RFR: 8311630: [s390] Implementation of Foreign Function & Memory API (Preview) [v5]

[sid8606]

> Implementation of "Foreign Function & Memory API" for s390x (Big Endian).

sid8606 has updated the pull request incrementally with one additional commit since the last revision:

  remove if statements around the spill/fill code
  
  See: #15025 (should_save_return_value being dependent on _needs_transition is a bug).

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14801/files
  - new: https://git.openjdk.org/jdk/pull/14801/files/75229b4c..107b971f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14801&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14801&range=03-04

  Stats: 15 lines in 1 file changed: 0 ins; 15 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14801.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14801/head:pull/14801

PR: https://git.openjdk.org/jdk/pull/14801