8359378: aarch64: crash when using -XX:+UseFPUForSpilling

[bulasevich]

AArch64 BarrierSetAssembler path assumes only FP/vector ideal regs reach the FP spill/restore encoding. With -XX:+UseFPUForSpilling Register Allocator may allocate scalar values in FP registers. When such values (Op_RegI/Op_RegN/Op_RegL/Op_RegP) hit BarrierSetAssembler::encode_float_vector_register_size, we trip ShouldNotReachHere in release build and "unexpected ideal register" assertion in debug build.

Fix: teach the encoder to handle scalar ideal regs when they physically live in FP regs:

• treat Op_RegI / Op_RegN as 32-bit (single slot) - same class as Op_RegF
• treat Op_RegL / Op_RegP as 64-bit (two slots) - same class as Op_RegD

Related:

• reproduced since 8334060: Implementation of Late Barrier Expansion for G1 #19746
• spilling logic:
  • 8330685: ZGC: share barrier spilling logic #18967
  • 8326541: [AArch64] ZGC C2 load barrier stub should consider the length of live registers when spilling registers #17977

Testing: tier1-3 with javaoptions -Xcomp -Xbatch -XX:+UseFPUForSpilling on AARCH

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8359378: aarch64: crash when using -XX:+UseFPUForSpilling (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/27350/head:pull/27350
$ git checkout pull/27350

Update a local copy of the PR:
$ git checkout pull/27350
$ git pull https://git.openjdk.org/jdk.git pull/27350/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 27350

View PR using the GUI difftool:
$ git pr show -t 27350

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/27350.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back bulasevich! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@bulasevich The following label will be automatically applied to this pull request:

• hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (9503349d)