141 lines
5.3 KiB
Plaintext
141 lines
5.3 KiB
Plaintext
/* ARM assembly Raspberry PI */
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/* program loopdowhile.s */
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/* Constantes */
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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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/*********************************/
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/* Initialized data */
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/*********************************/
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.data
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szMessResult: .ascii "Counter = " @ message result
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sMessValeur: .fill 12, 1, ' '
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.asciz "\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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mov r4,#0
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1: @ begin loop
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mov r0,r4
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ldr r1,iAdrsMessValeur @ display value
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bl conversion10 @ call function with 2 parameter (r0,r1)
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ldr r0,iAdrszMessResult
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bl affichageMess @ display message
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add r4,#1 @ increment counter
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mov r0,r4
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mov r1,#6 @ division conuter by 6
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bl division
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cmp r3,#0 @ remainder = zéro ?
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bne 1b @ no ->begin loop one
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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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iAdrszMessResult: .int szMessResult
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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 */
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/******************************************************************/
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/* r0 contains value and r1 address area */
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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,#10
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1: @ start loop
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bl divisionpar10 @ 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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sub r2,#1 @ previous position
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cmp r0,#0 @ stop if quotient = 0 */
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bne 1b @ else loop
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@ and move spaces in first on area
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mov r1,#' ' @ space
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2:
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strb r1,[r3,r2] @ store space in area
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subs r2,#1 @ @ previous position
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bge 2b @ loop if r2 >= zéro
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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 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 dividende */
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/* r0 quotient */
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/* r1 remainder */
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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 registers */
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mov r4,r0
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mov r3,#0x6667 @ r3 <- magic_number lower
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movt r3,#0x6666 @ r3 <- magic_number upper
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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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/***************************************************/
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/* integer division unsigned */
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/***************************************************/
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division:
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/* r0 contains dividend */
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/* r1 contains divisor */
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/* r2 returns quotient */
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/* r3 returns remainder */
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push {r4, lr}
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mov r2, #0 @ init quotient
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mov r3, #0 @ init remainder
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mov r4, #32 @ init counter bits
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b 2f
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1: @ loop
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movs r0, r0, LSL #1 @ r0 <- r0 << 1 updating cpsr (sets C if 31st bit of r0 was 1)
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adc r3, r3, r3 @ r3 <- r3 + r3 + C. This is equivalent to r3 ? (r3 << 1) + C
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cmp r3, r1 @ compute r3 - r1 and update cpsr
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subhs r3, r3, r1 @ if r3 >= r1 (C=1) then r3 ? r3 - r1
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adc r2, r2, r2 @ r2 <- r2 + r2 + C. This is equivalent to r2 <- (r2 << 1) + C
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2:
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subs r4, r4, #1 @ r4 <- r4 - 1
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bpl 1b @ if r4 >= 0 (N=0) then loop
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pop {r4, lr}
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bx lr
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