RFR: 8263577: C2: reachable nodes shouldn't have dead uses at the end of optimizations [v2]

[Roland Westrelin]

On Mon, 15 Mar 2021 13:50:48 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> Changes in `src/hotspot/share/opto/subtypenode.cpp` don't look relevant. I assume new verification logic uncovered a problem there. Does it make sense to integrate the fix separately?

In the case of subtypenode.cpp, some nodes were created and never attached to any use. 

Thanks for the review!

> src/hotspot/share/opto/node.hpp line 458:
> 
>> 456:   }
>> 457:   int replace_edge(Node* old, Node* neww, PhaseGVN* gvn = NULL);
>> 458:   int replace_edges_in_range(Node* old, Node* neww, int start, int end, PhaseGVN* gv);
> 
> s/gv/gvn/

right. Will fix that.

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PR: https://git.openjdk.java.net/jdk/pull/3012