RFR: 8265938: C2's conditional move optimization does not handle top Phi
thartmann at openjdk.java.net
Mon Apr 26 06:53:48 UTC 2021
C2's CCP optimization sets the type of a PhiNode to TOP because it became dead after loop unrolling. Now since that node is not reachable from the bottom due to an infinite loop at the end of the method, CCP does not enqueue the PhiNode for IGVN. As a result, the dead subgraph is not removed. During loop opts, the conditional move optimization fails on the PhiNode because its type is top. The expected behavior is to simply bail out with "COMPILE SKIPPED: infinite loop (retry at different tier)".
I suggest to fix this by simply handling a TOP Phi in the conditional move optimization code.
This issue was reported by John Jiang (johnsjiang at tencent.com).
- 8265938: C2's conditional move optimization does not handle top Phi
Stats: 71 lines in 2 files changed: 70 ins; 0 del; 1 mod
Fetch: git fetch https://git.openjdk.java.net/jdk pull/3684/head:pull/3684
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