RFR: 8298387: Implement JEP 497: Quantum-Resistant Module-Lattice-Based Digital Signature Algorithm [v30]

[Jamil Nimeh]

On Thu, 14 Nov 2024 23:24:33 GMT, Ben Perez <bperez at openjdk.org> wrote:

>> Java implementation of ML-DSA, the FIPS 204 post-quantum signature scheme https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.204.pdf. Depends on https://github.com/openjdk/jdk/pull/21167
>
> Ben Perez has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updated copyrite, changed classes in ML_DSA_Impls to sealed

Just a couple nit comments, not crucial to the initial integration.

src/java.base/share/classes/sun/security/provider/ML_DSA.java line 1029:

> 1027:                     int tmp = montMul(MONT_ZETAS_FOR_NTT[m], coeffs[j + l]);
> 1028:                     coeffs[j + l] = coeffs[j] - tmp;
> 1029:                     coeffs[j] = coeffs[j] + tmp;

Similar to how you land the array contents onto a couple of ints in `power2round`, I wonder if you might squeeze a few clock cycles out by putting `coeffs[j]` and maybe `coeffs[j + 1]` onto local int variables to increase register pressure.  You would save potentially a couple reaches into memory if that int lived on a register.  Not sure how much mileage you would get from it.

src/java.base/share/classes/sun/security/provider/ML_DSA.java line 1050:

> 1048:                     int tmp = coeffs[j];
> 1049:                     coeffs[j] = (tmp + coeffs[j + l]);
> 1050:                     coeffs[j + l] = montMul(tmp - coeffs[j + l], MONT_ZETAS_FOR_INVERSE_NTT[m]);

This might be another area where you can land `coeffs[j + 1]` on a local int.  Again, not sure if or how much it might help.

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Marked as reviewed by jnimeh (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21364#pullrequestreview-2447311809
PR Review Comment: https://git.openjdk.org/jdk/pull/21364#discussion_r1849474054
PR Review Comment: https://git.openjdk.org/jdk/pull/21364#discussion_r1849475269