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Square implementation #138

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Square implementation #138

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065a00b
add bigUintSquare
ColoCarletti Sep 26, 2023
3891703
refactor for loop
ColoCarletti Sep 26, 2023
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104 changes: 103 additions & 1 deletion precompiles/Modexp.yul
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,19 @@ object "ModExp" {

// HELPER FUNCTIONS

function overflowingAdd(augend, addend) -> sum, overflowed {
sum := add(augend, addend)
overflowed := lt(sum, augend)
}

/// @notice Retrieves the highest half of the multiplication result.
/// @param multiplicand The value to multiply.
/// @param multiplier The multiplier.
/// @return ret The highest half of the multiplication result.
function getHighestHalfOfMultiplication(multiplicand, multiplier) -> ret {
ret := verbatim_2i_1o("mul_high", multiplicand, multiplier)
}

/// @notice Checks whether a big number is zero.
/// @param start The pointer to the calldata where the big number starts.
/// @param len The number of bytes that the big number occupies.
Expand Down Expand Up @@ -67,6 +80,95 @@ object "ModExp" {
}
}

function bigUIntSqr(numberPtr, nLimbs, productPtr) {
let endOfProductPtr := add(productPtr, mul(mul(nLimbs, WORD_SIZE()), 2))
let hiPtr := productPtr
let loPtr := add(productPtr, mul(nLimbs, WORD_SIZE()))

let k, index, a_i, a_j, hi, lo, cs, overflow, c
for {let i := nLimbs} gt(i, 1) {i := sub(i, 1)} {
for {let j := i} gt(j, 0) {j := sub(j, 1)} {
k := add(i, j)
if or(gt(k, sub(i, 1)), eq(k, sub(i, 1))) {
index := sub(add(k, 1), nLimbs)
a_i := mload(add(numberPtr, mul(WORD_SIZE(), i)))
a_j := mload(add(numberPtr, mul(WORD_SIZE(), j)))
hi := getHighestHalfOfMultiplication(a_i, a_j)
lo := mul(a_i,a_j)
lo, overflow := overflowingAdd(lo, mload(add(loPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
lo, overflow := overflowingAdd(lo, c)
hi := add(hi, overflow)
c := hi
mstore(add(loPtr, mul(index, WORD_SIZE())), lo)
}
if lt(k, sub(i, 1)) {
index := sub(add(k, 1), nLimbs)
a_i := mload(add(numberPtr, mul(WORD_SIZE(), i)))
a_j := mload(add(numberPtr, mul(WORD_SIZE(), j)))
hi := getHighestHalfOfMultiplication(a_i, a_j)
lo := mul(a_i,a_j)
lo, overflow := overflowingAdd(lo, mload(add(hiPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
lo, overflow := overflowingAdd(lo, c)
hi := add(hi, overflow)
c := hi
mstore(add(hiPtr, mul(index, WORD_SIZE())), lo)
}
}
mstore(add(hiPtr, i), or(hi,lo))
}
let carry := shr(63, mload(loPtr))
// lo = shl(1, lo)
// hi = shl(1, hi)
// hi.limbs[NUM_LIMBS - 1] |= carry;

c := 0

for {let i := nLimbs} gt(i, 0) {i := sub(i, 1)} {
if or(lt(sub(nLimbs, 1), mul(i, 2)), eq(sub(nLimbs, 1), mul(i, 2))) {
index := sub(add(mul(2, i), 1), nLimbs)
a_i := mload(add(numberPtr, mul(WORD_SIZE(), i)))
hi := getHighestHalfOfMultiplication(a_i, a_i)
lo := mul(a_i,a_j)
lo, overflow := overflowingAdd(lo, mload(add(loPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
lo, overflow := overflowingAdd(lo, c)
hi := add(hi, overflow)
c := hi
mstore(add(loPtr, mul(index, WORD_SIZE())), lo)
}
if gt(sub(nLimbs, 1), mul(i, 2)) {
index := add(mul(2, i), 1)
a_i := mload(add(numberPtr, mul(WORD_SIZE(), i)))
hi := getHighestHalfOfMultiplication(a_i, a_i)
lo := mul(a_i,a_j)
lo, overflow := overflowingAdd(lo, mload(add(hiPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
lo, overflow := overflowingAdd(lo, c)
hi := add(hi, overflow)
c := hi
mstore(add(hiPtr, mul(index, WORD_SIZE())), lo)
}
if lt(sub(nLimbs, 1), mul(i, 2)) {
index := sub(mul(2, i), nLimbs)
hi := 0
lo, overflow := overflowingAdd(c, mload(add(hiPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
c := hi
mstore(add(loPtr, mul(index, WORD_SIZE())), lo)
}
if or(gt(sub(nLimbs, 1), mul(i, 2)),eq(sub(nLimbs, 1), mul(i, 2))) {
index := mul(2, i)
hi := 0
lo, overflow := overflowingAdd(c, mload(add(hiPtr, mul(index, WORD_SIZE()))))
hi := add(hi, overflow)
c := hi
mstore(add(hiPtr, mul(index, WORD_SIZE())), lo)
}
}
}

////////////////////////////////////////////////////////////////
// FALLBACK
////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -126,4 +228,4 @@ object "ModExp" {
// TODO: big arithmetics
}
}
}
}