8274328: C2: Redundant CFG edges fixup in block ordering

[kelthuzadx]

I think Trace::fixup_blocks is redundant because PhaseCFG::fixup_flow will nevertheless fix up the CFG flow(i.e. flip successor blocks of IfNode) right after PhaseBlockLayout pass, we can remove this step when doing PhaseBlockLayout pass.(Testing: jtreg/compiler/c2, presubmit test)

jdk/src/hotspot/share/opto/compile.cpp

Line 2765 in 5ec1cdc

cfg.fixup_flow();

jdk/src/hotspot/share/opto/block.cpp

Line 1679 in 5ec1cdc

tr->fixup_blocks(_cfg);

jdk/src/hotspot/share/opto/block.cpp

Lines 908 to 916 in 5ec1cdc

	// Fall-thru case in succs[0], so flip targets in succs map
	Block* tbs0 = block->_succs[0];
	Block* tbs1 = block->_succs[1];
	block->_succs.map(0, tbs1);
	block->_succs.map(1, tbs0);
	// Flip projection for each target
	ProjNode* tmp = proj0;
	proj0 = proj1;
	proj1 = tmp;

---

Progress

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Issue

• JDK-8274328: C2: Redundant CFG edges fixup in block ordering

Reviewers

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

Reviewing

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[bridgekeeper]

👋 Welcome back yyang! 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]

@kelthuzadx The following label will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 01: Full - Incremental (7d58a18f)
• 00: Full (46381c61)

[kelthuzadx]

PING :-

[TobiHartmann]

That looks good to me but I'm not an expert in that code. I submitted some testing and it all passed.

[TobiHartmann]

swap(proj0, proj1) can be used here.

[kelthuzadx]

Thanks Tobias for review. I have replaced above code with swap(pointer ref,pointer ref)

[openjdk]

@kelthuzadx 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:

8274328: C2: Redundant CFG edges fixup in block ordering

Reviewed-by: thartmann, kvn

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At the time when this comment was updated there had been 142 new commits pushed to the master branch:

• 59c3dcc: 8276746: Add section on reproducible builds in building.md
• 0e0dd33: 8276129: PretouchTask should page-align the chunk size
• a472433: 8276572: Fake libsyslookup.so library causes tooling issues
• b01f107: 8276252: java/nio/channels/Channels/TransferTo.java failed with OOM java heap space error
• 92d2176: 8273967: gtest os.dll_address_to_function_and_library_name_vm fails on macOS12
• a74a839: 8276571: C2: pass compilation options as structure
• c393ee8: 8276632: Use blessed modifier order in security-libs code
• 7023b3f: 8276628: Use blessed modifier order in serviceability code
• b933136: 8276641: Use blessed modifier order in jshell
• 0616d86: 8276635: Use blessed modifier order in compiler code
• ... and 132 more: https://git.openjdk.java.net/jdk/compare/9f75d5ce500886b32175cc541939b7f0eee190ca...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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[TobiHartmann]

Thanks, looks good.

[vnkozlov]

That looks good to me but I'm not an expert in that code. I submitted some testing and it all passed.

@TobiHartmann please add links to testing in RFE.

[vnkozlov]

Looks good.

[kelthuzadx]

Thanks @TobiHartmann and @vnkozlov for reviews!

/integrate

[openjdk]

Going to push as commit 44047f8.
Since your change was applied there have been 146 commits pushed to the master branch:

• 8849154: 8275846: read_base_archive_name() could read past the end of buffer
• 2653cfb: 8276688: Remove JLinkReproducibleXXXTest from ProblemList.txt
• c7095b2: 8276207: Properties.loadFromXML/storeToXML works incorrectly for supplementary characters
• ed7ecca: 8254739: G1: Optimize evacuation failure for regions with few failed objects
• 59c3dcc: 8276746: Add section on reproducible builds in building.md
• 0e0dd33: 8276129: PretouchTask should page-align the chunk size
• a472433: 8276572: Fake libsyslookup.so library causes tooling issues
• b01f107: 8276252: java/nio/channels/Channels/TransferTo.java failed with OOM java heap space error
• 92d2176: 8273967: gtest os.dll_address_to_function_and_library_name_vm fails on macOS12
• a74a839: 8276571: C2: pass compilation options as structure
• ... and 136 more: https://git.openjdk.java.net/jdk/compare/9f75d5ce500886b32175cc541939b7f0eee190ca...master

Your commit was automatically rebased without conflicts.

[openjdk]

@kelthuzadx Pushed as commit 44047f8.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[TobiHartmann]

@TobiHartmann please add links to testing in RFE.

Done.