8353730: TestSubNodeFloatDoubleNegation.java fails with native Float16 support

[mhaessig]

Due to insufficient testing on machines supporting FP16 arithmetic in their ISA, I missed that these machines generate two SUB_FH nodes and, crucially, an additional SUB_F node. We suspect that this comes from some kind of fallback code path (open issue; also see discussion in RISC-V PR fixing the same issue).

This PR fixes this issue for all architectures that support FP16 instructions (that I know of), by only matching SUB_HF nodes when the CPU supports FP16. The tests for ARM are currently commented out, due to the support for Float16 still being a work in progress (see PR #23748).

I tested the fix using software emulation of an x86_64 CPU with the avx512_fp16 feature. I also ran the sanity checks (the Alpine Linux build fails at configure, which is unrelated to this change) as well as tier1 through tier3 and Oracle internal testing.

---

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Issue

• JDK-8353730: TestSubNodeFloatDoubleNegation.java fails with native Float16 support (Bug - P4)

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer)
• Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

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8353730: TestSubNodeFloatDoubleNegation.java fails with native Float16 support

Reviewed-by: chagedorn, thartmann

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At the time when this comment was updated there had been 31 new commits pushed to the master branch:

• 8bb0ca4: 8353917: jnativescan: Simplify ClassResolver
• 36069f6: 8354234: Remove friends for ObjectMonitor
• d4e194b: 8354266: Fix non-UTF-8 text encoding
• ... and 28 more: https://git.openjdk.org/jdk/compare/f94a4f7accd11161912ec2cdae6e290d0957666a...master

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Webrevs

• 02: Full - Incremental (176cb067)
• 01: Full - Incremental (5eaedf2b)
• 00: Full (38de7c7a)

[chhagedorn]

Looks good to me.

[TobiHartmann]

Looks good to me too.

[mhaessig]

Thank you for the reviews!

/integrate

[openjdk]

@mhaessig
Your change (at version 176cb06) is now ready to be sponsored by a Committer.

[chhagedorn]

/sponsor

[openjdk]

Going to push as commit efb5a80.
Since your change was applied there have been 31 commits pushed to the master branch:

• 8bb0ca4: 8353917: jnativescan: Simplify ClassResolver
• 36069f6: 8354234: Remove friends for ObjectMonitor
• d4e194b: 8354266: Fix non-UTF-8 text encoding
• ... and 28 more: https://git.openjdk.org/jdk/compare/f94a4f7accd11161912ec2cdae6e290d0957666a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@chhagedorn @mhaessig Pushed as commit efb5a80.

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