIRECTIVE_EXT(parallel_for_simd, "parallel for simd")
 OPENMP_DIRECTIVE_EXT(parallel_sections, "parallel sections")
 OPENMP_DIRECTIVE_EXT(for_simd, "for simd")
 OPENMP_DIRECTIVE_EXT(cancellation_point, "cancellation point")
 OPENMP_DIRECTIVE_EXT(declare_reduction, "declare reduction")
+OPENMP_DIRECTIVE_EXT(declare_mapper, "declare mapper")
 OPENMP_DIRECTIVE_EXT(declare_simd, "declare simd")
 OPENMP_DIRECTIVE(taskloop)
 OPENMP_DIRECTIVE_EXT(taskloop_simd, "taskloop simd")
 OPENMP_DIRECTIVE(distribute)
 OPENMP_DIRECTIVE_EXT(declare_target, "declare target")
 OPENMP_DIRECTIVE_EXT(end_declare_target, "end declare target")
 OPENMP_DIRECTIVE_EXT(distribute_parallel_for, "distribute parallel for")
 OPENMP_DIRECTIVE_EXT(distribute_parallel_for_simd, "distribute parallel for simd")

 OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE(linear)
 OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE(aligned)
 OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE(safelen)
 OPENMP_TARGET_TEAMS_DISTRIBUTE_SIMD_CLAUSE(simdlen)
 
 // Clauses allowed for OpenMP directive 'taskgroup'.
 OPENMP_TASKGROUP_CLAUSE(task_reduction)
 
+// Clauses allowed for OpenMP directive 'declare mapper'.
+OPENMP_DECLARE_MAPPER_CLAUSE(map)
+
+#undef OPENMP_DECLARE_MAPPER_CLAUSE
 #undef OPENMP_TASKGROUP_CLAUSE
 #undef OPENMP_TASKLOOP_SIMD_CLAUSE
 #undef OPENMP_TASKLOOP_CLAUSE
 #undef OPENMP_LINEAR_KIND
 #undef OPENMP_DEPEND_KIND
 #undef OPENMP_SCHEDULE_MODIFIER
 #undef OPENMP_SCHEDULE_KIND
 #undef OPENMP_PROC_BIND_KIND

include/clang/Parse/Parser.h

DeclGroupPtrTy ParseOpenMPDeclarativeDirectiveWithExtDecl(
       DeclSpec::TST TagType = DeclSpec::TST_unspecified,
       Decl *TagDecl = nullptr);
   /// Parse 'omp declare reduction' construct.
   DeclGroupPtrTy ParseOpenMPDeclareReductionDirective(AccessSpecifier AS);
   /// Parses initializer for provided omp_priv declaration inside the reduction
   /// initializer.
   void ParseOpenMPReductionInitializerForDecl(VarDecl *OmpPrivParm);
 
+  /// Parses 'omp declare mapper' directive.
+  DeclGroupPtrTy ParseOpenMPDeclareMapperDirective(AccessSpecifier AS);
+  /// Parses variable declaration in 'omp declare mapper' directive.
+  TypeResult parseOpenMPDeclareMapperVarDecl(SourceRange &Range,
+                                             DeclarationName &Name,
+                                             AccessSpecifier AS = AS_none);
+
   /// Parses simple list of variables.
   ///
   /// \param Kind Kind of the directive.
   /// \param Callback Callback function to be called for the list elements.
   /// \param AllowScopeSpecifier true, if the variables can have fully
   /// qualified names.
   ///
   bool ParseOpenMPSimpleVarList(

include/clang/Sema/Sema.h

enum LookupNameKind {
     /// outside the innermost non-class scope. See C++11 [class.friend]p11.
     LookupLocalFriendName,
     /// Look up the name of an Objective-C protocol.
     LookupObjCProtocolName,
     /// Look up implicit 'self' parameter of an objective-c method.
     LookupObjCImplicitSelfParam,
     /// Look up the name of an OpenMP user-defined reduction operation.
     LookupOMPReductionName,
+    /// Look up the name of an OpenMP user-defined mapper.
+    LookupOMPMapperName,
     /// Look up any declaration with any name.
     LookupAnyName
   };
 
   /// Specifies whether (or how) name lookup is being performed for a
   /// redeclaration (vs. a reference).
   enum RedeclarationKind {
     /// The lookup is a reference to this name that is not for the
public:
   VarDecl *ActOnOpenMPDeclareReductionInitializerStart(Scope *S, Decl *D);
   /// Finish current declare reduction construct initializer.
   void ActOnOpenMPDeclareReductionInitializerEnd(Decl *D, Expr *Initializer,
                                                  VarDecl *OmpPrivParm);
   /// Called at the end of '#pragma omp declare reduction'.
   DeclGroupPtrTy ActOnOpenMPDeclareReductionDirectiveEnd(
       Scope *S, DeclGroupPtrTy DeclReductions, bool IsValid);
 
+  /// Check variable declaration in 'omp declare mapper' construct.
+  TypeResult ActOnOpenMPDeclareMapperVarDecl(Scope *S, Declarator &D);
+  /// Check if the specified type is allowed to be used in 'omp declare
+  /// mapper' construct.
+  QualType ActOnOpenMPDeclareMapperType(SourceLocation TyLoc,
+                                        TypeResult ParsedType);
+  /// Called on start of '#pragma omp declare mapper'.
+  OMPDeclareMapperDecl *ActOnOpenMPDeclareMapperDirectiveStart(
+      Scope *S, DeclContext *DC, DeclarationName Name, QualType MapperType,
+      SourceLocation StartLoc, DeclarationName VN, AccessSpecifier AS,
+      Decl *PrevDeclInScope = nullptr);
+  /// Build the mapper variable of '#pragma omp declare mapper'.
+  void ActOnOpenMPDeclareMapperDirectiveVarDecl(OMPDeclareMapperDecl *DMD,
+                                                Scope *S, QualType MapperType,
+                                                SourceLocation StartLoc,
+                                                DeclarationName VN);
+  /// Called at the end of '#pragma omp declare mapper'.
+  DeclGroupPtrTy
+  ActOnOpenMPDeclareMapperDirectiveEnd(OMPDeclareMapperDecl *D, Scope *S,
+                                       ArrayRef<OMPClause *> ClauseList);
+
   /// Called on the start of target region i.e. '#pragma omp declare target'.
   bool ActOnStartOpenMPDeclareTargetDirective(SourceLocation Loc);
   /// Called at the end of target region i.e. '#pragme omp end declare target'.
   void ActOnFinishOpenMPDeclareTargetDirective();
   /// Called on correct id-expression from the '#pragma omp declare target'.
   void ActOnOpenMPDeclareTargetName(Scope *CurScope, CXXScopeSpec &ScopeSpec,
                                     const DeclarationNameInfo &Id,
                                     OMPDeclareTargetDeclAttr::MapTypeTy MT,

include/clang/Serialization/ASTBitCodes.h

enum DeclCode {
       DECL_OMP_CAPTUREDEXPR,
 
       /// A PragmaCommentDecl record.
       DECL_PRAGMA_COMMENT,
 
       /// A PragmaDetectMismatchDecl record.
       DECL_PRAGMA_DETECT_MISMATCH,
 
+      /// An OMPDeclareMapperDecl record.
+      DECL_OMP_DECLARE_MAPPER,
+
       /// An OMPDeclareReductionDecl record.
       DECL_OMP_DECLARE_REDUCTION,
 
       DECL_LAST = DECL_OMP_DECLARE_REDUCTION
     };
 
     /// Record codes for each kind of statement or expression.
     ///

lib/AST/ASTDumper.cpp

public:
     }
 
     void VisitOMPDeclareReductionDecl(const OMPDeclareReductionDecl *D) {
       Visit(D->getCombiner());
       if (const auto *Initializer = D->getInitializer())
         Visit(Initializer);
     }
 
+    void VisitOMPDeclareMapperDecl(const OMPDeclareMapperDecl *D) {
+      for (const auto *C : D->clauselists())
+        Visit(C);
+    }
+
     void VisitOMPCapturedExprDecl(const OMPCapturedExprDecl *D) {
       Visit(D->getInit());
     }
 
     template <typename SpecializationDecl>
     void dumpTemplateDeclSpecialization(const SpecializationDecl *D,
                                         bool DumpExplicitInst,
                                         bool DumpRefOnly);
if (HasUndeserializedLookups) {
         OS << "<undeserialized lookups>";
       });
     }
   });
 }
 
 template <typename SpecializationDecl>
 void ASTDumper::dumpTemplateDeclSpecialization(const SpecializationDecl *D,
                                                bool DumpExplicitInst,
                                                bool DumpRefOnly) {
   bool DumpedAny = false;
   for (const auto *RedeclWithBadType : D->redecls()) {
     // FIXME: The redecls() range sometimes has elements of a less-specific
     // type. (In particular, ClassTemplateSpecializationDecl::redecls() gives
     // us TagDecls, and should give CXXRecordDecls).
     auto *Redecl = dyn_cast<SpecializationDecl>(RedeclWithBadType);
     if (!Redecl) {
       // Found the injected-class-name for a class template. This will be dumped
       // as part of its surrounding class so we don't need to dump it here.
       assert(isa<CXXRecordDecl>(RedeclWithBadType) &&
              "expected an injected-class-name");
       continue;
     }
 
     switch (Redecl->getTemplateSpecializationKind()) {
     case TSK_ExplicitInstantiationDeclaration:
     case TSK_ExplicitInstantiationDefinition:
       if (!DumpExplicitInst)
         break;
       LLVM_FALLTHROUGH;
     case TSK_Undeclared:
     case TSK_ImplicitInstantiation:
       if (DumpRefOnly)
         NodeDumper.dumpDeclRef(Redecl);

lib/AST/CXXInheritance.cpp

for (Path.Decls = BaseRecord->lookup(Name); !Path.Decls.empty();
        Path.Decls = Path.Decls.slice(1)) {
     if (Path.Decls.front()->isInIdentifierNamespace(IDNS_OMPReduction))
       return true;
   }
 
   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,
                               DeclarationName Name) {
   RecordDecl *BaseRecord =
     Specifier->getType()->castAs<RecordType>()->getDecl();
 
   for (Path.Decls = BaseRecord->lookup(Name);

lib/AST/DeclBase.cpp

switch (DeclKind) {
     case ClassTemplate:
     case TemplateTemplateParm:
     case TypeAliasTemplate:
       return IDNS_Ordinary | IDNS_Tag | IDNS_Type;
 
     case OMPDeclareReduction:
       return IDNS_OMPReduction;
 
+    case OMPDeclareMapper:
+      return IDNS_OMPMapper;
+
     // Never have names.
     case Friend:
     case FriendTemplate:
     case AccessSpec:
     case LinkageSpec:
     case Export:
     case FileScopeAsm:
     case StaticAssert:
DeclContext *DeclContext::getPrimaryContext() {
   switch (getDeclKind()) {
   case Decl::TranslationUnit:
   case Decl::ExternCContext:
   case Decl::LinkageSpec:
   case Decl::Export:
   case Decl::Block:
   case Decl::Captured:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPDeclareMapper:
     // There is only one DeclContext for these entities.
     return this;
 
   case Decl::Namespace:
     // The original namespace is our primary context.
     return static_cast<NamespaceDecl *>(this)->getOriginalNamespace();
 
   case Decl::ObjCMethod:

lib/AST/DeclOpenMP.cpp

 }
 const OMPDeclareReductionDecl *
 OMPDeclareReductionDecl::getPrevDeclInScope() const {
   return cast_or_null<OMPDeclareReductionDecl>(
       PrevDeclInScope.get(getASTContext().getExternalSource()));
 }
 
 //===----------------------------------------------------------------------===//
+// 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.
 //===----------------------------------------------------------------------===//
 
 void OMPCapturedExprDecl::anchor() {}
 
 OMPCapturedExprDecl *OMPCapturedExprDecl::Create(ASTContext &C, DeclContext *DC,
                                                  IdentifierInfo *Id, QualType T,
                                                  SourceLocation StartLoc) {

lib/AST/DeclPrinter.cpp

public:
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D);
     void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
     void VisitUsingDecl(UsingDecl *D);
     void VisitUsingShadowDecl(UsingShadowDecl *D);
     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);
     void printTemplateArguments(const TemplateArgumentList &Args,
                                 const TemplateParameterList *Params = nullptr);
     void prettyPrintAttributes(Decl *D);
     void prettyPrintPragmas(Decl *D);
     void printDeclType(QualType T, StringRef DeclName, bool Pack = false);
for (DeclContext::decl_iterator D = DC->decls_begin(), DEnd = DC->decls_end();
     }
 
     this->Indent();
     Visit(*D);
 
     // 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;
     else if (auto FD = dyn_cast<FunctionDecl>(*D)) {
       if (FD->isThisDeclarationADefinition())
         Terminator = nullptr;
       else
         Terminator = ";";
if (auto *Init = D->getInitializer()) {
       Init->printPretty(Out, nullptr, Policy, 0);
       if (D->getInitializerKind() == OMPDeclareReductionDecl::DirectInit)
         Out << ")";
       Out << ")";
     }
   }
 }
 
+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);
 }
 

lib/AST/ItaniumMangle.cpp

static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   // Perform the same check for block literals.
   if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
     if (ParmVarDecl *ContextParam
           = dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl()))
       return ContextParam->getDeclContext();
   }
 
   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));
   }
 
   if (const auto *VD = dyn_cast<VarDecl>(D))
     if (VD->isExternC())
       return VD->getASTContext().getTranslationUnitDecl();
 
   if (const auto *FD = dyn_cast<FunctionDecl>(D))

lib/AST/MicrosoftMangle.cpp

static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   // Perform the same check for block literals.
   if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
     if (ParmVarDecl *ContextParam =
             dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl()))
       return ContextParam->getDeclContext();
   }
 
   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));
   }
 
   return DC->getRedeclContext();
 }
 
 static const DeclContext *getEffectiveParentContext(const DeclContext *DC) {
   return getEffectiveDeclContext(cast<Decl>(DC));

lib/Basic/OpenMPKinds.cpp

 #define OPENMP_TASKGROUP_CLAUSE(Name)                                          \
   case OMPC_##Name:                                                            \
     return true;
 #include "clang/Basic/OpenMPKinds.def"
     default:
       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:
   case OMPD_threadprivate:
   case OMPD_section:
   case OMPD_master:
   case OMPD_taskyield:
   case OMPD_barrier:
void clang::getOpenMPCaptureRegions(
   case OMPD_threadprivate:
   case OMPD_taskyield:
   case OMPD_barrier:
   case OMPD_taskwait:
   case OMPD_cancellation_point:
   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:
   case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
   }
 }

lib/CodeGen/CGDecl.cpp

if (auto *DD = dyn_cast<DecompositionDecl>(&VD))
         if (auto *HD = B->getHoldingVar())
           EmitVarDecl(*HD);
     return;
   }
 
   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);
     QualType Ty = TD.getUnderlyingType();
 
     if (Ty->isVariablyModifiedType())
       EmitVariablyModifiedType(Ty);
   }

 
 void CodeGenModule::EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D,
                                             CodeGenFunction *CGF) {
   if (!LangOpts.OpenMP || (!LangOpts.EmitAllDecls && !D->isUsed()))
     return;
   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);
 }

lib/CodeGen/CGOpenMPRuntime.cpp

if (const auto *NestedDir = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
     case OMPD_teams_distribute_simd:
     case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_target_update:
     case OMPD_declare_simd:
     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:
     case OMPD_unknown:
       llvm_unreachable("Unexpected directive.");
     }
   }
 
if (RequiresDeviceCodegen) {
     case OMPD_teams_distribute_simd:
     case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_target_update:
     case OMPD_declare_simd:
     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:
     case OMPD_unknown:
       llvm_unreachable("Unknown target directive for OpenMP device codegen.");
     }
     return;
   }
auto &&ThenGen = [this, &D, Device, &InputInfo,
     case OMPD_teams_distribute:
     case OMPD_teams_distribute_simd:
     case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_declare_simd:
     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:
     case OMPD_target_simd:
     case OMPD_target_teams_distribute:
     case OMPD_target_teams_distribute_simd:
     case OMPD_target_teams_distribute_parallel_for:
     case OMPD_target_teams_distribute_parallel_for_simd:

lib/CodeGen/CGOpenMPRuntimeNVPTX.cpp

if (const auto *NestedDir = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
     case OMPD_teams_distribute_simd:
     case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_target_update:
     case OMPD_declare_simd:
     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:
     case OMPD_unknown:
       llvm_unreachable("Unexpected directive.");
     }
   }
 
static bool supportsSPMDExecutionMode(ASTContext &Ctx,
   case OMPD_teams_distribute_simd:
   case OMPD_teams_distribute_parallel_for:
   case OMPD_teams_distribute_parallel_for_simd:
   case OMPD_target_update:
   case OMPD_declare_simd:
   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:
   case OMPD_unknown:
     break;
   }
   llvm_unreachable(
       "Unknown programming model for OpenMP directive on NVPTX target.");
if (const auto *NestedDir = dyn_cast<OMPExecutableDirective>(ChildStmt)) {
     case OMPD_teams_distribute_simd:
     case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
     case OMPD_target_update:
     case OMPD_declare_simd:
     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:
     case OMPD_unknown:
       llvm_unreachable("Unexpected directive.");
     }
   }
 
static bool supportsLightweightRuntime(ASTContext &Ctx,
   case OMPD_teams_distribute_simd:
   case OMPD_teams_distribute_parallel_for:
   case OMPD_teams_distribute_parallel_for_simd:
   case OMPD_target_update:
   case OMPD_declare_simd:
   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:
   case OMPD_unknown:
     break;
   }
   llvm_unreachable(
       "Unknown programming model for OpenMP directive on NVPTX target.");

lib/CodeGen/CodeGenModule.h

public:
   /// Emit a code for threadprivate directive.
   /// \param D Threadprivate declaration.
   void EmitOMPThreadPrivateDecl(const OMPThreadPrivateDecl *D);
 
   /// Emit a code for declare reduction construct.
   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);
 
   /// Returns whether the given record has hidden LTO visibility and therefore
   /// may participate in (single-module) CFI and whole-program vtable
   /// optimization.
   bool HasHiddenLTOVisibility(const CXXRecordDecl *RD);

lib/CodeGen/CodeGenModule.cpp

if (LangOpts.OpenMP) {
     // If this is OpenMP device, check if it is legal to emit this global
     // normally.
     if (OpenMPRuntime && OpenMPRuntime->emitTargetGlobal(GD))
       return;
     if (auto *DRD = dyn_cast<OMPDeclareReductionDecl>(Global)) {
       if (MustBeEmitted(Global))
         EmitOMPDeclareReduction(DRD);
       return;
+    } else if (auto *DMD = dyn_cast<OMPDeclareMapperDecl>(Global)) {
+      if (MustBeEmitted(Global))
+        EmitOMPDeclareMapper(DMD);
+      return;
     }
   }
 
   // Ignore declarations, they will be emitted on their first use.
   if (const auto *FD = dyn_cast<FunctionDecl>(Global)) {
     // Forward declarations are emitted lazily on first use.
     if (!FD->doesThisDeclarationHaveABody()) {
       if (!FD->doesDeclarationForceExternallyVisibleDefinition())
void CodeGenModule::EmitTopLevelDecl(Decl *D) {
   case Decl::OMPThreadPrivate:
     EmitOMPThreadPrivateDecl(cast<OMPThreadPrivateDecl>(D));
     break;
 
   case Decl::OMPDeclareReduction:
     EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(D));
     break;
 
+  case Decl::OMPDeclareMapper:
+    EmitOMPDeclareMapper(cast<OMPDeclareMapperDecl>(D));
+    break;
+
   case Decl::OMPRequires:
     EmitOMPRequiresDecl(cast<OMPRequiresDecl>(D));
     break;
 
   default:
     // Make sure we handled everything we should, every other kind is a
     // non-top-level decl.  FIXME: Would be nice to have an isTopLevelDeclKind
     // function. Need to recode Decl::Kind to do that easily.

lib/Parse/ParseOpenMP.cpp

enum OpenMPDirectiveKindEx {
   OMPD_exit,
   OMPD_point,
   OMPD_reduction,
   OMPD_target_enter,
   OMPD_target_exit,
   OMPD_update,
   OMPD_distribute_parallel,
   OMPD_teams_distribute_parallel,
-  OMPD_target_teams_distribute_parallel
+  OMPD_target_teams_distribute_parallel,
+  OMPD_mapper,
 };
 
 class ThreadprivateListParserHelper final {
   SmallVector<Expr *, 4> Identifiers;
   Parser *P;
 
 public:
   ThreadprivateListParserHelper(Parser *P) : P(P) {}
return llvm::StringSwitch<unsigned>(S)
       .Case("data", OMPD_data)
       .Case("declare", OMPD_declare)
       .Case("end", OMPD_end)
       .Case("enter", OMPD_enter)
       .Case("exit", OMPD_exit)
       .Case("point", OMPD_point)
       .Case("reduction", OMPD_reduction)
       .Case("update", OMPD_update)
+      .Case("mapper", OMPD_mapper)
       .Default(OMPD_unknown);
 }
 
 static OpenMPDirectiveKind parseOpenMPDirectiveKind(Parser &P) {
   // Array of foldings: F[i][0] F[i][1] ===> F[i][2].
   // E.g.: OMPD_for OMPD_simd ===> OMPD_for_simd
   // TODO: add other combined directives in topological order.
   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},
       {OMPD_distribute_parallel, OMPD_for, OMPD_distribute_parallel_for},
       {OMPD_distribute_parallel_for, OMPD_simd,
        OMPD_distribute_parallel_for_simd},
       {OMPD_distribute, OMPD_simd, OMPD_distribute_simd},
       {OMPD_end, OMPD_declare, OMPD_end_declare},
if (Init.isInvalid()) {
       Actions.AddInitializerToDecl(OmpPrivParm, Init.get(),
                                    /*DirectInit=*/true);
     }
   } else {
     Actions.ActOnUninitializedDecl(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.
 /// OpenMP, 2.8.2 declare simd Construct
 /// The expressions appearing in the clauses of this directive are evaluated in
 /// the scope of the arguments of the function declaration or definition.
 class FNContextRAII final {
   Parser &P;

 ///       threadprivate-directive:
 ///         annot_pragma_openmp 'threadprivate' simple-variable-list
 ///         annot_pragma_openmp_end
 ///
 ///       declare-reduction-directive:
 ///        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
 ///         <function declaration/definition>
 ///
 ///       requires directive:
 ///         annot_pragma_openmp 'requires' <clause> [[[,] <clause>] ... ]
 ///         annot_pragma_openmp_end
if (DeclGroupPtrTy Res = ParseOpenMPDeclareReductionDirective(AS)) {
         while (Tok.isNot(tok::annot_pragma_openmp_end))
           ConsumeAnyToken();
       }
       // Skip the last annot_pragma_openmp_end.
       ConsumeAnnotationToken();
       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 }
     // <function-declaration-or-definition>
     //
     ConsumeToken();
     CachedTokens Toks;
     while(Tok.isNot(tok::annot_pragma_openmp_end)) {

 ///         annot_pragma_openmp_end
 ///
 ///       declare-reduction-directive:
 ///         annot_pragma_openmp 'declare' 'reduction' '(' <reduction_id> ':'
 ///         <type> {',' <type>} ':' <expression> ')' ['initializer' '('
 ///         ('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> ')' ] |
 ///         'parallel for' | 'parallel sections' | 'task' | 'taskyield' |
 ///         'barrier' | 'taskwait' | 'flush' | 'ordered' | 'atomic' |
 ///         'for simd' | 'parallel for simd' | 'target' | 'target data' |
 ///         'taskgroup' | 'teams' | 'taskloop' | 'taskloop simd' |
 ///         'distribute' | 'target enter data' | 'target exit data' |
if (DeclGroupPtrTy Res =
           ConsumeAnyToken();
       }
       ConsumeAnyToken();
       Directive = Actions.ActOnDeclStmt(Res, Loc, Tok.getLocation());
     } else {
       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;
       // Push copy of the current token back to stream to properly parse
       // pseudo-clause OMPFlushClause.
       PP.EnterToken(Tok);
     }
     LLVM_FALLTHROUGH;

lib/Sema/SemaDecl.cpp

if (S.getLangOpts().CUDA && (D->template hasAttr<CUDADeviceAttr>() ||
                                  D->template hasAttr<CUDAHostAttr>()))
       return false;
   }
   return D->isExternC();
 }
 
 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;
   if (DC->isRecord())
     return false;
   llvm_unreachable("Unexpected context");
 }
 
 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;
   llvm_unreachable("Unexpected context");
 }
 
 static bool hasParsedAttr(Scope *S, const Declarator &PD,
                           ParsedAttr::Kind Kind) {

lib/Sema/SemaExpr.cpp

bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
   if (LangOpts.OpenMP && DRD && !CurContext->containsDecl(D) &&
       isa<VarDecl>(D)) {
     Diag(Loc, diag::err_omp_wrong_var_in_declare_reduction)
         << getCurFunction()->HasOMPDeclareReductionCombiner;
     Diag(D->getLocation(), diag::note_entity_declared_at) << D;
     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);
 
   DiagnoseUnusedOfDecl(*this, D, Loc);
 
   diagnoseUseOfInternalDeclInInlineFunction(*this, D, Loc);
 
   return false;
#include "clang/AST/DeclNodes.inc"
     case Decl::ObjCIvar:
       llvm_unreachable("forming non-member reference to ivar?");
 
     // Enum constants are always r-values and never references.
     // Unresolved using declarations are dependent.
     case Decl::EnumConstant:
     case Decl::UnresolvedUsingValue:
     case Decl::OMPDeclareReduction:
+    case Decl::OMPDeclareMapper:
       valueKind = VK_RValue;
       break;
 
     // Fields and indirect fields that got here must be for
     // pointer-to-member expressions; we just call them l-values for
     // internal consistency, because this subexpression doesn't really
     // exist in the high-level semantics.
     case Decl::Field:

lib/Sema/SemaLookup.cpp

static inline unsigned getIDNS(Sema::LookupNameKind NameKind,
   case Sema::LookupObjCProtocolName:
     IDNS = Decl::IDNS_ObjCProtocol;
     break;
 
   case Sema::LookupOMPReductionName:
     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
       | Decl::IDNS_Type;
     break;
   }
   return IDNS;
 }
switch (R.getLookupKind()) {
     case LookupAnyName:
       BaseCallback = &LookupAnyMember;
       break;
 
     case LookupOMPReductionName:
       BaseCallback = &CXXRecordDecl::FindOMPReductionMember;
       break;
 
+    case LookupOMPMapperName:
+      BaseCallback = &CXXRecordDecl::FindOMPMapperMember;
+      break;
+
     case LookupUsingDeclName:
       // This lookup is for redeclarations only.
 
     case LookupOperatorName:
     case LookupNamespaceName:
     case LookupObjCProtocolName:
     case LookupLabel:
       // These lookups will never find a member in a C++ class (or base class).

lib/Sema/SemaOpenMP.cpp

void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
   case OMPD_threadprivate:
   case OMPD_taskyield:
   case OMPD_barrier:
   case OMPD_taskwait:
   case OMPD_cancellation_point:
   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:
   case OMPD_requires:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
   }
case OMPD_target_teams_distribute_simd:
     Res = ActOnOpenMPTargetTeamsDistributeSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_target);
     break;
   case OMPD_declare_target:
   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");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
   }
 
   for (const auto &P : VarsWithInheritedDSA) {
case OMPD_target_data:
       break;
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_teams:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
case OMPC_num_threads:
     case OMPD_taskloop_simd:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_teams:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
case OMPC_num_teams:
     case OMPD_target_parallel_for_simd:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
     case OMPD_section:
case OMPC_thread_limit:
     case OMPD_target_parallel_for_simd:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
     case OMPD_section:
case OMPC_schedule:
     case OMPD_parallel_sections:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_simd:
     case OMPD_sections:
     case OMPD_section:
     case OMPD_single:
     case OMPD_master:
case OMPC_dist_schedule:
     case OMPD_parallel_sections:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
     case OMPD_section:
case OMPC_device:
     case OMPD_parallel_for_simd:
     case OMPD_threadprivate:
     case OMPD_taskyield:
     case OMPD_barrier:
     case OMPD_taskwait:
     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:
     case OMPD_simd:
     case OMPD_for:
     case OMPD_for_simd:
     case OMPD_sections:
     case OMPD_section:
if (IsValid) {
                           /*AddToContext=*/false);
     } else {
       D->setInvalidDecl();
     }
   }
   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,
                                            SourceLocation EndLoc) {
   Expr *ValExpr = NumTeams;
   Stmt *HelperValStmt = nullptr;
 
   // OpenMP [teams Constrcut, Restrictions]
OMPClause *Sema::ActOnOpenMPNumTasksClause(Expr *NumTasks,
   return new (Context) OMPNumTasksClause(ValExpr, StartLoc, LParenLoc, EndLoc);
 }
 
 OMPClause *Sema::ActOnOpenMPHintClause(Expr *Hint, SourceLocation StartLoc,
                                        SourceLocation LParenLoc,
                                        SourceLocation EndLoc) {
   // OpenMP [2.13.2, critical construct, Description]
   // ... where hint-expression is an integer constant expression that evaluates
   // to a valid lock hint.
   ExprResult HintExpr = VerifyPositiveIntegerConstantInClause(Hint, OMPC_hint);
   if (HintExpr.isInvalid())
     return nullptr;
   return new (Context)
       OMPHintClause(HintExpr.get(), StartLoc, LParenLoc, EndLoc);
 }
 
 OMPClause *Sema::ActOnOpenMPDistScheduleClause(
if (!ChunkSize->isValueDependent() && !ChunkSize->isTypeDependent() &&
           PerformOpenMPImplicitIntegerConversion(ChunkSizeLoc, ChunkSize);
       if (Val.isInvalid())
         return nullptr;
 
       ValExpr = Val.get();
 
       // OpenMP [2.7.1, Restrictions]
       //  chunk_size must be a loop invariant integer expression with a positive
       //  value.
       llvm::APSInt Result;
       if (ValExpr->isIntegerConstantExpr(Result, Context)) {
         if (Result.isSigned() && !Result.isStrictlyPositive()) {
           Diag(ChunkSizeLoc, diag::err_omp_negative_expression_in_clause)
               << "dist_schedule" << ChunkSize->getSourceRange();
           return nullptr;
         }
       } else if (getOpenMPCaptureRegionForClause(
for (Expr *RefExpr : VarList) {
     if (!VD)
       Ref = buildCapture(*this, D, SimpleRefExpr, /*WithInit=*/true);
     MVLI.ProcessedVarList.push_back(VD ? RefExpr->IgnoreParens() : Ref);
     PrivateCopies.push_back(VDPrivateRefExpr);
     Inits.push_back(VDInitRefExpr);
 
     // We need to add a data sharing attribute for this variable to make sure it
     // is correctly captured. A variable that shows up in a use_device_ptr has
     // similar properties of a first private variable.
     DSAStack->addDSA(D, RefExpr->IgnoreParens(), OMPC_firstprivate, Ref);
 
     // Create a mappable component for the list item. List items in this clause
     // only need a component.
     MVLI.VarBaseDeclarations.push_back(D);
     MVLI.VarComponents.resize(MVLI.VarComponents.size() + 1);
     MVLI.VarComponents.back().push_back(
         OMPClauseMappableExprCommon::MappableComponent(SimpleRefExpr, D));

lib/Sema/SemaTemplateInstantiateDecl.cpp

Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
   }
 
   (void)SemaRef.ActOnOpenMPDeclareReductionDirectiveEnd(/*S=*/nullptr, DRD,
                                                         IsCorrect);
 
   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");
 }
 
 Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D) {
   return VisitFunctionDecl(D, nullptr);
 }
NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
   //    whose type is not instantiation dependent, do nothing to the decl
   //  - otherwise find its instantiated decl.
   if (isa<ParmVarDecl>(D) && !ParentDC->isDependentContext() &&
       !cast<ParmVarDecl>(D)->getType()->isInstantiationDependentType())
     return 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
     // declarations to their instantiations.
     if (CurrentInstantiationScope) {
       if (auto Found = CurrentInstantiationScope->findInstantiationOf(D)) {
         if (Decl *FD = Found->dyn_cast<Decl *>())
           return cast<NamedDecl>(FD);

lib/Serialization/ASTCommon.cpp

bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::Block:
   case Decl::Captured:
   case Decl::ClassScopeFunctionSpecialization:
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPRequires:
   case Decl::OMPCapturedExpr:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPDeclareMapper:
   case Decl::BuiltinTemplate:
   case Decl::Decomposition:
   case Decl::Binding:
     return false;
 
   // These indirectly derive from Redeclarable<T> but are not actually
   // redeclarable.
   case Decl::ImplicitParam:

lib/Serialization/ASTReader.cpp

void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
   auto NumVars = C->varlist_size();
   auto UniqueDecls = C->getUniqueDeclarationsNum();
   auto TotalLists = C->getTotalComponentListNum();
   auto TotalComponents = C->getTotalComponentsNum();
 
   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;
   Decls.reserve(UniqueDecls);
   for (unsigned i = 0; i < UniqueDecls; ++i)
     Decls.push_back(Record.readDeclAs<ValueDecl>());
   C->setUniqueDecls(Decls);
 
   SmallVector<unsigned, 16> ListsPerDecl;
   ListsPerDecl.reserve(UniqueDecls);
   for (unsigned i = 0; i < UniqueDecls; ++i)
     ListsPerDecl.push_back(Record.readInt());
   C->setDeclNumLists(ListsPerDecl);
 
   SmallVector<unsigned, 32> ListSizes;
   ListSizes.reserve(TotalLists);
   for (unsigned i = 0; i < TotalLists; ++i)
     ListSizes.push_back(Record.readInt());
   C->setComponentListSizes(ListSizes);
 
   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));
   }
   C->setComponents(Components, ListSizes);
 }
 
 void OMPClauseReader::VisitOMPNumTeamsClause(OMPNumTeamsClause *C) {

lib/Serialization/ASTReaderDecl.cpp

public:
     void VisitObjCImplDecl(ObjCImplDecl *D);
     void VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
     void VisitObjCImplementationDecl(ObjCImplementationDecl *D);
     void VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *D);
     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
     void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
+    void VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D);
     void VisitOMPRequiresDecl(OMPRequiresDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
   };
 
 } // namespace clang
 
 namespace {
 
void ASTDeclReader::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   Expr *Priv = Record.readExpr();
   D->setInitializerData(Orig, Priv);
   Expr *Init = Record.readExpr();
   auto IK = static_cast<OMPDeclareReductionDecl::InitKind>(Record.readInt());
   D->setInitializer(Init, IK);
   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);
 }
 
 //===----------------------------------------------------------------------===//
 // Attribute Reading
 //===----------------------------------------------------------------------===//
 
static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
 
   if (isa<FileScopeAsmDecl>(D) ||
       isa<ObjCProtocolDecl>(D) ||
       isa<ObjCImplDecl>(D) ||
       isa<ImportDecl>(D) ||
       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() &&
            (Var->isThisDeclarationADefinition() == VarDecl::Definition ||
             OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(Var));
   if (const auto *Func = dyn_cast<FunctionDecl>(D))
     return Func->doesThisDeclarationHaveABody() || HasBody;
 
case DECL_OMP_THREADPRIVATE:
     D = OMPThreadPrivateDecl::CreateDeserialized(Context, ID, Record.readInt());
     break;
   case DECL_OMP_REQUIRES:
     D = OMPRequiresDecl::CreateDeserialized(Context, ID, Record.readInt());
     break;
   case DECL_OMP_DECLARE_REDUCTION:
     D = OMPDeclareReductionDecl::CreateDeserialized(Context, ID);
     break;
+  case DECL_OMP_DECLARE_MAPPER:
+    D = OMPDeclareMapperDecl::CreateDeserialized(Context, ID, Record.readInt());
+    break;
   case DECL_OMP_CAPTUREDEXPR:
     D = OMPCapturedExprDecl::CreateDeserialized(Context, ID);
     break;
   case DECL_PRAGMA_COMMENT:
     D = PragmaCommentDecl::CreateDeserialized(Context, ID, Record.readInt());
     break;
   case DECL_PRAGMA_DETECT_MISMATCH:
     D = PragmaDetectMismatchDecl::CreateDeserialized(Context, ID,

lib/Serialization/ASTWriterDecl.cpp

public:
     void VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D);
     void VisitObjCImplementationDecl(ObjCImplementationDecl *D);
     void VisitObjCCompatibleAliasDecl(ObjCCompatibleAliasDecl *D);
     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     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.
     void AddObjCTypeParamList(ObjCTypeParamList *typeParams) {
       // Empty type parameter list.
       if (!typeParams) {
         Record.push_back(0);
         return;
void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
   Record.AddStmt(D->getInitOrig());
   Record.AddStmt(D->getInitPriv());
   Record.AddStmt(D->getInitializer());
   Record.push_back(D->getInitializerKind());
   Record.AddDeclRef(D->getPrevDeclInScope());
   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;
 }
 
 //===----------------------------------------------------------------------===//
 // ASTWriter Implementation
 //===----------------------------------------------------------------------===//

test/OpenMP/declare_mapper_ast_print.c

+// RUN: %clang_cc1 -verify -fopenmp -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+
+// RUN: %clang_cc1 -verify -fopenmp-simd -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp-simd -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp-simd -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+// CHECK: struct vec {
+struct vec {
+  int len;
+  double *data;
+};
+// CHECK: };
+
+// CHECK: struct dat {
+struct dat {
+  int i;
+  double d;
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : struct vec v) map(tofrom: v.len){{$}}
+};
+// CHECK: };
+
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : struct vec v) map(tofrom: v.len){{$}}
+#pragma omp declare mapper(default : struct vec kk) map(kk.len) map(kk.data[0:2])
+// CHECK: #pragma omp declare mapper (default : struct vec kk) map(tofrom: kk.len) map(tofrom: kk.data[0:2]){{$}}
+#pragma omp declare mapper(struct dat d) map(to: d.d)
+// CHECK: #pragma omp declare mapper (default : struct dat d) map(to: d.d){{$}}
+
+// CHECK: int main() {
+int main() {
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : struct vec v) map(tofrom: v.len)
+  {
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : struct vec v) map(tofrom: v.len)
+  }
+  return 0;
+}
+// CHECK: }
+
+#endif

test/OpenMP/declare_mapper_ast_print.cpp

+// RUN: %clang_cc1 -verify -fopenmp -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp -x c++ -std=c++11 -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+
+// RUN: %clang_cc1 -verify -fopenmp-simd -ast-print %s | FileCheck %s
+// RUN: %clang_cc1 -fopenmp-simd -x c++ -std=c++11 -emit-pch -o %t %s
+// RUN: %clang_cc1 -fopenmp-simd -std=c++11 -include-pch %t -fsyntax-only -verify %s -ast-print | FileCheck %s
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+// CHECK: namespace N1 {
+namespace N1
+{
+// CHECK: class vec {
+class vec {
+public:
+  int len;
+  double *data;
+};
+// CHECK: };
+
+#pragma omp declare mapper(id: vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len){{$}}
+};
+// CHECK: }
+// CHECK: ;
+
+template <class T>
+class dat {
+public:
+  class datin {
+  public:
+    T in;
+  };
+  int i;
+  T d;
+#pragma omp declare mapper(id: N1::vec v) map(v.len)
+#pragma omp declare mapper(id: datin v) map(v.in)
+};
+
+// CHECK: template <class T> class dat {
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len){{$}}
+// CHECK: #pragma omp declare mapper (id : dat::datin v) map(tofrom: v.in){{$}}
+// CHECK: };
+// CHECK: template<> class dat<double> {
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len){{$}}
+// CHECK: #pragma omp declare mapper (id : dat<double>::datin v) map(tofrom: v.in){{$}}
+// CHECK: };
+
+#pragma omp declare mapper(default : N1::vec kk) map(kk.len) map(kk.data[0:2])
+// CHECK: #pragma omp declare mapper (default : N1::vec kk) map(tofrom: kk.len) map(tofrom: kk.data[0:2]){{$}}
+#pragma omp declare mapper(dat<double> d) map(to: d.d)
+// CHECK: #pragma omp declare mapper (default : dat<double> d) map(to: d.d){{$}}
+
+template <typename T>
+T foo(T a) {
+  struct foodat {
+    T a;
+  };
+#pragma omp declare mapper(struct foodat v) map(v.a)
+#pragma omp declare mapper(id: N1::vec v) map(v.len)
+  {
+#pragma omp declare mapper(id: N1::vec v) map(v.len)
+  }
+  return 0;
+}
+
+// CHECK: template <typename T> T foo(T a) {
+// CHECK: #pragma omp declare mapper (default : struct foodat v) map(tofrom: v.a)
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+// CHECK: {
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+// CHECK: }
+// CHECK: }
+// CHECK: template<> int foo<int>(int a) {
+// CHECK: #pragma omp declare mapper (default : struct foodat v) map(tofrom: v.a)
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+// CHECK: {
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+// CHECK: }
+// CHECK: }
+
+// CHECK: int main() {
+int main() {
+#pragma omp declare mapper(id: N1::vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+  {
+#pragma omp declare mapper(id: N1::vec v) map(v.len)
+// CHECK: #pragma omp declare mapper (id : N1::vec v) map(tofrom: v.len)
+  }
+  return foo<int>(0);
+}
+// CHECK: }
+
+#endif

test/OpenMP/declare_mapper_messages.c

+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 %s
+
+// RUN: %clang_cc1 -verify -fopenmp-simd -ferror-limit 100 %s
+
+int temp; // expected-note {{'temp' declared here}}
+
+struct vec {                                                            // expected-note {{definition of 'struct vec' is not complete until the closing '}'}}
+  int len;
+#pragma omp declare mapper(id: struct vec v) map(v.len)                 // expected-error {{incomplete definition of type 'struct vec'}}
+  double *data;
+};
+
+#pragma omp declare mapper                                              // expected-error {{expected '(' after 'declare mapper'}}
+#pragma omp declare mapper {                                            // expected-error {{expected '(' after 'declare mapper'}}
+#pragma omp declare mapper(                                             // expected-error {{expected a type}} expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(#                                            // expected-error {{expected a type}} expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(struct v                                     // expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(struct vec                                   // expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(S v                                          // expected-error {{unknown type name 'S'}}
+#pragma omp declare mapper(struct vec v                                 // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare mapper(aa:struct vec v)                             // expected-error {{expected at least one clause on '#pragma omp declare mapper' directive}}
+#pragma omp declare mapper(bb:struct vec v) private(v)                  // expected-error {{expected at least one clause on '#pragma omp declare mapper' directive}} // expected-error {{unexpected OpenMP clause 'private' in directive '#pragma omp declare mapper'}}
+#pragma omp declare mapper(cc:struct vec v) map(v) (                    // expected-warning {{extra tokens at the end of '#pragma omp declare mapper' are ignored}}
+
+#pragma omp declare mapper(++: struct vec v) map(v.len)                 // expected-error {{illegal identifier on 'omp declare mapper' directive}}
+#pragma omp declare mapper(id1: struct vec v) map(v.len, temp)          // expected-error {{only variable v is allowed in map clauses of this 'omp declare mapper' directive}}
+#pragma omp declare mapper(default : struct vec kk) map(kk.data[0:2])   // expected-note {{previous definition is here}}
+#pragma omp declare mapper(struct vec v) map(v.len)                     // expected-error {{redefinition of user-defined mapper for type 'struct vec' with name 'default'}}
+#pragma omp declare mapper(int v) map(v)                                // expected-error {{mapper type must be of struct, union or class type}}
+
+int fun(int arg) {
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+  {
+#pragma omp declare mapper(id: struct vec v) map(v.len)                 // expected-note {{previous definition is here}}
+#pragma omp declare mapper(id: struct vec v) map(v.len)                 // expected-error {{redefinition of user-defined mapper for type 'struct vec' with name 'id'}}
+    {
+#pragma omp declare mapper(id: struct vec v) map(v.len)
+    }
+  }
+  return arg;
+}

test/OpenMP/declare_mapper_messages.cpp

+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 %s
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 -std=c++98 %s
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 -std=c++11 %s
+
+// RUN: %clang_cc1 -verify -fopenmp-simd -ferror-limit 100 %s
+// RUN: %clang_cc1 -verify -fopenmp-simd -ferror-limit 100 -std=c++98 %s
+// RUN: %clang_cc1 -verify -fopenmp-simd -ferror-limit 100 -std=c++11 %s
+
+int temp; // expected-note {{'temp' declared here}}
+
+class vec {                                                             // expected-note {{definition of 'vec' is not complete until the closing '}'}}
+private:
+  int p;                                                                // expected-note {{declared private here}}
+public:
+  int len;
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-error {{member access into incomplete type 'vec'}}
+  double *data;
+};
+
+#pragma omp declare mapper                                              // expected-error {{expected '(' after 'declare mapper'}}
+#pragma omp declare mapper {                                            // expected-error {{expected '(' after 'declare mapper'}}
+#pragma omp declare mapper(                                             // expected-error {{expected a type}} expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(#                                            // expected-error {{expected a type}} expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(v                                            // expected-error {{unknown type name 'v'}} expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(vec                                          // expected-error {{expected declarator on 'omp declare mapper' directive}}
+#pragma omp declare mapper(S v                                          // expected-error {{unknown type name 'S'}}
+#pragma omp declare mapper(vec v                                        // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare mapper(aa: vec v)                                   // expected-error {{expected at least one clause on '#pragma omp declare mapper' directive}}
+#pragma omp declare mapper(bb: vec v) private(v)                        // expected-error {{expected at least one clause on '#pragma omp declare mapper' directive}} // expected-error {{unexpected OpenMP clause 'private' in directive '#pragma omp declare mapper'}}
+#pragma omp declare mapper(cc: vec v) map(v) (                          // expected-warning {{extra tokens at the end of '#pragma omp declare mapper' are ignored}}
+
+#pragma omp declare mapper(++: vec v) map(v.len)                        // expected-error {{illegal identifier on 'omp declare mapper' directive}}
+#pragma omp declare mapper(id1: vec v) map(v.len, temp)                 // expected-error {{only variable v is allowed in map clauses of this 'omp declare mapper' directive}}
+#pragma omp declare mapper(default : vec kk) map(kk.data[0:2])          // expected-note {{previous definition is here}}
+#pragma omp declare mapper(vec v) map(v.len)                            // expected-error {{redefinition of user-defined mapper for type 'vec' with name 'default'}}
+#pragma omp declare mapper(int v) map(v)                                // expected-error {{mapper type must be of struct, union or class type}}
+#pragma omp declare mapper(id2: vec v) map(v.len, v.p)                  // expected-error {{'p' is a private member of 'vec'}}
+
+namespace N1 {
+template <class T>
+class stack {                                                           // expected-note {{template is declared here}}
+public:
+  int len;
+  T *data;
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-note {{previous definition is here}}
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-error {{redefinition of user-defined mapper for type 'vec' with name 'id'}}
+};
+};
+
+#pragma omp declare mapper(default : N1::stack s) map(s.len)            // expected-error {{use of class template 'N1::stack' requires template arguments}}
+#pragma omp declare mapper(id1: N1::stack<int> s) map(s.data)
+#pragma omp declare mapper(default : S<int> s) map(s.len)               // expected-error {{no template named 'S'}}
+
+template <class T>
+T foo(T a) {
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-note {{previous definition is here}}
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-error {{redefinition of user-defined mapper for type 'vec' with name 'id'}}
+}
+
+int fun(int arg) {
+#pragma omp declare mapper(id: vec v) map(v.len)
+  {
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-note {{previous definition is here}}
+    {
+#pragma omp declare mapper(id: vec v) map(v.len)
+    }
+#pragma omp declare mapper(id: vec v) map(v.len)                        // expected-error {{redefinition of user-defined mapper for type 'vec' with name 'id'}}
+  }
+  return arg;
+}

tools/libclang/CIndex.cpp

CXCursor clang_getCursorDefinition(CXCursor C) {
   case Decl::Captured:
   case Decl::OMPCapturedExpr:
   case Decl::Label:  // FIXME: Is this right??
   case Decl::ClassScopeFunctionSpecialization:
   case Decl::CXXDeductionGuide:
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPDeclareReduction:
+  case Decl::OMPDeclareMapper:
   case Decl::OMPRequires:
   case Decl::ObjCTypeParam:
   case Decl::BuiltinTemplate:
   case Decl::PragmaComment:
   case Decl::PragmaDetectMismatch:
   case Decl::UsingPack:
     return C;