8274795: AArch64: avoid spilling and restoring r18 in macro assembler

[lewurm]

r18 should not be used as it is reserved as platform register. Linux is fine with userspace using it, but Windows and also recently macOS (#301 (comment) ) are actually using it on the kernel side.

The macro assembler uses the bit pattern 0x7fff_ffff (== r0-r30) to specify which registers to spill. While spilling r18 is fine (e.g. for a register dump), we should never restore it.

Tested tier1 on Linux/AArch64 and macOS/AArch64 (the latter on top of the current patches from openjdk/aarch64-port#14 ).

---

Progress

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Issue

• JDK-8274795: AArch64: avoid spilling and restoring r18 in macro assembler

Reviewers

• Andrew Haley (@theRealAph - Reviewer)

Reviewing

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$ git checkout pull/744

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$ git checkout pull/744
$ git pull https://git.openjdk.java.net/jdk11u-dev pull/744/head

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$ git pr checkout 744

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https://git.openjdk.java.net/jdk11u-dev/pull/744.diff

[bridgekeeper]

👋 Welcome back burban! 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 backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (13762898)

[openjdk]

@lewurm This change now passes all automated pre-integration checks.

After integration, the commit message for the final commit will be:

8274795: AArch64: avoid spilling and restoring r18 in macro assembler

Reviewed-by: aph

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 46 new commits pushed to the master branch:

• 4a5caa0: 8193277: SimpleFileObject inconsistency between getName and getShortName
• e7b89f7: 8225559: assertion error at TransTypes.visitApply
• 5ab97c4: 8220634: SymLinkArchiveTest should handle not being able to create symlinks
• a29949b: 8214026: Canonicalized archive paths appearing in diagnostics
• 538013a: 8251126: nsk.share.GoldChecker should read golden file from ${test.src}
• fac0f5a: 8237798: rewrite vmTestbase/jit/tiered from shell to java
• f5ade3e: 8262134: compiler/uncommontrap/TestDeoptOOM.java failed with "guarantee(false) failed: wrong number of expression stack elements during deopt"
• 89f4d44: 8210194: [TESTBUG] jvmti_FollowRefObjects.cpp missing initializer for member _jvmtiHeapCallbacks::heap_reference_callback
• 898b8de: 8277441: CompileQueue::add fails with assert(_last->next() == __null) failed: not last
• e3da580: 8273704: DrawStringWithInfiniteXform.java failed : drawString with InfiniteXform transform takes long time
• ... and 36 more: https://git.openjdk.java.net/jdk11u-dev/compare/ec89f1b6c317932e937291f43e68d04ff77204b8...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[lewurm]

/integrate

[openjdk]

@lewurm
Your change (at version 1376289) is now ready to be sponsored by a Committer.

[VladimirKempik]

/sponsor

[openjdk]

Going to push as commit b5cae57.
Since your change was applied there have been 90 commits pushed to the master branch:

• 914d48c: 8232533: G1 uses only a single thread for pretouching the java heap
• ec03928: 8273933: [TESTBUG] Test must run without preallocated exceptions
• cba6c04: 8268542: serviceability/logging/TestFullNames.java tests only 1st test case
• 521144c: 8251998: remove usage of PropertyResolvingWrapper in vmTestbase/jit/t
• f69e75f: 8273438: Enable parallelism in vmTestbase/metaspace/stressHierarchy tests
• 574c04c: 8273433: Enable parallelism in vmTestbase_nsk_sysdict tests
• 5ffd40d: 8273341: Update Siphash to version 1.0
• 0c4803b: 8278871: [JVMCI] assert((uint)reason < 2* _trap_hist_limit) failed: oob
• 3352b56: 8275326: C2: assert(no_dead_loop) failed: dead loop detected
• ad94355: 8251127: clean up FileInstaller $test.src $cwd in remaining vmTestbase_vm_compiler tests
• ... and 80 more: https://git.openjdk.java.net/jdk11u-dev/compare/ec89f1b6c317932e937291f43e68d04ff77204b8...master

Your commit was automatically rebased without conflicts.

[openjdk]

@VladimirKempik @lewurm Pushed as commit b5cae57.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[lewurm]

Thank you Andrew, Goetz and Vladimir!