RFR: 8290892: C2: Intrinsify Reference.reachabilityFence [v3]

[Emanuel Peter]

On Mon, 16 Jun 2025 09:24:08 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   renaming
>
> src/hotspot/share/opto/callnode.cpp line 950:
> 
>> 948:               case CatchProjNode::catch_all_index:    projs->catchall_catchproj    = cpn; break;
>> 949:               default: {
>> 950:                 assert(cpn->_con > 1, ""); // exception table; rethrow case
> 
> Can we please turn this into a helpful assert message?

Can you quickly comment why you changed this?

> src/hotspot/share/opto/compile.cpp line 2526:
> 
>> 2524:     print_method(PHASE_ELIMINATE_REACHABILITY_FENCES, 2);
>> 2525:     if (failing())  return;
>> 2526:   }
> 
> You will have to check the impact on compile time here. Running an extra round of loop opts might be significant.
> 
> Do you really need to use a loop opts phase for this? Or would something like `process_for_post_loop_opts_igvn` work for it?

Might be helpful if you write in a comment if this eliminates all or just some of the reachability fences.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25315#discussion_r2149481075
PR Review Comment: https://git.openjdk.org/jdk/pull/25315#discussion_r2149507017