JDK-8293993 : C2: Check removal of Opaque2 nodes
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 20
  • Priority: P4
  • Status: Closed
  • Resolution: Duplicate
  • Submitted: 2022-09-19
  • Updated: 2022-12-06
  • Resolved: 2022-12-06
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Other
tbdResolved
Related Reports
Duplicate :  
JDK-8294540 - Remove Opaque2Node: it is broken and triggers assert
Relates :  
JDK-8292088 - C2: assert(is_OuterStripMinedLoop()) failed: invalid node class: IfTrue
Description
During the investigation of JDK-8292088, the question was raised if Opaque2 nodes are really useful anymore today. A closer analysis suggested that they are not fulfilling their original purpose anymore. This RFE should investigate if Opaque2 nodes could be completely removed (together with reorg_offsets()) by backing it up with some benchmark results. 

We could re-investigate in a separate RFE if it is worth to re-implement reorg_offsets() in a way that fulfills its original purpose to lower register pressure.

More detail can be found in the PR of JDK-8292088:
https://github.com/openjdk/jdk/pull/10306