common.asm

;; Start common.asm
;;
;; A file containing macros that may be useful to include. Mostly contains 
;; basic operations that would be included on a modern architecture.


; REGISTER DEFINITIONS: ----------

#ifnc LR
#constant LR R7
#endif

#ifnc SP
#constant SP R6
#endif

#ifnc FP
#constant FP R5
#endif


; STACK OPERATIONS: ----------

; Push
#ifnm PUSH
#macro PUSH RX
        ADD     R6, R6, #-1
        STR     RX, R6, #0
#endmacro
#endif

; Pop
#ifnm POP
#macro POP RX
        LDR     RX, R6, #0
        ADD     R6, R6, #1
#endmacro
#endif


; MATH AND LOGIC: ----------

; In-Place Add
; RA <- RA + P2
#ifnm ADDP
#macro ADDP RA, P2
        ADD     RA, RA, P2
#endmacro
#endif

; In-Place And
; RA <- RA & P2
#ifnm ANDP
#macro ANDP RA, P2
        AND     RA, RA, P2
#endmacro
#endif

; In-Place Not
; RX <- ~RX
#ifnm NOTP
#macro NOTP RX
        NOT     RX, RX
#endmacro
#endif

; Negation
; RD <- -RX
#ifnm NEG
#macro NEG RD, RX
        NOT     RD, RX
        ADD     RD, RD, #1
#endmacro
#endif

; Clear
; RD <- 0
#ifnm CLR
#macro CLR RD
        AND     RD, RD, #0
#endmacro
#endif

; Test
; Does nothing to the registers, but sets condition codes
#ifnm TST
#macro TST RX
        ADD     RX, #0
#endmacro
#endif

; Move
; Moves the specified immediate or register into the destination
#ifnm MOV
#macro MOV RD, P2
        AND     RD, RD, #0
        ADD     RD, RD, P2
#endmacro
#endif

; In-Place Subtraction
; Note that there is no arbitrary-destination subtraction. Doing that requires 
;   executing different code based on if RD is RA or RB
; We can ignore the edge case of RB being the same as RA. The code results in 
;   0 in RA, as it should
; RA <- RA - RB
#ifnm SUBP
#macro SUB RA, RB
        NOT     RB, RB
        ADD     RB, RB, #1
        ADD     RA, RA, RB
        NOT     RB, RB
        ADD     RB, RB, #1
#endmacro
#endif

; In-Place Or
; For the same reason as above, there is no arbitrary-destination or.
; Also, like above, the code still works
; RA <- RA | RB
#ifnm ORP
#macro ORP RA, RB
        NOT     RA, RA
        NOT     RB, RB
        AND     RA, RA, RB
        NOT     RA, RA
        NOT     RB, RB
#endmacro
#endif


;; End common.asm