RFR: 8375055: C2: Better dead loop detection printout [v4]

[Aleksey Shipilev]

On Tue, 13 Jan 2026 09:30:37 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Also print node idx
>>  - Indenting
>
> src/hotspot/share/opto/phaseX.cpp line 780:
> 
>> 778:       ss.print_cr("Dead loop detected, node references itself");
>> 779:       ss.print("#\n#  Node: ");
>> 780:       n->dump("", false, &ss);
> 
> A full node dump for the failure message seems a little verbose. We also already dump the node as part of `dump_bfs()` above. How about just printing `n->_idx` and `n->Name()` for the failure message itself to get a good first hint? Same below.

Yes, OK; name and idx is also already good to classify which dead node we are likely failing on. Did in new commit.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/29185#discussion_r2685959501