collapseos/apps/forth/stack.asm

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2020-03-07 12:13:15 -05:00
; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
; maintained by IX. This allows us to generally use push and pop freely because
; PS is the most frequently used. However, this causes a problem with routine
; calls: because in Forth, the stack isn't balanced within each call, our return
; offset, when placed by a CALL, messes everything up. This is one of the
; reasons why we need stack management routines below.
;
; This return stack contain "Interpreter pointers", that is a pointer to the
; address of a word, as seen in a compiled list of words.
; Push value HL to RS
pushRS:
ld (ix), l
inc ix
ld (ix), h
inc ix
ret
; Pop RS' TOS to HL
popRS:
dec ix
ld h, (ix)
dec ix
ld l, (ix)
ret