[jdk21u-dev] RFR: 8321599: Data loss in AVX3 Base64 decoding

[Oli Gillespie]

Hi all,

This pull request contains a backport of commit [13c11487](https://github.com/openjdk/jdk/commit/13c11487f7126a370d9ce8e62f661ea83eedefe6) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Scott Gibbons on 4 Jan 2024 and was reviewed by Sandhya Viswanathan and Vladimir Kozlov.

Thanks!

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Commit messages:
 - Backport 13c11487f7126a370d9ce8e62f661ea83eedefe6

Changes: https://git.openjdk.org/jdk21u-dev/pull/122/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=122&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321599
  Stats: 124 lines in 2 files changed: 121 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/122.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/122/head:pull/122

PR: https://git.openjdk.org/jdk21u-dev/pull/122