RFR: 8341013: Optimize x86/aarch64 MD5 intrinsics by reducing data dependency

[Oli Gillespie]

As suggested in https://github.com/animetosho/md5-optimisation?tab=readme-ov-file#dependency-shortcut-in-g-function, we can delay the dependency on 'b' by recognizing that the ((d & b) | (~d & c)) is equivalent to ((d & b) + (~d & c)) in this scenario, and we can perform those additions independently, leaving our dependency on b to the final addition. This speeds it up around 5%.

Benchmark results on my two hosts:


Benchmark                  (algorithm)  (dataSize)  (provider)   Mode  Cnt    Score   Error  Units

x86 Before:
MessageDigestBench.digest          MD5     1048576              thrpt   10  636.389 ± 0.240  ops/s

x86 After:
MessageDigestBench.digest          MD5     1048576              thrpt   10  671.611 ± 0.226  ops/s (+5.5%)


aarch64 Before:
MessageDigestBench.digest          MD5     1048576              thrpt   10  498.613 ± 0.359  ops/s

aarch64 After:
MessageDigestBench.digest          MD5     1048576              thrpt   10  526.008 ± 0.491  ops/s (+5.6%)

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Commit messages:
 - Optimize md5 intrinsic

Changes: https://git.openjdk.org/jdk/pull/21203/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21203&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341013
  Stats: 6 lines in 2 files changed: 3 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21203.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21203/head:pull/21203

PR: https://git.openjdk.org/jdk/pull/21203