136 lines
6.4 KiB
Text
136 lines
6.4 KiB
Text
/*********************************************/
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/* optimized version */
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/*********************************************/
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/* ARM assembly Raspberry PI */
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/* program 100doors.s */
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/************************************/
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/* Constantes */
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/************************************/
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.equ STDOUT, 1 @ Linux output console
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.equ EXIT, 1 @ Linux syscall
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.equ WRITE, 4 @ Linux syscall
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.equ NBDOORS, 100
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/*********************************/
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/* Initialized data */
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/*********************************/
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.data
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sMessResult: .ascii "The door "
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sMessValeur: .fill 11, 1, ' ' @ size => 11
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.asciz "is open.\n"
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/*********************************/
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/* UnInitialized data */
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/*********************************/
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.bss
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/*********************************/
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/* code section */
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/*********************************/
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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} @ saves 2 registers
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@ display first line
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mov r5,#3 @ start value of increment
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mov r4,#1 @ start doors
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@ loop display state doors
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1:
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mov r0,r4 @ open -> display message
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ldr r1,iAdrsMessValeur @ display value index
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bl conversion10 @ call function
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ldr r0,iAdrsMessResult
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bl affichageMess @ display message
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add r4,r5 @ add increment
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add r5,#2 @ new increment
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cmp r4,#NBDOORS
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ble 1b @ loop
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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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svc #0 @ perform the system call
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iAdrsMessValeur: .int sMessValeur
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iAdrsMessResult: .int sMessResult
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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 {r0,r1,r2,r7,lr} @ save 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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svc #0 @ call systeme
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pop {r0,r1,r2,r7,lr} @ restaur des 2 registres */
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bx lr @ return
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/******************************************************************/
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/* Converting a register to a decimal unsigned */
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/******************************************************************/
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/* r0 contains value and r1 address area */
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/* r0 return size of result (no zero final in area) */
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/* area size => 11 bytes */
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.equ LGZONECAL, 10
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conversion10:
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push {r1-r4,lr} @ save registers
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mov r3,r1
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mov r2,#LGZONECAL
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1: @ start loop
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bl divisionpar10U @ unsigned r0 <- dividende. quotient ->r0 reste -> r1
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add r1,#48 @ digit
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strb r1,[r3,r2] @ store digit on area
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cmp r0,#0 @ stop if quotient = 0
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subne r2,#1 @ else previous position
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bne 1b @ and loop
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@ and move digit from left of area
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mov r4,#0
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2:
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ldrb r1,[r3,r2]
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strb r1,[r3,r4]
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add r2,#1
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add r4,#1
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cmp r2,#LGZONECAL
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ble 2b
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@ and move spaces in end on area
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mov r0,r4 @ result length
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mov r1,#' ' @ space
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3:
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strb r1,[r3,r4] @ store space in area
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add r4,#1 @ next position
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cmp r4,#LGZONECAL
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ble 3b @ loop if r4 <= area size
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100:
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pop {r1-r4,lr} @ restaur registres
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bx lr @return
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/***************************************************/
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/* division par 10 unsigned */
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/***************************************************/
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/* r0 dividende */
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/* r0 quotient */
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/* r1 remainder */
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divisionpar10U:
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push {r2,r3,r4, lr}
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mov r4,r0 @ save value
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//mov r3,#0xCCCD @ r3 <- magic_number lower @ for raspberry 3
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//movt r3,#0xCCCC @ r3 <- magic_number upper @ for raspberry 3
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ldr r3,iMagicNumber @ for raspberry 1 2
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umull r1, r2, r3, r0 @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0)
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mov r0, r2, LSR #3 @ r2 <- r2 >> shift 3
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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,r3,r4,lr}
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bx lr @ leave function
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iMagicNumber: .int 0xCCCCCCCD
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