[flang][openacc] Disallow the zero modifier on the create clause with the declare directive

[clementval]

Summary

The OpenACC 3.3 specification does not allow the zero modifier
on the create clause used with the declare directive.

[razvanlupusoru]

Nice catch! I admit I did not know this despite being quite familiar with the OpenACC spec. Easy detail to miss! It does seem that it may not be an intentional omission, but I agree rejecting it for now.

[clementval]

In D156703#4548418, @razvanlupusoru wrote:

Nice catch! I admit I did not know this despite being quite familiar with the OpenACC spec. Easy detail to miss! It does seem that it may not be an intentional omission, but I agree rejecting it for now.

I agree that it might just be missing from the spec. I'll raise a question to the technical committee.

flang/lib/Lower/OpenACC.cpp

 static void
 genDeclareInModule(Fortran::lower::AbstractConverter &converter,
                    mlir::ModuleOp &moduleOp,
                    const Fortran::parser::AccClauseList &accClauseList) {
   mlir::OpBuilder modBuilder(moduleOp.getBodyRegion());
   for (const Fortran::parser::AccClause &clause : accClauseList.v) {
     if (const auto *createClause =
             std::get_if<Fortran::parser::AccClause::Create>(&clause.u)) {
-      genGlobalCtorsWithModifier<Fortran::parser::AccClause::Create,
-                                 mlir::acc::CreateOp, mlir::acc::DeleteOp>(
-          converter, modBuilder, createClause,
-          Fortran::parser::AccDataModifier::Modifier::Zero,
-          mlir::acc::DataClause::acc_create,
-          mlir::acc::DataClause::acc_create_zero);
+      const Fortran::parser::AccObjectListWithModifier &listWithModifier =
+          createClause->v;
+      const auto &accObjectList =
+          std::get<Fortran::parser::AccObjectList>(listWithModifier.t);
+      genGlobalCtors<mlir::acc::CreateOp, mlir::acc::DeleteOp>(
+          converter, modBuilder, accObjectList,
+          mlir::acc::DataClause::acc_create);
     } else if (const auto *copyinClause =
                    std::get_if<Fortran::parser::AccClause::Copyin>(&clause.u)) {
       genGlobalCtorsWithModifier<Fortran::parser::AccClause::Copyin,
                                  mlir::acc::CopyinOp, mlir::acc::CopyinOp>(
           converter, modBuilder, copyinClause,
           Fortran::parser::AccDataModifier::Modifier::ReadOnly,
           mlir::acc::DataClause::acc_copyin,
           mlir::acc::DataClause::acc_copyin_readonly);

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

if (modifier->v != parser::AccDataModifier::Modifier::Zero) {
       context_.Say(GetContext().clauseSource,
           "Only the ZERO modifier is allowed for the %s clause "
           "on the %s directive"_err_en_US,
           parser::ToUpperCaseLetters(
               llvm::acc::getOpenACCClauseName(llvm::acc::Clause::ACCC_create)
                   .str()),
           ContextDirectiveAsFortran());
     }
+    if (GetContext().directive == llvm::acc::Directive::ACCD_declare) {
+      context_.Say(GetContext().clauseSource,
+          "The ZERO modifier is not allowed for the %s clause "
+          "on the %s directive"_err_en_US,
+          parser::ToUpperCaseLetters(
+              llvm::acc::getOpenACCClauseName(llvm::acc::Clause::ACCC_create)
+                  .str()),
+          ContextDirectiveAsFortran());
+    }
   }
 }
 
 void AccStructureChecker::Enter(const parser::AccClause::Copyin &c) {
   CheckAllowed(llvm::acc::Clause::ACCC_copyin);
   const auto &modifierClause{c.v};
   if (const auto &modifier{
           std::get<std::optional<parser::AccDataModifier>>(modifierClause.t)}) {

flang/test/Lower/OpenACC/acc-declare.f90

 ! This test checks lowering of OpenACC declare directive.
 
 ! RUN: bbc -fopenacc -emit-fir %s -o - | FileCheck %s
 
 module acc_declare_test
  integer, parameter :: n = 100000
- real, dimension(n) :: data1, data2
- !$acc declare create(data1) create(zero: data2)
+ real, dimension(n) :: data1
+ !$acc declare create(data1)
 end module
 
 ! CHECK-LABEL: fir.global @_QMacc_declare_testEdata1 {acc.declare = #acc.declare<dataClause = acc_create>} : !fir.array<100000xf32>
 
 ! CHECK-LABEL: acc.global_ctor @_QMacc_declare_testEdata1_acc_ctor {
 ! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_testEdata1) {acc.declare = #acc.declare<dataClause = acc_create>} : !fir.ref<!fir.array<100000xf32>>
 ! CHECK:         %[[CREATE:.*]] = acc.create varPtr(%[[GLOBAL_ADDR]] : !fir.ref<!fir.array<100000xf32>>) -> !fir.ref<!fir.array<100000xf32>> {name = "data1", structured = false}
 ! CHECK:         acc.declare_enter dataOperands(%[[CREATE]] : !fir.ref<!fir.array<100000xf32>>)
 ! CHECK:         acc.terminator
 ! CHECK:       }
 
 ! CHECK-LABEL: acc.global_dtor @_QMacc_declare_testEdata1_acc_dtor {
 ! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_testEdata1) {acc.declare = #acc.declare<dataClause = acc_create>} : !fir.ref<!fir.array<100000xf32>>
 ! CHECK:         %[[DEVICEPTR:.*]] = acc.getdeviceptr varPtr(%[[GLOBAL_ADDR]] : !fir.ref<!fir.array<100000xf32>>) -> !fir.ref<!fir.array<100000xf32>> {dataClause = #acc<data_clause acc_create>, name = "data1", structured = false}
 ! CHECK:         acc.declare_exit dataOperands(%[[DEVICEPTR]] : !fir.ref<!fir.array<100000xf32>>)
 ! CHECK:         acc.delete accPtr(%[[DEVICEPTR]] : !fir.ref<!fir.array<100000xf32>>) {dataClause = #acc<data_clause acc_create>, name = "data1", structured = false}
 ! CHECK:         acc.terminator
 ! CHECK:       }
 
-! CHECK-LABEL: fir.global @_QMacc_declare_testEdata2 {acc.declare = #acc.declare<dataClause =  acc_create_zero>} : !fir.array<100000xf32>
-
-! CHECK-LABEL: acc.global_ctor @_QMacc_declare_testEdata2_acc_ctor {
-! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_testEdata2) {acc.declare = #acc.declare<dataClause =  acc_create_zero>} : !fir.ref<!fir.array<100000xf32>>
-! CHECK:         %[[CREATE:.*]] = acc.create varPtr(%[[GLOBAL_ADDR]] : !fir.ref<!fir.array<100000xf32>>) -> !fir.ref<!fir.array<100000xf32>> {dataClause = #acc<data_clause acc_create_zero>, name = "data2", structured = false}
-! CHECK:         acc.declare_enter dataOperands(%[[CREATE]] : !fir.ref<!fir.array<100000xf32>>)
-! CHECK:         acc.terminator
-! CHECK:       }
-
-! CHECK-LABEL: acc.global_dtor @_QMacc_declare_testEdata2_acc_dtor {
-! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_testEdata2) {acc.declare = #acc.declare<dataClause =  acc_create_zero>} : !fir.ref<!fir.array<100000xf32>>
-! CHECK:         %[[DEVICEPTR:.*]] = acc.getdeviceptr varPtr(%[[GLOBAL_ADDR]] : !fir.ref<!fir.array<100000xf32>>) -> !fir.ref<!fir.array<100000xf32>> {dataClause = #acc<data_clause acc_create_zero>, name = "data2", structured = false}
-! CHECK:         acc.declare_exit dataOperands(%[[DEVICEPTR]] : !fir.ref<!fir.array<100000xf32>>)
-! CHECK:         acc.delete accPtr(%[[DEVICEPTR]] : !fir.ref<!fir.array<100000xf32>>) {dataClause = #acc<data_clause acc_create_zero>, name = "data2", structured = false}
-! CHECK:         acc.terminator
-! CHECK:       }
-
 module acc_declare_copyin_test
  integer, parameter :: n = 100000
  real, dimension(n) :: data1
  !$acc declare copyin(data1)
 end module
 
 
 ! CHECK-LABEL: acc.global_ctor @_QMacc_declare_copyin_testEdata1_acc_ctor {

flang/test/Semantics/OpenACC/acc-declare-validity.f90

module openacc_declare_validity
   !$acc declare copy(ab)
 
   !ERROR: PRESENT clause is not allowed on the DECLARE directive in module declaration section
   !$acc declare present(ab)
 
   !ERROR: DEVICEPTR clause is not allowed on the DECLARE directive in module declaration section
   !$acc declare deviceptr(ab)
 
+  !ERROR: The ZERO modifier is not allowed for the CREATE clause on the DECLARE directive
+  !$acc declare create(zero: aa)
+
 contains
 
   subroutine sub1(cc, dd)
     real(8) :: cc(:)
     real(8) :: dd(:)
     !$acc declare present(cc, dd)
   end subroutine sub1