8251442: [lworld] C2 compilation fails with assert(value->bottom_type()->higher_equal(_type))

[TobiHartmann]

Similar to JDK-8242453 [1], the problem is that a load from a non-flat array can be pushed through an arraycopy from a flat array (see LoadNode::can_see_arraycopy_value) and end up with an inconsistent memory input (oop load from a flat array). The checks emitted by the arraycopy intrinsic will catch this and the load will be removed but other Ideal transformations can still be executed before that happens and encounter this inconsistent state.

The fix is to add CheckCastPPNodes to the arraycopy intrinsic that propagate the information that the src/dst array is not flat. This makes sure that the data path consistently dies if the input array is in fact a flat array. I've also removed the workaround from the JDK-8242453 [1] fix.

When updating the type of CheckCastPPNodes, we need to make sure that the not_null_free and not_flat properties of TypeAryPtr are propagated. This is done by TypeAryPtr::update_properties. A CheckCastPPNode that ends up with an inconsistent input is then simply replaced by TOP.

This change also includes:

• Optimize subtype checks based on not_null_free/not_flat properties of array types
• New tests to verify that checkcasts are folded if one array type is known to be not null-free/flat and the other type is null-free/flat
• Test suite should detect compilation bailouts and fail (currently, only completely missing compilations were detected)
• Renamed "flat_array" to "flatten_array" (which means "flattened in arrays") for consistency with runtime code. We should think about a better name.
• Lots of refactoring, removal of default arguments in calls and dead code

[1] https://bugs.openjdk.java.net/browse/JDK-8242453

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Progress

• Change must not contain extraneous whitespace

Issue

• JDK-8251442: [lworld] C2 compilation fails with assert(value->bottom_type()->higher_equal(_type))

Download

$ git fetch https://git.openjdk.java.net/valhalla pull/151/head:pull/151
$ git checkout pull/151

[bridgekeeper]

👋 Welcome back thartmann! A progress list of the required criteria for merging this PR into lworld will be added to the body of your pull request.

[openjdk]

@TobiHartmann This change now passes all automated pre-integration checks, type /integrate in a new comment to proceed. After integration, the commit message will be:

8251442: [lworld] C2 compilation fails with assert(value->bottom_type()->higher_equal(_type))

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Since the source branch of this PR was last updated there has been 1 commit pushed to the lworld branch:

• 248fdec: 8251940: [lworld] Incorrect Signature attribute in class file.

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid automatic rebasing, please merge lworld into your branch, and then specify the current head hash when integrating, like this: /integrate 248fdec9dccbff9fadf68669a400b743d05f3621.

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[mlbridge]

Webrevs

• 01: Full - Incremental (2699610)
• 00: Full (2a54ae8)

[TobiHartmann]

/integrate

[openjdk]

@TobiHartmann The following commits have been pushed to lworld since your change was applied:

• 248fdec: 8251940: [lworld] Incorrect Signature attribute in class file.

Your commit was automatically rebased without conflicts.

Pushed as commit 5d1350e.