RFR: 8320649: C2: Optimize scoped values [v4]

[Roland Westrelin]

On Wed, 17 Jan 2024 14:17:58 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   merge fix
>
> src/hotspot/share/opto/callGenerator.cpp line 1155:
> 
>> 1153:       CallProjections slow_projs;
>> 1154:       slow_call->extract_projections(&slow_projs, false);
>> 1155:       Node* fallthrough = slow_projs.fallthrough_catchproj->clone();
> 
> Why does that have to be cloned?

Control out of the slow call is redirected to new the `region_fast_slow`. It's one way to do that. The other would be to iterate over all uses of the projection, replace the edge leading to the projection with top and then add the projection as input to `region_fast_slow`. That doesn't seem simpler.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16966#discussion_r1469674991