RFR: 8357267: ZGC: Handle APX EGPRs spilling in ZRuntimeCallSpill [v4]

[Jatin Bhateja]

> Patch spills APX EGPRs across runtime calls to slow-path barriers using PUSH2P/POP2 instructions with PPX hints.
> These instructions operate over a pair of registers resulting into an smaller save/restoration JIT code, on the hind side they have hard alignment and balancing constraints, as they operate over 16-byte aligned stack address.
> ZRuntimeCallSpill is agnostic to live register, thus resulting SPILL sequence should not modify the contents of the register.
> 
> Patch has been verified using Intel SDE all test under test/hotspot/jtreg/compiler/gcbarriers are green.
> 
> Kindly review and share your feedback.
> 
> Best Regards,
> Jatin

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

  Axel's comments incorporated

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25351/files
  - new: https://git.openjdk.org/jdk/pull/25351/files/9b5c2ac4..bd8b9c51

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25351&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25351&range=02-03

  Stats: 8 lines in 1 file changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/25351.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25351/head:pull/25351

PR: https://git.openjdk.org/jdk/pull/25351