162 lines
6.1 KiB
Plaintext
162 lines
6.1 KiB
Plaintext
/* ARM assembly Raspberry PI */
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/* program binarydigit.s */
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/* Constantes */
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.equ STDOUT, 1
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.equ WRITE, 4
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.equ EXIT, 1
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/* Initialized data */
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.data
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sMessAffBin: .ascii "The decimal value "
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sZoneDec: .space 12,' '
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.ascii " should produce an output of "
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sZoneBin: .space 36,' '
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.asciz "\n"
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/* code section */
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.text
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.global main
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main: /* entry of program */
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push {fp,lr} /* save des 2 registres */
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mov r0,#5
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ldr r1,iAdrsZoneDec
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bl conversion10S @ decimal conversion
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bl conversion2 @ binary conversion and display résult
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mov r0,#50
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ldr r1,iAdrsZoneDec
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bl conversion10S
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bl conversion2
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mov r0,#-1
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ldr r1,iAdrsZoneDec
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bl conversion10S
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bl conversion2
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mov r0,#1
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ldr r1,iAdrsZoneDec
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bl conversion10S
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bl conversion2
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100: /* standard end of the program */
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mov r0, #0 @ return code
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pop {fp,lr} @restaur 2 registers
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mov r7, #EXIT @ request to exit program
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swi 0 @ perform the system call
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iAdrsZoneDec: .int sZoneDec
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/******************************************************************/
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/* register conversion in binary */
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/******************************************************************/
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/* r0 contains the register */
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conversion2:
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push {r0,lr} /* save registers */
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push {r1-r5} /* save others registers */
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ldr r1,iAdrsZoneBin @ address reception area
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clz r2,r0 @ number of left zeros bits
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rsb r2,#32 @ number of significant bits
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mov r4,#' ' @ space
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add r3,r2,#1 @ position counter in reception area
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1:
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strb r4,[r1,r3] @ space in other location of reception area
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add r3,#1
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cmp r3,#32 @ end of area ?
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ble 1b @ no! loop
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mov r3,r2 @ position counter of the written character
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2: @ loop
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lsrs r0,#1 @ shift right one bit with flags
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movcc r4,#48 @ carry clear => character 0
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movcs r4,#49 @ carry set => character 1
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strb r4,[r1,r3] @ character in reception area at position counter
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sub r3,r3,#1 @
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subs r2,r2,#1 @ 0 bits ?
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bgt 2b @ no! loop
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ldr r0,iAdrsZoneMessBin
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bl affichageMess
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100:
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pop {r1-r5} /* restaur others registers */
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pop {r0,lr}
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bx lr
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iAdrsZoneBin: .int sZoneBin
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iAdrsZoneMessBin: .int sMessAffBin
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/******************************************************************/
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/* display text with size calculation */
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/******************************************************************/
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/* r0 contains the address of the message */
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affichageMess:
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push {fp,lr} /* save registres */
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push {r0,r1,r2,r7} /* save others registres */
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mov r2,#0 /* counter length */
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1: /* loop length calculation */
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ldrb r1,[r0,r2] /* read octet start position + index */
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cmp r1,#0 /* if 0 its over */
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addne r2,r2,#1 /* else add 1 in the length */
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bne 1b /* and loop */
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/* so here r2 contains the length of the message */
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mov r1,r0 /* address message in r1 */
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mov r0,#STDOUT /* code to write to the standard output Linux */
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mov r7, #WRITE /* code call system "write" */
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swi #0 /* call systeme */
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pop {r0,r1,r2,r7} /* restaur others registres */
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pop {fp,lr} /* restaur des 2 registres */
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bx lr /* return */
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/***************************************************/
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/* conversion registre en décimal signé */
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/***************************************************/
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/* r0 contient le registre */
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/* r1 contient l adresse de la zone de conversion */
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conversion10S:
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push {fp,lr} /* save des 2 registres frame et retour */
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push {r0-r5} /* save autres registres */
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mov r2,r1 /* debut zone stockage */
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mov r5,#'+' /* par defaut le signe est + */
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cmp r0,#0 /* nombre négatif ? */
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movlt r5,#'-' /* oui le signe est - */
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mvnlt r0,r0 /* et inversion en valeur positive */
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addlt r0,#1
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mov r4,#10 /* longueur de la zone */
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1: /* debut de boucle de conversion */
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bl divisionpar10 /* division */
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add r1,#48 /* ajout de 48 au reste pour conversion ascii */
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strb r1,[r2,r4] /* stockage du byte en début de zone r5 + la position r4 */
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sub r4,r4,#1 /* position précedente */
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cmp r0,#0
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bne 1b /* boucle si quotient different de zéro */
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strb r5,[r2,r4] /* stockage du signe à la position courante */
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subs r4,r4,#1 /* position précedente */
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blt 100f /* si r4 < 0 fin */
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/* sinon il faut completer le debut de la zone avec des blancs */
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mov r3,#' ' /* caractere espace */
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2:
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strb r3,[r2,r4] /* stockage du byte */
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subs r4,r4,#1 /* position précedente */
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bge 2b /* boucle si r4 plus grand ou egal a zero */
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100: /* fin standard de la fonction */
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pop {r0-r5} /*restaur des autres registres */
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pop {fp,lr} /* restaur des 2 registres frame et retour */
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bx lr
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/***************************************************/
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/* division par 10 signé */
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/* Thanks to http://thinkingeek.com/arm-assembler-raspberry-pi/*
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/* and http://www.hackersdelight.org/ */
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/***************************************************/
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/* r0 contient le dividende */
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/* r0 retourne le quotient */
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/* r1 retourne le reste */
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divisionpar10:
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/* r0 contains the argument to be divided by 10 */
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push {r2-r4} /* save others registers */
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mov r4,r0
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ldr r3, .Ls_magic_number_10 /* r1 <- magic_number */
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smull r1, r2, r3, r0 /* r1 <- Lower32Bits(r1*r0). r2 <- Upper32Bits(r1*r0) */
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mov r2, r2, ASR #2 /* r2 <- r2 >> 2 */
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mov r1, r0, LSR #31 /* r1 <- r0 >> 31 */
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add r0, r2, r1 /* r0 <- r2 + r1 */
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add r2,r0,r0, lsl #2 /* r2 <- r0 * 5 */
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sub r1,r4,r2, lsl #1 /* r1 <- r4 - (r2 * 2) = r4 - (r0 * 10) */
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pop {r2-r4}
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bx lr /* leave function */
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.align 4
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.Ls_magic_number_10: .word 0x66666667
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