8292203: AArch64: Represent Registers as values

[iwanowww]

(It's a PR dependent on #9815.)

Along with x86 (JDK-8292153), I propose to refactor Register classes on AArch64 and migrate away from pointer-based representation.

The motivation is the same: improve compile-time checks and avoid ambiguities between overloads due to implicit conversions between pointers and integral types.

Proposed change hides pointer representation behind value class.

Pointer-based representation is kept to avoid massive migration of users (from -> to .) and to enable incremental migration on per-platform basis (pointer-based representation is assumed in shared code).

Code quality improves: GCC: https://godbolt.org/z/r6G36facj Clang: https://godbolt.org/z/x5oPdYEPM

(I noticed one downside: slowdebug builds become slower, because operator-> isn't inlined there. If it becomes a problem, migrating performance-sensitive places from -> to . should solve the problem.)

Testing: hs-tier1 - hs-tier5

PS: a number of cleanups are incorporated. In particular, I decided to expand all macros from register.hpp because IMO they add confusion rather than improve readability.

---

Progress

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Issue

• JDK-8292203: AArch64: Represent Registers as values

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer) ⚠️ Review applies to f8ebe8d3

Reviewing

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[openjdk[bot]]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8292203: AArch64: Represent Registers as values

Reviewed-by: kvn, 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 16 new commits pushed to the master branch:

• 5a20bc44b1fb4edb6ab714191cdc6c3f33ac9836: 8292715: Cleanup Problemlist
• 7b81a9c75d60f6eb2727515bacfffcf7cf15e128: 8289764: gc/lock tests failed with "OutOfMemoryError: Java heap space: failed reallocation of scalar replaced objects"
• 76ee5495cd00f5546a5748051cc36965a8e936db: 8292329: Enable CDS shared heap for zero builds
• 14623c6087105a4228ff190e9e27372729b2bc4b: 8292739: Invalid legacy entries may be returned by Provider.getServices() call
• 568be58e8521e5e87baca1872ba8cc1941607bb7: 8290469: Add new positioning options to PassFailJFrame test framework
• 69448f9c1a9b123be8ef63bb039111a8976a8da6: 8292679: Simplify thread creation in gtest and port 2 tests to new way
• 3c2289d65157fca3f303d2fe703b31ef53b2f5bf: 8215916: The failure reason of an optional JAAS LoginModule is not logged
• 71ab5c95af28497fb31aba8ba9597da71bc4d3d5: 8292816: GPL Classpath exception missing from assemblyprefix.h
• c0623972cffdbcd7f80e84a1ec344fd382a4a5cc: 8292713: Unsafe.allocateInstance should be intrinsified without UseUnalignedAccesses
• a45a4b9465d7d01715425000c4fd47c0aa3e76ca: 8292194: G1 nmethod entry barrier disarm value wraps around too early
• ... and 6 more: https://git.openjdk.org/jdk/compare/fe0544f8a7db5bf0e93313e16b54b31bcdff946a...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[merykitty]

Pointer-based representation is kept to avoid massive migration of users (from -> to .) and to enable incremental migration on per-platform basis (pointer-based representation is assumed in shared code).

I don't really understand this part. Can we overload the -> operator instead? I believe this works:

Register* operator->() {
    return this;
}

[theRealAph]

Pointer-based representation is kept to avoid massive migration of users (from -> to .) and to enable incremental migration on per-platform basis (pointer-based representation is assumed in shared code).

I don't really understand this part. Can we overload the -> operator instead? I believe this works:

Register* operator->() {
    return this;
}

I tried something like that before, and got poor code quality.

[openjdk[bot]]

@iwanowww this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout rwrapper.aarch64
git fetch https://git.openjdk.org/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[iwanowww]

Thanks for the review, Vladimir.

Anybody else planning to review? Otherwise, I'll push it tomorrow.

[iwanowww]

Thanks for the review, Andrew.

/integrate

[openjdk[bot]]

Going to push as commit 2fe0ce01485d7b84dc109d3d4f24bdd908c0e7cf. Since your change was applied there have been 22 commits pushed to the master branch:

• 251bff6beeafcd98824dab60e9831c0175fe0689: 8292877: java/util/concurrent/atomic/Serial.java uses {Double,Long}Accumulator incorrectly
• f57d34242c9b47936d137589fc75ab794d39a9d1: 8292867: RISC-V: Simplify weak CAS return value handling
• 88af204027ec51d6e13516fa61e1c217a9445c62: 8292494: Ensure SystemDictionary::set_platform_loader and set_system_loader are called only once
• 8d3d4397ccbfadab99fe572f0d0a8504d268a0dc: 8292903: enhance round_up_power_of_2 assertion output
• 054c23f484522881a0879176383d970a8de41201: 8290025: Remove the Sweeper
• dc7e2562f47edb1489f2fb0c8d6ec847fb7a6dc5: 8290376: G1: Refactor G1MMUTracker::when_sec
• 5a20bc44b1fb4edb6ab714191cdc6c3f33ac9836: 8292715: Cleanup Problemlist
• 7b81a9c75d60f6eb2727515bacfffcf7cf15e128: 8289764: gc/lock tests failed with "OutOfMemoryError: Java heap space: failed reallocation of scalar replaced objects"
• 76ee5495cd00f5546a5748051cc36965a8e936db: 8292329: Enable CDS shared heap for zero builds
• 14623c6087105a4228ff190e9e27372729b2bc4b: 8292739: Invalid legacy entries may be returned by Provider.getServices() call
• ... and 12 more: https://git.openjdk.org/jdk/compare/fe0544f8a7db5bf0e93313e16b54b31bcdff946a...master

Your commit was automatically rebased without conflicts.

[openjdk[bot]]

@iwanowww Pushed as commit 2fe0ce01485d7b84dc109d3d4f24bdd908c0e7cf.

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