[flang][optimizer] support aggregate types inside tuple and record type

This patch allows:
 - fir.box type to be a member of tuple<> or fir.type<> types,
 - tuple<> type to be a member of tuple<> type.

When a fir.box types are nested in tuple<> or fir.type<>, it is translated
to the struct type of a Fortran runtime descriptor, and not a
pointer to a descriptor. This is because the fir.box is owned by the tuple
or fir.type.

FIR type translation was also flattening nested tuple while lowering to LLVM
dialect types. There does not seem to be a deep reason for doing that
and doing it causes issues in fir.coordinate_of generated on such tuple
(a fir.coordinate_of getting tuple<B, C> in tuple<A, tuple<B, C>>
ended-up lowered to an LLVM GEP getting B).

Differential Revision: https://reviews.llvm.org/D118701

flang/lib/Optimizer/CodeGen/TypeConverter.h

@@ -111,11 +111,15 @@ public:
     });
     addConversion([&](mlir::TupleType tuple) {
       LLVM_DEBUG(llvm::dbgs() << "type convert: " << tuple << '\n');
-      llvm::SmallVector<mlir::Type> inMembers;
-      tuple.getFlattenedTypes(inMembers);
       llvm::SmallVector<mlir::Type> members;
-      for (auto mem : inMembers)
-        members.push_back(convertType(mem).cast<mlir::Type>());
+      for (auto mem : tuple.getTypes()) {
+        // Prevent fir.box from degenerating to a pointer to a descriptor in the
+        // context of a tuple type.
+        if (auto box = mem.dyn_cast<fir::BoxType>())
+          members.push_back(convertBoxTypeAsStruct(box));
+        else
+          members.push_back(convertType(mem).cast<mlir::Type>());
+      }
       return mlir::LLVM::LLVMStructType::getLiteral(&getContext(), members,
                                                     /*isPacked=*/false);
     });
@@ -140,7 +144,12 @@ public:
     }
     llvm::SmallVector<mlir::Type> members;
     for (auto mem : derived.getTypeList()) {
-      members.push_back(convertType(mem.second).cast<mlir::Type>());
+      // Prevent fir.box from degenerating to a pointer to a descriptor in the
+      // context of a record type.
+      if (auto box = mem.second.dyn_cast<fir::BoxType>())
+        members.push_back(convertBoxTypeAsStruct(box));
+      else
+        members.push_back(convertType(mem.second).cast<mlir::Type>());
     }
     if (mlir::failed(st.setBody(members, /*isPacked=*/false)))
       return failure();
@@ -227,6 +236,14 @@ public:
                                                /*isPacked=*/false));
   }
 
+  /// Convert fir.box type to the corresponding llvm struct type instead of a
+  /// pointer to this struct type.
+  mlir::Type convertBoxTypeAsStruct(BoxType box) {
+    return convertBoxType(box)
+        .cast<mlir::LLVM::LLVMPointerType>()
+        .getElementType();
+  }
+
   unsigned characterBitsize(fir::CharacterType charTy) {
     return kindMapping.getCharacterBitsize(charTy.getFKind());
   }

flang/lib/Optimizer/Dialect/FIRType.cpp

@@ -61,11 +61,11 @@ static bool isaIntegerType(mlir::Type ty) {
 }
 
 bool verifyRecordMemberType(mlir::Type ty) {
-  return !(ty.isa<BoxType>() || ty.isa<BoxCharType>() ||
-           ty.isa<BoxProcType>() || ty.isa<ShapeType>() ||
-           ty.isa<ShapeShiftType>() || ty.isa<ShiftType>() ||
-           ty.isa<SliceType>() || ty.isa<FieldType>() || ty.isa<LenType>() ||
-           ty.isa<ReferenceType>() || ty.isa<TypeDescType>());
+  return !(ty.isa<BoxCharType>() || ty.isa<BoxProcType>() ||
+           ty.isa<ShapeType>() || ty.isa<ShapeShiftType>() ||
+           ty.isa<ShiftType>() || ty.isa<SliceType>() || ty.isa<FieldType>() ||
+           ty.isa<LenType>() || ty.isa<ReferenceType>() ||
+           ty.isa<TypeDescType>());
 }
 
 bool verifySameLists(llvm::ArrayRef<RecordType::TypePair> a1,

flang/test/Fir/types-to-llvm.fir

@@ -400,3 +400,21 @@ func private @foo2(%arg : !fir.tdesc<f32>)
 func private @foo3(%arg : !fir.tdesc<!fir.type<derived7{f1:f32,f2:f32}>>)
 // CHECK-LABEL: foo3
 // CHECK-SAME:  !llvm.ptr<i8>
+
+// -----
+
+// Test nested tuple types
+func private @foo0(%arg0: tuple<i64, tuple<f32, i64>>)
+// CHECK-LABEL: foo0
+// CHECK-SAME: !llvm.struct<(i64, struct<(f32, i64)>)>
+
+// -----
+
+// Test that fir.box inside tuple and derived type are lowered to struct type.
+func private @foo0(%arg0: tuple<i64, !fir.box<i32>>)
+// CHECK-LABEL: foo0
+// CHECK-SAME: !llvm.struct<(i64, struct<(ptr<i32>, i{{.*}})>)>
+
+func private @foo1(%arg0: !fir.type<derived8{a:i64,b:!fir.box<i32>}>)
+// CHECK-LABEL: foo1
+// CHECK-SAME: !llvm.struct<"derived8", (i64, struct<(ptr<i32>, i{{.*}})>)>