JDK-8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

[tobiasholenstein]

The following assert had undefined behavior (UB) because of signed integer underflow/overflow:

    assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) || 
           stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), 
           "sanity"); 

Solution

The fix is to check for underflow/overflow (the purpose of the assert) without actually underflowing/overflowing.

---

Progress

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Issue

• JDK-8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer)
• Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back tholenstein! 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]

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[mlbridge]

Webrevs

• 00: Full (8c97939f)

[vnkozlov]

Looks good.

[openjdk]

@tobiasholenstein 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:

8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

Reviewed-by: kvn, thartmann

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 208 new commits pushed to the master branch:

• 655a712: 8301444: Port fdlibm hyperbolic transcendental functions to Java
• b242eef: 8280419: Remove dead code related to VerifyThread and verify_thread()
• 4ce493f: 8302225: SunJCE Provider doesn't validate key sizes when using 'constrained' transforms for AES/KW and AES/KWP
• a39cf2e: 8301753: AppendFile/WriteFile has differences between make 3.81 and 4+
• de80dd9: 8296010: AssertionError in annotationTargetType
• e5042dd: 8302671: libawt has a memmove decay error
• 574b48c: 8302678: validate_source fails after JDK-8293313
• 90e0922: 8293313: NMT: Rework MallocLimit
• f558a6c: 8298276: JFR: Update NMT events to make use of common periodic timestamp feature
• a58fa6e: 8302514: Misleading error generated when empty class file encountered
• ... and 198 more: https://git.openjdk.org/jdk/compare/59b7fb1a91c594f98f06b28cb95310a38565397d...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.

[TobiHartmann]

Looks good to me too.

[tobiasholenstein]

thanks @vnkozlov and @TobiHartmann !

/integrate

[openjdk]

Going to push as commit cd77fcf.
Since your change was applied there have been 217 commits pushed to the master branch:

• 57c9bc3: 8302335: IGV: Bytecode not showing
• 57fde75: 8302113: Improve CRC32 intrinsic with crypto pmull on AArch64
• b8c9d6c: 8302158: PPC: test/jdk/jdk/internal/vm/Continuation/Fuzz.java: AssertionError: res: false shouldPin: false
• dc55a7f: 8302202: Incorrect desugaring of null-allowed nested patterns
• c4ffe4b: 8301494: Replace NULL with nullptr in cpu/arm
• 4f1cffd: 8302674: Parallel: Remove unused methods in MutableNUMASpace
• c91cd28: 8301481: Replace NULL with nullptr in os/windows
• 47ca577: 8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument
• 49eb68b: 8296158: Refactor the verification of CDS region checksum
• 655a712: 8301444: Port fdlibm hyperbolic transcendental functions to Java
• ... and 207 more: https://git.openjdk.org/jdk/compare/59b7fb1a91c594f98f06b28cb95310a38565397d...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tobiasholenstein Pushed as commit cd77fcf.

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