RFR: 8316594: C2 SuperWord: wrong result with hand unrolled loops [v2]

[Emanuel Peter]

> Please read description in https://github.com/openjdk/jdk/pull/15864.
> 
> Currently, we only compare the first element of the load-pack with the StoreVector. This is not correct, we need to compare all elements of the load-pack with the StoreVector. Otherwise it may be that the first element lays below/before the memory region of the StoreVector (Less), but the last element of the load-pack for example could have overlap with the StoreVector (Equal).
> 
> Tier1-6 + stress-testing.
> Performance testing.

Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - manual merge master
 - whitespace
 - rm avx2 flag, not necessary
 - more comments
 - beautify code
 - fix tests
 - 8316594: C2 SuperWord: wrong result with hand unrolled loops

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Changes: https://git.openjdk.org/jdk/pull/15866/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15866&range=01
  Stats: 129 lines in 3 files changed: 122 ins; 5 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15866.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15866/head:pull/15866

PR: https://git.openjdk.org/jdk/pull/15866