[flang] Load unlimited polymorphic box the same way as other

Unlimited polymorphic descriptor have a set size and can be loaded the
same way as polymorphic or monomorphic descriptors. The descriptor
code gen as been set in D138587.
Of course, the data hold by those descriptors have an unknown size
at compile time.

Depends on D141383

Reviewed By: jeanPerier, PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D141390

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -3013,12 +3013,11 @@ struct LoadOpConversion : public FIROpConversion<fir::LoadOp> {
       auto inputBoxStorage = adaptor.getOperands()[0];
       mlir::Location loc = load.getLoc();
       fir::SequenceType seqTy = fir::unwrapUntilSeqType(boxTy);
-      mlir::Type eleTy = fir::unwrapPassByRefType(boxTy);
-      // fir.box of assumed rank and polymorphic entities do not have a storage
+      // fir.box of assumed rank do not have a storage
       // size that is know at compile time. The copy needs to be runtime driven
       // depending on the actual dynamic rank or type.
-      if (eleTy.isa<mlir::NoneType>() || (seqTy && seqTy.hasUnknownShape()))
-        TODO(loc, "loading polymorphic or assumed rank fir.box");
+      if (seqTy && seqTy.hasUnknownShape())
+        TODO(loc, "loading or assumed rank fir.box");
       mlir::Type boxPtrTy = inputBoxStorage.getType();
       auto boxValue = rewriter.create<mlir::LLVM::LoadOp>(
           loc, boxPtrTy.cast<mlir::LLVM::LLVMPointerType>().getElementType(),

flang/test/Fir/polymorphic.fir

@@ -159,4 +159,27 @@ func.func @_QQmain() {
 // CHECK: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD]], ptr %[[DESC]]
 // CHECK: call void @_QMmod1Psub1(ptr %[[DESC]])
 
+fir.global @_QMmod2Ep : !fir.class<!fir.ptr<none>> {
+  %0 = fir.zero_bits !fir.ptr<none>
+  %1 = fir.embox %0 : (!fir.ptr<none>) -> !fir.class<!fir.ptr<none>>
+  fir.has_value %1 : !fir.class<!fir.ptr<none>>
+}
+func.func @_QMmod2Pinitp(%arg0: !fir.ref<!fir.class<!fir.ptr<none>>> {fir.bindc_name = "target"}) {
+  %0 = fir.address_of(@_QMmod2Ep) : !fir.ref<!fir.class<!fir.ptr<none>>>
+  %1 = fir.load %arg0 : !fir.ref<!fir.class<!fir.ptr<none>>>
+  %2 = fir.convert %0 : (!fir.ref<!fir.class<!fir.ptr<none>>>) -> !fir.ref<!fir.box<none>>
+  %3 = fir.convert %1 : (!fir.class<!fir.ptr<none>>) -> !fir.box<none>
+  %4 = fir.call @_FortranAPointerAssociate(%2, %3) fastmath<contract> : (!fir.ref<!fir.box<none>>, !fir.box<none>) -> none
+  return
+}
+func.func private @_FortranAPointerAssociate(!fir.ref<!fir.box<none>>, !fir.box<none>) -> none attributes {fir.runtime}
+
+// CHECK-LABEL: define void @_QMmod2Pinitp(
+// CHECK-SAME: ptr %[[ARG0:.*]]) {
+// CHECK: %[[ALLOCA_CLASS_NONE:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }
+// CHECK: %[[LOAD:.*]] = load { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] }, ptr %[[ARG0]]
+// CHECK: store { ptr, i64, i32, i8, i8, i8, i8, ptr, [1 x i64] } %[[LOAD]], ptr %[[ALLOCA_CLASS_NONE]]
+// CHECK: %{{.*}} = call {} @_FortranAPointerAssociate(ptr @_QMmod2Ep, ptr %[[ALLOCA_CLASS_NONE]])
+// CHECK: ret void
+