Receive two integers a and p and print x such that ax ≡ 1 (mod p)
p is prime and a is not a multiple of p
The code works perfectly in MARS, but in QTSpim it complains about overlfow (immediate value 825265 out of range) and accuses error when p and prime. Why this difference between the two?
.data
message1: .asciiz "Invali Input\n"
message2: .asciiz "inverse = "
message3: .asciiz "The module is not a prime\n"
finalLine: .asciiz "\n"
.text
main:
li $v0, 5
syscall
move $t8, $v0
li $v0, 5
syscall
move $t9, $v0
beq $t8, 2, verifyMult
ble $t8, 1, invalidInput
ble $t9, 1, invalidInput
j pr
verifyMult:
div $t9, $t8
mfhi $s1
beq $s1, 0, invalidInput
j modInverse
main3:
li $v0, 4
la $a0, message2
syscall
li $v0, 1
move $a0, $t4
syscall
li $v0, 4
la $a0, finalLine
syscall
li $v0, 10
syscall
invalidInput:
li $v0, 4
la $a0, message1
syscall
li $v0, 10
syscall
invalidMod:
li $v0, 4
la $a0, message3
syscall
li $v0, 10
syscall
modInverse:
move $t0, $t8
move $t1, $t9
addi $t2, $t0, 0
addi $t3, $zero, 0
addi $t4, $zero, 1
while:
ble $t1, 1, exit
div $t1, $t0
mflo $t5
addi $t6, $t0, 0
mfhi $t0
addi $t1, $t6, 0
addi $t6, $t3, 0
mult $t5, $t3
mflo $s0
sub $t3, $t4, $s0
addi $t4, $t6, 0
j while
exit:
blt $t4, 0, makePositive
j main3
makePositive:
add $t4, $t4, $t2
j main3
pr:
add $s5, $t8, $zero
andi $t1,$s5,1
beq $t1,$zero, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,561
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,1105
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,1729
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,2465
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,2821
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,6601
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,8911
beq $s5,$t0, invalidMod
xor $t0,$t0,$t0
addiu $t0,$t0,10585
beq $s5,$t0, invalidMod
addiu $t2,$t2,41041
beq $s5,$t2, invalidMod
addiu $t3,$t3,825265
beq $s5, $t3 , invalidMod
addiu $t4,$t4,321197185
beq $s5,$t4, invalidMod
move $s1,$s5
xor $t2,$t2,$t2
xor $t3,$t3,$t3
xor $t4,$t4,$t4
addiu $t4,$t4,2
loop_exponent:
andi $t1,$s5,1
beq $t1,$zero, even_exponent
subiu $s5,$s5,1
sll $t2,$t2,1
addiu $t2,$t2,1
j next_iteration
even_exponent:
sll $t2,$t2,1
srl $s5,$s5,1
next_iteration:
addiu $t3,$t3,1
bne $s5,$t4, loop_exponent
sll $t2,$t2,1
addiu $t3,$t3,1
xor $t5,$t5,$t5
addiu $t5,$t5,3
xor $t6,$t6,$t6
addiu $t6,$t6,3
loop_compute_mod:
andi $t1,$t2,1
beq $t1,$zero, even
multu $t5,$t6
mflo $t5
divu $t5,$s1
mfhi $t5
j next_exponent_bit
even:
multu $t5,$t5
mflo $t5
divu $t5,$s1
mfhi $t5
next_exponent_bit:
subiu $t3,$t3,1
srl $t2,$t2,1
bgtz $t3, loop_compute_mod
divu $t6,$s1
mfhi $t6
beq $t5,$t6,verifyMult
j invalidMod
