RFR: 8346280: C2: implement late barrier elision for G1

[Roberto Castañeda Lozano]

On Thu, 23 Jan 2025 10:24:12 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> We have seen many crashes in JFR tests like jdk/jfr/api/consumer/streaming/TestFilledChunks.java on PPC64:
> 
> ```
> #  SIGSEGV (0xb) at pc=0x00007fff9ef80948, pid=285054, tid=285751
> # V  [libjvm.so+0x620948]  get_base_and_offset(MachNode const*, long&)+0x2c8
> 
> V  [libjvm.so+0x620948]  get_base_and_offset(MachNode const*, long&)+0x2c8  (type.hpp:994)
> V  [libjvm.so+0x629e4c]  BarrierSetC2::is_allocation(Node const*)+0x10c  (barrierSetC2.cpp:1048)
> V  [libjvm.so+0xd1c708]  G1BarrierSetC2::analyze_dominating_barriers() const+0x628  (g1BarrierSetC2.cpp:554)
> V  [libjvm.so+0x17686d8]  PhaseOutput::perform_mach_node_analysis()+0xe8  (output.cpp:258)
> V  [libjvm.so+0x177ceb4]  PhaseOutput::Output()+0xc74  (output.cpp:346)
> V  [libjvm.so+0xa4b450]  Compile::Code_Gen()+0x650  (compile.cpp:3030)
> V  [libjvm.so+0xa50100]  Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1c20  (compile.cpp:884)
> V  [libjvm.so+0x7fb294]  C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x1c4  (c2compiler.cpp:141)
> ```

Thanks for the report, Martin. Have you tried running this test with ZGC? ZGC exercises the same logic (even before this changeset) so it could be subject to the same issue.

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PR Comment: https://git.openjdk.org/jdk/pull/23235#issuecomment-2609751843