[jdk16u] RFR: 8256215: Shenandoah: re-organize saving/restoring machine state in assembler code [v2]

[Aleksey Shipilev]

> This unbreaks x86_32 tests with Shenandoah.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug tier1,2
>  - [x] Linux x86_32 fastdebug tier1,2 `-XX:+UseShenandoahGC -XX:+UseSSE=1`
>  - [x] Linux x86_32 fastdebug tier1,2 `-XX:+UseShenandoahGC -XX:+UseSSE=2`

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 two additional commits since the last revision:

 - Merge branch 'master' into JDK-8256215-sh-regsaves
 - Backport a97aedff9f622ba6816b7550588f1d429bff2483

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

Changes:
  - all: https://git.openjdk.java.net/jdk16u/pull/69/files
  - new: https://git.openjdk.java.net/jdk16u/pull/69/files/1a010fed..5f827070

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=69&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=69&range=00-01

  Stats: 326 lines in 17 files changed: 281 ins; 13 del; 32 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/69.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/69/head:pull/69

PR: https://git.openjdk.java.net/jdk16u/pull/69