JDK-8287009 : Useless CastPPs added by PhiNode::Ideal optimization
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 19,20
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2022-05-19
  • Updated: 2022-10-04
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Other
tbdUnresolved
Related Reports
Relates :  
JDK-8139771 - Eliminating CastPP nodes at Phis when they all come from a unique input may cause crash
Relates :  
JDK-8280696 - C2 compilation hits assert(is_dominator(c, n_ctrl)) failed
Description
As described in the PR of JDK-8280696 (https://github.com/openjdk/jdk/pull/8770), the following code might add a useless CastPP with a strong dependency that blocks other optimizations:
https://github.com/openjdk/jdk/blob/aa7ccdf44549a52cce9e99f6569097d3343d9ee4/src/hotspot/share/opto/cfgnode.cpp#L2013-L2016

The code was originally introduced by 8139771.