path: root/src/uxn-core.s

.file "uxn-core.s"
.section .iwram, "ax", %progbits
.extern uxn_ram
.align

@
@ Core variables
@

.global wst
wst: .space 256
.global wst_ptr
wst_ptr: .word wst

.global rst
rst: .space 256
.global rst_ptr
rst_ptr: .word rst

.global io_ports
io_ports: .space 256

@ UXN evaluation function.
@
@   r0: PC pointer (argument is offset from RAM).
@   r1: Stack pointer (wst/rst).
@   r2: Ram ptr.
@   r3-r7: Scratch registers.
@
.global uxn_eval_asm
uxn_eval_asm:
    @ Initialization.
    push {r4-r7}
    ldr  r1, wst_ptr
    ldr  r2, =uxn_ram
    add  r0, r0, r2

uxn_decode:
    ldrb r3, [r0], #1 @ current OP value / table index

    @ TODO: Setup wst/rst? or fill operations accordingly?
    @ str  r3, [r1], #1 @ Push to stack: Debugging

    @ Decode OP based on table lookup.
    adr  r4, op_table         @ decoding table
    ldr  r4, [r4, r3, lsl #2] @ op_table[idx * 4]
    bx   r4                   @ op_table[idx * 4]()

uxn_ret:
    @ Update stack pointer and return.
    adr  r0, wst_ptr
    str  r1, [r0]
    pop  {r4-r7}
    bx   lr

@
@ OP implementations.
@

brk:
    b uxn_ret

jci:
    b uxn_decode

jmi:
    b uxn_decode

jsi:
    b uxn_decode

litr:
    ldrb r3, [r0], #1
    strb r3, [r1], #1
    b uxn_decode

lit2r:
    ldrb r3, [r0], #1
    ldrb r4, [r0], #1
    strb r3, [r1], #1
    strb r4, [r1], #1
    b uxn_decode

inc:
    b uxn_decode

inc2:
    b uxn_decode

pop:
    b uxn_decode

pop2:
    b uxn_decode

nip:
    b uxn_decode

nip2:
    b uxn_decode

swp:
    b uxn_decode

swp2:
    b uxn_decode

rot:
    b uxn_decode

rot2:
    b uxn_decode

dup:
    b uxn_decode

dup2:
    b uxn_decode

ovr:
    b uxn_decode

ovr2:
    b uxn_decode

equ:
    b uxn_decode

equ2:
    b uxn_decode

neq:
    b uxn_decode

neq2:
    b uxn_decode

gth:
    b uxn_decode

gth2:
    b uxn_decode

lth:
    b uxn_decode

lth2:
    b uxn_decode

jmp:
    b uxn_decode

jmp2:
    b uxn_decode

jcn:
    b uxn_decode

jcn2:
    b uxn_decode

jsr:
    b uxn_decode

jsr2:
    b uxn_decode

sth:
    b uxn_decode

sth2:
    b uxn_decode

ldz:
    b uxn_decode

ldz2:
    b uxn_decode

stz:
    b uxn_decode

stz2:
    b uxn_decode

ldr:
    b uxn_decode

ldr2:
    b uxn_decode

str:
    b uxn_decode

str2:
    b uxn_decode

lda:
    b uxn_decode

lda2:
    b uxn_decode

sta:
    b uxn_decode

sta2:
    b uxn_decode

dei:
    b uxn_decode

dei2:
    b uxn_decode

deo:
    b uxn_decode

deo2:
    b uxn_decode

add:
    ldr  r3, [r1, #-1]!
    ldr  r4, [r1, #-1]!
    add  r3, r3, r4
    strb r3, [r1], #1
    b uxn_decode

add2:
    ldrb r3, [r1, #-1]!
    lsl  r3, #8
    ldrb r5, [r1, #-1]!
    add  r3, r5
    ldrb r4, [r1, #-1]!
    ldrb r5, [r1, #-1]!
    lsl  r4, #8
    add  r4, r5
    add  r3, r3, r4
    strb r3, [r1], #1
    lsr  r3, #8
    strb r3, [r1], #1
    b uxn_decode

sub:
    ldr  r3, [r1, #-1]!
    ldr  r4, [r1, #-1]!
    sub  r4, r4, r3
    strb r4, [r1], #1
    b uxn_decode

sub2:
    ldrb r3, [r1, #-1]!
    ldrb r5, [r1, #-1]!
    lsl  r3, #8
    add  r3, r5
    ldrb r4, [r1, #-1]!
    ldrb r5, [r1, #-1]!
    lsl  r4, #8
    add  r4, r5
    sub  r3, r4, r3
    strb r3, [r1], #1
    lsr  r3, #8
    strb r3, [r1], #1
    b uxn_decode

mul:
    b uxn_decode

mul2:
    b uxn_decode

div:
    b uxn_decode

div2:
    b uxn_decode

and:
    b uxn_decode

and2:
    b uxn_decode

ora:
    b uxn_decode

ora2:
    b uxn_decode

eor:
    b uxn_decode

eor2:
    b uxn_decode

sft:
    b uxn_decode

sft2:
    b uxn_decode

@ OP table
op_table:
    .word brk     @ 0x00
    .word inc     @ 0x01
    .word pop     @ 0x02
    .word nip     @ 0x03
    .word swp     @ 0x04
    .word rot     @ 0x05
    .word dup     @ 0x06
    .word ovr     @ 0x07
    .word equ     @ 0x08
    .word neq     @ 0x09
    .word gth     @ 0x0a
    .word lth     @ 0x0b
    .word jmp     @ 0x0c
    .word jcn     @ 0x0d
    .word jsr     @ 0x0e
    .word sth     @ 0x0f
    .word ldz     @ 0x00
    .word stz     @ 0x11
    .word ldr     @ 0x12
    .word str     @ 0x13
    .word lda     @ 0x14
    .word sta     @ 0x15
    .word dei     @ 0x16
    .word deo     @ 0x17
    .word add     @ 0x18
    .word sub     @ 0x19
    .word mul     @ 0x1a
    .word div     @ 0x1b
    .word and     @ 0x1c
    .word ora     @ 0x1d
    .word eor     @ 0x1e
    .word sft     @ 0x1f
    .word brk     @ 0x20
    .word inc2    @ 0x21
    .word pop2    @ 0x22
    .word nip2    @ 0x23
    .word swp2    @ 0x24
    .word rot2    @ 0x25
    .word dup2    @ 0x26
    .word ovr2    @ 0x27
    .word equ2    @ 0x28
    .word neq2    @ 0x29
    .word gth2    @ 0x2a
    .word lth2    @ 0x2b
    .word jmp2    @ 0x2c
    .word jcn2    @ 0x2d
    .word jsr2    @ 0x2e
    .word sth2    @ 0x2f
    .word ldz2    @ 0x30
    .word stz2    @ 0x31
    .word ldr2    @ 0x32
    .word str2    @ 0x33
    .word lda2    @ 0x34
    .word sta2    @ 0x35
    .word dei2    @ 0x36
    .word deo2    @ 0x37
    .word add2    @ 0x38
    .word sub2    @ 0x39
    .word mul2    @ 0x3a
    .word div2    @ 0x3b
    .word and2    @ 0x3c
    .word ora2    @ 0x3d
    .word eor2    @ 0x3e
    .word sft2    @ 0x3f
@ TODO: Can we mask this instead of having empty space?
    .word brk    @ 0x40
    .word brk    @ 0x41
    .word brk    @ 0x42
    .word brk    @ 0x43
    .word brk    @ 0x44
    .word brk    @ 0x45
    .word brk    @ 0x46
    .word brk    @ 0x47
    .word brk    @ 0x48
    .word brk    @ 0x49
    .word brk    @ 0x4a
    .word brk    @ 0x4b
    .word brk    @ 0x4c
    .word brk    @ 0x4d
    .word brk    @ 0x4e
    .word brk    @ 0x4f
    .word brk    @ 0x50
    .word brk    @ 0x51
    .word brk    @ 0x52
    .word brk    @ 0x53
    .word brk    @ 0x54
    .word brk    @ 0x55
    .word brk    @ 0x56
    .word brk    @ 0x57
    .word brk    @ 0x58
    .word brk    @ 0x59
    .word brk    @ 0x5a
    .word brk    @ 0x5b
    .word brk    @ 0x5c
    .word brk    @ 0x5d
    .word brk    @ 0x5e
    .word brk    @ 0x5f
    .word brk    @ 0x60
    .word brk    @ 0x61
    .word brk    @ 0x62
    .word brk    @ 0x63
    .word brk    @ 0x64
    .word brk    @ 0x65
    .word brk    @ 0x66
    .word brk    @ 0x67
    .word brk    @ 0x68
    .word brk    @ 0x69
    .word brk    @ 0x6a
    .word brk    @ 0x6b
    .word brk    @ 0x6c
    .word brk    @ 0x6d
    .word brk    @ 0x6e
    .word brk    @ 0x6f
    .word brk    @ 0x70
    .word brk    @ 0x71
    .word brk    @ 0x72
    .word brk    @ 0x73
    .word brk    @ 0x74
    .word brk    @ 0x75
    .word brk    @ 0x76
    .word brk    @ 0x77
    .word brk    @ 0x78
    .word brk    @ 0x79
    .word brk    @ 0x7a
    .word brk    @ 0x7b
    .word brk    @ 0x7c
    .word brk    @ 0x7d
    .word brk    @ 0x7e
    .word brk    @ 0x7f
    .word litr   @ 0x80
    .word brk    @ 0x81
    .word brk    @ 0x82
    .word brk    @ 0x83
    .word brk    @ 0x84
    .word brk    @ 0x85
    .word brk    @ 0x86
    .word brk    @ 0x87
    .word brk    @ 0x88
    .word brk    @ 0x89
    .word brk    @ 0x8a
    .word brk    @ 0x8b
    .word brk    @ 0x8c
    .word brk    @ 0x8d
    .word brk    @ 0x8e
    .word brk    @ 0x8f
    .word brk    @ 0x90
    .word brk    @ 0x91
    .word brk    @ 0x92
    .word brk    @ 0x93
    .word brk    @ 0x94
    .word brk    @ 0x95
    .word brk    @ 0x96
    .word brk    @ 0x97
    .word brk    @ 0x98
    .word brk    @ 0x99
    .word brk    @ 0x9a
    .word brk    @ 0x9b
    .word brk    @ 0x9c
    .word brk    @ 0x9d
    .word brk    @ 0x9e
    .word brk    @ 0x9f
    .word lit2r  @ 0xa0
    .word brk    @ 0xa1
    .word brk    @ 0xa2
    .word brk    @ 0xa3
    .word brk    @ 0xa4
    .word brk    @ 0xa5
    .word brk    @ 0xa6
    .word brk    @ 0xa7
    .word brk    @ 0xa8
    .word brk    @ 0xa9
    .word brk    @ 0xaa
    .word brk    @ 0xab
    .word brk    @ 0xac
    .word brk    @ 0xad
    .word brk    @ 0xae
    .word brk    @ 0xaf
    .word brk    @ 0xb0
    .word brk    @ 0xb1
    .word brk    @ 0xb2
    .word brk    @ 0xb3
    .word brk    @ 0xb4
    .word brk    @ 0xb5
    .word brk    @ 0xb6
    .word brk    @ 0xb7
    .word brk    @ 0xb8
    .word brk    @ 0xb9
    .word brk    @ 0xba
    .word brk    @ 0xbb
    .word brk    @ 0xbc
    .word brk    @ 0xbd
    .word brk    @ 0xbe
    .word brk    @ 0xbf
    .word brk    @ 0xc0
    .word brk    @ 0xc1
    .word brk    @ 0xc2
    .word brk    @ 0xc3
    .word brk    @ 0xc4
    .word brk    @ 0xc5
    .word brk    @ 0xc6
    .word brk    @ 0xc7
    .word brk    @ 0xc8
    .word brk    @ 0xc9
    .word brk    @ 0xca
    .word brk    @ 0xcb
    .word brk    @ 0xcc
    .word brk    @ 0xcd
    .word brk    @ 0xce
    .word brk    @ 0xcf
    .word brk    @ 0xd0
    .word brk    @ 0xd1
    .word brk    @ 0xd2
    .word brk    @ 0xd3
    .word brk    @ 0xd4
    .word brk    @ 0xd5
    .word brk    @ 0xd6
    .word brk    @ 0xd7
    .word brk    @ 0xd8
    .word brk    @ 0xd9
    .word brk    @ 0xda
    .word brk    @ 0xdb
    .word brk    @ 0xdc
    .word brk    @ 0xdd
    .word brk    @ 0xde
    .word brk    @ 0xdf
    .word brk    @ 0xe0
    .word brk    @ 0xe1
    .word brk    @ 0xe2
    .word brk    @ 0xe3
    .word brk    @ 0xe4
    .word brk    @ 0xe5
    .word brk    @ 0xe6
    .word brk    @ 0xe7
    .word brk    @ 0xe8
    .word brk    @ 0xe9
    .word brk    @ 0xea
    .word brk    @ 0xeb
    .word brk    @ 0xec
    .word brk    @ 0xed
    .word brk    @ 0xee
    .word brk    @ 0xef
    .word brk    @ 0xf0
    .word brk    @ 0xf1
    .word brk    @ 0xf2
    .word brk    @ 0xf3
    .word brk    @ 0xf4
    .word brk    @ 0xf5
    .word brk    @ 0xf6
    .word brk    @ 0xf7
    .word brk    @ 0xf8
@ TODO: Can we mask this instead of having empty space?
    .word lit2r   @ 0xf9
    .word litr    @ 0xfa
    .word lit2r   @ 0xfb
    .word litr    @ 0xfc
    .word jsi     @ 0xfd
    .word jmi     @ 0xfe
    .word jci     @ 0xff