Optimize ADDMOD for elliptic curve context #206
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In elliptic curve context the x and y arguments are already reduced modulo mod. Here we can pick up similar condition and provide optimized implementation for such case. This case is 2x faster with little overhead for other cases. Based on holiman/uint256#86.
axic
reviewed
Dec 17, 2021
| // Fast path for mod >= 2^192, with x and y at most slightly bigger than mod. | ||
| // This is always the case when x and y are already reduced modulo mod. | ||
| // Based on https://github.com/holiman/uint256/pull/86. | ||
| if ((mod[3] != 0) && (x[3] <= mod[3]) && (y[3] <= mod[3])) |
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How does this handle the mod[4] != 0 case? i.e. shouldn't it be (mod[4] | mod[3]) != 0?
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There is no mod[4]. The mod[3] is the most significant word.
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