;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-

;; A file containing 16-bit macro arithmatic.
;; You may add ,! ass a 5:th parameter to skipp flagg clearing.
;; This will make it run faster but will have unintended behavior.

;;Se below for some fast 16bit logic
;;http://6502.org/tutorials/compare_beyond.html

;; Addition always uses the A register
;; a = a + b
.macro Add_16 a_low, a_hi, b_low, b_hi, fast_unsafe
;; IF to run it fast
.ifblank fast_unsafe
    CLC
.endif
.if .not .match ({b_low}, a)
	LDA b_low
.endif ;;untested
	ADC a_low
	STA a_low
.if .match ({b_hi}, x) ;;Untested
        TXA
.else
	LDA b_hi
.endif
	ADC a_hi
	STA a_hi
.endmacro


;; Subtraction uses always uses A register
;; a = a - b
.macro Sub_16 a_low, a_hi, b_low, b_hi, fast_unsafe
;; IF to run it fast
.ifblank fast_unsafe
        SEC
.endif
;; if b_low = A and b_hi =A
.if .match({b_low}, a) .and .match({b_hi}, a) ;;untested
        .LOCAL rewrite
        .LOCAL rewrite2
        STA rewrite +1
        STA rewrite2 + 1
        LDA a_low
        rewrite:
        SBC #b_low
        STA a_low
        LDA a_hi
        rewrite2:
        SBC #b_hi
        STA a_hi
;; if b_low = A
.elseif .match({b_low}, a) ;;untested
        .LOCAL rewrite
        STA rewrite +1
        LDA a_low
        rewrite:
        SBC #b_low
        STA a_low
        LDA a_hi
        SBC b_hi
        STA a_hi
.elseif .match({b_hi}, a) ;;untested
        .LOCAL rewrite
        STA rewrite +1
        LDA a_low
        SBC b_low
        STA a_low
        LDA a_hi
        rewrite:
        SBC #b_hi
        STA a_hi
.else
        LDA a_low
        SBC b_low
        STA a_low
        LDA a_hi
        SBC b_hi
        STA a_hi
.endif
.endmacro

;; Subtraction uses always uses A register
;; a = (A, a_hi) - b
.macro Sub_16_A a_low, a_hi, b_low, b_hi, fast_unsafe
;; IF to run it fast
.ifblank fast_unsafe
        SEC
.endif
        SBC b_low
        STA a_low
        LDA a_hi
        SBC b_hi
        STA a_hi
.endmacro


;; Multiplication of 2
;; a = a*2
.macro Mult_16 low_, hi_, NOT_ROL
;; IF NOT_ROL
.ifblank fast_unsafe
        ASL low_
        ROL hi_
.else
        ROL low_
	ROL hi_
.endif
.endmacro

.macro Mov_16 a_low, a_hi, b_low, b_hi
        LDA b_low
        STA a_low
        LDA b_hi
        STA a_hi
.endmacro

;;http://www.6502.org/tutorials/compare_beyond.html
;;Larger then operation, uses the A register
;;IF a < b then: jump to label
; C =0 if jump to LABEL
.macro Lag_16 a_low, a_hi, b_low, b_hi, label
        .LOCAL LABEL
        LDA a_hi
        CMP b_hi
        BCC label
        BNE LABEL
        LDA a_low
.if .match ({b_low}, a)
        .LOCAL next
        STY next +1
next:
        CMP #$ff
.else
        CMP b_low
.endif
        BCC label
        LABEL:
.endmacro