RFR: 8371864: GaloisCounterMode.implGCMCrypt0 AVX512/AVX2 intrinsics stubs cause AES-GCM encryption failure for certain payload sizes [v2]

[Jiangli Zhou]

> Please review the fix in StubGenerator::aesgcm_avx512 and StubGenerator::aesgcm_avx2 to handle some edge cases with input sizes that are not multiple of the block size. 
> 
> Thanks to Thomas Holenstein and Lukas Zobernig for analyzing the issue and providing the test case!

Jiangli Zhou has updated the pull request incrementally with four additional commits since the last revision:

 - Address shipilev coments:
   - Replace time-bound loop with an iteration of three runs.
   - Add encrypt part and check to make sure the encrypted message is the same as the original.
 - Address shipilev's comments:
   - Rename test to TestGCMSplitBound.java
   - Change test range to [SPLIT_LEN - 300; SPLIT_LEN + 300].
 - Stylistic change: '256' to '16 * 16'.
 - Fix indentation.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28363/files
  - new: https://git.openjdk.org/jdk/pull/28363/files/338a99d0..f1e7291b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28363&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28363&range=00-01

  Stats: 249 lines in 3 files changed: 135 ins; 113 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28363.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28363/head:pull/28363

PR: https://git.openjdk.org/jdk/pull/28363