[flang] Lower VALUE derived types in BIND(C) interface

flang/lib/Lower/ConvertCall.cpp

@@ -360,9 +360,8 @@ fir::ExtendedValue Fortran::lower::genCallOpAndResult(
       if (fir::isa_builtin_cptr_type(fromTy) &&
           Fortran::lower::isCPtrArgByValueType(snd)) {
         cast = genRecordCPtrValueArg(builder, loc, fst, fromTy);
-      } else if (fir::isa_derived(snd)) {
-        // FIXME: This seems like a serious bug elsewhere in lowering. Paper
-        // over the problem for now.
+      } else if (fir::isa_derived(snd) && !fir::isa_derived(fst.getType())) {
+        // TODO: remove this TODO once the old lowering is gone.
         TODO(loc, "derived type argument passed by value");
       } else {
         cast = builder.convertWithSemantics(loc, snd, fst,
@@ -1188,8 +1187,18 @@ genUserCall(Fortran::lower::PreparedActualArguments &loweredActuals,
           value =
               hlfir::Entity{genRecordCPtrValueArg(builder, loc, value, eleTy)};
         }
+      } else if (fir::isa_derived(value.getFortranElementType())) {
+        // BIND(C), VALUE derived type. The derived type value must really
+        // be loaded here.
+        auto [derived, cleanup] = hlfir::convertToValue(loc, builder, value);
+        mlir::Value loadedValue = fir::getBase(derived);
+        if (fir::isa_ref_type(loadedValue.getType()))
+          loadedValue = builder.create<fir::LoadOp>(loc, loadedValue);
+        caller.placeInput(arg, loadedValue);
+        if (cleanup)
+          (*cleanup)();
+        break;
       }
-
       caller.placeInput(arg, builder.createConvert(loc, argTy, value));
     } break;
     case PassBy::BaseAddressValueAttribute:

flang/lib/Lower/ConvertVariable.cpp

@@ -2138,8 +2138,6 @@ void Fortran::lower::mapSymbolAttributes(
       if (isCptrByVal || !fir::conformsWithPassByRef(argType)) {
         // Dummy argument passed in register. Place the value in memory at that
         // point since lowering expect symbols to be mapped to memory addresses.
-        if (argType.isa<fir::RecordType>())
-          TODO(loc, "derived type argument passed by value");
         mlir::Type symType = converter.genType(sym);
         addr = builder.create<fir::AllocaOp>(loc, symType);
         if (isCptrByVal) {

flang/test/Lower/HLFIR/bindc-value-derived.f90

@@ -0,0 +1,37 @@
+! Test lowering of derived types passed with VALUE attribute in BIND(C)
+! interface. They are passed as fir.type<T> value. The actual C struct
+! passing ABI is done in code generation according to the target.
+
+! RUN: bbc -emit-hlfir -o - -I nw %s 2>&1 | FileCheck %s
+
+module bindc_byval
+  type, bind(c) :: t
+    integer :: i
+  end type
+contains
+  subroutine test(x) bind(c)
+    type(t), value :: x
+    call use_it(x%i)
+  end subroutine
+! CHECK-LABEL:   func.func @test(
+! CHECK-SAME:                    %[[VAL_0:.*]]: !fir.type<_QMbindc_byvalTt{i:i32}> {fir.bindc_name = "x"}) attributes {fir.bindc_name = "test"} {
+! CHECK:           %[[VAL_1:.*]] = fir.alloca !fir.type<_QMbindc_byvalTt{i:i32}>
+! CHECK:           fir.store %[[VAL_0]] to %[[VAL_1]] : !fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>
+! CHECK:           %[[VAL_2:.*]]:2 = hlfir.declare %[[VAL_1]] {fortran_attrs = #fir.var_attrs<value>, uniq_name = "_QMbindc_byvalFtestEx"} : (!fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>) -> (!fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>, !fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>)
+! CHECK:           %[[VAL_3:.*]] = hlfir.designate %[[VAL_2]]#0{"i"}   : (!fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>) -> !fir.ref<i32>
+! CHECK:           fir.call @_QPuse_it(%[[VAL_3]]) fastmath<contract> : (!fir.ref<i32>) -> ()
+! CHECK:           return
+! CHECK:         }
+
+  subroutine call_it(x)
+    type(t) x
+    call test(x)
+  end subroutine
+! CHECK-LABEL:   func.func @_QMbindc_byvalPcall_it(
+! CHECK-SAME:                                      %[[VAL_0:.*]]: !fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>> {fir.bindc_name = "x"}) {
+! CHECK:           %[[VAL_1:.*]]:2 = hlfir.declare %[[VAL_0]] {uniq_name = "_QMbindc_byvalFcall_itEx"} : (!fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>) -> (!fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>, !fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>)
+! CHECK:           %[[VAL_2:.*]] = fir.load %[[VAL_1]]#1 : !fir.ref<!fir.type<_QMbindc_byvalTt{i:i32}>>
+! CHECK:           fir.call @test(%[[VAL_2]]) fastmath<contract> : (!fir.type<_QMbindc_byvalTt{i:i32}>) -> ()
+! CHECK:           return
+! CHECK:         }
+end module