175 lines
3.6 KiB
NASM
175 lines
3.6 KiB
NASM
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; ops
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; - [ ] nat (positive integers)
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; - [ ] * mult (i think anything bigger than 16 bits just gets cut off, george does not need big numbers rite)
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; - [ ] / div (what do we do w fractions/remainders)
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; - [ ] + add (same w *)
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; - [ ] - sub (what should happen when y > x & x - y? )
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; - [ ] int (pos/neg 2s complement numbers) (lots of the above applies)
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; - [ ] * mult
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; - [ ] / div
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; - [ ] + add
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; - [ ] - sub
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; - [ ] bool
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; - [ ] & and
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; - [ ] | or
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;
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; literals (these will be macros here, meaning when i implement them in the compiler they will depend on what literals r being pushed)
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; - [ ] bool
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; - [ ] num
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; - [ ] str
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; - [ ] char
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;
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; i/o
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; - [ ] write (pop off an address and some data and store it)
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; - [ ] read (pop off an address and push the data at that address onto the stack)
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; - [ ] key (stealing algo from forth: pause execution until there's a key pressed, then push that key on the stack, i don't think this breaks anything, this could probably be written easily in fuzzy w/ write and read words)
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;
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; control flow
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; - [ ] if (pop off a bool and jump to word, this will also depend on compiler, so writing as macro)
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; for example
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; a is nat: 5
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; b is nat: 3
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; c bool is nat: if[a | b] *we'll figure out syntax later*
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; true c
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;
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; (assuming c gets inlined since it's only referenced in the body)
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; compiles to
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; a:
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; lda 5
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; dex
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; dex
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; sta 0, x
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; rts
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;
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; b:
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; lda 3
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; dex
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; dex
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; sta 0, x
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; rts
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;
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; main:
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; lda #1
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; dex
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; dex
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; sta 0, x
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; stz 1,x
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; lda #1
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; inx
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; inx
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; bit 2, x
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; beq .falsy
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; jsr a
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; .falsy:
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; jsr b
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; stp ; or whatever here
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; literals - the important thing is what the actual value is, each of these functions/macros are the same for any type, since the val is always just a 16 bit number
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.macro lit, val
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lda val
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dex
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dex
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sta 0, x
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stz 1, x
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.endm
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; control flow
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.macro if, bool, addr ; condition, where to jump if true; pops a bool off the stack
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lda #1
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; in either case we pop a cell off the top
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inx
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inx
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; but still need to check the bool on top
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; TODO: make sure this works
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bit 2, x
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beq .falsy
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; TODO: words will be defined as subroutines ig,
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; and will be returned from after execution
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jsr addr
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.falsy:
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.endm
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; ops
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nat_plus:
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clc
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lda 0, x
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adc 2, x
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sta 2, x
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lda 1, x
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adc 3, x
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sta 3, x
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inx
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inx
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rts
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nat_mult_2:
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asl 0, x
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rol 1, x
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rts
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; after a silly escapade plotting u16 overflow charts
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; i am making the executive decision that the vast majority
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; of results (those that overflow 2 bytes) will be wrong :)
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; for the sake of all results being 1 cell wide :)
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; see this plot: ./overflow.png
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; algo here: https://www.llx.com/Neil/a2/mult.html
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nat_mult:
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result = $200
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lda #0 ; initialize result to 0
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sta result+2
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ldy #16 ; 16 bits in NUM2
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.1:
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lsr 0, x ; low byte of first number
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ror 1, x
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bcc .2 ; 0 or 1?
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phy ; some register shuffling so we don't lose x stack pointer
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tay
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clc
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lda 2, x ; low byte of second number
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adc result + 2 ; add it to low byte of result
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sta result + 2
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tya
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ply
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adc 3, x ;
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.2:
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ror
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ror result + 2
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ror result + 1
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ror result
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dey
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bne .1
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sta result + 3
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dex
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dex
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; TODO: double check endianness of result
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lda result + 3 ; store high byte of result
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sta 0, x
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lda result + 2 ; store low byte of result
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sta 1, x
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rts
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; i/o
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read:
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lda (0, x)
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sta 0, x
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stz 1, x
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rts
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write:
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lda 0, x
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sta (2, x)
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inx
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inx
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inx
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inx
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rts
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key:
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;TODO
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