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165 lines
2.7 KiB
ArmAsm
165 lines
2.7 KiB
ArmAsm
; helper routines for arithmetic on 32 bit numbers
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.include "zeropage.inc"
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.include "../inc/common.inc"
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.bss
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temp_ax: .res 2
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.code
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; no 16bit operand as can just use AX
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.exportzp acc32 = ptr1 ; 32bit accumulater (pointer)
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.exportzp op32 = ptr2 ; 32 bit operand (pointer)
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.exportzp acc16 = acc32 ; 16bit accumulater (value, NOT pointer)
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.export add_32_32
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.export add_16_32
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.export sub_16_16
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.export cmp_32_32
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.export cmp_16_16
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.export mul_8_16
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; compare 2 32bit numbers
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; on exit, zero flag clear iff acc32==op32
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cmp_32_32:
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ldy #0
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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@exit:
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rts
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; compare 2 16bit numbers
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; on exit, zero flag clear iff acc16==AX
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cmp_16_16:
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cmp acc16
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bne @exit
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txa
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cmp acc16+1
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@exit:
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rts
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; subtract 2 16 bit numbers
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; acc16=acc16-AX
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sub_16_16:
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stax temp_ax
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sec
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lda acc16
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sbc temp_ax
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sta acc16
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lda acc16+1
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sbc temp_ax+1
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sta acc16+1
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rts
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; add a 32bit operand to the 32 bit accumulater
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; acc32=acc32+op32
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add_32_32:
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clc
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ldy #0
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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rts
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; add a 16bit operand to the 32 bit accumulater
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; acc32=acc32+AX
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add_16_32:
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clc
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ldy #0
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adc (acc32),y
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sta (acc32),y
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iny
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txa
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adc (acc32),y
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sta (acc32),y
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iny
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lda #0
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adc (acc32),y
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sta (acc32),y
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iny
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lda #0
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adc (acc32),y
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sta (acc32),y
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rts
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; multiply a 16 bit number by an 8 bit number
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; acc16=acc16*a
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mul_8_16:
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tax
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beq @operand_is_zero
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lda acc16
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sta temp_ax
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lda acc16+1
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sta temp_ax+1
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@addition_loop:
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dex
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beq @done
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clc
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lda acc16
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adc temp_ax
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sta acc16
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lda acc16+1
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adc temp_ax+1
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sta acc16+1
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jmp @addition_loop
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@done:
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rts
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@operand_is_zero:
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sta acc16
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sta acc16+1
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rts
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; -- LICENSE FOR arithmetic.s --
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; The contents of this file are subject to the Mozilla Public License
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; Version 1.1 (the "License"); you may not use this file except in
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; compliance with the License. You may obtain a copy of the License at
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; http://www.mozilla.org/MPL/
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;
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; Software distributed under the License is distributed on an "AS IS"
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; basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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; License for the specific language governing rights and limitations
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; under the License.
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;
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; The Original Code is ip65.
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;
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; The Initial Developer of the Original Code is Jonno Downes,
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; jonno@jamtronix.com.
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; Portions created by the Initial Developer are Copyright (C) 2009
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; Jonno Downes. All Rights Reserved.
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; -- LICENSE END --
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