[OPENMP 4.0] Initial support for 'omp declare reduction' construct.

Add parsing, sema analysis and serialization/deserialization for 'declare reduction' construct.
User-defined reductions are defined as

#pragma omp declare reduction( reduction-identifier : typename-list : combiner ) [initializer ( initializer-expr )]
These custom reductions may be used in 'reduction' clauses of OpenMP constructs. The combiner specifies how partial results can be combined into a single value. The
combiner can use the special variable identifiers omp_in and omp_out that are of the type of the variables being reduced with this reduction-identifier. Each of them will
denote one of the values to be combined before executing the combiner. It is assumed that the special omp_out identifier will refer to the storage that holds the resulting
combined value after executing the combiner.
As the initializer-expr value of a user-defined reduction is not known a priori the initializer-clause can be used to specify one. Then the contents of the initializer-clause
will be used as the initializer for private copies of reduction list items where the omp_priv identifier will refer to the storage to be initialized. The special identifier
omp_orig can also appear in the initializer-clause and it will refer to the storage of the original variable to be reduced.
Differential Revision: http://reviews.llvm.org/D11182

llvm-svn: 262582

clang/include/clang/AST/DeclBase.h

@@ -166,7 +166,10 @@ public:
     /// 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
+    IDNS_LocalExtern         = 0x0800,
+
+    /// This declaration is an OpenMP user defined reduction construction.
+    IDNS_OMPReduction        = 0x1000
   };
 
   /// ObjCDeclQualifier - 'Qualifiers' written next to the return and
@@ -256,7 +259,7 @@ private:
   SourceLocation Loc;
 
   /// DeclKind - This indicates which class this is.
-  unsigned DeclKind : 8;
+  unsigned DeclKind : 7;
 
   /// InvalidDecl - This indicates a semantic error occurred.
   unsigned InvalidDecl :  1;
@@ -296,7 +299,7 @@ protected:
   unsigned Hidden : 1;
   
   /// IdentifierNamespace - This specifies what IDNS_* namespace this lives in.
-  unsigned IdentifierNamespace : 12;
+  unsigned IdentifierNamespace : 13;
 
   /// \brief If 0, we have not computed the linkage of this declaration.
   /// Otherwise, it is the linkage + 1.
@@ -1117,6 +1120,7 @@ public:
 ///   ObjCContainerDecl
 ///   LinkageSpecDecl
 ///   BlockDecl
+///   OMPDeclareReductionDecl
 ///
 class DeclContext {
   /// DeclKind - This indicates which class this is.

clang/include/clang/AST/DeclCXX.h

@@ -1570,6 +1570,14 @@ public:
   static bool FindOrdinaryMember(const CXXBaseSpecifier *Specifier,
                                  CXXBasePath &Path, DeclarationName Name);
 
+  /// \brief Base-class lookup callback that determines whether there exists
+  /// 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);
+
   /// \brief Base-class lookup callback that determines whether there exists
   /// a member with the given name that can be used in a nested-name-specifier.
   ///

clang/include/clang/AST/DeclOpenMP.h

@@ -15,12 +15,14 @@
 #ifndef LLVM_CLANG_AST_DECLOPENMP_H
 #define LLVM_CLANG_AST_DECLOPENMP_H
 
-#include "clang/AST/DeclBase.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExternalASTSource.h"
+#include "clang/AST/Type.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/TrailingObjects.h"
 
 namespace clang {
-class Expr;
 
 /// \brief This represents '#pragma omp threadprivate ...' directive.
 /// For example, in the following, both 'a' and 'A::b' are threadprivate:
@@ -87,6 +89,83 @@ public:
   static bool classofKind(Kind K) { return K == OMPThreadPrivate; }
 };
 
+/// \brief This represents '#pragma omp declare reduction ...' directive.
+/// For example, in the following, declared reduction 'foo' for types 'int' and
+/// 'float':
+///
+/// \code
+/// #pragma omp declare reduction (foo : int,float : omp_out += omp_in) \
+///                     initializer (omp_priv = 0)
+/// \endcode
+///
+/// Here 'omp_out += omp_in' is a combiner and 'omp_priv = 0' is an initializer.
+class OMPDeclareReductionDecl final : public NamedDecl, public DeclContext {
+private:
+  friend class ASTDeclReader;
+  /// \brief Combiner for declare reduction construct.
+  Expr *Combiner;
+  /// \brief Initializer for declare reduction construct.
+  Expr *Initializer;
+  /// \brief Reference to the previous declare reduction construct in the same
+  /// scope with the same name. Required for proper templates instantiation if
+  /// the declare reduction construct is declared inside compound statement.
+  LazyDeclPtr PrevDeclInScope;
+  /// \brief Type of declare reduction construct.
+  QualType Ty;
+
+  virtual void anchor();
+
+  OMPDeclareReductionDecl(Kind DK, DeclContext *DC, SourceLocation L,
+                          DeclarationName Name, QualType Ty,
+                          OMPDeclareReductionDecl *PrevDeclInScope)
+      : NamedDecl(DK, DC, L, Name), DeclContext(DK), Combiner(nullptr),
+        Initializer(nullptr), PrevDeclInScope(PrevDeclInScope), Ty(Ty) {}
+
+  void setPrevDeclInScope(OMPDeclareReductionDecl *Prev) {
+    PrevDeclInScope = Prev;
+  }
+  void setType(QualType T) { Ty = T; }
+
+public:
+  /// \brief Create declare reduction node.
+  static OMPDeclareReductionDecl *
+  Create(ASTContext &C, DeclContext *DC, SourceLocation L, DeclarationName Name,
+         QualType T, OMPDeclareReductionDecl *PrevDeclInScope);
+  /// \brief Create deserialized declare reduction node.
+  static OMPDeclareReductionDecl *CreateDeserialized(ASTContext &C,
+                                                     unsigned ID);
+
+  /// \brief Get combiner expression of the declare reduction construct.
+  Expr *getCombiner() { return Combiner; }
+  const Expr *getCombiner() const { return Combiner; }
+  /// \brief Set combiner expression for the declare reduction construct.
+  void setCombiner(Expr *E) { Combiner = E; }
+
+  /// \brief Get initializer expression (if specified) of the declare reduction
+  /// construct.
+  Expr *getInitializer() { return Initializer; }
+  const Expr *getInitializer() const { return Initializer; }
+  /// \brief Set initializer expression for the declare reduction construct.
+  void setInitializer(Expr *E) { Initializer = E; }
+
+  /// \brief Get reference to previous declare reduction construct in the same
+  /// scope with the same name.
+  OMPDeclareReductionDecl *getPrevDeclInScope();
+  const OMPDeclareReductionDecl *getPrevDeclInScope() const;
+
+  QualType getType() const { return Ty; }
+
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) { return K == OMPDeclareReduction; }
+  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));
+  }
+};
+
 /// Pseudo declaration for capturing expressions. Also is used for capturing of
 /// non-static data members in non-static member functions.
 ///

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -1467,6 +1467,14 @@ DEF_TRAVERSE_DECL(OMPThreadPrivateDecl, {
   }
 })
 
+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(OMPCapturedExprDecl, { TRY_TO(TraverseVarHelper(D)); })
 
 // A helper method for TemplateDecl's children.

clang/include/clang/Basic/DeclNodes.td

@@ -75,6 +75,7 @@ def Named : Decl<1>;
       def ObjCImplementation : DDecl<ObjCImpl>;
   def ObjCProperty : DDecl<Named>;
   def ObjCCompatibleAlias : DDecl<Named>;
+  def OMPDeclareReduction : DDecl<Named>, DeclContext;
 def LinkageSpec : Decl, DeclContext;
 def ObjCPropertyImpl : Decl;
 def FileScopeAsm : Decl;

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -939,6 +939,8 @@ def err_omp_immediate_directive : Error<
   "'#pragma omp %0' %select{|with '%2' clause }1cannot be an immediate substatement">;
 def err_omp_expected_identifier_for_critical : Error<
   "expected identifier specifying the name of the 'omp critical' directive">;
+def err_omp_expected_reduction_identifier : Error<
+  "expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'">;
 def err_omp_unknown_map_type : Error<
   "incorrect map type, expected one of 'to', 'from', 'tofrom', 'alloc', 'release', or 'delete'">;
 def err_omp_unknown_map_type_modifier : Error<

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -7992,6 +7992,9 @@ 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_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">;

clang/include/clang/Basic/OpenMPKinds.def

@@ -155,6 +155,7 @@ 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(taskloop)
 OPENMP_DIRECTIVE_EXT(taskloop_simd, "taskloop simd")
 OPENMP_DIRECTIVE(distribute)

clang/include/clang/Parse/Parser.h

@@ -2454,7 +2454,9 @@ private:
   //===--------------------------------------------------------------------===//
   // OpenMP: Directives and clauses.
   /// \brief Parses declarative OpenMP directives.
-  DeclGroupPtrTy ParseOpenMPDeclarativeDirective();
+  DeclGroupPtrTy ParseOpenMPDeclarativeDirective(AccessSpecifier AS);
+  /// \brief Parse 'omp declare reduction' construct.
+  DeclGroupPtrTy ParseOpenMPDeclareReductionDirective(AccessSpecifier AS);
   /// \brief Parses simple list of variables.
   ///
   /// \param Kind Kind of the directive.

clang/include/clang/Sema/ScopeInfo.h

@@ -104,6 +104,9 @@ public:
   /// \brief Whether a statement was dropped because it was invalid.
   bool HasDroppedStmt : 1;
 
+  /// \brief True if current scope is for OpenMP declare reduction combiner.
+  bool HasOMPDeclareReductionCombiner;
+
   /// A flag that is set when parsing a method that must call super's
   /// implementation, such as \c -dealloc, \c -finalize, or any method marked
   /// with \c __attribute__((objc_requires_super)).
@@ -341,6 +344,10 @@ public:
     HasDroppedStmt = true;
   }
 
+  void setHasOMPDeclareReductionCombiner() {
+    HasOMPDeclareReductionCombiner = true;
+  }
+
   void setHasCXXTry(SourceLocation TryLoc) {
     setHasBranchProtectedScope();
     FirstCXXTryLoc = TryLoc;
@@ -363,6 +370,7 @@ public:
       HasBranchIntoScope(false),
       HasIndirectGoto(false),
       HasDroppedStmt(false),
+      HasOMPDeclareReductionCombiner(false),
       ObjCShouldCallSuper(false),
       ObjCIsDesignatedInit(false),
       ObjCWarnForNoDesignatedInitChain(false),

clang/include/clang/Sema/Sema.h

@@ -145,6 +145,7 @@ namespace clang {
   class ObjCPropertyDecl;
   class ObjCProtocolDecl;
   class OMPThreadPrivateDecl;
+  class OMPDeclareReductionDecl;
   class OMPClause;
   struct OverloadCandidate;
   class OverloadCandidateSet;
@@ -2671,6 +2672,8 @@ public:
     LookupObjCProtocolName,
     /// Look up implicit 'self' parameter of an objective-c method.
     LookupObjCImplicitSelfParam,
+    /// \brief Look up the name of an OpenMP user-defined reduction operation.
+    LookupOMPReductionName,
     /// \brief Look up any declaration with any name.
     LookupAnyName
   };
@@ -7872,6 +7875,26 @@ public:
   OMPThreadPrivateDecl *CheckOMPThreadPrivateDecl(
                                      SourceLocation Loc,
                                      ArrayRef<Expr *> VarList);
+  /// \brief Check if the specified type is allowed to be used in 'omp declare
+  /// reduction' construct.
+  QualType ActOnOpenMPDeclareReductionType(SourceLocation TyLoc,
+                                           TypeResult ParsedType);
+  /// \brief Called on start of '#pragma omp declare reduction'.
+  DeclGroupPtrTy ActOnOpenMPDeclareReductionDirectiveStart(
+      Scope *S, DeclContext *DC, DeclarationName Name,
+      ArrayRef<std::pair<QualType, SourceLocation>> ReductionTypes,
+      AccessSpecifier AS, Decl *PrevDeclInScope = nullptr);
+  /// \brief Initialize declare reduction construct initializer.
+  void ActOnOpenMPDeclareReductionCombinerStart(Scope *S, Decl *D);
+  /// \brief Finish current declare reduction construct initializer.
+  void ActOnOpenMPDeclareReductionCombinerEnd(Decl *D, Expr *Combiner);
+  /// \brief Initialize declare reduction construct initializer.
+  void ActOnOpenMPDeclareReductionInitializerStart(Scope *S, Decl *D);
+  /// \brief Finish current declare reduction construct initializer.
+  void ActOnOpenMPDeclareReductionInitializerEnd(Decl *D, Expr *Initializer);
+  /// \brief Called at the end of '#pragma omp declare reduction'.
+  DeclGroupPtrTy ActOnOpenMPDeclareReductionDirectiveEnd(
+      Scope *S, DeclGroupPtrTy DeclReductions, bool IsValid);
 
   /// \brief Initialization of captured region for OpenMP region.
   void ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope);

clang/include/clang/Serialization/ASTBitCodes.h

@@ -1174,7 +1174,9 @@ namespace clang {
       /// \brief A PragmaCommentDecl record.
       DECL_PRAGMA_COMMENT,
       /// \brief A PragmaDetectMismatchDecl record.
-      DECL_PRAGMA_DETECT_MISMATCH
+      DECL_PRAGMA_DETECT_MISMATCH,
+      /// \brief An OMPDeclareReductionDecl record.
+      DECL_OMP_DECLARE_REDUCTION,
     };
 
     /// \brief Record codes for each kind of statement or expression.

clang/lib/AST/CXXInheritance.cpp

@@ -405,6 +405,21 @@ bool CXXRecordDecl::FindOrdinaryMember(const CXXBaseSpecifier *Specifier,
   return false;
 }
 
+bool CXXRecordDecl::FindOMPReductionMember(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_OMPReduction))
+      return true;
+  }
+
+  return false;
+}
+
 bool CXXRecordDecl::
 FindNestedNameSpecifierMember(const CXXBaseSpecifier *Specifier, 
                               CXXBasePath &Path,

clang/lib/AST/Decl.cpp

@@ -18,6 +18,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"

clang/lib/AST/DeclBase.cpp

@@ -633,6 +633,9 @@ unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
     case TemplateTemplateParm:
       return IDNS_Ordinary | IDNS_Tag | IDNS_Type;
 
+    case OMPDeclareReduction:
+      return IDNS_OMPReduction;
+
     // Never have names.
     case Friend:
     case FriendTemplate:
@@ -963,6 +966,7 @@ DeclContext *DeclContext::getPrimaryContext() {
   case Decl::LinkageSpec:
   case Decl::Block:
   case Decl::Captured:
+  case Decl::OMPDeclareReduction:
     // There is only one DeclContext for these entities.
     return this;
 

clang/lib/AST/DeclOpenMP.cpp

@@ -53,6 +53,36 @@ void OMPThreadPrivateDecl::setVars(ArrayRef<Expr *> VL) {
   std::uninitialized_copy(VL.begin(), VL.end(), getTrailingObjects<Expr *>());
 }
 
+//===----------------------------------------------------------------------===//
+// OMPDeclareReductionDecl Implementation.
+//===----------------------------------------------------------------------===//
+
+void OMPDeclareReductionDecl::anchor() {}
+
+OMPDeclareReductionDecl *OMPDeclareReductionDecl::Create(
+    ASTContext &C, DeclContext *DC, SourceLocation L, DeclarationName Name,
+    QualType T, OMPDeclareReductionDecl *PrevDeclInScope) {
+  return new (C, DC) OMPDeclareReductionDecl(OMPDeclareReduction, DC, L, Name,
+                                             T, PrevDeclInScope);
+}
+
+OMPDeclareReductionDecl *
+OMPDeclareReductionDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
+  return new (C, ID) OMPDeclareReductionDecl(
+      OMPDeclareReduction, /*DC=*/nullptr, SourceLocation(), DeclarationName(),
+      QualType(), /*PrevDeclInScope=*/nullptr);
+}
+
+OMPDeclareReductionDecl *OMPDeclareReductionDecl::getPrevDeclInScope() {
+  return cast_or_null<OMPDeclareReductionDecl>(
+      PrevDeclInScope.get(getASTContext().getExternalSource()));
+}
+const OMPDeclareReductionDecl *
+OMPDeclareReductionDecl::getPrevDeclInScope() const {
+  return cast_or_null<OMPDeclareReductionDecl>(
+      PrevDeclInScope.get(getASTContext().getExternalSource()));
+}
+
 //===----------------------------------------------------------------------===//
 // OMPCapturedExprDecl Implementation.
 //===----------------------------------------------------------------------===//

clang/lib/AST/DeclPrinter.cpp

@@ -92,6 +92,7 @@ namespace {
     void VisitUsingDecl(UsingDecl *D);
     void VisitUsingShadowDecl(UsingShadowDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
+    void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
     void PrintTemplateParameters(const TemplateParameterList *Params,
@@ -334,7 +335,7 @@ void DeclPrinter::VisitDeclContext(DeclContext *DC, bool Indent) {
 
     // FIXME: Need to be able to tell the DeclPrinter when
     const char *Terminator = nullptr;
-    if (isa<OMPThreadPrivateDecl>(*D))
+    if (isa<OMPThreadPrivateDecl>(*D) || isa<OMPDeclareReductionDecl>(*D))
       Terminator = nullptr;
     else if (isa<FunctionDecl>(*D) &&
              cast<FunctionDecl>(*D)->isThisDeclarationADefinition())
@@ -1367,6 +1368,37 @@ void DeclPrinter::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
   }
 }
 
+void DeclPrinter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
+  if (!D->isInvalidDecl()) {
+    Out << "#pragma omp declare reduction (";
+    if (D->getDeclName().getNameKind() == DeclarationName::CXXOperatorName) {
+      static const char *const OperatorNames[NUM_OVERLOADED_OPERATORS] = {
+          nullptr,
+#define OVERLOADED_OPERATOR(Name, Spelling, Token, Unary, Binary, MemberOnly)  \
+          Spelling,
+#include "clang/Basic/OperatorKinds.def"
+      };
+      const char *OpName =
+          OperatorNames[D->getDeclName().getCXXOverloadedOperator()];
+      assert(OpName && "not an overloaded operator");
+      Out << OpName;
+    } else {
+      assert(D->getDeclName().isIdentifier());
+      D->printName(Out);
+    }
+    Out << " : ";
+    D->getType().print(Out, Policy);
+    Out << " : ";
+    D->getCombiner()->printPretty(Out, nullptr, Policy, 0);
+    Out << ")";
+    if (auto *Init = D->getInitializer()) {
+      Out << " initializer(";
+      Init->printPretty(Out, nullptr, Policy, 0);
+      Out << ")";
+    }
+  }
+}
+
 void DeclPrinter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   D->getInit()->printPretty(Out, nullptr, Policy, Indentation);
 }

clang/lib/AST/ItaniumMangle.cpp

@@ -20,6 +20,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
@@ -66,8 +67,9 @@ static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   }
   
   const DeclContext *DC = D->getDeclContext();
-  if (const CapturedDecl *CD = dyn_cast<CapturedDecl>(DC))
-    return getEffectiveDeclContext(CD);
+  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC)) {
+    return getEffectiveDeclContext(cast<Decl>(DC));
+  }
 
   if (const auto *VD = dyn_cast<VarDecl>(D))
     if (VD->isExternC())

clang/lib/AST/MicrosoftMangle.cpp

@@ -19,6 +19,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
@@ -58,8 +59,9 @@ static const DeclContext *getEffectiveDeclContext(const Decl *D) {
   }
 
   const DeclContext *DC = D->getDeclContext();
-  if (const CapturedDecl *CD = dyn_cast<CapturedDecl>(DC))
-    return getEffectiveDeclContext(CD);
+  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC)) {
+    return getEffectiveDeclContext(cast<Decl>(DC));
+  }
 
   return DC;
 }

clang/lib/Basic/OpenMPKinds.cpp

@@ -554,6 +554,7 @@ bool clang::isAllowedClauseForDirective(OpenMPDirectiveKind DKind,
   case OMPD_taskwait:
   case OMPD_taskgroup:
   case OMPD_cancellation_point:
+  case OMPD_declare_reduction:
     break;
   }
   return false;

clang/lib/CodeGen/CGDecl.cpp

@@ -21,6 +21,7 @@
 #include "clang/AST/CharUnits.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
@@ -118,6 +119,9 @@ void CodeGenFunction::EmitDecl(const Decl &D) {
     return EmitVarDecl(VD);
   }
 
+  case Decl::OMPDeclareReduction:
+    return CGM.EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(&D));
+
   case Decl::Typedef:      // typedef int X;
   case Decl::TypeAlias: {  // using X = int; [C++0x]
     const TypedefNameDecl &TD = cast<TypedefNameDecl>(D);
@@ -1862,3 +1866,7 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
   if (D.hasAttr<AnnotateAttr>())
     EmitVarAnnotations(&D, DeclPtr.getPointer());
 }
+
+void CodeGenModule::EmitOMPDeclareReduction(
+    const OMPDeclareReductionDecl * /*D*/) {}
+

clang/lib/CodeGen/CodeGenModule.cpp

@@ -3796,6 +3796,10 @@ void CodeGenModule::EmitTopLevelDecl(Decl *D) {
     break;
   }
 
+  case Decl::OMPDeclareReduction:
+    EmitOMPDeclareReduction(cast<OMPDeclareReductionDecl>(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

clang/lib/CodeGen/CodeGenModule.h

@@ -21,6 +21,7 @@
 #include "clang/AST/Attr.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/DeclOpenMP.h"
 #include "clang/AST/GlobalDecl.h"
 #include "clang/AST/Mangle.h"
 #include "clang/Basic/ABI.h"
@@ -1110,6 +1111,9 @@ public:
   /// \param D Threadprivate declaration.
   void EmitOMPThreadPrivateDecl(const OMPThreadPrivateDecl *D);
 
+  /// \brief Emit a code for declare reduction construct.
+  void EmitOMPDeclareReduction(const OMPDeclareReductionDecl *D);
+
   /// Returns whether we need bit sets attached to vtables.
   bool NeedVTableBitSets();
 

clang/lib/Parse/ParseDecl.cpp

@@ -3644,13 +3644,11 @@ void Parser::ParseStructUnionBody(SourceLocation RecordLoc,
     }
 
     if (Tok.is(tok::annot_pragma_openmp)) {
-      // Result can be ignored, because it must be always empty.
-      auto Res = ParseOpenMPDeclarativeDirective();
-      assert(!Res);
-      // Silence possible warnings.
-      (void)Res;
+      // There may be declared reduction operator inside structure/union.
+      (void)ParseOpenMPDeclarativeDirective(AS_public);
       continue;
     }
+
     if (!Tok.is(tok::at)) {
       auto CFieldCallback = [&](ParsingFieldDeclarator &FD) {
         // Install the declarator into the current TagDecl.

clang/lib/Parse/ParseDeclCXX.cpp

@@ -2910,7 +2910,7 @@ Parser::DeclGroupPtrTy Parser::ParseCXXClassMemberDeclarationWithPragmas(
   }
 
   if (Tok.is(tok::annot_pragma_openmp))
-    return ParseOpenMPDeclarativeDirective();
+    return ParseOpenMPDeclarativeDirective(AS);
 
   // Parse all the comma separated declarators.
   return ParseCXXClassMemberDeclaration(AS, AccessAttrs.getList());

clang/lib/Parse/ParseOpenMP.cpp

@@ -30,9 +30,11 @@ namespace {
 enum OpenMPDirectiveKindEx {
   OMPD_cancellation = OMPD_unknown + 1,
   OMPD_data,
+  OMPD_declare,
   OMPD_enter,
   OMPD_exit,
   OMPD_point,
+  OMPD_reduction,
   OMPD_target_enter,
   OMPD_target_exit
 };
@@ -48,9 +50,11 @@ static unsigned getOpenMPDirectiveKindEx(StringRef S) {
   return llvm::StringSwitch<unsigned>(S)
       .Case("cancellation", OMPD_cancellation)
       .Case("data", OMPD_data)
+      .Case("declare", OMPD_declare)
       .Case("enter", OMPD_enter)
       .Case("exit", OMPD_exit)
       .Case("point", OMPD_point)
+      .Case("reduction", OMPD_reduction)
       .Default(OMPD_unknown);
 }
 
@@ -60,6 +64,7 @@ static OpenMPDirectiveKind ParseOpenMPDirectiveKind(Parser &P) {
   // 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_target, OMPD_data, OMPD_target_data },
     { OMPD_target, OMPD_enter, OMPD_target_enter },
     { OMPD_target, OMPD_exit, OMPD_target_exit },
@@ -73,6 +78,7 @@ static OpenMPDirectiveKind ParseOpenMPDirectiveKind(Parser &P) {
     { OMPD_target, OMPD_parallel, OMPD_target_parallel },
     { OMPD_target_parallel, OMPD_for, OMPD_target_parallel_for }
   };
+  enum { CancellationPoint = 0, DeclareReduction = 1, TargetData = 2 };
   auto Tok = P.getCurToken();
   unsigned DKind =
       Tok.isAnnotation()
@@ -98,16 +104,226 @@ static OpenMPDirectiveKind ParseOpenMPDirectiveKind(Parser &P) {
       DKind = F[i][2];
     }
   }
-  return DKind <= OMPD_unknown ? static_cast<OpenMPDirectiveKind>(DKind)
-                               : OMPD_unknown;
+  return DKind < OMPD_unknown ? static_cast<OpenMPDirectiveKind>(DKind)
+                              : OMPD_unknown;
+}
+
+static DeclarationName parseOpenMPReductionId(Parser &P) {
+  const Token Tok = P.getCurToken();
+  Sema &Actions = P.getActions();
+  OverloadedOperatorKind OOK = OO_None;
+  switch (Tok.getKind()) {
+  case tok::plus: // '+'
+    OOK = OO_Plus;
+    break;
+  case tok::minus: // '-'
+    OOK = OO_Minus;
+    break;
+  case tok::star: // '*'
+    OOK = OO_Star;
+    break;
+  case tok::amp: // '&'
+    OOK = OO_Amp;
+    break;
+  case tok::pipe: // '|'
+    OOK = OO_Pipe;
+    break;
+  case tok::caret: // '^'
+    OOK = OO_Caret;
+    break;
+  case tok::ampamp: // '&&'
+    OOK = OO_AmpAmp;
+    break;
+  case tok::pipepipe: // '||'
+    OOK = OO_PipePipe;
+    break;
+  case tok::identifier: // identifier
+    break;
+  default:
+    P.Diag(Tok.getLocation(), diag::err_omp_expected_reduction_identifier);
+    P.SkipUntil(tok::colon, tok::r_paren, tok::annot_pragma_openmp_end,
+                Parser::StopBeforeMatch);
+    return DeclarationName();
+  }
+  P.ConsumeToken();
+  auto &DeclNames = Actions.getASTContext().DeclarationNames;
+  return OOK == OO_None ? DeclNames.getIdentifier(Tok.getIdentifierInfo())
+                        : DeclNames.getCXXOperatorName(OOK);
+}
+
+/// \brief Parse 'omp declare reduction' construct.
+///
+///       declare-reduction-directive:
+///        annot_pragma_openmp 'declare' 'reduction'
+///        '(' <reduction_id> ':' <type> {',' <type>} ':' <expression> ')'
+///        ['initializer' '(' ('omp_priv' '=' <expression>)|<function_call> ')']
+///        annot_pragma_openmp_end
+/// <reduction_id> is either a base language identifier or one of the following
+/// operators: '+', '-', '*', '&', '|', '^', '&&' and '||'.
+///
+Parser::DeclGroupPtrTy
+Parser::ParseOpenMPDeclareReductionDirective(AccessSpecifier AS) {
+  // Parse '('.
+  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
+  if (T.expectAndConsume(diag::err_expected_lparen_after,
+                         getOpenMPDirectiveName(OMPD_declare_reduction))) {
+    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
+    return DeclGroupPtrTy();
+  }
+
+  DeclarationName Name = parseOpenMPReductionId(*this);
+  if (Name.isEmpty() && Tok.is(tok::annot_pragma_openmp_end))
+    return DeclGroupPtrTy();
+
+  // Consume ':'.
+  bool IsCorrect = !ExpectAndConsume(tok::colon);
+
+  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
+    return DeclGroupPtrTy();
+
+  if (Tok.is(tok::colon) || Tok.is(tok::annot_pragma_openmp_end)) {
+    Diag(Tok.getLocation(), diag::err_expected_type);
+    IsCorrect = false;
+  }
+
+  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
+    return DeclGroupPtrTy();
+
+  SmallVector<std::pair<QualType, SourceLocation>, 8> ReductionTypes;
+  // Parse list of types until ':' token.
+  do {
+    ColonProtectionRAIIObject ColonRAII(*this);
+    SourceRange Range;
+    TypeResult TR = ParseTypeName(&Range, Declarator::PrototypeContext, AS);
+    if (TR.isUsable()) {
+      auto ReductionType =
+          Actions.ActOnOpenMPDeclareReductionType(Range.getBegin(), TR);
+      if (!ReductionType.isNull()) {
+        ReductionTypes.push_back(
+            std::make_pair(ReductionType, Range.getBegin()));
+      }
+    } else {
+      SkipUntil(tok::comma, tok::colon, tok::annot_pragma_openmp_end,
+                StopBeforeMatch);
+    }
+
+    if (Tok.is(tok::colon) || Tok.is(tok::annot_pragma_openmp_end))
+      break;
+
+    // Consume ','.
+    if (ExpectAndConsume(tok::comma)) {
+      IsCorrect = false;
+      if (Tok.is(tok::annot_pragma_openmp_end)) {
+        Diag(Tok.getLocation(), diag::err_expected_type);
+        return DeclGroupPtrTy();
+      }
+    }
+  } while (Tok.isNot(tok::annot_pragma_openmp_end));
+
+  if (ReductionTypes.empty()) {
+    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
+    return DeclGroupPtrTy();
+  }
+
+  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
+    return DeclGroupPtrTy();
+
+  // Consume ':'.
+  if (ExpectAndConsume(tok::colon))
+    IsCorrect = false;
+
+  if (Tok.is(tok::annot_pragma_openmp_end)) {
+    Diag(Tok.getLocation(), diag::err_expected_expression);
+    return DeclGroupPtrTy();
+  }
+
+  DeclGroupPtrTy DRD = Actions.ActOnOpenMPDeclareReductionDirectiveStart(
+      getCurScope(), Actions.getCurLexicalContext(), Name, ReductionTypes, AS);
+
+  // Parse <combiner> expression and then parse initializer if any for each
+  // correct type.
+  unsigned I = 0, E = ReductionTypes.size();
+  for (auto *D : DRD.get()) {
+    TentativeParsingAction TPA(*this);
+    ParseScope OMPDRScope(this, Scope::FnScope | Scope::DeclScope |
+                                    Scope::OpenMPDirectiveScope);
+    // Parse <combiner> expression.
+    Actions.ActOnOpenMPDeclareReductionCombinerStart(getCurScope(), D);
+    ExprResult CombinerResult =
+        Actions.ActOnFinishFullExpr(ParseAssignmentExpression().get(),
+                                    D->getLocation(), /*DiscardedValue=*/true);
+    Actions.ActOnOpenMPDeclareReductionCombinerEnd(D, CombinerResult.get());
+
+    if (CombinerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
+        Tok.isNot(tok::annot_pragma_openmp_end)) {
+      TPA.Commit();
+      IsCorrect = false;
+      break;
+    }
+    IsCorrect = !T.consumeClose() && IsCorrect && CombinerResult.isUsable();
+    ExprResult InitializerResult;
+    if (Tok.isNot(tok::annot_pragma_openmp_end)) {
+      // Parse <initializer> expression.
+      if (Tok.is(tok::identifier) &&
+          Tok.getIdentifierInfo()->isStr("initializer"))
+        ConsumeToken();
+      else {
+        Diag(Tok.getLocation(), diag::err_expected) << "'initializer'";
+        TPA.Commit();
+        IsCorrect = false;
+        break;
+      }
+      // Parse '('.
+      BalancedDelimiterTracker T(*this, tok::l_paren,
+                                 tok::annot_pragma_openmp_end);
+      IsCorrect =
+          !T.expectAndConsume(diag::err_expected_lparen_after, "initializer") &&
+          IsCorrect;
+      if (Tok.isNot(tok::annot_pragma_openmp_end)) {
+        ParseScope OMPDRScope(this, Scope::FnScope | Scope::DeclScope |
+                                        Scope::OpenMPDirectiveScope);
+        // Parse expression.
+        Actions.ActOnOpenMPDeclareReductionInitializerStart(getCurScope(), D);
+        InitializerResult = Actions.ActOnFinishFullExpr(
+            ParseAssignmentExpression().get(), D->getLocation(),
+            /*DiscardedValue=*/true);
+        Actions.ActOnOpenMPDeclareReductionInitializerEnd(
+            D, InitializerResult.get());
+        if (InitializerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
+            Tok.isNot(tok::annot_pragma_openmp_end)) {
+          TPA.Commit();
+          IsCorrect = false;
+          break;
+        }
+        IsCorrect =
+            !T.consumeClose() && IsCorrect && !InitializerResult.isInvalid();
+      }
+    }
+
+    ++I;
+    // Revert parsing if not the last type, otherwise accept it, we're done with
+    // parsing.
+    if (I != E)
+      TPA.Revert();
+    else
+      TPA.Commit();
+  }
+  return Actions.ActOnOpenMPDeclareReductionDirectiveEnd(getCurScope(), DRD,
+                                                         IsCorrect);
 }
 
 /// \brief Parsing of declarative OpenMP directives.
 ///
 ///       threadprivate-directive:
 ///         annot_pragma_openmp 'threadprivate' simple-variable-list
+///         annot_pragma_openmp_end
 ///
-Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirective() {
+///       declare-reduction-directive:
+///        annot_pragma_openmp 'declare' 'reduction' [...]
+///        annot_pragma_openmp_end
+///
+Parser::DeclGroupPtrTy
+Parser::ParseOpenMPDeclarativeDirective(AccessSpecifier AS) {
   assert(Tok.is(tok::annot_pragma_openmp) && "Not an OpenMP directive!");
   ParenBraceBracketBalancer BalancerRAIIObj(*this);
 
@@ -131,6 +347,22 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirective() {
       return Actions.ActOnOpenMPThreadprivateDirective(Loc, Identifiers);
     }
     break;
+  case OMPD_declare_reduction:
+    ConsumeToken();
+    if (auto Res = ParseOpenMPDeclareReductionDirective(AS)) {
+      // The last seen token is annot_pragma_openmp_end - need to check for
+      // extra tokens.
+      if (Tok.isNot(tok::annot_pragma_openmp_end)) {
+        Diag(Tok, diag::warn_omp_extra_tokens_at_eol)
+            << getOpenMPDirectiveName(OMPD_declare_reduction);
+        while (Tok.isNot(tok::annot_pragma_openmp_end))
+          ConsumeAnyToken();
+      }
+      // Skip the last annot_pragma_openmp_end.
+      ConsumeToken();
+      return Res;
+    }
+    break;
   case OMPD_unknown:
     Diag(Tok, diag::err_omp_unknown_directive);
     break;
@@ -170,7 +402,9 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirective() {
         << getOpenMPDirectiveName(DKind);
     break;
   }
-  SkipUntil(tok::annot_pragma_openmp_end);
+  while (Tok.isNot(tok::annot_pragma_openmp_end))
+    ConsumeAnyToken();
+  ConsumeAnyToken();
   return nullptr;
 }
 
@@ -180,6 +414,12 @@ Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirective() {
 ///         annot_pragma_openmp 'threadprivate' simple-variable-list
 ///         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
+///
 ///       executable-directive:
 ///         annot_pragma_openmp 'parallel' | 'simd' | 'for' | 'sections' |
 ///         'section' | 'single' | 'master' | 'critical' [ '(' <name> ')' ] |
@@ -231,6 +471,22 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
     }
     SkipUntil(tok::annot_pragma_openmp_end);
     break;
+  case OMPD_declare_reduction:
+    ConsumeToken();
+    if (auto Res = ParseOpenMPDeclareReductionDirective(/*AS=*/AS_none)) {
+      // The last seen token is annot_pragma_openmp_end - need to check for
+      // extra tokens.
+      if (Tok.isNot(tok::annot_pragma_openmp_end)) {
+        Diag(Tok, diag::warn_omp_extra_tokens_at_eol)
+            << getOpenMPDirectiveName(OMPD_declare_reduction);
+        while (Tok.isNot(tok::annot_pragma_openmp_end))
+          ConsumeAnyToken();
+      }
+      ConsumeAnyToken();
+      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;

clang/lib/Parse/Parser.cpp

@@ -659,7 +659,7 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs,
     HandlePragmaOpenCLExtension();
     return nullptr;
   case tok::annot_pragma_openmp:
-    return ParseOpenMPDeclarativeDirective();
+    return ParseOpenMPDeclarativeDirective(/*AS=*/AS_none);
   case tok::annot_pragma_ms_pointers_to_members:
     HandlePragmaMSPointersToMembers();
     return nullptr;

clang/lib/Sema/ScopeInfo.cpp

@@ -28,6 +28,7 @@ void FunctionScopeInfo::Clear() {
   HasBranchIntoScope = false;
   HasIndirectGoto = false;
   HasDroppedStmt = false;
+  HasOMPDeclareReductionCombiner = false;
   ObjCShouldCallSuper = false;
   ObjCIsDesignatedInit = false;
   ObjCWarnForNoDesignatedInitChain = false;

clang/lib/Sema/SemaDecl.cpp

@@ -5640,7 +5640,7 @@ static bool isIncompleteDeclExternC(Sema &S, const T *D) {
 
 static bool shouldConsiderLinkage(const VarDecl *VD) {
   const DeclContext *DC = VD->getDeclContext()->getRedeclContext();
-  if (DC->isFunctionOrMethod())
+  if (DC->isFunctionOrMethod() || isa<OMPDeclareReductionDecl>(DC))
     return VD->hasExternalStorage();
   if (DC->isFileContext())
     return true;
@@ -5651,7 +5651,8 @@ static bool shouldConsiderLinkage(const VarDecl *VD) {
 
 static bool shouldConsiderLinkage(const FunctionDecl *FD) {
   const DeclContext *DC = FD->getDeclContext()->getRedeclContext();
-  if (DC->isFileContext() || DC->isFunctionOrMethod())
+  if (DC->isFileContext() || DC->isFunctionOrMethod() ||
+      isa<OMPDeclareReductionDecl>(DC))
     return true;
   if (DC->isRecord())
     return false;

clang/lib/Sema/SemaExpr.cpp

@@ -376,6 +376,19 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, SourceLocation Loc,
         DeduceReturnType(FD, Loc))
       return true;
   }
+
+  // [OpenMP 4.0], 2.15 declare reduction Directive, Restrictions
+  // Only the variables omp_in and omp_out are allowed in the combiner.
+  // Only the variables omp_priv and omp_orig are allowed in the
+  // initializer-clause.
+  auto *DRD = dyn_cast<OMPDeclareReductionDecl>(CurContext);
+  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;
+  }
   DiagnoseAvailabilityOfDecl(*this, D, Loc, UnknownObjCClass,
                              ObjCPropertyAccess);
 

clang/lib/Sema/SemaLookup.cpp

@@ -280,6 +280,10 @@ static inline unsigned getIDNS(Sema::LookupNameKind NameKind,
     IDNS = Decl::IDNS_ObjCProtocol;
     break;
 
+  case Sema::LookupOMPReductionName:
+    IDNS = Decl::IDNS_OMPReduction;
+    break;
+
   case Sema::LookupAnyName:
     IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member
       | Decl::IDNS_Using | Decl::IDNS_Namespace | Decl::IDNS_ObjCProtocol
@@ -2015,6 +2019,10 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
       BaseCallback = &LookupAnyMember;
       break;
 
+    case LookupOMPReductionName:
+      BaseCallback = &CXXRecordDecl::FindOMPReductionMember;
+      break;
+
     case LookupUsingDeclName:
       // This lookup is for redeclarations only.
 

clang/lib/Sema/SemaOpenMP.cpp

@@ -21,6 +21,7 @@
 #include "clang/AST/StmtCXX.h"
 #include "clang/AST/StmtOpenMP.h"
 #include "clang/AST/StmtVisitor.h"
+#include "clang/AST/TypeOrdering.h"
 #include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Lex/Preprocessor.h"
@@ -1698,6 +1699,7 @@ void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
   case OMPD_flush:
   case OMPD_target_enter_data:
   case OMPD_target_exit_data:
+  case OMPD_declare_reduction:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
@@ -3139,6 +3141,7 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
                                          EndLoc, VarsWithInheritedDSA);
     break;
   case OMPD_threadprivate:
+  case OMPD_declare_reduction:
     llvm_unreachable("OpenMP Directive is not allowed");
   case OMPD_unknown:
     llvm_unreachable("Unknown OpenMP directive");
@@ -9584,6 +9587,235 @@ Sema::ActOnOpenMPMapClause(OpenMPMapClauseKind MapTypeModifier,
                               MapLoc);
 }
 
+QualType Sema::ActOnOpenMPDeclareReductionType(SourceLocation TyLoc,
+                                               TypeResult ParsedType) {
+  assert(ParsedType.isUsable());
+
+  QualType ReductionType = GetTypeFromParser(ParsedType.get());
+  if (ReductionType.isNull())
+    return QualType();
+
+  // [OpenMP 4.0], 2.15 declare reduction Directive, Restrictions, C\C++
+  // A type name in a declare reduction directive cannot be a function type, an
+  // array type, a reference type, or a type qualified with const, volatile or
+  // restrict.
+  if (ReductionType.hasQualifiers()) {
+    Diag(TyLoc, diag::err_omp_reduction_wrong_type) << 0;
+    return QualType();
+  }
+
+  if (ReductionType->isFunctionType()) {
+    Diag(TyLoc, diag::err_omp_reduction_wrong_type) << 1;
+    return QualType();
+  }
+  if (ReductionType->isReferenceType()) {
+    Diag(TyLoc, diag::err_omp_reduction_wrong_type) << 2;
+    return QualType();
+  }
+  if (ReductionType->isArrayType()) {
+    Diag(TyLoc, diag::err_omp_reduction_wrong_type) << 3;
+    return QualType();
+  }
+  return ReductionType;
+}
+
+Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareReductionDirectiveStart(
+    Scope *S, DeclContext *DC, DeclarationName Name,
+    ArrayRef<std::pair<QualType, SourceLocation>> ReductionTypes,
+    AccessSpecifier AS, Decl *PrevDeclInScope) {
+  SmallVector<Decl *, 8> Decls;
+  Decls.reserve(ReductionTypes.size());
+
+  LookupResult Lookup(*this, Name, SourceLocation(), LookupOMPReductionName,
+                      ForRedeclaration);
+  // [OpenMP 4.0], 2.15 declare reduction Directive, Restrictions
+  // A reduction-identifier may not be re-declared 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;
+  OMPDeclareReductionDecl *PrevDRD = 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<OMPDeclareReductionDecl *, bool> UsedAsPrevious;
+    auto Filter = Lookup.makeFilter();
+    while (Filter.hasNext()) {
+      auto *PrevDecl = cast<OMPDeclareReductionDecl>(Filter.next());
+      if (InCompoundScope) {
+        auto I = UsedAsPrevious.find(PrevDecl);
+        if (I == UsedAsPrevious.end())
+          UsedAsPrevious[PrevDecl] = false;
+        if (auto *D = PrevDecl->getPrevDeclInScope())
+          UsedAsPrevious[D] = true;
+      }
+      PreviousRedeclTypes[PrevDecl->getType().getCanonicalType()] =
+          PrevDecl->getLocation();
+    }
+    Filter.done();
+    if (InCompoundScope) {
+      for (auto &PrevData : UsedAsPrevious) {
+        if (!PrevData.second) {
+          PrevDRD = PrevData.first;
+          break;
+        }
+      }
+    }
+  } else if (PrevDeclInScope != nullptr) {
+    auto *PrevDRDInScope = PrevDRD =
+        cast<OMPDeclareReductionDecl>(PrevDeclInScope);
+    do {
+      PreviousRedeclTypes[PrevDRDInScope->getType().getCanonicalType()] =
+          PrevDRDInScope->getLocation();
+      PrevDRDInScope = PrevDRDInScope->getPrevDeclInScope();
+    } while (PrevDRDInScope != nullptr);
+  }
+  for (auto &TyData : ReductionTypes) {
+    auto I = PreviousRedeclTypes.find(TyData.first.getCanonicalType());
+    bool Invalid = false;
+    if (I != PreviousRedeclTypes.end()) {
+      Diag(TyData.second, diag::err_omp_declare_reduction_redefinition)
+          << TyData.first;
+      Diag(I->second, diag::note_previous_definition);
+      Invalid = true;
+    }
+    PreviousRedeclTypes[TyData.first.getCanonicalType()] = TyData.second;
+    auto *DRD = OMPDeclareReductionDecl::Create(Context, DC, TyData.second,
+                                                Name, TyData.first, PrevDRD);
+    DC->addDecl(DRD);
+    DRD->setAccess(AS);
+    Decls.push_back(DRD);
+    if (Invalid)
+      DRD->setInvalidDecl();
+    else
+      PrevDRD = DRD;
+  }
+
+  return DeclGroupPtrTy::make(
+      DeclGroupRef::Create(Context, Decls.begin(), Decls.size()));
+}
+
+void Sema::ActOnOpenMPDeclareReductionCombinerStart(Scope *S, Decl *D) {
+  auto *DRD = cast<OMPDeclareReductionDecl>(D);
+
+  // Enter new function scope.
+  PushFunctionScope();
+  getCurFunction()->setHasBranchProtectedScope();
+  getCurFunction()->setHasOMPDeclareReductionCombiner();
+
+  if (S != nullptr)
+    PushDeclContext(S, DRD);
+  else
+    CurContext = DRD;
+
+  PushExpressionEvaluationContext(PotentiallyEvaluated);
+
+  QualType ReductionType = DRD->getType();
+  // Create 'T omp_in;' implicit param.
+  auto *OmpInParm =
+      ImplicitParamDecl::Create(Context, DRD, D->getLocation(),
+                                &Context.Idents.get("omp_in"), ReductionType);
+  // Create 'T* omp_parm;T omp_out;'. All references to 'omp_out' will
+  // be replaced by '*omp_parm' during codegen. This required because 'omp_out'
+  // uses semantics of argument handles by value, but it should be passed by
+  // reference. C lang does not support references, so pass all parameters as
+  // pointers.
+  // Create 'T omp_out;' variable.
+  auto *OmpOutParm =
+      buildVarDecl(*this, D->getLocation(), ReductionType, "omp_out");
+  if (S != nullptr) {
+    PushOnScopeChains(OmpInParm, S);
+    PushOnScopeChains(OmpOutParm, S);
+  } else {
+    DRD->addDecl(OmpInParm);
+    DRD->addDecl(OmpOutParm);
+  }
+}
+
+void Sema::ActOnOpenMPDeclareReductionCombinerEnd(Decl *D, Expr *Combiner) {
+  auto *DRD = cast<OMPDeclareReductionDecl>(D);
+  DiscardCleanupsInEvaluationContext();
+  PopExpressionEvaluationContext();
+
+  PopDeclContext();
+  PopFunctionScopeInfo();
+
+  if (Combiner != nullptr)
+    DRD->setCombiner(Combiner);
+  else
+    DRD->setInvalidDecl();
+}
+
+void Sema::ActOnOpenMPDeclareReductionInitializerStart(Scope *S, Decl *D) {
+  auto *DRD = cast<OMPDeclareReductionDecl>(D);
+
+  // Enter new function scope.
+  PushFunctionScope();
+  getCurFunction()->setHasBranchProtectedScope();
+
+  if (S != nullptr)
+    PushDeclContext(S, DRD);
+  else
+    CurContext = DRD;
+
+  PushExpressionEvaluationContext(PotentiallyEvaluated);
+
+  QualType ReductionType = DRD->getType();
+  // Create 'T omp_orig;' implicit param.
+  auto *OmpOrigParm =
+      ImplicitParamDecl::Create(Context, DRD, D->getLocation(),
+                                &Context.Idents.get("omp_orig"), ReductionType);
+  // Create 'T* omp_parm;T omp_priv;'. All references to 'omp_priv' will
+  // be replaced by '*omp_parm' during codegen. This required because 'omp_priv'
+  // uses semantics of argument handles by value, but it should be passed by
+  // reference. C lang does not support references, so pass all parameters as
+  // pointers.
+  // Create 'T omp_priv;' variable.
+  auto *OmpPrivParm =
+      buildVarDecl(*this, D->getLocation(), ReductionType, "omp_priv");
+  if (S != nullptr) {
+    PushOnScopeChains(OmpPrivParm, S);
+    PushOnScopeChains(OmpOrigParm, S);
+  } else {
+    DRD->addDecl(OmpPrivParm);
+    DRD->addDecl(OmpOrigParm);
+  }
+}
+
+void Sema::ActOnOpenMPDeclareReductionInitializerEnd(Decl *D,
+                                                     Expr *Initializer) {
+  auto *DRD = cast<OMPDeclareReductionDecl>(D);
+  DiscardCleanupsInEvaluationContext();
+  PopExpressionEvaluationContext();
+
+  PopDeclContext();
+  PopFunctionScopeInfo();
+
+  if (Initializer != nullptr)
+    DRD->setInitializer(Initializer);
+  else
+    DRD->setInvalidDecl();
+}
+
+Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareReductionDirectiveEnd(
+    Scope *S, DeclGroupPtrTy DeclReductions, bool IsValid) {
+  for (auto *D : DeclReductions.get()) {
+    if (IsValid) {
+      auto *DRD = cast<OMPDeclareReductionDecl>(D);
+      if (S != nullptr)
+        PushOnScopeChains(DRD, S, /*AddToContext=*/false);
+    } else
+      D->setInvalidDecl();
+  }
+  return DeclReductions;
+}
+
 OMPClause *Sema::ActOnOpenMPNumTeamsClause(Expr *NumTeams, 
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -2503,6 +2503,81 @@ Decl *TemplateDeclInstantiator::VisitOMPThreadPrivateDecl(
   return TD;
 }
 
+Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
+    OMPDeclareReductionDecl *D) {
+  // Instantiate type and check if it is allowed.
+  QualType SubstReductionType = SemaRef.ActOnOpenMPDeclareReductionType(
+      D->getLocation(),
+      ParsedType::make(SemaRef.SubstType(D->getType(), TemplateArgs,
+                                         D->getLocation(), DeclarationName())));
+  if (SubstReductionType.isNull())
+    return nullptr;
+  bool IsCorrect = !SubstReductionType.isNull();
+  // Create instantiated copy.
+  std::pair<QualType, SourceLocation> ReductionTypes[] = {
+      std::make_pair(SubstReductionType, D->getLocation())};
+  auto *PrevDeclInScope = D->getPrevDeclInScope();
+  if (PrevDeclInScope && !PrevDeclInScope->isInvalidDecl()) {
+    PrevDeclInScope = cast<OMPDeclareReductionDecl>(
+        SemaRef.CurrentInstantiationScope->findInstantiationOf(PrevDeclInScope)
+            ->get<Decl *>());
+  }
+  auto DRD = SemaRef.ActOnOpenMPDeclareReductionDirectiveStart(
+      /*S=*/nullptr, Owner, D->getDeclName(), ReductionTypes, D->getAccess(),
+      PrevDeclInScope);
+  auto *NewDRD = cast<OMPDeclareReductionDecl>(DRD.get().getSingleDecl());
+  if (isDeclWithinFunction(NewDRD))
+    SemaRef.CurrentInstantiationScope->InstantiatedLocal(D, NewDRD);
+  Expr *SubstCombiner = nullptr;
+  Expr *SubstInitializer = nullptr;
+  // Combiners instantiation sequence.
+  if (D->getCombiner()) {
+    SemaRef.ActOnOpenMPDeclareReductionCombinerStart(
+        /*S=*/nullptr, NewDRD);
+    const char *Names[] = {"omp_in", "omp_out"};
+    for (auto &Name : Names) {
+      DeclarationName DN(&SemaRef.Context.Idents.get(Name));
+      auto OldLookup = D->lookup(DN);
+      auto Lookup = NewDRD->lookup(DN);
+      if (!OldLookup.empty() && !Lookup.empty()) {
+        assert(Lookup.size() == 1 && OldLookup.size() == 1);
+        SemaRef.CurrentInstantiationScope->InstantiatedLocal(OldLookup.front(),
+                                                             Lookup.front());
+      }
+    }
+    SubstCombiner = SemaRef.SubstExpr(D->getCombiner(), TemplateArgs).get();
+    SemaRef.ActOnOpenMPDeclareReductionCombinerEnd(NewDRD, SubstCombiner);
+    // Initializers instantiation sequence.
+    if (D->getInitializer()) {
+      SemaRef.ActOnOpenMPDeclareReductionInitializerStart(
+          /*S=*/nullptr, NewDRD);
+      const char *Names[] = {"omp_orig", "omp_priv"};
+      for (auto &Name : Names) {
+        DeclarationName DN(&SemaRef.Context.Idents.get(Name));
+        auto OldLookup = D->lookup(DN);
+        auto Lookup = NewDRD->lookup(DN);
+        if (!OldLookup.empty() && !Lookup.empty()) {
+          assert(Lookup.size() == 1 && OldLookup.size() == 1);
+          SemaRef.CurrentInstantiationScope->InstantiatedLocal(
+              OldLookup.front(), Lookup.front());
+        }
+      }
+      SubstInitializer =
+          SemaRef.SubstExpr(D->getInitializer(), TemplateArgs).get();
+      SemaRef.ActOnOpenMPDeclareReductionInitializerEnd(NewDRD,
+                                                        SubstInitializer);
+    }
+    IsCorrect = IsCorrect && SubstCombiner &&
+                (!D->getInitializer() || SubstInitializer);
+  } else
+    IsCorrect = false;
+
+  (void)SemaRef.ActOnOpenMPDeclareReductionDirectiveEnd(/*S=*/nullptr, DRD,
+                                                        IsCorrect);
+
+  return NewDRD;
+}
+
 Decl *TemplateDeclInstantiator::VisitOMPCapturedExprDecl(
     OMPCapturedExprDecl * /*D*/) {
   llvm_unreachable("Should not be met in templates");

clang/lib/Serialization/ASTCommon.cpp

@@ -332,6 +332,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::Import:
   case Decl::OMPThreadPrivate:
   case Decl::OMPCapturedExpr:
+  case Decl::OMPDeclareReduction:
   case Decl::BuiltinTemplate:
     return false;
 

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -356,6 +356,7 @@ namespace clang {
     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
+    void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
     /// We've merged the definition \p MergedDef into the existing definition
@@ -2394,6 +2395,15 @@ void ASTDeclReader::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
   D->setVars(Vars);
 }
 
+void ASTDeclReader::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
+  VisitNamedDecl(D);
+  D->setLocation(Reader.ReadSourceLocation(F, Record, Idx));
+  D->setCombiner(Reader.ReadExpr(F));
+  D->setInitializer(Reader.ReadExpr(F));
+  D->PrevDeclInScope = Reader.ReadDeclID(F, Record, Idx);
+  D->setType(Reader.readType(F, Record, Idx));
+}
+
 void ASTDeclReader::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   VisitVarDecl(D);
 }
@@ -2449,7 +2459,8 @@ static bool isConsumerInterestedIn(Decl *D, bool HasBody) {
       isa<ImportDecl>(D) ||
       isa<PragmaCommentDecl>(D) ||
       isa<PragmaDetectMismatchDecl>(D) ||
-      isa<OMPThreadPrivateDecl>(D))
+      isa<OMPThreadPrivateDecl>(D) ||
+      isa<OMPDeclareReductionDecl>(D))
     return true;
   if (VarDecl *Var = dyn_cast<VarDecl>(D))
     return Var->isFileVarDecl() &&
@@ -3363,6 +3374,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_OMP_THREADPRIVATE:
     D = OMPThreadPrivateDecl::CreateDeserialized(Context, ID, Record[Idx++]);
     break;
+  case DECL_OMP_DECLARE_REDUCTION:
+    D = OMPDeclareReductionDecl::CreateDeserialized(Context, ID);
+    break;
   case DECL_OMP_CAPTUREDEXPR:
     D = OMPCapturedExprDecl::CreateDeserialized(Context, ID);
     break;

clang/lib/Serialization/ASTWriterDecl.cpp

@@ -133,6 +133,7 @@ namespace clang {
     void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
     void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
     void VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D);
+    void VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D);
     void VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D);
 
     /// Add an Objective-C type parameter list to the given record.
@@ -1653,6 +1654,16 @@ void ASTDeclWriter::VisitOMPThreadPrivateDecl(OMPThreadPrivateDecl *D) {
   Code = serialization::DECL_OMP_THREADPRIVATE;
 }
 
+void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
+  VisitNamedDecl(D);
+  Writer.AddSourceLocation(D->getLocStart(), Record);
+  Writer.AddStmt(D->getCombiner());
+  Writer.AddStmt(D->getInitializer());
+  Writer.AddDeclRef(D->getPrevDeclInScope(), Record);
+  Writer.AddTypeRef(D->getType(), Record);
+  Code = serialization::DECL_OMP_DECLARE_REDUCTION;
+}
+
 void ASTDeclWriter::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
   VisitVarDecl(D);
   Code = serialization::DECL_OMP_CAPTUREDEXPR;

clang/test/OpenMP/declare_reduction_ast_print.c

@@ -0,0 +1,42 @@
+// 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
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+#pragma omp declare reduction(+ : int, char : omp_out *= omp_in)
+// CHECK: #pragma omp declare reduction (+ : int : omp_out *= omp_in)
+// CHECK-NEXT: #pragma omp declare reduction (+ : char : omp_out *= omp_in)
+
+#pragma omp declare reduction(fun : float : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+// CHECK: #pragma omp declare reduction (fun : float : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+
+// CHECK: struct SSS {
+struct SSS {
+  int field;
+#pragma omp declare reduction(+ : int, char : omp_out *= omp_in)
+  // CHECK: #pragma omp declare reduction (+ : int : omp_out *= omp_in)
+  // CHECK-NEXT: #pragma omp declare reduction (+ : char : omp_out *= omp_in)
+};
+// CHECK: };
+
+void init(struct SSS *priv, struct SSS orig);
+
+#pragma omp declare reduction(fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+// CHECK: #pragma omp declare reduction (fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+
+// CHECK: int main() {
+int main() {
+#pragma omp declare reduction(fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+  // CHECK: #pragma omp declare reduction (fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+  {
+#pragma omp declare reduction(fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+  // CHECK: #pragma omp declare reduction (fun : struct SSS : omp_out = omp_in) initializer(init(&omp_priv, omp_orig))
+  }
+  return 0;
+}
+// CHECK: }
+
+#endif

clang/test/OpenMP/declare_reduction_ast_print.cpp

@@ -0,0 +1,69 @@
+// 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
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+
+#pragma omp declare reduction(+ : int, char : omp_out *= omp_in)
+// CHECK: #pragma omp declare reduction (+ : int : omp_out *= omp_in)
+// CHECK-NEXT: #pragma omp declare reduction (+ : char : omp_out *= omp_in)
+
+// CHECK: #pragma omp declare reduction (fun : int : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+
+template <class T>
+class SSS {
+public:
+#pragma omp declare reduction(fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+  // CHECK: #pragma omp declare reduction (fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+};
+
+SSS<int> d;
+
+void init(SSS<int> &lhs, SSS<int> rhs);
+
+#pragma omp declare reduction(fun : SSS < int > : omp_out = omp_in) initializer(init(omp_priv, omp_orig))
+// CHECK: #pragma omp declare reduction (fun : SSS<int> : omp_out = omp_in) initializer(init(omp_priv, omp_orig))
+
+// CHECK: template <typename T = int> int foo(int a) {
+// CHECK: #pragma omp declare reduction (fun : int : omp_out += omp_in) initializer(omp_priv = omp_orig + 15);
+// CHECK: {
+// CHECK: #pragma omp declare reduction (fun : int : omp_out += omp_in) initializer(omp_priv = omp_orig + 15);
+// CHECK: }
+// CHECK: return a;
+// CHECK: }
+
+// CHECK: template <typename T> T foo(T a) {
+// CHECK: #pragma omp declare reduction (fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15);
+// CHECK: {
+// CHECK: #pragma omp declare reduction (fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15);
+// CHECK: }
+// CHECK: return a;
+// CHECK: }
+template <typename T>
+T foo(T a) {
+#pragma omp declare reduction(fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+  {
+#pragma omp declare reduction(fun : T : omp_out += omp_in) initializer(omp_priv = omp_orig + 15)
+  }
+  return a;
+}
+
+int main() {
+  int i = 0;
+  SSS<int> sss;
+  // TODO: Add support for scoped reduction identifiers
+  //  #pragma omp parallel reduction(SSS<int>::fun : i)
+  // TODO-CHECK: #pragma omp parallel reduction(SSS<int>::fun: i)
+  {
+    i += 1;
+  }
+  // #pragma omp parallel reduction(::fun:sss)
+  // TODO-CHECK: #pragma omp parallel reduction(::fun: sss)
+  {
+  }
+  return foo(15);
+}
+
+#endif

clang/test/OpenMP/declare_reduction_messages.c

@@ -0,0 +1,52 @@
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 %s
+
+int temp; // expected-note 6 {{'temp' declared here}}
+
+#pragma omp declare reduction                                              // expected-error {{expected '(' after 'declare reduction'}}
+#pragma omp declare reduction {                                            // expected-error {{expected '(' after 'declare reduction'}}
+#pragma omp declare reduction(                                             // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(#                                            // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(/                                            // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(+                                            // expected-error {{expected ':'}}
+#pragma omp declare reduction(for                                          // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(if:                                          // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}} expected-error {{expected a type}}
+#pragma omp declare reduction(oper:                                        // expected-error {{expected a type}}
+#pragma omp declare reduction(oper;                                        // expected-error {{expected ':'}} expected-error {{expected a type}}
+#pragma omp declare reduction(fun : int                                    // expected-error {{expected ':'}} expected-error {{expected expression}}
+#pragma omp declare reduction(+ : const int:                               // expected-error {{reduction type cannot be qualified with 'const', 'volatile' or 'restrict'}}
+#pragma omp declare reduction(- : volatile int:                            // expected-error {{reduction type cannot be qualified with 'const', 'volatile' or 'restrict'}}
+#pragma omp declare reduction(* : int;                                     // expected-error {{expected ','}} expected-error {{expected a type}}
+#pragma omp declare reduction(& : double char:                             // expected-error {{cannot combine with previous 'double' declaration specifier}} expected-error {{expected expression}}
+#pragma omp declare reduction(^ : double, char, :                          // expected-error {{expected a type}} expected-error {{expected expression}}
+#pragma omp declare reduction(&& : int, S:                                 // expected-error {{unknown type name 'S'}} expected-error {{expected expression}}
+#pragma omp declare reduction(|| : int, double : temp += omp_in)           // expected-error 2 {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(| : char, float : omp_out += temp)           // expected-error 2 {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(fun : long : omp_out += omp_in) {            // expected-error {{expected 'initializer'}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun : unsigned : omp_out += temp))           // expected-error {{expected 'initializer'}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}} expected-error {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(fun : long(void) : omp_out += omp_in)        // expected-error {{reduction type cannot be a function type}}
+#pragma omp declare reduction(fun : long[3] : omp_out += omp_in)           // expected-error {{reduction type cannot be an array type}}
+#pragma omp declare reduction(fun23 : long, int, long : omp_out += omp_in) // expected-error {{redefinition of user-defined reduction for type 'long'}} expected-note {{previous definition is here}}
+
+#pragma omp declare reduction(fun222 : long : omp_out += omp_in)
+#pragma omp declare reduction(fun1 : long : omp_out += omp_in) initializer                 // expected-error {{expected '(' after 'initializer'}}
+#pragma omp declare reduction(fun2 : long : omp_out += omp_in) initializer {               // expected-error {{expected '(' after 'initializer'}} expected-error {{expected expression}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun3 : long : omp_out += omp_in) initializer[                // expected-error {{expected '(' after 'initializer'}} expected-error {{expected expression}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun4 : long : omp_out += omp_in) initializer()               // expected-error {{expected expression}}
+#pragma omp declare reduction(fun5 : long : omp_out += omp_in) initializer(temp)           // expected-error {{only 'omp_priv' or 'omp_orig' variables are allowed in initializer expression}}
+#pragma omp declare reduction(fun6 : long : omp_out += omp_in) initializer(omp_orig        // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun7 : long : omp_out += omp_in) initializer(omp_priv 12)    // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun8 : long : omp_out += omp_in) initializer(omp_priv = 23)  // expected-note {{previous definition is here}}
+#pragma omp declare reduction(fun8 : long : omp_out += omp_in) initializer(omp_priv = 23)) // expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}} expected-error {{redefinition of user-defined reduction for type 'long'}}
+#pragma omp declare reduction(fun9 : long : omp_out += omp_in) initializer(omp_priv = )    // expected-error {{expected expression}}
+
+int fun(int arg) {
+#pragma omp declare reduction(red : int : omp_out++)
+  {
+#pragma omp declare reduction(red : int : omp_out++) // expected-note {{previous definition is here}}
+#pragma omp declare reduction(red : int : omp_out++) // expected-error {{redefinition of user-defined reduction for type 'int'}}
+    {
+#pragma omp declare reduction(red : int : omp_out++)
+    }
+  }
+  return arg;
+}

clang/test/OpenMP/declare_reduction_messages.cpp

@@ -0,0 +1,106 @@
+// RUN: %clang_cc1 -verify -fopenmp -ferror-limit 100 %s
+
+int temp; // expected-note 7 {{'temp' declared here}}
+
+#pragma omp declare reduction                                              // expected-error {{expected '(' after 'declare reduction'}}
+#pragma omp declare reduction {                                            // expected-error {{expected '(' after 'declare reduction'}}
+#pragma omp declare reduction(                                             // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(#                                            // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(/                                            // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(+                                            // expected-error {{expected ':'}}
+#pragma omp declare reduction(operator                                     // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}}
+#pragma omp declare reduction(operator:                                    // expected-error {{expected identifier or one of the following operators: '+', '-', '*', '&', '|', '^', '&&', or '||'}} expected-error {{expected a type}}
+#pragma omp declare reduction(oper:                                        // expected-error {{expected a type}}
+#pragma omp declare reduction(oper;                                        // expected-error {{expected ':'}} expected-error {{expected a type}}
+#pragma omp declare reduction(fun : int                                    // expected-error {{expected ':'}} expected-error {{expected expression}}
+#pragma omp declare reduction(+ : const int:                               // expected-error {{reduction type cannot be qualified with 'const', 'volatile' or 'restrict'}}
+#pragma omp declare reduction(- : volatile int:                            // expected-error {{reduction type cannot be qualified with 'const', 'volatile' or 'restrict'}}
+#pragma omp declare reduction(* : int;                                     // expected-error {{expected ','}} expected-error {{expected a type}}
+#pragma omp declare reduction(& : double char:                             // expected-error {{cannot combine with previous 'double' declaration specifier}} expected-error {{expected expression}}
+#pragma omp declare reduction(^ : double, char, :                          // expected-error {{expected a type}} expected-error {{expected expression}}
+#pragma omp declare reduction(&& : int, S:                                 // expected-error {{unknown type name 'S'}} expected-error {{expected expression}}
+#pragma omp declare reduction(|| : int, double : temp += omp_in)           // expected-error 2 {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(| : char, float : omp_out += ::temp)         // expected-error 2 {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(fun : long : omp_out += omp_in) {            // expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}} expected-error {{expected 'initializer'}}
+#pragma omp declare reduction(fun : unsigned : omp_out += ::temp))         // expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}} expected-error {{expected 'initializer'}} expected-error {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(fun : long & : omp_out += omp_in)            // expected-error {{reduction type cannot be a reference type}}
+#pragma omp declare reduction(fun : long(void) : omp_out += omp_in)        // expected-error {{reduction type cannot be a function type}}
+#pragma omp declare reduction(fun : long[3] : omp_out += omp_in)           // expected-error {{reduction type cannot be an array type}}
+#pragma omp declare reduction(fun23 : long, int, long : omp_out += omp_in) // expected-error {{redefinition of user-defined reduction for type 'long'}} expected-note {{previous definition is here}}
+
+template <class T>
+class Class1 {
+ T a;
+public:
+  Class1() : a() {}
+#pragma omp declare reduction(fun : T : temp)               // expected-error {{only 'omp_in' or 'omp_out' variables are allowed in combiner expression}}
+#pragma omp declare reduction(fun1 : T : omp_out++)         // expected-note {{previous definition is here}} expected-error {{reduction type cannot be a reference type}}
+#pragma omp declare reduction(fun1 : T : omp_out += omp_in) // expected-error {{redefinition of user-defined reduction for type 'T'}}
+#pragma omp declare reduction(fun2 : T, T : omp_out++)      // expected-error {{reduction type cannot be a reference type}} expected-error {{redefinition of user-defined reduction for type 'T'}} expected-note {{previous definition is here}}
+#pragma omp declare reduction(foo : T : omp_out += this->a) // expected-error {{invalid use of 'this' outside of a non-static member function}}
+};
+
+Class1<char &> e; // expected-note {{in instantiation of template class 'Class1<char &>' requested here}}
+
+template <class T>
+class Class2 : public Class1<T> {
+#pragma omp declare reduction(fun : T : omp_out += omp_in)
+};
+
+#pragma omp declare reduction(fun222 : long : omp_out += omp_in)                                        // expected-note {{previous definition is here}}
+#pragma omp declare reduction(fun222 : long : omp_out += omp_in)                                        // expected-error {{redefinition of user-defined reduction for type 'long'}}
+#pragma omp declare reduction(fun1 : long : omp_out += omp_in) initializer                              // expected-error {{expected '(' after 'initializer'}}
+#pragma omp declare reduction(fun2 : long : omp_out += omp_in) initializer {                            // expected-error {{expected '(' after 'initializer'}} expected-error {{expected expression}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun3 : long : omp_out += omp_in) initializer[                             // expected-error {{expected '(' after 'initializer'}} expected-error {{expected expression}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun4 : long : omp_out += omp_in) initializer()                            // expected-error {{expected expression}}
+#pragma omp declare reduction(fun5 : long : omp_out += omp_in) initializer(temp)                        // expected-error {{only 'omp_priv' or 'omp_orig' variables are allowed in initializer expression}}
+#pragma omp declare reduction(fun6 : long : omp_out += omp_in) initializer(omp_orig                     // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun7 : long : omp_out += omp_in) initializer(omp_priv Class1 < int > ())  // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun77 : long : omp_out += omp_in) initializer(omp_priv Class2 < int > ()) // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun8 : long : omp_out += omp_in) initializer(omp_priv 23)                 // expected-error {{expected ')'}} expected-note {{to match this '('}}
+#pragma omp declare reduction(fun88 : long : omp_out += omp_in) initializer(omp_priv 23))               // expected-error {{expected ')'}} expected-note {{to match this '('}} expected-warning {{extra tokens at the end of '#pragma omp declare reduction' are ignored}}
+#pragma omp declare reduction(fun9 : long : omp_out += omp_priv) initializer(omp_in = 23)               // expected-error {{use of undeclared identifier 'omp_priv'; did you mean 'omp_in'?}} expected-note {{'omp_in' is an implicit parameter}}
+#pragma omp declare reduction(fun10 : long : omp_out += omp_in) initializer(omp_priv = 23)
+
+template <typename T>
+T fun(T arg) {
+#pragma omp declare reduction(red : T : omp_out++)
+  {
+#pragma omp declare reduction(red : T : omp_out++) // expected-note {{previous definition is here}}
+#pragma omp declare reduction(red : T : omp_out++) // expected-error {{redefinition of user-defined reduction for type 'T'}}
+#pragma omp declare reduction(fun : T : omp_out += omp_in) initializer(omp_priv = 23)
+  }
+  return arg;
+}
+
+template <typename T>
+T foo(T arg) {
+  {
+#pragma omp declare reduction(red : T : omp_out++)
+#pragma omp declare reduction(red1 : T : omp_out++)   // expected-note {{previous definition is here}}
+#pragma omp declare reduction(red1 : int : omp_out++) // expected-error {{redefinition of user-defined reduction for type 'int'}}
+  }
+  {
+#pragma omp declare reduction(red1 : int : omp_out++) // expected-note {{previous definition is here}}
+#pragma omp declare reduction(red : T : omp_out++)
+#pragma omp declare reduction(red1 : T : omp_out++) // expected-error {{redefinition of user-defined reduction for type 'int'}}
+  }
+  return arg;
+}
+
+#pragma omp declare reduction(foo : int : ({int a = omp_in; a = a * 2; omp_out += a; }))
+int main() {
+  Class1<int> c1;
+  int i;
+  // TODO: Add support for scoped reduction identifiers
+  //  #pragma omp parallel reduction (::fun : c1)
+  {
+  }
+  //  #pragma omp parallel reduction (::Class1<int>::fun : c1)
+  {
+  }
+  //  #pragma omp parallel reduction (::Class2<int>::fun : i)
+  {
+  }
+  return fun(15) + foo(15); // expected-note {{in instantiation of function template specialization 'foo<int>' requested here}}
+}

clang/tools/libclang/CIndex.cpp

@@ -5584,6 +5584,7 @@ CXCursor clang_getCursorDefinition(CXCursor C) {
   case Decl::ClassScopeFunctionSpecialization:
   case Decl::Import:
   case Decl::OMPThreadPrivate:
+  case Decl::OMPDeclareReduction:
   case Decl::ObjCTypeParam:
   case Decl::BuiltinTemplate:
   case Decl::PragmaComment: