[flang][debug] Support ClassType.

This PR adds the handling of ClassType. It is treated as pointer to
the underlying type. Note that ClassType when passed to the function
have double indirection so it is represented as pointer to type
(and not type as a RecordType will be for example).

If ClassType wraps a pointer or allocatable then we take care to
avoid double indirection.

This is how it looks like in the debugger.

subroutine test_proc (this)
    class(test_type), intent (inout) :: this
    allocate (this%b (3, 2))
    call fill_array_2d (this%b)
    print *, this%a
end

(gdb) p this
$6 = (PTR TO -> ( Type test_type )) 0x2052a0
(gdb) p this%a
$7 = 0
(gdb) p this%b
$8 = ((1, 2, 3) (4, 5, 6))
(gdb)

Author: abidh

flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp

@@ -668,6 +668,20 @@ DebugTypeGenerator::convertType(mlir::Type Ty, mlir::LLVM::DIFileAttr fileAttr,
     return convertRecordType(recTy, fileAttr, scope, declOp);
   } else if (auto tupleTy = mlir::dyn_cast_if_present<mlir::TupleType>(Ty)) {
     return convertTupleType(tupleTy, fileAttr, scope, declOp);
+  } else if (auto classTy = mlir::dyn_cast_if_present<fir::ClassType>(Ty)) {
+    // ClassType when passed to the function have double indirection so it
+    // is represented as pointer to type (and not type as a RecordType will be
+    // for example). If ClassType wraps a pointer or allocatable then we get
+    // the real underlying type to avoid translating the Ty to
+    // Ptr -> Ptr -> type.
+    mlir::Type elTy = classTy.getEleTy();
+    if (auto ptrTy = mlir::dyn_cast_if_present<fir::PointerType>(elTy))
+      elTy = ptrTy.getElementType();
+    else if (auto heapTy = mlir::dyn_cast_if_present<fir::HeapType>(elTy))
+      elTy = heapTy.getElementType();
+    return convertPointerLikeType(elTy, fileAttr, scope, declOp,
+                                  /*genAllocated=*/false,
+                                  /*genAssociated=*/false);
   } else if (auto refTy = mlir::dyn_cast_if_present<fir::ReferenceType>(Ty)) {
     auto elTy = refTy.getEleTy();
     return convertPointerLikeType(elTy, fileAttr, scope, declOp,

flang/test/Transforms/debug-class-type.fir

@@ -0,0 +1,27 @@
+// RUN: fir-opt --add-debug-info --mlir-print-debuginfo %s | FileCheck %s
+
+module attributes {dlti.dl_spec = #dlti.dl_spec<>} {
+  fir.type_info @_QTtest_type nofinal : !fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}> dispatch_table {
+    fir.dt_entry "test_proc", @_QPtest_proc
+  } loc(#loc1)
+  func.func private @_QPtest_proc(%arg0: !fir.class<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>)
+
+    func.func @test()  {
+    %0 = fir.address_of(@_QFEx) : !fir.ref<!fir.class<!fir.heap<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>>
+    %1 = fircg.ext_declare %0 {uniq_name = "_QFEx"} : (!fir.ref<!fir.class<!fir.heap<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>>) -> !fir.ref<!fir.class<!fir.heap<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>> loc(#loc3)
+    %2 = fir.address_of(@_QFEy) : !fir.ref<!fir.class<!fir.ptr<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>>
+    %3 = fircg.ext_declare %2 {uniq_name = "_QFEy"} : (!fir.ref<!fir.class<!fir.ptr<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>>) -> !fir.ref<!fir.class<!fir.ptr<!fir.type<_QTtest_type{a:i32,b:!fir.box<!fir.heap<!fir.array<?x?xf32>>>}>>>> loc(#loc4)
+    return
+  } loc(#loc2)
+}
+
+#loc1 = loc("./simple.f90":2:1)
+#loc2 = loc("./simple.f90":10:1)
+#loc3 = loc("./simple.f90":15:1)
+#loc4 = loc("./simple.f90":22:1)
+
+// CHECK-DAG: #[[TY1:.*]] = #llvm.di_composite_type<{{.*}}name = "test_type"{{.*}}>
+// CHECK-DAG: #[[TY2:.*]] = #llvm.di_derived_type<tag = DW_TAG_pointer_type, name = "", baseType = #[[TY1]]{{.*}}>
+// CHECK-DAG: #llvm.di_subroutine_type<callingConvention = DW_CC_normal, types = #di_null_type, #[[TY2]]>
+// CHECK-DAG: #llvm.di_local_variable<{{.*}}name = "x"{{.*}}type = #[[TY2]]>
+// CHECK-DAG: #llvm.di_local_variable<{{.*}}name = "y"{{.*}}type = #[[TY2]]>