RFR: 8348853: Fold layout helper check for objects implementing non-array interfaces
Marc Chevalier
mchevalier at openjdk.org
Wed Mar 26 10:14:19 UTC 2025
If `TypeInstKlassPtr` represents an array type, it has to be `java.lang.Object`. From contraposition, if it is not `java.lang.Object`, we can conclude it is not an array, and we can skip some array checks, for instance.
In this PR, we improve this deduction with an interface base reasoning: arrays implements only Cloneable and Serializable, so if a type implements anything else, it cannot be an array.
This change partially reverts the changes from [JDK-8348631](https://bugs.openjdk.org/browse/JDK-8348631) (#23331) (in `LibraryCallKit::generate_array_guard_common`) and the test still passes.
The way interfaces are check might be done differently. The current situation is a balance between visibility (not to leak too much things explicitly private), having not overly general methods for one use-case and avoiding too concrete (and brittle) interfaces.
Tested with tier1..3, hs-precheckin-comp and hs-comp-stress
Thanks,
Marc
-------------
Commit messages:
- Revert now useless fix
- Generalize the not-array proof
Changes: https://git.openjdk.org/jdk/pull/24245/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24245&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8348853
Stats: 46 lines in 5 files changed: 35 ins; 7 del; 4 mod
Patch: https://git.openjdk.org/jdk/pull/24245.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/24245/head:pull/24245
PR: https://git.openjdk.org/jdk/pull/24245
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