package field import "math/bits" // uint128 holds a 128-bit number as two 64-bit limbs, for use with the // bits.Mul64 and bits.Add64 intrinsics. type uint128 struct { lo, hi uint64 } // mul64 returns a * b. func mul64(a, b uint64) uint128 { hi, lo := bits.Mul64(a, b) return uint128{lo, hi} } // addMul64 returns v + a * b. func addMul64(v uint128, a, b uint64) uint128 { hi, lo := bits.Mul64(a, b) lo, c := bits.Add64(lo, v.lo, 0) hi, _ = bits.Add64(hi, v.hi, c) return uint128{lo, hi} } // shiftRightBy51...