RFR: 8371768: AArch64: test/hotspot/jtreg/compiler/loopopts/superword/TestReductions.java fails on SVE after JDK-8340093 [v2]

[Aleksey Shipilev]

> Looks like the test should be more resilient with UseSVE > 0, which _can_ vectorise. It does not look all that reliable to me to failOn when vectorization actually happens. So I dropped some non-arch-specific rules, and amended AArch64-specific rules for UseSVE.
> 
> Testing:
>  - [x] Linux AArch64 server fastdebug, affected test on machine with UseSVE=1 by default
>  - [x] Linux AArch64 server fastdebug, affected test on machine with UseSVE=0 overridden

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into JDK-8371768-testbug-reduction
 - A bit of mop up
 - UseSVE works

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28423/files
  - new: https://git.openjdk.org/jdk/pull/28423/files/c5e4a3cc..0d922cb8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28423&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28423&range=00-01

  Stats: 47164 lines in 640 files changed: 33290 ins; 9786 del; 4088 mod
  Patch: https://git.openjdk.org/jdk/pull/28423.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28423/head:pull/28423

PR: https://git.openjdk.org/jdk/pull/28423