Started with r10 (between 20191215 and 20200105) :


$ cat z1.f90
program p
   type t
   end type
   class(t), allocatable :: a(:)
   !$acc update host(a)
end


$ gfortran-10-20191215 -c z1.f90 -fopenacc
z1.f90:5:21:

    5 |    !$acc update host(a)
      |                     1
Error: ALLOCATABLE object 'a' of polymorphic type in MAP clause at (1)


$ gfortran-11-20210418 -c z1.f90 -fopenacc
z1.f90:5:23:

    5 |    !$acc update host(a)
      |                       ^
internal compiler error: in gimplify_expr, at gimplify.c:15095
0x9aa933 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*), int)
        ../../gcc/gimplify.c:15095
0x9aa593 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*), int)
        ../../gcc/gimplify.c:14204
0x9a2651 gimplify_scan_omp_clauses
        ../../gcc/gimplify.c:9430
0x9a7bf3 gimplify_omp_target_update
        ../../gcc/gimplify.c:13413
0x9a7bf3 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*), int)
        ../../gcc/gimplify.c:14623
0x9aa978 gimplify_stmt(tree_node**, gimple**)
        ../../gcc/gimplify.c:6877
0x9a8d33 gimplify_statement_list
        ../../gcc/gimplify.c:1879
0x9a8d33 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*), int)
        ../../gcc/gimplify.c:14528
0x9aa978 gimplify_stmt(tree_node**, gimple**)
        ../../gcc/gimplify.c:6877
0x9aaed1 gimplify_bind_expr
        ../../gcc/gimplify.c:1421
0x9a85f2 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*), int)
        ../../gcc/gimplify.c:14284
0x9aa978 gimplify_stmt(tree_node**, gimple**)
        ../../gcc/gimplify.c:6877
0x9ab99d gimplify_body(tree_node*, bool)
        ../../gcc/gimplify.c:15320
0x9abdff gimplify_function_tree(tree_node*)
        ../../gcc/gimplify.c:15474
0x8480f7 cgraph_node::analyze()
        ../../gcc/cgraphunit.c:670
0x84aa47 analyze_functions
        ../../gcc/cgraphunit.c:1236
0x84b40d symbol_table::finalize_compilation_unit()
        ../../gcc/cgraphunit.c:2510