RFR: 8348631: Crash in PredictedCallGenerator::generate after JDK-8347006

[Tobias Hartmann]

We crash / assert during C2 compilation of intrinsics like `_getLength` because the cast emitted by the array guard added by [JDK-8347006](https://bugs.openjdk.org/browse/JDK-8347006) is folded to top:
https://github.com/openjdk/jdk/blob/c33c1cfe7349ac657cd7bf54861227709d3c8f1b/src/hotspot/share/opto/library_call.cpp#L4302-L4305

This happens when C2's type system determines that the type of the object that we cast implements an interface other than `Serializable` or `Cloneable` and therefore can't be an array. This is possible since [JDK-8297933](https://bugs.openjdk.org/browse/JDK-8297933). Now unfortunately, control via the layout helper check is not (yet) folded due to:
https://github.com/openjdk/jdk/blob/c33c1cfe7349ac657cd7bf54861227709d3c8f1b/src/hotspot/share/opto/memnode.cpp#L2215-L2223

This is probably an oversight from [JDK-8297933](https://bugs.openjdk.org/browse/JDK-8297933). Given that this is a regression in JDK 24, I'm going with a conservative approach of simply checking the cast for top and not using it if that's the case. In addition, I made the code more robust and added a compilation bailout (assert in debug) if an intrinsic produces a `top` result.

We should then properly fix this by making sure that the layout helper check is folded. I filed [JDK-8348853](https://bugs.openjdk.org/browse/JDK-8348853) for this.

Big thanks to @cushon for reporting this just in time for fixing in JDK 24!

Best regards,
Tobias

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Commit messages:
 - Trailing ws
 - Fix
 - 8348631: Crash in PredictedCallGenerator::generate after JDK-8347006

Changes: https://git.openjdk.org/jdk/pull/23331/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23331&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348631
  Stats: 77 lines in 4 files changed: 76 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23331.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23331/head:pull/23331

PR: https://git.openjdk.org/jdk/pull/23331