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

flang/lib/Lower/OpenMP/ClauseProcessor.cpp

@@ -1402,10 +1402,14 @@ 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/Semantics/resolve-names.cpp

@@ -1824,21 +1824,24 @@ 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>()};
+      const Symbol &ultimate{symbol->GetUltimate()};
+      auto *misc{const_cast<Symbol &>(ultimate).detailsIf<MiscDetails>()};
       if (!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;
@@ -3614,10 +3617,18 @@ 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. However, allow OpenMP mapper identifiers,
+      // which are currently represented with MiscDetails::ConstructName.
+      bool isMapper{false};
+      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/test/Lower/OpenMP/declare-mapper.f90

@@ -6,7 +6,8 @@
 ! 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 %t/omp-declare-mapper-7.f90 -o - | FileCheck %t/omp-declare-mapper-7.f90
 
 !--- omp-declare-mapper-1.f90
 subroutine declare_mapper_1
@@ -301,3 +302,25 @@ subroutine declare_mapper_nested_parent
     r%real_arr = r%base_arr(1) + r%inner%deep_arr(1)
   !$omp end target
 end subroutine declare_mapper_nested_parent
+
+!--- omp-declare-mapper-7.f90
+! Check mappers declared inside modules and used via USE association.
+module m_mod
+  implicit none
+  type :: mty
+    integer :: x
+  end type mty
+  !$omp declare mapper(mymap : mty :: v) map(tofrom: v%x)
+end module m_mod
+
+program use_module_mapper
+  use m_mod
+  implicit none
+  type(mty) :: a
+
+  ! CHECK: omp.declare_mapper @[[MODMAP:[^ ]*mymap]]
+  ! CHECK: %{{.*}} = omp.map.info {{.*}} mapper(@[[MODMAP]]) {{.*}} {name = "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/map-clause-symbols.f90

@@ -1,14 +1,12 @@
-! RUN: %flang_fc1 -fdebug-dump-symbols -fopenmp -fopenmp-version=50 %s | FileCheck %s
+! RUN: not %flang_fc1 -fopenmp -fopenmp-version=50 %s 2>&1 | FileCheck %s
 program main
-!CHECK-LABEL:  MainProgram scope: MAIN
   integer, parameter :: n = 256
   real(8) :: a(256)
   !$omp target map(mapper(xx), from:a)
   do i=1,n
      a(i) = 4.2
   end do
   !$omp end target
-!CHECK:    OtherConstruct scope: size=0 alignment=1 sourceRange=74 bytes
-!CHECK:    OtherClause scope: size=0 alignment=1 sourceRange=0 bytes
-!CHECK:    xx: Misc ConstructName
 end program main
+
+! CHECK: error: '{{.*}}' not declared