/* ARM assembly Raspberry PI */ /* program kprime.s */ /************************************/ /* Constantes */ /************************************/ .equ STDOUT, 1 @ Linux output console .equ EXIT, 1 @ Linux syscall .equ WRITE, 4 @ Linux syscall .equ MAXI, 10 .equ MAXIK, 5 /*********************************/ /* Initialized data */ /*********************************/ .data sMessDeb: .ascii "k=" sMessValeurDeb: .fill 11, 1, ' ' @ size => 11 sMessResult: .ascii " " sMessValeur: .fill 11, 1, ' ' @ size => 11 szCarriageReturn: .asciz "\n" /*********************************/ /* UnInitialized data */ /*********************************/ .bss /*********************************/ /* code section */ /*********************************/ .text .global main main: @ entry of program mov r3,#1 @ k 1: @ start loop k mov r0,r3 ldr r1,iAdrsMessValeurDeb bl conversion10 @ call conversion decimal ldr r0,iAdrsMessValeurDeb mov r1,#':' strb r1,[r0,#2] @ write : after k value mov r1,#0 strb r1,[r0,#3] @ final zéro ldr r0,iAdrsMessDeb bl affichageMess @ display message mov r4,#2 @ n mov r5,#0 @ result counter 2: @ start loop n mov r0,r4 mov r1,r3 bl kprime @ is kprine ? cmp r0,#0 beq 3f @ no mov r0,r4 ldr r1,iAdrsMessValeur bl conversion10 @ call conversion decimal ldr r0,iAdrsMessValeur mov r1,#0 strb r1,[r0,#4] @ final zéro ldr r0,iAdrsMessResult bl affichageMess @ display message add r5,#1 @ increment counter 3: add r4,#1 @ increment n cmp r5,#MAXI @ maxi ? blt 2b @ no -> loop ldr r0,iAdrszCarriageReturn bl affichageMess @ display carriage return add r3,#1 @ increment k cmp r3,#MAXIK @ maxi ? ble 1b @ no -> loop 100: @ standard end of the program mov r0, #0 @ return code mov r7, #EXIT @ request to exit program svc #0 @ perform the system call iAdrsMessValeur: .int sMessValeur iAdrszCarriageReturn: .int szCarriageReturn iAdrsMessResult: .int sMessResult iAdrsMessValeurDeb: .int sMessValeurDeb iAdrsMessDeb: .int sMessDeb /******************************************************************/ /* compute kprime (n,k) */ /******************************************************************/ /* r0 contains n */ /* r1 contains k */ kprime: push {r1-r7,lr} @ save registers mov r5,r0 @ save n mov r7,r1 @ save k mov r4,#0 @ counter product mov r1,#2 @ divisor 1: @ start loop cmp r4,r7 @ counter >= k bge 4f @ yes -> end mul r6,r1,r1 @ compute product cmp r6,r5 @ > n bgt 4f @ yes -> end 2: @ start loop division mov r0,r5 @ dividende bl division @ by r1 cmp r3,#0 @ remainder = 0 ? bne 3f @ no mov r5,r2 @ yes -> n = n / r1 add r4,#1 @ increment counter b 2b @ and loop 3: add r1,#1 @ increment divisor b 1b @ and loop 4: @ end compute cmp r5,#1 @ n > 1 addgt r4,#1 @ yes increment counter cmp r4,r7 @ counter = k ? movne r0,#0 @ no -> no kprime moveq r0,#1 @ yes -> kprime 100: pop {r1-r7,lr} @ restaur registers bx lr @return /******************************************************************/ /* display text with size calculation */ /******************************************************************/ /* r0 contains the address of the message */ affichageMess: push {r0,r1,r2,r7,lr} @ save registres mov r2,#0 @ counter length 1: @ loop length calculation ldrb r1,[r0,r2] @ read octet start position + index cmp r1,#0 @ if 0 its over addne r2,r2,#1 @ else add 1 in the length bne 1b @ and loop @ so here r2 contains the length of the message mov r1,r0 @ address message in r1 mov r0,#STDOUT @ code to write to the standard output Linux mov r7, #WRITE @ code call system "write" svc #0 @ call systeme pop {r0,r1,r2,r7,lr} @ restaur des 2 registres */ bx lr @ return /******************************************************************/ /* Converting a register to a decimal unsigned */ /******************************************************************/ /* r0 contains value and r1 address area */ /* r0 return size of result (no zero final in area) */ /* area size => 11 bytes */ .equ LGZONECAL, 10 conversion10: push {r1-r4,lr} @ save registers mov r3,r1 mov r2,#LGZONECAL 1: @ start loop bl divisionpar10U @ unsigned r0 <- dividende. quotient ->r0 reste -> r1 add r1,#48 @ digit strb r1,[r3,r2] @ store digit on area cmp r0,#0 @ stop if quotient = 0 subne r2,#1 @ else previous position bne 1b @ and loop @ and move digit from left of area mov r4,#0 2: ldrb r1,[r3,r2] strb r1,[r3,r4] add r2,#1 add r4,#1 cmp r2,#LGZONECAL ble 2b @ and move spaces in end on area mov r0,r4 @ result length mov r1,#' ' @ space 3: strb r1,[r3,r4] @ store space in area add r4,#1 @ next position cmp r4,#LGZONECAL ble 3b @ loop if r4 <= area size 100: pop {r1-r4,lr} @ restaur registres bx lr @return /***************************************************/ /* division par 10 unsigned */ /***************************************************/ /* r0 dividende */ /* r0 quotient */ /* r1 remainder */ divisionpar10U: push {r2,r3,r4, lr} mov r4,r0 @ save value ldr r3,iMagicNumber @ r3 <- magic_number raspberry 1 2 umull r1, r2, r3, r0 @ r1<- Lower32Bits(r1*r0) r2<- Upper32Bits(r1*r0) mov r0, r2, LSR #3 @ r2 <- r2 >> shift 3 add r2,r0,r0, lsl #2 @ r2 <- r0 * 5 sub r1,r4,r2, lsl #1 @ r1 <- r4 - (r2 * 2) = r4 - (r0 * 10) pop {r2,r3,r4,lr} bx lr @ leave function iMagicNumber: .int 0xCCCCCCCD /***************************************************/ /* integer division unsigned */ /***************************************************/ division: /* r0 contains dividend */ /* r1 contains divisor */ /* r2 returns quotient */ /* r3 returns remainder */ push {r4, lr} mov r2, #0 @ init quotient mov r3, #0 @ init remainder mov r4, #32 @ init counter bits b 2f 1: @ loop movs r0, r0, LSL #1 @ r0 <- r0 << 1 updating cpsr (sets C if 31st bit of r0 was 1) adc r3, r3, r3 @ r3 <- r3 + r3 + C. This is equivalent to r3 ? (r3 << 1) + C cmp r3, r1 @ compute r3 - r1 and update cpsr subhs r3, r3, r1 @ if r3 >= r1 (C=1) then r3 <- r3 - r1 adc r2, r2, r2 @ r2 <- r2 + r2 + C. This is equivalent to r2 <- (r2 << 1) + C 2: subs r4, r4, #1 @ r4 <- r4 - 1 bpl 1b @ if r4 >= 0 (N=0) then loop pop {r4, lr} bx lr