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examples-zmips

README.md

ZMIPS ISA

zMIPS is our extension to the MIPS ISA to support programming ZKPs. Below we provide the zMIPS enhanced ISA:

Instruction Description
add $ri, $rj, A $ri = $rj + A
sub $ri, $rj, A $ri = $rj - A
mult $ri, $rj, A $ri = $rj * A
div $ri, $rj, A $ri = $rj / A
mod $ri, $rj, A $ri = $rj % A
move $ri, A $ri = A
la $ri, L $ri = L
and $ri, $rj, A $ri = $rj & A
or $ri, $rj, A $ri = $rj | A
xor $ri, $rj, A $ri = $rj ^ A
not $ri, A $ri = ~A
sll $ri, $rj, A $ri = $rj << A
srl $ri, $rj, A $ri = $rj >> A
beq $ri, $rj, L if $ri == $rj goto L
bne $ri, $rj, L if $ri != $rj goto L
blt $ri, $rj, L if $ri < $rj goto L
ble $ri, $rj, L if $ri <= $rj goto L
seq $ri, $rj, A if $ri = ($rj == A)
sne $ri, $rj, A if $ri = ($rj != A)
slt $ri, $rj, A if $ri = ($rj < A)
sle $ri, $rj, A if $ri = ($rj <= A)
j L goto label L
jr $ri goto instrcution pointed by $ri
sw $ri, A($rj) [A+$rj] = $ri
lw $ri, A($rj) $ri = [A+$rj]
pubread $ri $ri = next from public
secread $ri $ri = next from private
pubseek $ri, A $ri = public[A]
secseek $ri, A $ri = private[A]
print $ri print ri
answer $ri return ri

Labels

In Zilch, both the prefix and the suffix of a the label should be __. For instance __labelName__.

zMIPS Input: Enhanced read from tapes instructions

  • pubread $ri : Consumes the next word from the public tape (if it has remaining words) and stores it in $ri.

  • secread $ri : Consumes the next word from the private tape (if it has remaining words) and stores it in $ri.

  • pubseek $ri, $rj : seek is a random access read command. pubseek consumes the word in offset $rj from the public tape. In case the tape does not have at least $rj words, this instruction raises an error.

  • secseek $ri, $rj : secseek consumes the word in offset $rj from the private tape. In case the tape does not have at least $rj words, this instruction raises an error.

User-defined Macros

In macros.json the user can define her own custom zMIPS macro-instructions.

For instance, we have defined inc, dec and min macro-instructions as shown below :

"inc": {
    "reg1": "$x",
    "macro": "add $x, $x, 1"
}

This means that inc uses one register. A zMIPS program can use the inc instruction as

move $r0, $r0, 5
inc $r0
answer $r0

the answer would be 6.

The min macro-instruction uses three registers and also labels:

"min": {
    "reg1": "$x",
    "reg2": "$y",
    "reg3": "$z",
    "uses_label" : "true",
    "macro" : "blt $y, $z, __min_label__
            move $x, $z
            j __end_min_label__
            __min_label__
            move $x, $y
            __end_min_label__"
    }

move $r0, 5
move $r1, 9
min $r2, $r0, $r1
answer $r2

the answer would be 5.