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precompiles: Add Fq2 sqr() and use it in BN254 pairing helpers #1539

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precompiles: Add Fq2 sqr() and use it in BN254 pairing helpers #1539

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10 changes: 10 additions & 0 deletions lib/evmone_precompiles/pairing/bn254/fields.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,16 @@ constexpr Fq2 multiply(const Fq2& a, const Fq2& b)
return Fq2({a0 * b0 - a1 * b1, a1 * b0 + a0 * b1});
}

/// Squares an Fq^2 field element.
constexpr Fq2 sqr(const Fq2& a)
{
const auto& [a0, a1] = a.coeffs;

// (a0 + a1*u)^2 = (a0+a1)*(a0-a1) + 2a0a1*u.
const auto a0a1 = a0 * a1;
return Fq2({(a0 + a1) * (a0 - a1), a0a1 + a0a1});
}

/// Multiplies two Fq^6 field elements
constexpr Fq6 multiply(const Fq6& a, const Fq6& b)
{
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8 changes: 7 additions & 1 deletion lib/evmone_precompiles/pairing/field_template.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -68,8 +68,14 @@ struct ExtFieldElem
return ExtFieldElem(ret);
}

friend constexpr ExtFieldElem operator*(const ExtFieldElem& e1, const ExtFieldElem& e2) noexcept
[[gnu::always_inline]] friend constexpr ExtFieldElem operator*(
const ExtFieldElem& e1, const ExtFieldElem& e2) noexcept
{
if constexpr (requires { sqr(e1); }) // Use sqr() if available.
{
if (&e1 == &e2)
return sqr(e1);
}
return multiply(e1, e2);
}

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