[flang][openacc] Lower acc declare link for module variable

[clementval]

Summary

This patch adds support to lower the link clause on OpenACC
declare construct in module declaration.

Depends on D156463

[razvanlupusoru]

This change looks great to me. Just one small question about error reporting to ensure that the unsupported clause case here is already properly reported by frontend.

flang/lib/Lower/OpenACC.cpp

2446

Do you know if we already inform user of the following limitation from spec:
"In a Fortran module declaration section, only create, copyin, device_resident, and link clauses are allowed."
If yes, then this error here as-is is fine. Since the frontend will already catch and report proper info.

[clementval]

flang/lib/Lower/OpenACC.cpp

2446

Yes, we have a semantic check for that.

flang/lib/Lower/OpenACC.cpp

auto moduleOp =
         builder.getBlock()->getParent()->getParentOfType<mlir::ModuleOp>();
     auto funcOp =
         builder.getBlock()->getParent()->getParentOfType<mlir::func::FuncOp>();
     if (funcOp) {
       TODO(funcOp.getLoc(), "OpenACC declare in function/subroutine");
     } else if (moduleOp) {
       mlir::OpBuilder modBuilder(moduleOp.getBodyRegion());
       for (const Fortran::parser::AccClause &clause : accClauseList.v) {
-        mlir::Location clauseLocation = converter.genLocation(clause.source);
         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);
         } 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);
         } else if (const auto *deviceResidentClause =
                 std::get_if<Fortran::parser::AccClause::DeviceResident>(&clause.u)) {
           genGlobalCtors<mlir::acc::DeclareDeviceResidentOp,
                          mlir::acc::DeclareDeviceResidentOp>(converter,
               modBuilder, deviceResidentClause->v,
               mlir::acc::DataClause::acc_declare_device_resident);
+        } else if (const auto *linkClause =
+                       std::get_if<Fortran::parser::AccClause::Link>(
+                           &clause.u)) {
+          genGlobalCtors<mlir::acc::DeclareLinkOp, mlir::acc::DeclareLinkOp>(
+              converter, modBuilder, linkClause->v,
+              mlir::acc::DataClause::acc_declare_link);
         } else {
-          TODO(clauseLocation, "OpenACC declare clause");
+          llvm::report_fatal_error("unsupported clause on DECLARE directive");
         }
       }
     }
     return;
   }
   llvm_unreachable("unsupported declarative directive");
 }
 

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

 ! CHECK-LABEL: fir.global @_QMacc_declare_device_resident_testEdata1 {acc.declare = #acc.declare<dataClause =  acc_declare_device_resident>} : !fir.array<5000xi32>
 
 ! CHECK-LABEL: acc.global_ctor @_QMacc_declare_device_resident_testEdata1_acc_ctor {
 ! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_device_resident_testEdata1) {acc.declare = #acc.declare<dataClause =  acc_declare_device_resident>} : !fir.ref<!fir.array<5000xi32>>
 ! CHECK:         %[[DEVICERESIDENT:.*]] = acc.declare_device_resident varPtr(%0 : !fir.ref<!fir.array<5000xi32>>) -> !fir.ref<!fir.array<5000xi32>> {name = "data1"}
 ! CHECK:         acc.declare_enter dataOperands(%[[DEVICERESIDENT]] : !fir.ref<!fir.array<5000xi32>>)
 ! CHECK:         acc.terminator
 ! CHECK:       }
+
+module acc_declare_device_link_test
+ integer, parameter :: n = 5000
+ integer, dimension(n) :: data1
+ !$acc declare link(data1)
+end module
+
+! CHECK-LABEL: fir.global @_QMacc_declare_device_link_testEdata1 {acc.declare = #acc.declare<dataClause =  acc_declare_link>} : !fir.array<5000xi32> {
+
+! CHECK-LABEL: acc.global_ctor @_QMacc_declare_device_link_testEdata1_acc_ctor {
+! CHECK:         %[[GLOBAL_ADDR:.*]] = fir.address_of(@_QMacc_declare_device_link_testEdata1) {acc.declare = #acc.declare<dataClause =  acc_declare_link>} : !fir.ref<!fir.array<5000xi32>>
+! CHECK:         %[[LINK:.*]] = acc.declare_link varPtr(%[[GLOBAL_ADDR]] : !fir.ref<!fir.array<5000xi32>>) -> !fir.ref<!fir.array<5000xi32>> {name = "data1"}
+! CHECK:         acc.declare_enter dataOperands(%[[LINK]] : !fir.ref<!fir.array<5000xi32>>)
+! CHECK:         acc.terminator
+! CHECK:       }