PIC code in function prologue

[kernel coder]

hi,
    I'm having some trouble while understanding the following pic
code in function prologue of cris architecture.

if (current_function_uses_pic_offset_table)
   {
     /* A reference may have been optimized out (like the abort () in
        fde_split in unwind-dw2-fde.c, at least 3.2.1) so check that
        it's still used.  */
     push_topmost_sequence ();
     got_really_used
       = reg_used_between_p (pic_offset_table_rtx, get_insns (), NULL_RTX);
     pop_topmost_sequence ();
   }

Is this pic offset table ,the same global offset table.Does
current_function_uses_pic_offset_table means that call to current
function is made through GOT.where this variable
(current_function_uses_pic_offset_table) is being set.

What is happening in next 3 lines
    push_topmost_sequence ();
     got_really_used
       = reg_used_between_p (pic_offset_table_rtx, get_insns (), NULL_RTX);
     pop_topmost_sequence ();

what does  pic_offset_table_rtx contain.

thanks,
shahzad