RFR: 8333583: Crypto-XDH.generateSecret regression after JDK-8329538

[Volodymyr Paprotski]

On Fri, 14 Jun 2024 20:23:04 GMT, Volodymyr Paprotski <duke at openjdk.org> wrote:

> This fix recovers XDH performance but removes some of the P256 gains (~-8-14%). Still faster, but not as much.
> 
> The fix is to undo 'int' return type on mult()/square(), which allowed to return partially reduced result (i.e. this avoids extra reductions when mult() result is fed into addition). This is the behaviour before the Montgomery ECC PR.
> 
> I have a slightly better mult() intrinsic that does reduction at the end, but decided to use a more conservative fix and just keep the reduction in Java (i.e. original mult() refactored into multImpl() and reducePositive()) Will commit these optimizations I discovered while working on this in next release.
> 
> ---
> 
> Performance before Montgomery PR:
> 
> Benchmark                        (algorithm)  (dataSize)  (keyLength)  (provider)   Mode  Cnt     Score    Error  Units
> SignatureBench.ECDSA.sign    SHA256withECDSA        1024          256              thrpt    3  6398.727 ±  7.400  ops/s
> SignatureBench.ECDSA.sign    SHA256withECDSA       16384          256              thrpt    3  6129.739 ±  5.995  ops/s
> SignatureBench.ECDSA.verify  SHA256withECDSA        1024          256              thrpt    3  1889.928 ± 54.660  ops/s
> SignatureBench.ECDSA.verify  SHA256withECDSA       16384          256              thrpt    3  1866.339 ± 42.438  ops/s
> Benchmark                                            (algorithm)  (keyLength)  (kpgAlgorithm)  (provider)   Mode  Cnt     Score    Error  Units
> o.o.b.j.c.full.KeyAgreementBench.EC.generateSecret          ECDH          256              EC              thrpt    3  1350.745 ± 28.514  ops/s
> o.o.b.j.c.small.KeyAgreementBench.EC.generateSecret         ECDH          256              EC              thrpt    3  1349.393 ± 32.050  ops/s
> Benchmark                             (algorithm)  (keyLength)  (kpgAlgorithm)  (provider)   Mode  Cnt     Score    Error  Units
> KeyAgreementBench.XDH.generateSecret          XDH          255             XDH              thrpt    3  8435.277 ± 27.230  ops/s
> 
> Performance in master without mult() intrinsic
> 
> Benchmark                        (algorithm)  (dataSize)  (keyLength)  (provider)   Mode  Cnt     Score     Error  Units
> SignatureBench.ECDSA.sign    SHA256withECDSA        1024          256              thrpt    3  6539.589 ± 132.844  ops/s
> SignatureBench.ECDSA.sign    SHA256withECDSA       16384          256              thrpt    3  6202.530 ± 124.496  ops/s
> SignatureBench.ECDSA.verify  SHA256withECDSA        1024          256              thrpt    3  1967.0...

@ascarpino Would you mind reviewing this again please? Mostly java you reviewed before.

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PR Comment: https://git.openjdk.org/jdk/pull/19728#issuecomment-2168728473