JDK-8214763 : add compiler intrinsic to materialize objects
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 12
  • Priority: P2
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2018-12-04
  • Updated: 2023-11-08
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Other
tbdUnresolved
Related Reports
Relates :  
JDK-8214584 - stackwalk returns null for scalar-replaced value
Relates :  
JDK-8259316 - [REDO] C1/C2 compiler support for blackholes
Relates :  
JDK-8214585 - LiveStackFrameInfo.getLocals does not materialize virtual objects
Relates :  
JDK-8214583 - AccessController.getContext may return wrong value after JDK-8212605
Description
The C2 and Graal compilers can eliminate allocations, producing virtual objects, if escape analysis determines that the objects never escape.  However, in order to ensure that the objects show up in stack walks, we need a way to materialize these objects (as if they always escape).

One way to do this is to pass the object to a native method, but a compiler intrinsic would be better.
Comments
[~cslucas] For example, java.security.AccessController.executePrivileged() uses the native method ensureMaterializedForStackWalk() to prevent the JIT compiler from optimizing out the allocation. However this has overhead because it is a native method call. It would be nice to have something that has zero overhead, perhaps along the lines of java.lang.ref.Reference.reachabilityFence() or blackholes.
20-01-2023
Hi Dean, I'm working on something that seems related to this issue and perhaps I can work on both in "parallel". Can you please elaborate a bit your idea here? Thanks.
18-01-2023