On Sunday, July 28, 2002, at 07:50 PM, Erik Eid wrote:
I also replaced the jsr-jmp pairs in StageJumpTable with jsr-rts
pairs. I
put the indirect jump in its own subroutine, which allowed me to use rts
to get out of the jump table after each stage routine finished. (A side
effect was that I only had to multiply the stage number by four instead
of
six, saving a few bytes more.) Since the jump table is fairly long,
please
see the source if you are interested in looking at it.
If you have a jsr instruction followed by an rts instruction, you can
replace the jsr instruction with a jmp instruction, removing the rts.
This was commonly done in C-64 programs. It saves stack space, and
instruction cycles. Normally, you would remove the rts, but your
calculation is relying on the entry points being offset by four bytes.
You could replace the rts instruction with nop, to make it clear that
the rts is not required.
a two byte instruction as a three byte bit instruction to a memory
location.)
Every byte and every cycle is important.
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