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Update sketch to suggest use of `*ADDR`

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n loewen 2023-08-15 21:31:35 +01:00
parent 4e01a0943c
commit 8f9f50e28c
1 changed files with 50 additions and 39 deletions
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89
test-programs/subroutines.asm
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@ -1,5 +1,10 @@
;; sketching around subroutines with return stack ;; sketching around subroutines with return stack
; I think the sketching below contains some useful ideas,
; but the new `*ADDR` assembly op should make this a whole lot simpler
; sketches follow ..........
; jump table ; jump table
; ---------- ; ----------
; each function has a label ; each function has a label
@ -10,53 +15,59 @@
; then when the subroutine ends, it jumps here ; then when the subroutine ends, it jumps here
; where that number gets mapped back onto the function's label ; where that number gets mapped back onto the function's label
lda $1 =*reentryPoint
=routine1 $1
lda =routine1
sto $19 ; contains ID # for the next fn to jump to sto $19 ; contains ID # for the next fn to jump to
@jump_table @jump_table
hop $1 hop $1
jmp @jt2 jmp @jt2
jmp @example_computation jmp @example_computation
@jt2
hop $2 @jt2
; jmp @jt3 hop $2
nop ; jmp @jt3
; etc … nop
jmp @end ; etc …
jmp @end
@example_computation @example_computation
lda 5 lda 5
sto $20 sto $20
lda 3 lda 3
sto $21 sto $21
; $19 still has the # for this routine ; $19 still has the # for this routine
; but let’s pretend it doesn’t and demonstrate updating it ; but let’s pretend it doesn’t and demonstrate updating it
lda $1 lda $1
sto $19 sto $19
jmp @greater? jmp @greater?
; call with numbers to test in $20 and $21 ; call with numbers to test in $20 and $21
; result is stored in acc ; result is stored in acc
@greater? @greater?
; lda ($20) ; lda ($20)
; sub ($21) ; sub ($21)
; todo… ; todo…
; wouldn’t it be great to have a “hop if neg” op… ; wouldn’t it be great to have a “hop if neg” op…
; do we have to just subtract numbers until we get 0? ; do we have to just subtract numbers until we get 0?
; no! ; no!
; here’s an approach that’s at least better than that ; here’s an approach that’s at least better than that
lda ($21) lda ($21)
sto $22 ; stash sto $22 ; stash
@loop @loop
lda ($21) lda ($21)
sub $1 sub $1
sto $22 ; stash sto $22 ; stash
sub ($20) sub ($20)
hop $0 hop $0
jmp @loop jmp @loop
sto $1 sto $1
jmp $jmp_table jmp $jmp_table
; ok this isn’t quite it… we also need to chexk if we hit 0 by just deceementinf and if so retuen 0 ; ok this isn’t quite it… we also need to chexk if we hit 0 by just deceementinf and if so retuen 0
jmp @jump_table @end
END