On Fri, 24 Mar 2023 23:57:07 GMT, Cesar Soares Lucas <cslu...@openjdk.org>
wrote:
>> src/hotspot/share/opto/callnode.hpp line 511:
>>
>>> 509: // by a SafePoint; 2) A scalar replaced object is participating in an
>>> allocation
>>> 510: // merge (Phi) and the Phi is referenced by a SafePoint. The
>>> schematics of how
>>> 511: // 'spobj' is used in both scenarios are described below.
>>
>> I am not comfortable with reusing SafePointScalarObjectNode for 2) since it
>> describes totally different information.
>> I think it should be separate Node which points to array of SFSO id (in
>> addition to Phis) similar how we do now if SFSO is referenced in other
>> SFSO's field. SFSO could be created before the merge. Consider:
>>
>> Point p = new Point();
>> Point q = foo();
>> if (cond) {
>> q = p;
>> }
>> trap(p, q);
>
> I had considered that but decided not to do it to prevent adding a new IR
> node. I'll give that a shot and update this thread with how it goes.
It **will** complicate your DebugInfo code (packing/unpacking) information. But
I think it is right thing to do to avoid duplicated re-allocations during
deoptimization - you should have only one new object.
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PR Review Comment: https://git.openjdk.org/jdk/pull/12897#discussion_r1148154060
