[flang] Changes to correctly map variables in link clause of declare target

As per the standard, "If a variable appears in a link clause on a
declare target directive that does not have a device_type clause with
the nohost device-type-description then it is treated as if it had
appeared in a map clause with a map-type of tofrom" is an implicit mapping rule.
Before this change, such variables were mapped as to by default.

Author: anchuraj

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -1120,7 +1120,21 @@ genTargetOp(Fortran::lower::AbstractConverter &converter,
         if (auto refType = baseOp.getType().dyn_cast<fir::ReferenceType>())
           eleType = refType.getElementType();
 
-        if (fir::isa_trivial(eleType) || fir::isa_char(eleType)) {
+        // If a variable is specified in declare target link and if device
+        // type is nohost, it needs to be mapped tofrom
+        mlir::ModuleOp mod = converter.getFirOpBuilder().getModule();
+        mlir::Operation *op = mod.lookupSymbol(converter.mangleName(sym));
+        auto declareTargetOp =
+            llvm::dyn_cast_if_present<mlir::omp::DeclareTargetInterface>(op);
+        if (declareTargetOp && declareTargetOp.isDeclareTarget()) {
+          if (declareTargetOp.getDeclareTargetCaptureClause() ==
+                  mlir::omp::DeclareTargetCaptureClause::link &&
+              declareTargetOp.getDeclareTargetDeviceType() !=
+                  mlir::omp::DeclareTargetDeviceType::nohost) {
+            mapFlag |= llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_TO;
+            mapFlag |= llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_FROM;
+          }
+        } else if (fir::isa_trivial(eleType) || fir::isa_char(eleType)) {
           captureKind = mlir::omp::VariableCaptureKind::ByCopy;
         } else if (!fir::isa_builtin_cptr_type(eleType)) {
           mapFlag |= llvm::omp::OpenMPOffloadMappingFlags::OMP_MAP_TO;

flang/test/Lower/OpenMP/declare-target-link-tarop-cap.f90

@@ -0,0 +1,55 @@
+!RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
+!RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-is-device %s -o - | FileCheck %s
+!RUN: bbc -emit-hlfir -fopenmp %s -o - | FileCheck %s
+!RUN: bbc -emit-hlfir -fopenmp -fopenmp-is-target-device %s -o - | FileCheck %s
+
+program test_link
+
+integer :: test_int = 1
+!$omp declare target link(test_int)
+
+integer :: test_array_1d(3) = (/1,2,3/)
+!$omp declare target link(test_array_1d)
+
+integer, pointer :: test_ptr1
+!$omp declare target link(test_ptr1)
+
+integer, target :: test_target = 1
+!$omp declare target link(test_target)
+
+integer, pointer :: test_ptr2
+!$omp declare target link(test_ptr2)
+
+!CHECK-DAG: {{%.*}} = omp.map_info var_ptr({{%.*}} : !fir.ref<i32>, i32) map_clauses(implicit, tofrom) capture(ByRef) -> !fir.ref<i32> {name = "test_int"}
+!$omp target
+  test_int = test_int + 1
+!$omp end target
+
+
+!CHECK-DAG: {{%.*}} = omp.map_info var_ptr({{%.*}} : !fir.ref<!fir.array<3xi32>>, !fir.array<3xi32>) map_clauses(implicit, tofrom) capture(ByRef) bounds({{%.*}}) -> !fir.ref<!fir.array<3xi32>> {name = "test_array_1d"}
+!$omp target
+  do i = 1,3
+    test_array_1d(i) = i * 2
+  end do
+!$omp end target
+
+allocate(test_ptr1)
+test_ptr1 = 1
+!CHECK-DAG: {{%.*}} = omp.map_info var_ptr({{%.*}} : !fir.ref<!fir.box<!fir.ptr<i32>>>, !fir.box<!fir.ptr<i32>>) map_clauses(implicit, tofrom) capture(ByRef) members({{%.*}} : !fir.llvm_ptr<!fir.ref<i32>>) -> !fir.ref<!fir.box<!fir.ptr<i32>>> {name = "test_ptr1"}
+!$omp target
+  test_ptr1 = test_ptr1 + 1
+!$omp end target
+
+!CHECK-DAG: {{%.*}} = omp.map_info var_ptr({{%.*}} : !fir.ref<i32>, i32) map_clauses(implicit, tofrom) capture(ByRef) -> !fir.ref<i32> {name = "test_target"}
+!$omp target
+  test_target = test_target + 1
+!$omp end target
+
+
+!CHECK-DAG: {{%.*}} = omp.map_info var_ptr({{%.*}} : !fir.ref<!fir.box<!fir.ptr<i32>>>, !fir.box<!fir.ptr<i32>>) map_clauses(implicit, tofrom) capture(ByRef) members({{%.*}} : !fir.llvm_ptr<!fir.ref<i32>>) -> !fir.ref<!fir.box<!fir.ptr<i32>>> {name = "test_ptr2"}
+test_ptr2 => test_target
+!$omp target
+  test_ptr2 = test_ptr2 + 1
+!$omp end target
+
+end