RFR: 8290892: C2: Intrinsify Reference.reachabilityFence [v2]

[Vladimir Ivanov]

On Wed, 21 May 2025 05:12:06 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   review feedback
>
> src/hotspot/share/opto/phasetype.hpp line 88:
> 
>> 86:   flags(PHASEIDEALLOOP2,                "PhaseIdealLoop 2") \
>> 87:   flags(PHASEIDEALLOOP3,                "PhaseIdealLoop 3") \
>> 88:   flags(OPTIMIZE_RF,                    "Optimize Reachability Fences") \
> 
> Another drive-by comment: I suggest to use the full word since most people are probably not aware of this abbreviation when looking at graph dumps in IGV. You should also add this phase to the IR framework [CompilePhases](https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/lib/ir_framework/CompilePhase.java).
> 
> Suggestion:
> 
>   flags(OPTIMIZE_REACHABILITY_FENCES,   "Optimize Reachability Fences") \

IMO it doesn't clarify things much. It's enum constant name and it's not shown in IGV.

It is used in a single place [1] where it's clear what it refers to. 

[1]

  { // No more loop opts. It is safe to eliminate reachability fence nodes.
    TracePhase tp(_t_idealLoop);
    PhaseIdealLoop::optimize(igvn, LoopOptsEliminateRFs);
    print_method(PHASE_OPTIMIZE_RF, 2);
    if (failing())  return;
  }

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PR Review Comment: https://git.openjdk.org/jdk/pull/25315#discussion_r2103476549