8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded

[0zzy0sbourne]

This is a backport of JDK-8375010

The check vect->is_Vector() || vect->is_LoadVector() in expand_vbox_node_helper does not handle Proj nodes that resolve to vector types, causing an assertion failure when such nodes flow through a Phi into VectorBox. The fix handles these two additional cases (VectorBox inside a Phi or Proj node), preventing the assert crash.

Tested: VectorBoxExpandPhi.java and VectorBoxExpandProj.java pass.

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Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8374903 needs maintainer approval
• JDK-8375010 needs maintainer approval

Issues

• JDK-8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded (Bug - P3 - Requested)
• JDK-8374903: C2 VectorAPI: assert(vbox->as_Phi()->region() == vect->as_Phi()->region()) failed (Bug - P3 - Requested)

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[openjdk]

This backport pull request has now been updated with issues from the original commit.

[openjdk]

⚠️ @0zzy0sbourne This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

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• 00: Full (c3f755c6)

[0zzy0sbourne]

/approval request for backport of JDK-8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded.

This is a bug where expand_vbox_node_helper hits a fatal assert when the vector box node is not a CheckCastPP as expected. The check vect->is_Vector() || vect->is_LoadVector() does not handle Proj nodes that resolve to vector types, causing an assertion failure when such nodes flow through a Phi into VectorBox. Fixing this is important as it causes a hard JVM crash during Vector API compilation with no recovery path. The fix handles these two additional cases (VectorBox inside a Phi or Proj node), preventing the assert crash. The risk is low, the change is well-contained within expand_vbox_node_helper and adds handling for previously unhandled graph shapes without modifying existing logic. The patch from the JDK Project applies cleanly with no conflicts. Test coverage: VectorBoxExpandPhi.java and VectorBoxExpandProj.java pass.

[openjdk]

@0zzy0sbourne
8375010: The approval request has been created successfully.
8374903: The approval request has been created successfully.