JDK-8278228 : C2: Improve identical back-to-back if elimination
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 18
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2021-12-03
  • Updated: 2022-11-23
  • Resolved: 2022-01-10
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JDK 19
19 b05Fixed
Related Reports
Relates :  
JDK-8275610 - C2: Object field load floats above its null check resulting in a segfault
Relates :  
JDK-8297345 - C2: SIGSEGV in PhaseIdealLoop::push_pinned_nodes_thru_region
Relates :  
JDK-8143542 - C2 doesn't eliminate identical checks
Description
The original back-to-back if optimization added by JDK-8143542 relies on using split-if to nicely fold the dominated (and to be removed) if away afterwards in IGVN. However, it does not handle data dependencies correctly which could lead to crashes in rare cases (JDK-8275610). The fix for JDK-8275610 simply disables JDK-8143542 if there are data dependencies involved. This RFE aims to improve the back-to-back if optimization to also work correctly with data dependencies.
Comments
Changeset: 8d1a1e83 Author: Roland Westrelin <roland@openjdk.org> Date: 2022-01-10 07:52:18 +0000 URL: https://git.openjdk.java.net/jdk/commit/8d1a1e83f40f7a147e033be6b2221c1bb1abd8ab
10-01-2022
A pull request was submitted for review. URL: https://git.openjdk.java.net/jdk/pull/6882 Date: 2021-12-17 13:52:56 +0000
17-12-2021