8314580: PhaseIdealLoop::transform_long_range_checks fails with assert "was tested before"

[rwestrel]

For long counted loops, PhaseIdealLoop::create_loop_nest() first
goes over the loop body to collect range checks, then transforms the
long counted loop into a loop nest and then goes over the list of
range checks it collected to transfrom them. For that last step,
PhaseIdealLoop::transform_long_range_checks() needs to extract the
parameters of the range check from the range check expression. It
should still recognize the range check expression even though the loop
was transformed in the meantime. That's what fails here. The reason is
that the range check expression uses the long loop increment as input
which, in the creation of the loop nest, is transformed to outer phi + inner incr. That breaks pattern matching of the range check
expression. I propose removing the transformation:

incr=>(outer_phi+inner_incr)

entireley. After looking at this code again, I don't think it's
needed. The transformation:

phi=>(outer_phi+inner_phi)

should be all that's needed to correctly transform the loop.

---

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Issue

• JDK-8314580: PhaseIdealLoop::transform_long_range_checks fails with assert "was tested before" (Bug - P3)

Reviewers

• Christian Hagedorn (@chhagedorn - Reviewer)
• Vladimir Kozlov (@vnkozlov - Reviewer)

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[chhagedorn]

Looks reasonable to me.

[openjdk]

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

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

8314580: PhaseIdealLoop::transform_long_range_checks fails with assert "was tested before"

Reviewed-by: chagedorn, kvn

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At the time when this comment was updated there had been 116 new commits pushed to the master branch:

• 3eac890: 8315061: Make LockingMode a product flag
• 8419a53: 8315072: Remove unneeded AdaptivePaddedAverage::operator new
• c90cd2c: 8286789: Test forceEarlyReturn002.java timed out
• 89d18ea: 8312018: Improve reservation of class space and CDS
• dd64a4a: 8315241: (fs) Move toRealPath tests in java/nio/file/Path/Misc.java to separate JUnit 5 test
• 8e4cda0: 8314834: serviceability/jdwp/AllModulesCommandTest.java ignores VM flags
• 1ea6463: 8314835: gtest wrappers should be marked as flagless
• 93e82c0: 8314824: Fix serviceability/jvmti/8036666/GetObjectLockCount.java to use vm flags
• 7daae1f: 8314263: Signed jars triggering Logger finder recursion and StackOverflowError
• 6701eba: 8315117: Update Zlib Data Compression Library to Version 1.3
• ... and 106 more: https://git.openjdk.org/jdk/compare/8939d15d92982300f090bc1c51f59550529eaaf3...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.

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[vnkozlov]

Looks good to me too. Thank you for explaining the issue in details.

[rwestrel]

@chhagedorn @vnkozlov thanks for the reviews.

[rwestrel]

/integrate

[openjdk]

Going to push as commit 9def453.
Since your change was applied there have been 162 commits pushed to the master branch:

• 6c821f5: 8315545: C1: x86 cmove can use short branches
• d7e4087: 8315369: [JVMCI] failure to attach to a libgraal isolate during shutdown should not be fatal
• d1cabe4: 8315566: [JVMCI] deadlock in JVMCI startup when bad option specified
• 94a74a0: 8315534: Incorrect warnings about implicit annotation processing
• 84425a6: 8315452: Erroneous AST missing modifiers for partial input
• 3094fd1: 8314662: jshell shows duplicated signatures of javap
• 0d52c82: 8310220: IGV: dump graph after each IGVN step at level 4
• adfc1d6: 8313323: javac -g on a java file which uses unnamed variable leads to ClassFormatError when launching that class
• 2dc930d: 8314997: Missing optimization opportunities due to missing try_clean_mem_phi() calls
• ab12c5d: 8315549: CITime misreports code/total nmethod sizes
• ... and 152 more: https://git.openjdk.org/jdk/compare/8939d15d92982300f090bc1c51f59550529eaaf3...master

Your commit was automatically rebased without conflicts.

[openjdk]

@rwestrel Pushed as commit 9def453.

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