[flang][OpenMP] Parse lastprivate modifier, add TODO to lowering

flang/include/flang/Parser/dump-parse-tree.h

@@ -522,6 +522,8 @@ class ParseTreeDumper {
   NODE(parser, OmpEndSectionsDirective)
   NODE(parser, OmpIfClause)
   NODE_ENUM(OmpIfClause, DirectiveNameModifier)
+  NODE_ENUM(OmpLastprivateClause, LastprivateModifier)
+  NODE(parser, OmpLastprivateClause)
   NODE(parser, OmpLinearClause)
   NODE(OmpLinearClause, WithModifier)
   NODE(OmpLinearClause, WithoutModifier)

flang/include/flang/Parser/parse-tree.h

@@ -3648,6 +3648,15 @@ struct OmpAtomicDefaultMemOrderClause {
       OmpAtomicDefaultMemOrderClause, common::OmpAtomicDefaultMemOrderType);
 };
 
+// OMP 5.0 2.19.4.5 lastprivate-clause ->
+//                    LASTPRIVATE ([lastprivate-modifier :] list)
+//                  lastprivate-modifier -> CONDITIONAL
+struct OmpLastprivateClause {
+  TUPLE_CLASS_BOILERPLATE(OmpLastprivateClause);
+  ENUM_CLASS(LastprivateModifier, Conditional);
+  std::tuple<std::optional<LastprivateModifier>, OmpObjectList> t;
+};
+
 // OpenMP Clauses
 struct OmpClause {
   UNION_CLASS_BOILERPLATE(OmpClause);

flang/lib/Lower/OpenMP/Clauses.cpp

@@ -783,9 +783,22 @@ IsDevicePtr make(const parser::OmpClause::IsDevicePtr &inp,
 
 Lastprivate make(const parser::OmpClause::Lastprivate &inp,
                  semantics::SemanticsContext &semaCtx) {
-  // inp.v -> parser::OmpObjectList
-  return Lastprivate{{/*LastprivateModifier=*/std::nullopt,
-                      /*List=*/makeObjects(inp.v, semaCtx)}};
+  // inp.v -> parser::OmpLastprivateClause
+  using wrapped = parser::OmpLastprivateClause;
+
+  CLAUSET_ENUM_CONVERT( //
+      convert, parser::OmpLastprivateClause::LastprivateModifier,
+      Lastprivate::LastprivateModifier,
+      // clang-format off
+      MS(Conditional, Conditional)
+      // clang-format on
+  );
+
+  auto &t0 = std::get<std::optional<wrapped::LastprivateModifier>>(inp.v.t);
+  auto &t1 = std::get<parser::OmpObjectList>(inp.v.t);
+
+  return Lastprivate{{/*LastprivateModifier=*/maybeApply(convert, t0),
+                      /*List=*/makeObjects(t1, semaCtx)}};
 }
 
 Linear make(const parser::OmpClause::Linear &inp,

flang/lib/Lower/OpenMP/DataSharingProcessor.cpp

@@ -151,6 +151,8 @@ void DataSharingProcessor::collectSymbolsForPrivatization() {
                                  explicitlyPrivatizedSymbols);
     } else if (const auto &lastPrivateClause =
                    std::get_if<omp::clause::Lastprivate>(&clause.u)) {
+      lastprivateModifierNotSupported(*lastPrivateClause,
+                                      converter.getCurrentLocation());
       const ObjectList &objects = std::get<ObjectList>(lastPrivateClause->t);
       collectOmpObjectListSymbol(objects, explicitlyPrivatizedSymbols);
     }

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -1554,7 +1554,9 @@ genSectionsOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
 
   for (const Clause &clause : item->clauses) {
     if (clause.id == llvm::omp::Clause::OMPC_lastprivate) {
-      lastprivates.push_back(&std::get<clause::Lastprivate>(clause.u));
+      auto &lastp = std::get<clause::Lastprivate>(clause.u);
+      lastprivateModifierNotSupported(lastp, converter.getCurrentLocation());
+      lastprivates.push_back(&lastp);
     } else {
       switch (clause.id) {
       case llvm::omp::Clause::OMPC_firstprivate:

flang/lib/Lower/OpenMP/Utils.cpp

@@ -17,6 +17,7 @@
 #include <flang/Lower/ConvertType.h>
 #include <flang/Lower/PFTBuilder.h>
 #include <flang/Optimizer/Builder/FIRBuilder.h>
+#include <flang/Optimizer/Builder/Todo.h>
 #include <flang/Parser/parse-tree.h>
 #include <flang/Parser/tools.h>
 #include <flang/Semantics/tools.h>
@@ -356,6 +357,18 @@ semantics::Symbol *getOmpObjectSymbol(const parser::OmpObject &ompObject) {
   return sym;
 }
 
+void lastprivateModifierNotSupported(const omp::clause::Lastprivate &lastp,
+                                     mlir::Location loc) {
+  using Lastprivate = omp::clause::Lastprivate;
+  auto &maybeMod =
+      std::get<std::optional<Lastprivate::LastprivateModifier>>(lastp.t);
+  if (maybeMod) {
+    assert(*maybeMod == Lastprivate::LastprivateModifier::Conditional &&
+           "Unexpected lastprivate modifier");
+    TODO(loc, "lastprivate clause with CONDITIONAL modifier");
+  }
+}
+
 } // namespace omp
 } // namespace lower
 } // namespace Fortran

flang/lib/Lower/OpenMP/Utils.h

@@ -100,6 +100,9 @@ void genObjectList(const ObjectList &objects,
                    lower::AbstractConverter &converter,
                    llvm::SmallVectorImpl<mlir::Value> &operands);
 
+void lastprivateModifierNotSupported(const omp::clause::Lastprivate &lastp,
+                                     mlir::Location loc);
+
 } // namespace omp
 } // namespace lower
 } // namespace Fortran

flang/lib/Parser/openmp-parsers.cpp

@@ -232,6 +232,12 @@ TYPE_PARSER(construct<OmpOrderClause>(
 TYPE_PARSER(
     construct<OmpObject>(designator) || construct<OmpObject>("/" >> name / "/"))
 
+// OMP 5.0 2.19.4.5 LASTPRIVATE ([lastprivate-modifier :] list)
+TYPE_PARSER(construct<OmpLastprivateClause>(
+    maybe("CONDITIONAL" >>
+        pure(OmpLastprivateClause::LastprivateModifier::Conditional) / ":"),
+    Parser<OmpObjectList>{}))
+
 TYPE_PARSER(
     "ACQUIRE" >> construct<OmpClause>(construct<OmpClause::Acquire>()) ||
     "ACQ_REL" >> construct<OmpClause>(construct<OmpClause::AcqRel>()) ||
@@ -289,7 +295,7 @@ TYPE_PARSER(
     "IS_DEVICE_PTR" >> construct<OmpClause>(construct<OmpClause::IsDevicePtr>(
                            parenthesized(Parser<OmpObjectList>{}))) ||
     "LASTPRIVATE" >> construct<OmpClause>(construct<OmpClause::Lastprivate>(
-                         parenthesized(Parser<OmpObjectList>{}))) ||
+                         parenthesized(Parser<OmpLastprivateClause>{}))) ||
     "LINEAR" >> construct<OmpClause>(construct<OmpClause::Linear>(
                     parenthesized(Parser<OmpLinearClause>{}))) ||
     "LINK" >> construct<OmpClause>(construct<OmpClause::Link>(

flang/lib/Parser/unparse.cpp

@@ -2067,6 +2067,12 @@ class UnparseVisitor {
                   },
         x.u);
   }
+  void Unparse(const OmpLastprivateClause &x) {
+    Walk(
+        std::get<std::optional<OmpLastprivateClause::LastprivateModifier>>(x.t),
+        ":");
+    Walk(std::get<OmpObjectList>(x.t));
+  }
   void Unparse(const OmpMapType::Always &) { Word("ALWAYS,"); }
   void Unparse(const OmpMapClause &x) {
     Walk(std::get<std::optional<OmpMapType>>(x.t), ":");
@@ -2764,6 +2770,8 @@ class UnparseVisitor {
   WALK_NESTED_ENUM(OmpDefaultClause, Type) // OMP DEFAULT
   WALK_NESTED_ENUM(OmpDefaultmapClause, ImplicitBehavior) // OMP DEFAULTMAP
   WALK_NESTED_ENUM(OmpDefaultmapClause, VariableCategory) // OMP DEFAULTMAP
+  WALK_NESTED_ENUM(
+      OmpLastprivateClause, LastprivateModifier) // OMP lastprivate-modifier
   WALK_NESTED_ENUM(OmpScheduleModifierType, ModType) // OMP schedule-modifier
   WALK_NESTED_ENUM(OmpLinearModifier, Type) // OMP linear-modifier
   WALK_NESTED_ENUM(OmpDependenceType, Type) // OMP dependence-type

flang/lib/Semantics/check-omp-structure.cpp

@@ -3174,11 +3174,13 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Copyprivate &x) {
 void OmpStructureChecker::Enter(const parser::OmpClause::Lastprivate &x) {
   CheckAllowedClause(llvm::omp::Clause::OMPC_lastprivate);
 
-  CheckIsVarPartOfAnotherVar(GetContext().clauseSource, x.v, "LASTPRIVATE");
+  const auto &objectList{std::get<parser::OmpObjectList>(x.v.t)};
+  CheckIsVarPartOfAnotherVar(
+      GetContext().clauseSource, objectList, "LASTPRIVATE");
 
   DirectivesClauseTriple dirClauseTriple;
   SymbolSourceMap currSymbols;
-  GetSymbolsInObjectList(x.v, currSymbols);
+  GetSymbolsInObjectList(objectList, currSymbols);
   CheckDefinableObjects(currSymbols, GetClauseKindForParserClass(x));
   CheckCopyingPolymorphicAllocatable(
       currSymbols, llvm::omp::Clause::OMPC_lastprivate);
@@ -3193,6 +3195,21 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Lastprivate &x) {
 
   CheckPrivateSymbolsInOuterCxt(
       currSymbols, dirClauseTriple, GetClauseKindForParserClass(x));
+
+  using LastprivateModifier = parser::OmpLastprivateClause::LastprivateModifier;
+  const auto &maybeMod{std::get<std::optional<LastprivateModifier>>(x.v.t)};
+  if (maybeMod) {
+    unsigned version{context_.langOptions().OpenMPVersion};
+    unsigned allowedInVersion = 50;
+    if (version < allowedInVersion) {
+      std::string thisVersion{
+          std::to_string(version / 10) + "." + std::to_string(version % 10)};
+      context_.Say(GetContext().clauseSource,
+          "LASTPRIVATE clause with CONDITIONAL modifier is not "
+          "allowed in OpenMP v%s, try -fopenmp-version=%d"_err_en_US,
+          thisVersion, allowedInVersion);
+    }
+  }
 }
 
 void OmpStructureChecker::Enter(const parser::OmpClause::Copyin &x) {
@@ -3617,18 +3634,17 @@ const parser::OmpObjectList *OmpStructureChecker::GetOmpObjectList(
     const parser::OmpClause &clause) {
 
   // Clauses with OmpObjectList as its data member
-  using MemberObjectListClauses =
-      std::tuple<parser::OmpClause::Copyprivate, parser::OmpClause::Copyin,
-          parser::OmpClause::Firstprivate, parser::OmpClause::From,
-          parser::OmpClause::Lastprivate, parser::OmpClause::Link,
-          parser::OmpClause::Private, parser::OmpClause::Shared,
-          parser::OmpClause::To, parser::OmpClause::Enter,
-          parser::OmpClause::UseDevicePtr, parser::OmpClause::UseDeviceAddr>;
+  using MemberObjectListClauses = std::tuple<parser::OmpClause::Copyprivate,
+      parser::OmpClause::Copyin, parser::OmpClause::Firstprivate,
+      parser::OmpClause::From, parser::OmpClause::Link,
+      parser::OmpClause::Private, parser::OmpClause::Shared,
+      parser::OmpClause::To, parser::OmpClause::Enter,
+      parser::OmpClause::UseDevicePtr, parser::OmpClause::UseDeviceAddr>;
 
   // Clauses with OmpObjectList in the tuple
-  using TupleObjectListClauses =
-      std::tuple<parser::OmpClause::Allocate, parser::OmpClause::Map,
-          parser::OmpClause::Reduction, parser::OmpClause::Aligned>;
+  using TupleObjectListClauses = std::tuple<parser::OmpClause::Allocate,
+      parser::OmpClause::Lastprivate, parser::OmpClause::Map,
+      parser::OmpClause::Reduction, parser::OmpClause::Aligned>;
 
   // TODO:: Generate the tuples using TableGen.
   // Handle other constructs with OmpObjectList such as OpenMPThreadprivate.

flang/lib/Semantics/resolve-directives.cpp

@@ -455,7 +455,8 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
     return false;
   }
   bool Pre(const parser::OmpClause::Lastprivate &x) {
-    ResolveOmpObjectList(x.v, Symbol::Flag::OmpLastPrivate);
+    const auto &objList{std::get<parser::OmpObjectList>(x.v.t)};
+    ResolveOmpObjectList(objList, Symbol::Flag::OmpLastPrivate);
     return false;
   }
   bool Pre(const parser::OmpClause::Copyin &x) {

flang/test/Lower/OpenMP/Todo/lastprivate-conditional.f90

@@ -0,0 +1,12 @@
+! RUN: %not_todo_cmd bbc -emit-fir -fopenmp -fopenmp-version=50 -o - %s 2>&1 | FileCheck %s
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -fopenmp-version=50 -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: lastprivate clause with CONDITIONAL modifier
+subroutine foo()
+  integer :: x, i
+  x = 1
+  !$omp parallel do lastprivate(conditional: x)
+  do i = 1, 100
+    x = x + 1
+  enddo
+end

flang/test/Parser/OpenMP/lastprivate-clause.f90

@@ -0,0 +1,54 @@
+! RUN: %flang_fc1 -fdebug-unparse -fopenmp -fopenmp-version=50 %s | FileCheck --ignore-case --check-prefix="UNPARSE" %s 
+! RUN: %flang_fc1 -fdebug-dump-parse-tree -fopenmp -fopenmp-version=50 %s | FileCheck --check-prefix="PARSE-TREE" %s
+
+subroutine foo1()
+  integer :: x, i
+  x = 1
+  !$omp parallel do lastprivate(x)
+  do i = 1, 100
+    x = x + 1
+  enddo
+end
+
+!UNPARSE: SUBROUTINE foo1
+!UNPARSE:  INTEGER x, i
+!UNPARSE:   x=1_4
+!UNPARSE: !$OMP PARALLEL DO  LASTPRIVATE(x)
+!UNPARSE:  DO i=1_4,100_4
+!UNPARSE:    x=x+1_4
+!UNPARSE:  END DO
+!UNPARSE: END SUBROUTINE
+
+!PARSE-TREE: SubroutineStmt
+!PARSE-TREE:   Name = 'foo1'
+!PARSE-TREE: OmpLoopDirective -> llvm::omp::Directive = parallel do
+!PARSE-TREE: OmpClauseList -> OmpClause -> Lastprivate -> OmpLastprivateClause
+!PARSE-TREE:   OmpObjectList -> OmpObject -> Designator -> DataRef -> Name = 'x'
+!PARSE-TREE: EndSubroutineStmt
+
+
+subroutine foo2()
+  integer :: x, i
+  x = 1
+  !$omp parallel do lastprivate(conditional: x)
+  do i = 1, 100
+    x = x + 1
+  enddo
+end
+
+!UNPARSE: SUBROUTINE foo2
+!UNPARSE:  INTEGER x, i
+!UNPARSE:   x=1_4
+!UNPARSE: !$OMP PARALLEL DO  LASTPRIVATE(CONDITIONAL:x)
+!UNPARSE:  DO i=1_4,100_4
+!UNPARSE:    x=x+1_4
+!UNPARSE:  END DO
+!UNPARSE: END SUBROUTINE
+
+!PARSE-TREE: SubroutineStmt
+!PARSE-TREE:   Name = 'foo2'
+!PARSE-TREE: OmpLoopDirective -> llvm::omp::Directive = parallel do
+!PARSE-TREE: OmpClauseList -> OmpClause -> Lastprivate -> OmpLastprivateClause
+!PARSE-TREE:   LastprivateModifier = Conditional
+!PARSE-TREE:   OmpObjectList -> OmpObject -> Designator -> DataRef -> Name = 'x'
+!PARSE-TREE: EndSubroutineStmt

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -229,7 +229,7 @@ def OMPC_IsDevicePtr : Clause<"is_device_ptr"> {
 }
 def OMPC_LastPrivate : Clause<"lastprivate"> {
   let clangClass = "OMPLastprivateClause";
-  let flangClass = "OmpObjectList";
+  let flangClass = "OmpLastprivateClause";
 }
 def OMPC_Linear : Clause<"linear"> {
   let clangClass = "OMPLinearClause";