[Flang][OpenMP] Update declare mapper lookup via use-module

flang/include/flang/Lower/OpenMP.h

@@ -97,6 +97,13 @@ bool markOpenMPDeferredDeclareTargetFunctions(
     AbstractConverter &);
 void genOpenMPRequires(mlir::Operation *, const Fortran::semantics::Symbol *);
 
+// Materialize omp.declare_mapper ops for mapper declarations found in
+// imported modules. If \p scope is null, materialize for the whole
+// semantics global scope; otherwise, operate recursively starting at \p scope.
+void materializeOpenMPDeclareMappers(
+    Fortran::lower::AbstractConverter &, Fortran::semantics::SemanticsContext &,
+    const Fortran::semantics::Scope *scope = nullptr);
+
 } // namespace lower
 } // namespace Fortran
 

flang/include/flang/Semantics/symbol.h

@@ -777,14 +777,32 @@ class UserReductionDetails {
   DeclVector declList_;
 };
 
+// Used for OpenMP DECLARE MAPPER, it holds the declaration constructs
+// so they can be serialized into module files and later re-parsed when
+// USE-associated.
+class MapperDetails {
+public:
+  using DeclVector = std::vector<const parser::OpenMPDeclarativeConstruct *>;
+
+  MapperDetails() = default;
+
+  void AddDecl(const parser::OpenMPDeclarativeConstruct *decl) {
+    declList_.emplace_back(decl);
+  }
+  const DeclVector &GetDeclList() const { return declList_; }
+
+private:
+  DeclVector declList_;
+};
+
 class UnknownDetails {};
 
 using Details = std::variant<UnknownDetails, MainProgramDetails, ModuleDetails,
     SubprogramDetails, SubprogramNameDetails, EntityDetails,
     ObjectEntityDetails, ProcEntityDetails, AssocEntityDetails,
     DerivedTypeDetails, UseDetails, UseErrorDetails, HostAssocDetails,
     GenericDetails, ProcBindingDetails, NamelistDetails, CommonBlockDetails,
-    TypeParamDetails, MiscDetails, UserReductionDetails>;
+    TypeParamDetails, MiscDetails, UserReductionDetails, MapperDetails>;
 llvm::raw_ostream &operator<<(llvm::raw_ostream &, const Details &);
 std::string DetailsToString(const Details &);
 

flang/lib/Lower/Bridge.cpp

@@ -448,6 +448,13 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       }
     });
 
+    // Ensure imported OpenMP declare mappers are materialized at module
+    // scope before lowering any constructs that may reference them.
+    createBuilderOutsideOfFuncOpAndDo([&]() {
+      Fortran::lower::materializeOpenMPDeclareMappers(
+          *this, bridge.getSemanticsContext());
+    });
+
     // Create definitions of intrinsic module constants.
     createBuilderOutsideOfFuncOpAndDo(
         [&]() { createIntrinsicModuleDefinitions(pft); });

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -1392,10 +1392,14 @@ bool ClauseProcessor::processMap(
     }
     if (mappers) {
       assert(mappers->size() == 1 && "more than one mapper");
-      mapperIdName = mappers->front().v.id().symbol->name().ToString();
-      if (mapperIdName != "default")
-        mapperIdName = converter.mangleName(
-            mapperIdName, mappers->front().v.id().symbol->owner());
+      const semantics::Symbol *mapperSym = mappers->front().v.id().symbol;
+      mapperIdName = mapperSym->name().ToString();
+      if (mapperIdName != "default") {
+        // Mangle with the ultimate owner so that use-associated mapper
+        // identifiers resolve to the same symbol as their defining scope.
+        const semantics::Symbol &ultimate = mapperSym->GetUltimate();
+        mapperIdName = converter.mangleName(mapperIdName, ultimate.owner());
+      }
     }
 
     processMapObjects(stmtCtx, clauseLocation,

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -3543,10 +3543,10 @@ genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
     TODO(converter.getCurrentLocation(), "OpenMPDeclareSimdConstruct");
 }
 
-static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
-                   semantics::SemanticsContext &semaCtx,
-                   lower::pft::Evaluation &eval,
-                   const parser::OpenMPDeclareMapperConstruct &construct) {
+static void genOpenMPDeclareMapperImpl(
+    lower::AbstractConverter &converter, semantics::SemanticsContext &semaCtx,
+    const parser::OpenMPDeclareMapperConstruct &construct,
+    const semantics::Symbol *mapperSymOpt = nullptr) {
   mlir::Location loc = converter.genLocation(construct.source);
   fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
   const parser::OmpArgumentList &args = construct.v.Arguments();
@@ -3562,8 +3562,17 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
          "Expected derived type");
 
   std::string mapperNameStr = mapperName;
-  if (auto *sym = converter.getCurrentScope().FindSymbol(mapperNameStr))
+  if (mapperSymOpt && mapperNameStr != "default") {
+    mapperNameStr = converter.mangleName(mapperNameStr, mapperSymOpt->owner());
+  } else if (auto *sym =
+                 converter.getCurrentScope().FindSymbol(mapperNameStr)) {
     mapperNameStr = converter.mangleName(mapperNameStr, sym->owner());
+  }
+
+  // If the mapper op already exists (e.g., created by regular lowering or by
+  // materialization of imported mappers), do not recreate it.
+  if (converter.getModuleOp().lookupSymbol(mapperNameStr))
+    return;
 
   // Save current insertion point before moving to the module scope to create
   // the DeclareMapperOp
@@ -3586,6 +3595,13 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   mlir::omp::DeclareMapperInfoOp::create(firOpBuilder, loc, clauseOps.mapVars);
 }
 
+static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
+                   semantics::SemanticsContext &semaCtx,
+                   lower::pft::Evaluation &eval,
+                   const parser::OpenMPDeclareMapperConstruct &construct) {
+  genOpenMPDeclareMapperImpl(converter, semaCtx, construct);
+}
+
 static void
 genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
        semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
@@ -4229,3 +4245,36 @@ void Fortran::lower::genOpenMPRequires(mlir::Operation *mod,
     offloadMod.setRequires(mlirFlags);
   }
 }
+
+// Walk scopes and materialize omp.declare_mapper ops for mapper declarations
+// found in imported modules. If \p scope is null, start from the global scope.
+void Fortran::lower::materializeOpenMPDeclareMappers(
+    Fortran::lower::AbstractConverter &converter,
+    semantics::SemanticsContext &semaCtx, const semantics::Scope *scope) {
+  const semantics::Scope &root = scope ? *scope : semaCtx.globalScope();
+
+  // Recurse into child scopes first (modules, submodules, etc.).
+  for (const semantics::Scope &child : root.children())
+    materializeOpenMPDeclareMappers(converter, semaCtx, &child);
+
+  // Only consider module scopes to avoid duplicating local constructs.
+  if (!root.IsModule())
+    return;
+
+  // Only materialize for modules coming from mod files to avoid duplicates.
+  if (!root.symbol() || !root.symbol()->test(semantics::Symbol::Flag::ModFile))
+    return;
+
+  // Scan symbols in this module scope for MapperDetails.
+  for (auto &it : root) {
+    const semantics::Symbol &sym = *it.second;
+    if (auto *md = sym.detailsIf<semantics::MapperDetails>()) {
+      for (const auto *decl : md->GetDeclList()) {
+        if (const auto *mapperDecl =
+                std::get_if<parser::OpenMPDeclareMapperConstruct>(&decl->u)) {
+          genOpenMPDeclareMapperImpl(converter, semaCtx, *mapperDecl, &sym);
+        }
+      }
+    }
+  }
+}

flang/lib/Semantics/mod-file.cpp

@@ -59,6 +59,7 @@ static void PutBound(llvm::raw_ostream &, const Bound &);
 static void PutShapeSpec(llvm::raw_ostream &, const ShapeSpec &);
 static void PutShape(
     llvm::raw_ostream &, const ArraySpec &, char open, char close);
+static void PutMapper(llvm::raw_ostream &, const Symbol &, SemanticsContext &);
 
 static llvm::raw_ostream &PutAttr(llvm::raw_ostream &, Attr);
 static llvm::raw_ostream &PutType(llvm::raw_ostream &, const DeclTypeSpec &);
@@ -938,6 +939,7 @@ void ModFileWriter::PutEntity(llvm::raw_ostream &os, const Symbol &symbol) {
           [&](const ProcEntityDetails &) { PutProcEntity(os, symbol); },
           [&](const TypeParamDetails &) { PutTypeParam(os, symbol); },
           [&](const UserReductionDetails &) { PutUserReduction(os, symbol); },
+          [&](const MapperDetails &) { PutMapper(decls_, symbol, context_); },
           [&](const auto &) {
             common::die("PutEntity: unexpected details: %s",
                 DetailsToString(symbol.details()).c_str());
@@ -1101,6 +1103,16 @@ void ModFileWriter::PutUserReduction(
   }
 }
 
+static void PutMapper(
+    llvm::raw_ostream &os, const Symbol &symbol, SemanticsContext &context) {
+  const auto &details{symbol.get<MapperDetails>()};
+  // Emit each saved DECLARE MAPPER construct as-is, so that consumers of the
+  // module can reparse it and recreate the mapper symbol and semantics state.
+  for (const auto *decl : details.GetDeclList()) {
+    Unparse(os, *decl, context.langOptions());
+  }
+}
+
 void PutInit(llvm::raw_ostream &os, const Symbol &symbol, const MaybeExpr &init,
     const parser::Expr *unanalyzed, SemanticsContext &context) {
   if (IsNamedConstant(symbol) || symbol.owner().IsDerivedType()) {

flang/lib/Semantics/resolve-names.cpp

@@ -1852,21 +1852,25 @@ bool OmpVisitor::Pre(const parser::OmpMapClause &x) {
       // TODO: Do we need a specific flag or type here, to distinghuish against
       // other ConstructName things? Leaving this for the full implementation
       // of mapper lowering.
-      auto *misc{symbol->detailsIf<MiscDetails>()};
-      if (!misc || misc->kind() != MiscDetails::Kind::ConstructName)
+      auto &ultimate{symbol->GetUltimate()};
+      auto *misc{ultimate.detailsIf<MiscDetails>()};
+      auto *md{ultimate.detailsIf<MapperDetails>()};
+      if (!md && (!misc || misc->kind() != MiscDetails::Kind::ConstructName))
         context().Say(mapper->v.source,
             "Name '%s' should be a mapper name"_err_en_US, mapper->v.source);
       else
         mapper->v.symbol = symbol;
     } else {
-      mapper->v.symbol =
-          &MakeSymbol(mapper->v, MiscDetails{MiscDetails::Kind::ConstructName});
-      // TODO: When completing the implementation, we probably want to error if
-      // the symbol is not declared, but right now, testing that the TODO for
-      // OmpMapClause happens is obscured by the TODO for declare mapper, so
-      // leaving this out. Remove the above line once the declare mapper is
-      // implemented. context().Say(mapper->v.source, "'%s' not
-      // declared"_err_en_US, mapper->v.source);
+      // Allow the special 'default' mapper identifier without prior
+      // declaration so lowering can recognize and handle it. Emit an
+      // error for any other missing mapper identifier.
+      if (mapper->v.source.ToString() == "default") {
+        mapper->v.symbol = &MakeSymbol(
+            mapper->v, MiscDetails{MiscDetails::Kind::ConstructName});
+      } else {
+        context().Say(
+            mapper->v.source, "'%s' not declared"_err_en_US, mapper->v.source);
+      }
     }
   }
   return true;
@@ -1880,8 +1884,15 @@ void OmpVisitor::ProcessMapperSpecifier(const parser::OmpMapperSpecifier &spec,
   // the type has been fully processed.
   BeginDeclTypeSpec();
   auto &mapperName{std::get<std::string>(spec.t)};
-  MakeSymbol(parser::CharBlock(mapperName), Attrs{},
-      MiscDetails{MiscDetails::Kind::ConstructName});
+  // Create or update the mapper symbol with MapperDetails and
+  // keep track of the declarative construct for module emission.
+  Symbol &mapperSym{MakeSymbol(parser::CharBlock(mapperName), Attrs{})};
+  if (auto *md{mapperSym.detailsIf<MapperDetails>()}) {
+    md->AddDecl(declaratives_.back());
+  } else if (mapperSym.has<UnknownDetails>() || mapperSym.has<MiscDetails>()) {
+    mapperSym.set_details(MapperDetails{});
+    mapperSym.get<MapperDetails>().AddDecl(declaratives_.back());
+  }
   PushScope(Scope::Kind::OtherConstruct, nullptr);
   Walk(std::get<parser::TypeSpec>(spec.t));
   auto &varName{std::get<parser::Name>(spec.t)};
@@ -3611,10 +3622,20 @@ void ModuleVisitor::Post(const parser::UseStmt &x) {
           rename.u);
     }
     for (const auto &[name, symbol] : *useModuleScope_) {
+      // Default USE imports public names, excluding intrinsic-only and most
+      // miscellaneous details. Allow OpenMP mapper identifiers represented
+      // as MapperDetails, and also legacy MiscDetails::ConstructName.
+      bool isMapper{symbol->has<MapperDetails>()};
+      if (!isMapper) {
+        if (const auto *misc{symbol->detailsIf<MiscDetails>()}) {
+          isMapper = misc->kind() == MiscDetails::Kind::ConstructName;
+        }
+      }
       if (symbol->attrs().test(Attr::PUBLIC) && !IsUseRenamed(symbol->name()) &&
           (!symbol->implicitAttrs().test(Attr::INTRINSIC) ||
               symbol->has<UseDetails>()) &&
-          !symbol->has<MiscDetails>() && useNames.count(name) == 0) {
+          (!symbol->has<MiscDetails>() || isMapper) &&
+          useNames.count(name) == 0) {
         SourceName location{x.moduleName.source};
         if (auto *localSymbol{FindInScope(name)}) {
           DoAddUse(location, localSymbol->name(), *localSymbol, *symbol);

flang/lib/Semantics/symbol.cpp

@@ -338,7 +338,8 @@ std::string DetailsToString(const Details &details) {
           [](const TypeParamDetails &) { return "TypeParam"; },
           [](const MiscDetails &) { return "Misc"; },
           [](const AssocEntityDetails &) { return "AssocEntity"; },
-          [](const UserReductionDetails &) { return "UserReductionDetails"; }},
+          [](const UserReductionDetails &) { return "UserReductionDetails"; },
+          [](const MapperDetails &) { return "MapperDetails"; }},
       details);
 }
 
@@ -379,6 +380,7 @@ bool Symbol::CanReplaceDetails(const Details &details) const {
             [&](const UserReductionDetails &) {
               return has<UserReductionDetails>();
             },
+            [&](const MapperDetails &) { return has<MapperDetails>(); },
             [](const auto &) { return false; },
         },
         details);
@@ -685,6 +687,8 @@ llvm::raw_ostream &operator<<(llvm::raw_ostream &os, const Details &details) {
               DumpType(os, type);
             }
           },
+          // Avoid recursive streaming for MapperDetails; nothing more to dump
+          [&](const MapperDetails &) {},
           [&](const auto &x) { os << x; },
       },
       details);

flang/test/Lower/OpenMP/declare-mapper.f90

@@ -6,7 +6,9 @@
 ! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 %t/omp-declare-mapper-3.f90 -o - | FileCheck %t/omp-declare-mapper-3.f90
 ! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 %t/omp-declare-mapper-4.f90 -o - | FileCheck %t/omp-declare-mapper-4.f90
 ! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 %t/omp-declare-mapper-5.f90 -o - | FileCheck %t/omp-declare-mapper-5.f90
-! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=51 %t/omp-declare-mapper-6.f90 -o - | FileCheck %t/omp-declare-mapper-6.f90
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 %t/omp-declare-mapper-6.f90 -o - | FileCheck %t/omp-declare-mapper-6.f90
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 -module-dir %t %t/omp-declare-mapper-7.mod.f90 -o - >/dev/null
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=50 -J %t %t/omp-declare-mapper-7.use.f90 -o - | FileCheck %t/omp-declare-mapper-7.use.f90
 
 !--- omp-declare-mapper-1.f90
 subroutine declare_mapper_1
@@ -301,3 +303,25 @@ subroutine declare_mapper_nested_parent
     r%real_arr = r%base_arr(1) + r%inner%deep_arr(1)
   !$omp end target
 end subroutine declare_mapper_nested_parent
+
+!--- omp-declare-mapper-7.mod.f90
+! Module with DECLARE MAPPER to be compiled separately
+module m_mod
+  implicit none
+  type :: mty
+    integer :: x
+  end type mty
+  !$omp declare mapper(mymap : mty :: v) map(tofrom: v%x)
+end module m_mod
+
+!--- omp-declare-mapper-7.use.f90
+! Consumer program that USEs the module and applies the mapper by name.
+! CHECK: %{{.*}} = omp.map.info {{.*}} mapper(@{{.*mymap}}) {{.*}} {name = "a"}
+program use_module_mapper
+  use m_mod
+  implicit none
+  type(mty) :: a
+  !$omp target map(mapper(mymap) : a)
+    a%x = 42
+  !$omp end target
+end program use_module_mapper

flang/test/Parser/OpenMP/map-modifiers.f90

@@ -320,7 +320,7 @@ subroutine f21(x, y)
   integer :: x(10)
   integer :: y
   integer, parameter :: p = 23
-  !$omp target map(mapper(xx), from: x)
+  !$omp target map(mapper(default), from: x)
   x = x + 1
   !$omp end target
 end
@@ -329,15 +329,15 @@ subroutine f21(x, y)
 !UNPARSE:  INTEGER x(10_4)
 !UNPARSE:  INTEGER y
 !UNPARSE:  INTEGER, PARAMETER :: p = 23_4
-!UNPARSE: !$OMP TARGET  MAP(MAPPER(XX), FROM: X)
+!UNPARSE: !$OMP TARGET  MAP(MAPPER(DEFAULT), FROM: X)
 !UNPARSE:   x=x+1_4
 !UNPARSE: !$OMP END TARGET
 !UNPARSE: END SUBROUTINE
 
 !PARSE-TREE: OmpBeginDirective
 !PARSE-TREE: | OmpDirectiveName -> llvm::omp::Directive = target
 !PARSE-TREE: | OmpClauseList -> OmpClause -> Map -> OmpMapClause
-!PARSE-TREE: | | Modifier -> OmpMapper -> Name = 'xx'
+!PARSE-TREE: | | Modifier -> OmpMapper -> Name = 'default'
 !PARSE-TREE: | | Modifier -> OmpMapType -> Value = From
 !PARSE-TREE: | | OmpObjectList -> OmpObject -> Designator -> DataRef -> Name = 'x'
 
@@ -375,4 +375,3 @@ subroutine f22(x)
 !PARSE-TREE: | | SectionSubscript -> Integer -> Expr = 'i'
 !PARSE-TREE: | | | Designator -> DataRef -> Name = 'i'
 !PARSE-TREE: | bool = 'true'
-

flang/test/Semantics/OpenMP/declare-mapper-modfile.f90

@@ -0,0 +1,14 @@
+! RUN: split-file %s %t
+! RUN: %flang_fc1 -fsyntax-only -fopenmp -fopenmp-version=50 -module-dir %t %t/m.f90
+! RUN: cat %t/m.mod | FileCheck --ignore-case %s
+
+!--- m.f90
+module m
+  implicit none
+  type :: t
+    integer :: x
+  end type t
+  !$omp declare mapper(mymap : t :: v) map(v%x)
+end module m
+
+!CHECK: !$OMP DECLARE MAPPER(mymap:t::v) MAP(v%x)