JDK-8212610 : Fix handling of memory in PhaseIdealLoop::clone_loop_predicates()
- Type: Bug
- Component: hotspot
- Sub-Component: compiler
- Affected Version: 12
- Priority: P3
- Status: Resolved
- Resolution: Fixed
- Submitted: 2018-10-17
- Updated: 2019-08-23
- Resolved: 2018-11-05
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| JDK 12 |
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12 b19Fixed  |
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Description
We have: Predicate 1 .. Predicate n profile predicate 1 .. profile predicate n loop head Shenandoah write barriers produce memory, can be hoisted out of loop but can also depend on some predicate so may end up with: Predicate 1 .. Predicate n profile predicate 1 .. write barrier ... profile predicate n loop head In that case, all predicates branch to a region that dominates the uncommon trap call. Same is true for profile predicates. Because of the write barrier, the region for profile predicates has a memory phi to merge memory state before the barrier and after the barrier. Now when clone_loop_predicates() is called: Predicate 1 .. Predicate n profile predicate 1 .. write barrier ... profile predicate n cloned predicate cloned profile predicate loop head the cloned predicate branches to the region shared by all predicates. Same goes for the cloned profile predicate and the profile predicates. The memory state for the cloned predicate should be the one following the barrier but after cloning it's the one from the predicate n, before the barrier. That memory state needs to be adjusted.
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