RFR: 8297830: aarch64: Make Address a discriminated union internally [v2]

[Kim Barrett]

> Please review this change to the aarch64 Address class.  It now uses an
> internal union, separating the literal and nonliteral cases.
> 
> This avoids leaving some fields uninitialized or initializing them to dummy
> values.  It also reduces the size of the Address class somewhat, though it's
> unclear whether that makes any noticeable difference.
> 
> Testing:
> mach5 tier1 for linux-aarch64 and macosx-aarch64
> mach5 tier2-5 for linux-aarch64

Kim Barrett 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 two additional commits since the last revision:

 - Merge branch 'master' into unionize2
 - unionize

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11429/files
  - new: https://git.openjdk.org/jdk/pull/11429/files/eb4f70b8..5b0571cc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11429&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11429&range=00-01

  Stats: 8750 lines in 270 files changed: 4843 ins; 2321 del; 1586 mod
  Patch: https://git.openjdk.org/jdk/pull/11429.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11429/head:pull/11429

PR: https://git.openjdk.org/jdk/pull/11429