RFR: 8263227: C2: inconsistent spilling due to dead nodes in exception block

Nils Eliasson neliasso at openjdk.java.net
Tue Apr 6 09:54:21 UTC 2021

On Tue, 6 Apr 2021 09:42:01 GMT, Nils Eliasson <neliasso at openjdk.org> wrote:

>> This change eliminates dead multi-nodes created by call-catch cleanup after GCM. Eliminating all dead code created by call-catch cleanup avoids potential issues when splitting the live range of call result values, see the analysis in the [bug report](https://bugs.openjdk.java.net/browse/JDK-8263227) for details. This solution is the least invasive of the three alternatives proposed in the bug report (the other two are constraining global code motion and extending live-range splitting).
>> The change also extends the control-flow graph verification pass to catch similar live-range splitting issues earlier (with `+VerifyRegisterAllocator`).
>> Tested on:
>> - original bug reproducer
>> - hs-tier1-5 (windows-x64, linux-x64, linux-aarch64, and macosx-x64) with `+VerifyRegisterAllocator`
>> - hs-tier1-3 (windows-x64, linux-x64, linux-aarch64, and macosx-x64) with `+VerifyRegisterAllocator` and `+StressGCM` (5 repetitions)
> Looks good!

And thanks for the PDF with the excellent walk through!


PR: https://git.openjdk.java.net/jdk/pull/3303

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