SixtyPical/doc/Emitting.markdown

Emitting Ophis from SixtyPical Programs
=======================================

    -> Tests for functionality "Emit ASM for SixtyPical program"
    
    -> Functionality "Emit ASM for SixtyPical program" is implemented by
    -> shell command "bin/sixtypical emit %(test-file)"

Big test for parsing and emitting instructions.

    | reserve word vword
    | reserve byte vbyte
    | assign byte table table 1024
    | routine main {
    |    lda #4
    |    ldx #0
    |    ldy #$FF
    |    lda vbyte
    |    lda table, x
    |    lda table, y
    |    lda (vword), y
    |    lda <vword
    |    lda >vword
    |    inc vbyte
    |    tax
    |    inx
    |    dex
    |    stx vbyte
    |    tay
    |    iny
    |    dey
    |    sty vbyte
    |    cmp vbyte
    |    cmp #30
    |    cmp <vword
    |    cmp >vword
    |    ldx vbyte
    |    cpx vbyte
    |    cpx #31
    |    txa
    |    ldy vbyte
    |    cpy vbyte
    |    cpy #32
    |    tya
    |    sta vbyte
    |    sta table, x
    |    sta table, y
    |    sta (vword), y
    |    sta <vword
    |    sta >vword
    |    dec vbyte
    |    clc
    |    cld
    |    clv
    |    sec
    |    sed
    |    adc #8
    |    adc vbyte
    |    and #8
    |    and vbyte
    |    sbc #8
    |    sbc vbyte
    |    ora #8
    |    ora vbyte
    | }
    = main:
    =   lda #4
    =   ldx #0
    =   ldy #255
    =   lda vbyte
    =   lda table, x
    =   lda table, y
    =   lda (vword), y
    =   lda vword
    =   lda vword+1
    =   inc vbyte
    =   tax
    =   inx
    =   dex
    =   stx vbyte
    =   tay
    =   iny
    =   dey
    =   sty vbyte
    =   cmp vbyte
    =   cmp #30
    =   cmp vword
    =   cmp vword+1
    =   ldx vbyte
    =   cpx vbyte
    =   cpx #31
    =   txa
    =   ldy vbyte
    =   cpy vbyte
    =   cpy #32
    =   tya
    =   sta vbyte
    =   sta table, x
    =   sta table, y
    =   sta (vword), y
    =   sta vword
    =   sta vword+1
    =   dec vbyte
    =   clc
    =   cld
    =   clv
    =   sec
    =   sed
    =   adc #8
    =   adc vbyte
    =   and #8
    =   and vbyte
    =   sbc #8
    =   sbc vbyte
    =   ora #8
    =   ora vbyte
    =   rts
    = 
    = vword: .word 0
    = vbyte: .byte 0
    = .alias table 1024

    | reserve word vword
    | reserve byte vbyte
    | assign byte table table 1024
    | routine main {
    |    asl
    |    asl vbyte
    |    lsr
    |    lsr vbyte
    |    rol
    |    rol vbyte
    |    ror
    |    ror vbyte
    |    bit vbyte
    |    eor #5
    |    eor vbyte
    | }
    = main:
    =   asl
    =   asl vbyte
    =   lsr
    =   lsr vbyte
    =   rol
    =   rol vbyte
    =   ror
    =   ror vbyte
    =   bit vbyte
    =   eor #5
    =   eor vbyte
    =   rts
    = 
    = vword: .word 0
    = vbyte: .byte 0
    = .alias table 1024

Emitting an `if`.

    | assign byte screen $0400
    | routine main {
    |    lda screen
    |    cmp screen
    |    if beq {
    |        tax
    |    } else {
    |        tay
    |    }
    |    sta screen
    | }
    = main:
    =   lda screen
    =   cmp screen
    =   BEQ _label_1
    =   tay
    =   jmp _past_1
    = _label_1:
    =   tax
    = _past_1:
    =   sta screen
    =   rts
    = 
    = .alias screen 1024

Emitting a `repeat`.

    | assign byte screen 1024
    | reserve byte zero
    | routine main {
    |    ldy zero
    |    repeat bne {
    |       inc screen
    |       dey
    |       cpy zero
    |    }
    |    sty screen
    | }
    = main:
    =   ldy zero
    =   
    = _repeat_1:
    =   inc screen
    =   dey
    =   cpy zero
    =   BNE _repeat_1
    =   sty screen
    =   rts
    = 
    = .alias screen 1024
    = zero: .byte 0

Nested ifs.

    | routine main {
    |   if beq {
    |     if bcc {
    |       lda #0
    |     } else {
    |       if bvs {
    |         lda #1
    |       } else {
    |         lda #2
    |       }
    |     }
    |   } else {
    |     lda #3
    |   }
    | }
    = main:
    =   BEQ _label_3
    =   lda #3
    =   jmp _past_3
    = _label_3:
    =   BCC _label_2
    =   BVS _label_1
    =   lda #2
    =   jmp _past_1
    = _label_1:
    =   lda #1
    = _past_1:
    =   jmp _past_2
    = _label_2:
    =   lda #0
    = _past_2:
    = _past_3:
    =   rts

Installing an interrupt handler (at the Kernal level, i.e. with CINV)

    | assign byte screen 1024
    | assign vector cinv 788
    | reserve vector save_cinv
    | 
    | routine main {
    |   sei {
    |     copy vector cinv to save_cinv
    |     copy routine our_cinv to cinv
    |   }
    | }
    | 
    | routine our_cinv {
    |   inc screen
    |   jmp save_cinv
    | }
    = main:
    =   sei
    =   lda cinv
    =   sta save_cinv
    =   lda cinv+1
    =   sta save_cinv+1
    =   lda #<our_cinv
    =   sta cinv
    =   lda #>our_cinv
    =   sta cinv+1
    =   cli
    =   rts
    = 
    = our_cinv:
    =   inc screen
    =   jmp (save_cinv)
    =   rts
    = 
    = .alias screen 1024
    = .alias cinv 788
    = save_cinv: .word 0