JDK-8224996 : Investigate memory access C2 optimizations
  • Type: Enhancement
  • Component: core-libs
  • Sub-Component: java.lang.foreign
  • Affected Version: repo-panama
  • Priority: P3
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2019-05-29
  • Updated: 2022-05-18
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Other
repo-panamaUnresolved
Related Reports
Relates :  
JDK-8226411 - C2: Avoid memory barriers around off-heap unsafe accesses
Relates :  
JDK-8132243 - Optimize Final Field Loads In Generated Code
Relates :  
JDK-8235143 - C2: No memory state needed in Thread::currentThread() intrinsic
Description
The var-handle based memory access API is currently slower than a plain Unsafe access. This seems to be caused by two factors:

* the JIT has trouble in hoisting Scope liveness checks outside a loop

* when addresses are non-constant (e.g. because memory is allocated and accessed inside a try-with-resources), it seems like bound checks are also not optimized.