JDK-8370936 : C2 MergeStores: move process_for_merge_stores_igvn after allocation elimination
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 26
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2025-10-30
  • Updated: 2025-11-03
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tbdUnresolved
Related Reports
Relates :  
JDK-8371122 - C2 Allocation Elimination: handle some mismatched accesses to arrays
Description
We saw in JDK-8370405, that MergeStores introduces mismatched stores, and that prevents allocation removal.

As a quick-fix, we could just move process_for_merge_stores_igvn to a later point.

This would allow allocation elimination to have a chance to work. And if it still fails, we can still do MergeStores.

Long-term, we might want to allow allocation elimination to deal with some mismatched stores.

We might also want to refactor MergeStores and the eventual MergeLoads JDK-8345485 not to work with IGVN, and so work even later. But that is more work, and we can do that later.