[Flang]: Lowering reference to functions that return a procedure pointer

flang/lib/Lower/CallInterface.cpp

@@ -371,7 +371,7 @@ bool Fortran::lower::CallerInterface::mustMapInterfaceSymbols() const {
   const std::optional<Fortran::evaluate::characteristics::FunctionResult>
       &result = characteristic->functionResult;
   if (!result || result->CanBeReturnedViaImplicitInterface() ||
-      !getInterfaceDetails())
+      !getInterfaceDetails() || result->IsProcedurePointer())
     return false;
   bool allResultSpecExprConstant = true;
   auto visitor = [&](const Fortran::lower::SomeExpr &e) {
@@ -1111,39 +1111,40 @@ class Fortran::lower::CallInterfaceImpl {
       const Fortran::evaluate::characteristics::FunctionResult &result) {
     using Attr = Fortran::evaluate::characteristics::FunctionResult::Attr;
     mlir::Type mlirType;
-    if (auto proc{result.IsProcedurePointer()})
+    if (auto proc{result.IsProcedurePointer()}) {
       mlirType = fir::BoxProcType::get(
           &mlirContext, getProcedureType(*proc, interface.converter));
-    else {
-      const Fortran::evaluate::characteristics::TypeAndShape *typeAndShape =
-          result.GetTypeAndShape();
-      assert(typeAndShape && "expect type for non proc pointer result");
-      mlirType = translateDynamicType(typeAndShape->type());
-      const auto *resTypeAndShape{result.GetTypeAndShape()};
-      bool resIsPolymorphic =
-          resTypeAndShape && resTypeAndShape->type().IsPolymorphic();
-      bool resIsAssumedType =
-          resTypeAndShape && resTypeAndShape->type().IsAssumedType();
-      if (std::optional<fir::SequenceType::Shape> bounds =
-              getBounds(*typeAndShape))
-        mlirType = fir::SequenceType::get(*bounds, mlirType);
-      if (result.attrs.test(Attr::Allocatable))
-        mlirType = fir::wrapInClassOrBoxType(
-            fir::HeapType::get(mlirType), resIsPolymorphic, resIsAssumedType);
-      if (result.attrs.test(Attr::Pointer))
-        mlirType =
-            fir::wrapInClassOrBoxType(fir::PointerType::get(mlirType),
-                                      resIsPolymorphic, resIsAssumedType);
-
-      if (fir::isa_char(mlirType)) {
-        // Character scalar results must be passed as arguments in lowering so
-        // that an assumed length character function callee can access the
-        // result length. A function with a result requiring an explicit
-        // interface does not have to be compatible with assumed length
-        // function, but most compilers supports it.
-        handleImplicitCharacterResult(typeAndShape->type());
-        return;
-      }
+      addFirResult(mlirType, FirPlaceHolder::resultEntityPosition,
+                   Property::Value);
+      return;
+    }
+    const Fortran::evaluate::characteristics::TypeAndShape *typeAndShape =
+        result.GetTypeAndShape();
+    assert(typeAndShape && "expect type for non proc pointer result");
+    mlirType = translateDynamicType(typeAndShape->type());
+    const auto *resTypeAndShape{result.GetTypeAndShape()};
+    bool resIsPolymorphic =
+        resTypeAndShape && resTypeAndShape->type().IsPolymorphic();
+    bool resIsAssumedType =
+        resTypeAndShape && resTypeAndShape->type().IsAssumedType();
+    if (std::optional<fir::SequenceType::Shape> bounds =
+            getBounds(*typeAndShape))
+      mlirType = fir::SequenceType::get(*bounds, mlirType);
+    if (result.attrs.test(Attr::Allocatable))
+      mlirType = fir::wrapInClassOrBoxType(fir::HeapType::get(mlirType),
+                                           resIsPolymorphic, resIsAssumedType);
+    if (result.attrs.test(Attr::Pointer))
+      mlirType = fir::wrapInClassOrBoxType(fir::PointerType::get(mlirType),
+                                           resIsPolymorphic, resIsAssumedType);
+
+    if (fir::isa_char(mlirType)) {
+      // Character scalar results must be passed as arguments in lowering so
+      // that an assumed length character function callee can access the
+      // result length. A function with a result requiring an explicit
+      // interface does not have to be compatible with assumed length
+      // function, but most compilers supports it.
+      handleImplicitCharacterResult(typeAndShape->type());
+      return;
     }
 
     addFirResult(mlirType, FirPlaceHolder::resultEntityPosition,

flang/lib/Lower/ConvertCall.cpp

@@ -1379,6 +1379,9 @@ genUserCall(Fortran::lower::PreparedActualArguments &loweredActuals,
       loc, callContext.converter, callContext.symMap, callContext.stmtCtx,
       caller, callSiteType, callContext.resultType,
       callContext.isElementalProcWithArrayArgs());
+  // For procedure pointer function result, just return the call.
+  if (callContext.resultType && callContext.resultType->isa<fir::BoxProcType>())
+    return hlfir::EntityWithAttributes(fir::getBase(result));
 
   /// Clean-up associations and copy-in.
   for (auto cleanUp : callCleanUps)

flang/lib/Lower/ConvertExprToHLFIR.cpp

@@ -1433,9 +1433,13 @@ class HlfirBuilder {
   }
 
   hlfir::EntityWithAttributes gen(const Fortran::evaluate::ProcedureRef &expr) {
-    TODO(
-        getLoc(),
-        "lowering function references that return procedure pointers to HLFIR");
+    Fortran::evaluate::ProcedureDesignator proc{expr.proc()};
+    auto procTy{Fortran::lower::translateSignature(proc, getConverter())};
+    auto result = Fortran::lower::convertCallToHLFIR(getLoc(), getConverter(),
+                                                     expr, procTy.getResult(0),
+                                                     getSymMap(), getStmtCtx());
+    assert(result.has_value());
+    return *result;
   }
 
   template <typename T>

flang/lib/Optimizer/Builder/IntrinsicCall.cpp

@@ -2158,9 +2158,13 @@ fir::ExtendedValue
 IntrinsicLibrary::genAssociated(mlir::Type resultType,
                                 llvm::ArrayRef<fir::ExtendedValue> args) {
   assert(args.size() == 2);
-  if (fir::isBoxProcAddressType(fir::getBase(args[0]).getType())) {
+  mlir::Type ptrTy = fir::getBase(args[0]).getType();
+  if (ptrTy &&
+      (fir::isBoxProcAddressType(ptrTy) || ptrTy.isa<fir::BoxProcType>())) {
     mlir::Value pointerBoxProc =
-        builder.create<fir::LoadOp>(loc, fir::getBase(args[0]));
+        fir::isBoxProcAddressType(ptrTy)
+            ? builder.create<fir::LoadOp>(loc, fir::getBase(args[0]))
+            : fir::getBase(args[0]);
     mlir::Value pointerTarget =
         builder.create<fir::BoxAddrOp>(loc, pointerBoxProc);
     if (isStaticallyAbsent(args[1]))

flang/test/Lower/HLFIR/procedure-pointer.f90

@@ -2,6 +2,7 @@
 ! 1. declaration and initialization
 ! 2. pointer assignment and invocation
 ! 3. procedure pointer argument passing.
+! 3. procedure pointer function result.
 ! RUN: bbc -emit-hlfir -o - %s | FileCheck %s
 
 module m
@@ -244,6 +245,67 @@ subroutine sub9()
 ! CHECK: fir.call @_QPfoo2(%[[VAL_10]]) fastmath<contract> : (!fir.ref<!fir.boxproc<() -> ()>>) -> ()
 end
 
+subroutine sub10()
+use m
+
+  procedure(real_func), pointer :: p1
+! CHECK: %[[VAL_0:.*]] = fir.alloca !fir.boxproc<(!fir.ref<f32>) -> f32> {bindc_name = "p1", uniq_name = "_QFsub10Ep1"}
+! CHECK: %[[VAL_1:.*]] = fir.zero_bits (!fir.ref<f32>) -> f32
+! CHECK: %[[VAL_2:.*]] = fir.emboxproc %[[VAL_1]] : ((!fir.ref<f32>) -> f32) -> !fir.boxproc<(!fir.ref<f32>) -> f32>
+! CHECK: fir.store %[[VAL_2]] to %[[VAL_0]] : !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>
+! CHECK: %[[VAL_3:.*]]:2 = hlfir.declare %[[VAL_0]] {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFsub10Ep1"} : (!fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>) -> (!fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>, !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>)
+
+  p1 => reffunc(5)
+! CHECK: %c5_i32 = arith.constant 5 : i32
+! CHECK: %[[VAL_4:.*]]:3 = hlfir.associate %c5_i32 {adapt.valuebyref} : (i32) -> (!fir.ref<i32>, !fir.ref<i32>, i1)
+! CHECK: %[[VAL_5:.*]] = fir.call @_QFsub10Preffunc(%[[VAL_4]]#1) fastmath<contract> : (!fir.ref<i32>) -> !fir.boxproc<(!fir.ref<f32>) -> f32>
+! CHECK: fir.store %[[VAL_5]] to %[[VAL_3]]#0 : !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>
+
+contains
+  function reffunc(arg) result(pp)
+    integer :: arg
+    procedure(real_func), pointer :: pp
+! CHECK: %[[VAL_0:.*]]:2 = hlfir.declare %arg0 {uniq_name = "_QFsub10FreffuncEarg"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[VAL_1:.*]] = fir.alloca !fir.boxproc<(!fir.ref<f32>) -> f32> {bindc_name = "pp", uniq_name = "_QFsub10FreffuncEpp"}
+! CHECK: %[[VAL_2:.*]] = fir.zero_bits (!fir.ref<f32>) -> f32
+! CHECK: %[[VAL_3:.*]] = fir.emboxproc %[[VAL_2]] : ((!fir.ref<f32>) -> f32) -> !fir.boxproc<(!fir.ref<f32>) -> f32>
+! CHECK: fir.store %[[VAL_3]] to %[[VAL_1]] : !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>
+! CHECK: %[[VAL_4:.*]]:2 = hlfir.declare %[[VAL_1]] {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFsub10FreffuncEpp"} : (!fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>) -> (!fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>, !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>)
+
+    pp => real_func
+! CHECK: %[[VAL_5:.*]] = fir.address_of(@_QPreal_func) : (!fir.ref<f32>) -> f32
+! CHECK: %[[VAL_6:.*]] = fir.emboxproc %[[VAL_5]] : ((!fir.ref<f32>) -> f32) -> !fir.boxproc<() -> ()>
+! CHECK: %[[VAL_7:.*]] = fir.convert %[[VAL_6]] : (!fir.boxproc<() -> ()>) -> !fir.boxproc<(!fir.ref<f32>) -> f32>
+! CHECK: fir.store %[[VAL_7]] to %[[VAL_4]]#0 : !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>
+! CHECK: %[[VAL_8:.*]] = fir.load %[[VAL_4]]#1 : !fir.ref<!fir.boxproc<(!fir.ref<f32>) -> f32>>
+! CHECK: return %[[VAL_8]] : !fir.boxproc<(!fir.ref<f32>) -> f32>
+  end
+end
+
+subroutine sub11()
+use m
+  interface
+    function reffunc(arg) result(pp)
+      import
+      integer :: arg
+      procedure(char_func), pointer :: pp
+    end
+  end interface
+
+  procedure(char_func), pointer :: p1
+! CHECK: %[[VAL_0:.*]] = fir.alloca !fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>> {bindc_name = "p1", uniq_name = "_QFsub11Ep1"}
+! CHECK: %[[VAL_1:.*]] = fir.zero_bits (!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>
+! CHECK: %[[VAL_2:.*]] = fir.emboxproc %[[VAL_1]] : ((!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>) -> !fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>
+! CHECK: fir.store %[[VAL_2]] to %[[VAL_0]] : !fir.ref<!fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>>
+! CHECK: %[[VAL_3:.*]]:2 = hlfir.declare %[[VAL_0]] {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFsub11Ep1"} : (!fir.ref<!fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>>) -> (!fir.ref<!fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>>, !fir.ref<!fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>>)
+
+  p1 => reffunc(5)
+! CHECK: %c5_i32 = arith.constant 5 : i32
+! CHECK: %[[VAL_4:.*]]:3 = hlfir.associate %c5_i32 {adapt.valuebyref} : (i32) -> (!fir.ref<i32>, !fir.ref<i32>, i1)
+! CHECK: %[[VAL_5:.*]] = fir.call @_QPreffunc(%4#1) fastmath<contract> : (!fir.ref<i32>) -> !fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>
+! CHECK: fir.store %[[VAL_5]] to %[[VAL_3]]#0 : !fir.ref<!fir.boxproc<(!fir.ref<i32>) -> !fir.box<!fir.ptr<!fir.char<1,?>>>>>
+! CHECK: return
+end
 
 ! CHECK-LABEL: fir.global internal @_QFsub1Ep2 : !fir.boxproc<(!fir.ref<f32>) -> f32> {
 ! CHECK: %[[VAL_0:.*]] = fir.zero_bits (!fir.ref<f32>) -> f32

flang/test/Lower/Intrinsics/associated-proc-pointers.f90

@@ -114,3 +114,31 @@ character(10) function char_func()
 ! CHECK:           %[[VAL_18:.*]] = arith.cmpi ne, %[[VAL_17]], %[[VAL_14]] : i64
 ! CHECK:           %[[VAL_19:.*]] = arith.andi %[[VAL_16]], %[[VAL_18]] : i1
 ! CHECK:           %[[VAL_20:.*]] = fir.convert %[[VAL_19]] : (i1) -> !fir.logical<4>
+
+subroutine test_proc_pointer_6()
+  interface
+    real function func()
+    end
+  end interface
+  logical :: ll
+  ll = associated(reffunc(), func)
+contains
+  function reffunc() result(pp)
+    procedure(func), pointer :: pp
+  end
+end
+! CHECK: %[[VAL_0:.*]] = fir.alloca !fir.logical<4> {bindc_name = "ll", uniq_name = "_QFtest_proc_pointer_6Ell"}
+! CHECK: %[[VAL_1:.*]]:2 = hlfir.declare %[[VAL_0]] {uniq_name = "_QFtest_proc_pointer_6Ell"} : (!fir.ref<!fir.logical<4>>) -> (!fir.ref<!fir.logical<4>>, !fir.ref<!fir.logical<4>>)
+! CHECK: %[[VAL_2:.*]] = fir.call @_QFtest_proc_pointer_6Preffunc() fastmath<contract> : () -> !fir.boxproc<() -> f32>
+! CHECK: %[[VAL_3:.*]] = fir.address_of(@_QPfunc) : () -> f32
+! CHECK: %[[VAL_4:.*]] = fir.emboxproc %[[VAL_3]] : (() -> f32) -> !fir.boxproc<() -> ()>
+! CHECK: %[[VAL_5:.*]] = fir.box_addr %[[VAL_2]] : (!fir.boxproc<() -> f32>) -> (() -> f32)
+! CHECK: %[[VAL_6:.*]] = fir.box_addr %[[VAL_4]] : (!fir.boxproc<() -> ()>) -> (() -> ())
+! CHECK: %[[VAL_7:.*]] = fir.convert %[[VAL_5]] : (() -> f32) -> i64
+! CHECK: %[[VAL_8:.*]] = fir.convert %[[VAL_6]] : (() -> ()) -> i64
+! CHECK: %[[VAL_9:.*]] = arith.cmpi eq, %[[VAL_7]], %[[VAL_8]] : i64
+! CHECK: %c0_i64 = arith.constant 0 : i64
+! CHECK: %[[VAL_10:.*]] = arith.cmpi ne, %c0_i64, %[[VAL_7]] : i64
+! CHECK: %[[VAL_11:.*]] = arith.andi %[[VAL_9]], %[[VAL_10]] : i1
+! CHECK: %[[VAL_12:.*]] = fir.convert %[[VAL_11]] : (i1) -> !fir.logical<4>
+! CHECK: hlfir.assign %[[VAL_12]] to %[[VAL_1]]#0 : !fir.logical<4>, !fir.ref<!fir.logical<4>>