1 files changed, 567 insertions, 0 deletions

diff --git a/src/uxn-core.s b/src/uxn-core.s
new file mode 100644
index 0000000..2e7a165
--- /dev/null
+++ b/src/uxn-core.s
@@ -0,0 +1,567 @@
+.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
+
+@
+@ r0 is our custom stack pointer
+@ r1 is the value we want to insert/extract
+@
+@ When the stack grows downwards:
+@    push {r1} == str r1, [sp, #-4]!
+@    pop  {r1} == ldr r1, [sp], #4
+@
+@ In our case the stack grow upwards:
+@
+@ 8bit:
+@    push {r1} == strb r1, [sp], #1
+@    pop  {r1} == ldrb r1, [sp, #-1]!
+@
+@ 32bit:
+@    push {r1} == str r1, [sp], #4
+@    pop  {r1} == ldr r1, [sp, #-4]!
+@
+
+.global uxn_init_asm
+uxn_init_asm:
+    @ DEBUG: Initialize the stack for testing purposes.
+    ldr  r0, wst_ptr
+    mov  r1, #4
+    strb r1, [r0], #1
+    sub  r1, r1, #1
+    strb r1, [r0], #1
+    sub  r1, r1, #1
+    strb r1, [r0], #1
+    sub  r1, r1, #1
+    strb r1, [r0], #1
+    adr  r1, wst_ptr
+    str  r0, [r1]
+    bx lr
+
+@ 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_ret
+
+jmi:
+    b uxn_ret
+
+jsi:
+    b uxn_ret
+
+litr:
+    ldrb r3, [r0], #1
+    strb r3, [r1], #1
+    b uxn_decode
+
+lit2r:
+    b uxn_ret
+
+inc:
+    b uxn_ret
+
+inc2:
+    b uxn_ret
+
+pop:
+    b uxn_ret
+
+pop2:
+    b uxn_ret
+
+nip:
+    b uxn_ret
+
+nip2:
+    b uxn_ret
+
+swp:
+    b uxn_ret
+
+swp2:
+    b uxn_ret
+
+rot:
+    b uxn_ret
+
+rot2:
+    b uxn_ret
+
+dup:
+    b uxn_ret
+
+dup2:
+    b uxn_ret
+
+ovr:
+    b uxn_ret
+
+ovr2:
+    b uxn_ret
+
+equ:
+    b uxn_ret
+
+equ2:
+    b uxn_ret
+
+neq:
+    b uxn_ret
+
+neq2:
+    b uxn_ret
+
+gth:
+    b uxn_ret
+
+gth2:
+    b uxn_ret
+
+lth:
+    b uxn_ret
+
+lth2:
+    b uxn_ret
+
+jmp:
+    b uxn_ret
+
+jmp2:
+    b uxn_ret
+
+jcn:
+    b uxn_ret
+
+jcn2:
+    b uxn_ret
+
+jsr:
+    b uxn_ret
+
+jsr2:
+    b uxn_ret
+
+sth:
+    b uxn_ret
+
+sth2:
+    b uxn_ret
+
+ldz:
+    b uxn_ret
+
+ldz2:
+    b uxn_ret
+
+stz:
+    b uxn_ret
+
+stz2:
+    b uxn_ret
+
+ldr:
+    b uxn_ret
+
+ldr2:
+    b uxn_ret
+
+str:
+    b uxn_ret
+
+str2:
+    b uxn_ret
+
+lda:
+    b uxn_ret
+
+lda2:
+    b uxn_ret
+
+sta:
+    b uxn_ret
+
+sta2:
+    b uxn_ret
+
+dei:
+    b uxn_ret
+
+dei2:
+    b uxn_ret
+
+deo:
+    b uxn_ret
+
+deo2:
+    b uxn_ret
+
+add:
+    ldr r3, [r1, #-1]!
+    ldr r4, [r1, #-1]!
+    add r3, r3, r4
+    strb r3, [r1], #1
+    b uxn_ret @ NOTE: This should return to the next loop iteration.
+
+add2:
+    b uxn_ret
+
+sub:
+    @ ldr r2, [r0, #-1]!
+    @ ldr r1, [r0, #-1]!
+    @ sub r1, r1, r2
+    @ strb r1, [r0], #1
+    b uxn_ret @ NOTE: This should return to the next loop iteration.
+
+sub2:
+    b uxn_ret
+
+mul:
+    b uxn_ret
+
+mul2:
+    b uxn_ret
+
+div:
+    b uxn_ret
+
+div2:
+    b uxn_ret
+
+and:
+    b uxn_ret
+
+and2:
+    b uxn_ret
+
+ora:
+    b uxn_ret
+
+ora2:
+    b uxn_ret
+
+eor:
+    b uxn_ret
+
+eor2:
+    b uxn_ret
+
+sft:
+    b uxn_ret
+
+sft2:
+    b uxn_ret
+
+@ 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 brk    @ 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