Primality by trial division: Difference between revisions
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=={{header|68000 Assembly}}==
<lang 68000devpac>isPrime:
; REG USAGE:
; D0 = input (unsigned 32-bit integer)
; D1 = temp storage for D0
; D2 = candidates for possible factors
; D3 = temp storage for quotient/remainder
; D4 = total count of proper divisors.
MOVEM.L D1-D4,-(SP) ;push data regs except D0
MOVE.L #0,D1
MOVEM.L D1,D2-D4 ;clear regs D1 thru D4
CMP.L #0,D0
BEQ notPrime
CMP.L #1,D0
BEQ notPrime
CMP.L #2,D0
BEQ wasPrime
MOVE.L D0,D1 ;D1 will be used for temp storage.
AND.L #1,D1 ;is D1 even?
BEQ notPrime ;if so, it's not prime!
MOVE.L D0,D1 ;restore D1
MOVE.L #3,D2 ;start with 3
computeFactors:
DIVU D2,D1 ;remainder is in top 2 bytes, quotient in bottom 2.
MOVE.L D1,D3 ;temporarily store into D3 to check the remainder
SWAP D3 ;swap the high and low words of D3. Now bottom 2 bytes contain remainder.
CMP.W #0,D3 ;is the bottom word equal to 0?
BNE D2_Wasnt_A_Divisor ;if not, D2 was not a factor of D1.
ADDQ.L #1,D4 ;increment the count of proper divisors.
D2_Wasnt_A_Divisor:
MOVE.L D0,D1 ;restore D1.
ADDQ.L #1,D2 ;increment D2
CMP.L D2,D1 ;is D2 now greater than D1?
BLS computeFactors ;if not, loop again
CMP.L #1,D4 ;was there only one factor?
BEQ wasPrime ;if so, D0 was prime.
notPrime:
;end of program
MOVE.L #0,D0
MOVEM.L (SP)+,D1-D4 ;pop D1-D4
RTS
wasPrime:
MOVE.L #1,D0
MOVEM.L (SP)+,D1-D4 ;pop D1-D4
RTS</lang>
=={{header|AArch64 Assembly}}==
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