8390441: RISC-V: Fix C2 stack-to-stack spill copies with large offsets

[zifeihan]

Hi, this patch is a backport of openjdk/jdk#32387 . this is a risc-v specific change. risk is low.

This backport is not clean:

1. jdk17u-dev doesn't have predicate register support
2. In jdk17u-dev, the vector stack-to-stack copy goes through spill_copy_vector_stack_to_stack, where the data is transferred via v0 and t0 is only used for address computation (capable of handling large offsets), so there is no conflict. The scalar path's sd(t0, Address(sp, dst_offset)) only uses t0 as an address temporary when the offset exceeds simm12, which would clobber the value; therefore, only the scalar case's dst_offset needs to be checked.

Testing: the test TestRiscvLargeStackToStack.java[1], which previously had test failures, has now passed.

[1] https://bugs.openjdk.org/secure/attachment/121298/TestRiscvLargeStackToStack.java

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• JDK-8390441 needs maintainer approval
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Issue

• JDK-8390441: RISC-V: Fix C2 stack-to-stack spill copies with large offsets (Bug - P4)

Reviewers

• Fei Yang (@RealFYang - Reviewer)

Reviewing

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[bridgekeeper]

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[zifeihan]

/approval request
Same issue is there in jdk17u-dev repo. This is a RISC-V specific change, risk is low.
Testing: the test TestRiscvLargeStackToStack, which previously had test failures, has now passed.

[openjdk]

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

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

@zifeihan
8390441: The approval request has been created successfully.

[mlbridge]

Webrevs

• 00: Full (5d6f66a1)

[RealFYang]

Thanks!

[GoeLin]

Hi @zifeihan
please do 21 first. removing the label in the meantime.

[openjdk]

⚠️ @zifeihan This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.