8344010: RISC-V: Zacas do not work with LW locking

[robehn]

Hi all, please consider.

Light weight locking fails:

• We need to add cas acquire.
• Register result may shadow new_val (same register).
  (NOTE this second item can effect many other cases, unclear)

As the code becomes much cleaner by calling amocas_d/w directly I removed the aliases.
Which fixes the first issue with cas acquire.

By using t0 instead of result we fix the other issue.

This is a short bugfix, there are so many dragons here that I do not want to address them while fixing the bug.
There are also several performance optimizations we can do here, specially for LR/SC case.
So I'll do a couple of more iterations of this code in seperate PR's.

Testing a bunch of local cherry-picked tests which failed.
I'll start tier1 over the weekend.

Thanks, Robbin

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Issue

• JDK-8344010: RISC-V: Zacas do not work with LW locking (Bug - P3)

Reviewers

• Fei Yang (@RealFYang - Reviewer)
• Hamlin Li (@Hamlin-Li - Reviewer)

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8344010: RISC-V: Zacas do not work with LW locking

Reviewed-by: fyang, mli

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At the time when this comment was updated there had been 107 new commits pushed to the master branch:

• cf158bc: 8341631: JShell should auto-import java.io.IO.*
• 5b12a87: 8344060: Remove doPrivileged calls from shared implementation code in the java.desktop module : part 1
• 587f2b4: 8343827: RISC-V: set AlignVector as false if applicable to enable SLP
• 189fc8d: 8344381: [s390x] Test failures with error: Register type is not known
• 8a1f9f0: 8343476: Remove unnecessary @SuppressWarnings annotations (client)
• 4ddd3de: 8344356: Aarch64: implement -XX:+VerifyActivationFrameSize
• bc7eabd: 8344350: Add '.gdbinit' and '.lldbinit' to file '.gitignore'
• f525290: 8341935: javac states that -proc:full is the default but the default as of 23 is -proc:none
• acdbf83: 8341553: Remove UseCompactObjectHeaders extra CDS archives
• 81e4311: 8344077: Remove security manager dependency in java.io
• ... and 97 more: https://git.openjdk.org/jdk/compare/5e2760856c3844d9ad6200fef0c09ece0acac73a...master

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[RealFYang]

Good catch. Thanks for carrying out the test. Looks good modulo one minor question.

[robehn]

Good catch. Thanks for carrying out the test. Looks good modulo one minor question.

Thanks! I found some failures in testing, investigating.

Update:
The failure is there regradless of this patch:
CASandCAEwithNegExpected.java using -XX:+UnlockExperimentalVMOptions -XX:+UseZacas -XX:LockingMode=0

Which means zacas is still broken after this patch, but at least LW locking is working.
(failure seems to be related to weak cmpxchg)
I'll continue that work in: https://bugs.openjdk.org/browse/JDK-8344382

[Hamlin-Li]

Nice catch and cleanup, looks much better!
Just one minor comment.

[robehn]

Nice catch and cleanup, looks much better! Just one minor comment.

Thanks!

[Hamlin-Li]

Thanks, current fix looks good!

[robehn]

Thanks, current fix looks good!

Thanks!

[robehn]

/integrate

[openjdk]

Going to push as commit ea7e722.
Since your change was applied there have been 110 commits pushed to the master branch:

• e2f8f1a: 8344621: ProblemList runtime/CommandLine/OptionsValidation/TestOptionsWithRanges.java
• afee740: 8343541: C1: Plain memory accesses are emitted with membars with +AlwaysAtomicAccesses
• 3a4a9b7: 8340145: Problem with generic pattern matching results in internal compiler error
• cf158bc: 8341631: JShell should auto-import java.io.IO.*
• 5b12a87: 8344060: Remove doPrivileged calls from shared implementation code in the java.desktop module : part 1
• 587f2b4: 8343827: RISC-V: set AlignVector as false if applicable to enable SLP
• 189fc8d: 8344381: [s390x] Test failures with error: Register type is not known
• 8a1f9f0: 8343476: Remove unnecessary @SuppressWarnings annotations (client)
• 4ddd3de: 8344356: Aarch64: implement -XX:+VerifyActivationFrameSize
• bc7eabd: 8344350: Add '.gdbinit' and '.lldbinit' to file '.gitignore'
• ... and 100 more: https://git.openjdk.org/jdk/compare/5e2760856c3844d9ad6200fef0c09ece0acac73a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@robehn Pushed as commit ea7e722.

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