[jdk16] RFR: 8260585: AArch64: Wrong code generated for shifting right and accumulating four unsigned short integers [v6]

[Dong Bo]

> This is a typo introduced by JDK-8255949.
> Compiler will generate `ushr` for shifting right and accumulating four short integers.
> It produces wrong results for specific case. The instruction should be `usra`.

Dong Bo has updated the pull request incrementally with one additional commit since the last revision:

  Update tests to match .2I. Still cannot match ssra for .8B, sshr+add are not combined.

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Changes:
  - all: https://git.openjdk.java.net/jdk16/pull/136/files
  - new: https://git.openjdk.java.net/jdk16/pull/136/files/ca3d2192..693f8cbd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk16&pr=136&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk16&pr=136&range=04-05

  Stats: 88 lines in 1 file changed: 39 ins; 41 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/136.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/136/head:pull/136

PR: https://git.openjdk.java.net/jdk16/pull/136