8341831: PhaseCFG::insert_anti_dependences asserts with "no loads"

[veresov]

CacheWB nodes are peculiar in a sense that they both are anti-dependent and produce memory. I think it's reasonable to relax the assert in insert_anti_dependences() to work around their properties.

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Issue

• JDK-8341831: PhaseCFG::insert_anti_dependences asserts with "no loads" (Bug - P3)

Reviewers

• Vladimir Kozlov (@vnkozlov - Reviewer) Review applies to ae69ee4b
• Dean Long (@dean-long - Reviewer)

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

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8341831: PhaseCFG::insert_anti_dependences asserts with "no loads"

Reviewed-by: dlong, kvn

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At the time when this comment was updated there had been 25 new commits pushed to the master branch:

• 2db3397: 8341797: Fix ExceptionOccurred in jdk.jdi
• c4965d9: 8341794: Fix ExceptionOccurred in jdk.attach
• 3f53d57: 8340327: A common framework to support public key algorithms with standard parameter sets
• 0a57fe1: 8341178: TypeRawPtr::add_offset may be "miscompiled" due to UB
• 1f6bd0c: 8341972: java/awt/dnd/DnDRemoveFocusOwnerCrashTest.java timed out after JDK-8341257
• 7276a1b: 8341784: Refactor TypeVect to use a BasicType instead of a const Type*
• 6133866: 8341070: javac fails with an exception when compiling import module under source level 8
• 519544c: 8341909: G1: Add region index to region printer output
• 7c0dbf8: 8341820: Check return value of hcreate_r
• ae41daf: 8341880: RISC-V: riscv_vector.h native build fails with gcc13 after JDK-8320500
• ... and 15 more: https://git.openjdk.org/jdk/compare/6e0138450ab4b0af917cbf61701b0d1d17eeaa44...master

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[vnkozlov]

Please add comment into code explaining change.

[veresov]

Please add comment into code explaining change.

Done.

[vnkozlov]

LoadStore nodes should have the same issue. Why they are not affected?

[veresov]

LoadStore nodes should have the same issue. Why they are not affected?

Because LoadStore is an official store. It consumes a memory state and produces memory state. CacheWB is not really a store, that is it doesn't produce memory effects from the perspective of the backend (its match rule is not a Set). It's hard to tell what's the best way to model it, so I just decided not to mess with its semantics right now.

[vnkozlov]

Okay

[dean-long]

LoadStore nodes should have the same issue. Why they are not affected?

Because LoadStore is an official store. It consumes a memory state and produces memory state. CacheWB is not really a store, that is it doesn't produce memory effects from the perspective of the backend (its match rule is not a Set). It's hard to tell what's the best way to model it, so I just decided not to mess with its semantics right now.

Should it be treated like a memory barrier?

[veresov]

LoadStore nodes should have the same issue. Why they are not affected?

Because LoadStore is an official store. It consumes a memory state and produces memory state. CacheWB is not really a store, that is it doesn't produce memory effects from the perspective of the backend (its match rule is not a Set). It's hard to tell what's the best way to model it, so I just decided not to mess with its semantics right now.

Should it be treated like a memory barrier?

I'm not sure why it's not, I guess they wanted a more relaxed behavior? It's more like the opposite of prefetch really. I didn't want to touch the semantics of it in this bug fix because it feels like it will likely open another can of worms.

[veresov]

/integrate

[openjdk]

Going to push as commit a8a8b2d.
Since your change was applied there have been 38 commits pushed to the master branch:

• 9e262df: 8342002: sun/security/tools/keytool/GenKeyPairSigner.java failed due to missing certificate output
• f56a154: 8341881: [REDO] java/nio/file/attribute/BasicFileAttributeView/CreationTime.java#tmp fails on alinux3
• ba3774d: 8341637: java/net/Socket/UdpSocket.java fails with "java.net.BindException: Address already in use" (macos-aarch64)
• 1581508: 8335091: NMT: VMATree reserve_mapping and commit_mapping APIs need MEMFLAGS while un/-committing API has no MEMFLAGS arg
• b20c5c7: 8341967: Unify os::current_file_offset and os::seek_to_file_offset across posix platforms
• dcac4b0: 8341471: Reversed field layout caused by unstable sorting
• e3f6503: 8341893: AArch64: Micro-optimize compressed ptr decoding
• 037f11b: 8341708: Optimize safepoint poll encoding with smaller poll data offset
• 8d0975a: 8336726: C2: assert(!do_asserts || projs->fallthrough_ioproj != nullptr) failed: must be found
• fe98f86: 8226938: [TEST_BUG]GTK L&F: There is no Details button in FileChooser Dialog
• ... and 28 more: https://git.openjdk.org/jdk/compare/6e0138450ab4b0af917cbf61701b0d1d17eeaa44...master

Your commit was automatically rebased without conflicts.

[openjdk]

@veresov Pushed as commit a8a8b2d.

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