eis_tester documentation of -io option confused

[canthony]

AR97-3 System Diagnostic Aids, page 2-50:

"-io N

defines the instruction offset. It is used to position the instruction
relative to a page boundary. The default is 0. This places the
instruction at word 0 of the second page of the instruction area. X
indicates the number of words of the instruction to be placed in the
first page of the instruction are. The maximum value of X is 3."

The source code (bound_eis_test_.s$et_inst.pl1) is a bit clearer:

• h) -io X X defines the Instruction Offset. It is used to position
• the instruction on a page boundary. The default is 0. This
• will place the instruction at word 0 of the second page
• of the instruction area. X indicates the number of words of
• the instruction which will be placed in the first page of the
• instruction area. The maximum value of X is 3.

However, it is still internally inconsistent. Is X the offset or the length?

Looking at the code (bound_eis_tester.s$et.pl1), is seems to be offset:

/* Get a pointer to where we must place the instruction. Note, the instruction

• area words that are not used are left as nops. Once we have the pointer
• we will move the instruction word. Note, the instruction offset defined by
• the user is backwards as far as we are concerned. We need the offset from the
• beginning of the instruction area. We will convert it.

*/

our_offset = (instr_offset - 3)* (-1);

instr_ptr = addrel (addr (etx$instruction_area), our_offset);

instr_ptr -> eis_map.instruction = instr_word;