RFR: 8322692: ZGC: avoid over-unrolling due to hidden barrier size [v2]

[Roberto Castañeda Lozano]

On Tue, 16 Jan 2024 10:25:18 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Roberto Castañeda Lozano has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Update copyright years
>>  - Exclude size of slow path from estimation
>
> src/hotspot/share/opto/loopTransform.cpp line 1003:
> 
>> 1001:   // Also count ModL, DivL, MulL, and other nodes that expand mightly
>> 1002:   for (uint k = 0; k < _body.size(); k++) {
>> 1003:     Node* n = _body.at(k);
> 
> A lot of functions here are used to do the same thing (that is to estimate the size of a node), I think we should consolidate them, and use a specified value such as number of machine instructions instead. Maybe that could be done later?

Yes, that sounds like a good idea for a later enhancement, please feel free to file a RFE. Note that the body size unit currently used by the heuristic is Ideal nodes (as opposed to machine instructions).

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PR Review Comment: https://git.openjdk.org/jdk/pull/17367#discussion_r1453242353