question in porting gcc front end

[zouq]

i write a front-end , and compile it with gcc-3.4.1 source code,
and it errors in function rest_of_compilation()
void
rest_of_compilation (tree decl)
{
  rtx insns;

  timevar_push (TV_REST_OF_COMPILATION);

  rtl_register_cfg_hooks ();

  generating_concat_p = 0;

  cse_not_expected = ! optimize;

                                                                                
                                             /*
First,
make
sure
that
NOTE_BLOCK
is
set
correctly
for
each
     NOTE_INSN_BLOCK_BEG/NOTE_INSN_BLOCK_END note.  */
  if (!cfun->x_whole_function_mode_p)
    identify_blocks ();

   ....................

}

:internal compiler error: in identify_blocks_1, at function.c:6090

idendify_blocks()
{
................
  last_block_vector = identify_blocks_1 (get_insns (),
                     block_vector + 1,
                     block_vector + n_blocks,
                     block_stack);

   .................................
}

it seems that i haven`t give the block information for current_function_decl.
because when i gdb it, the n_blocks=1;

when should i build the block structure?