RFR: 8333258: C2: high memory usage in PhaseCFG::insert_anti_dependences()

[Emanuel Peter]

On Thu, 20 Jun 2024 13:50:12 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> src/hotspot/share/opto/gcm.cpp line 689:
>> 
>>> 687: 
>>> 688:     if (op == Op_MachProj || op == Op_Catch)   continue;
>>> 689:     if (store->needs_anti_dependence_check())  continue;  // not really a store
>> 
>> Why did you remove this?
>
> I didn't remove it, I moved it. It's what this:
> 
> 
> The fix I propose for this is to test before pushing on the work list
> whether a node is a store or not.
> 
> 
> refers to. What we do today is that we push all uses and then filter out those that are not of interest when they are popped. What I propose is to filter out what's not useful before it's pushed so the queue doesn't grow large with nodes that are going to be discarded anyway.

Ok, then I suggest that you at least replace this line with an `assert`. That could also help readability ;)

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PR Review Comment: https://git.openjdk.org/jdk/pull/19791#discussion_r1647621134