RFR: 8286179: Node::find(int) should not traverse from new to old nodes [v2]

[Christian Hagedorn]

On Mon, 9 May 2022 14:04:08 GMT, Emanuel Peter <duke at openjdk.java.net> wrote:

>> src/hotspot/share/opto/node.cpp line 1617:
>> 
>>> 1615: Node* find_old_node(const int idx) {
>>> 1616:   Node* root = old_root();
>>> 1617:   assert(root != nullptr, "must have old_root() to find old nodes");
>> 
>> I think it's better to avoid assertions here and below and do nothing instead (you already print a warning in `old_root()` which is fine I think) since it would crash and stop the current debugging session.
>
> Ok, personally verified with @chhagedorn , his idea was to return `nullptr`, will do that now.

I did not know about `set unwindonsignal on`, that's good trick! I agree that you can still trigger assertions while debugging but I think we should try to reduce that chance as much as we can with sane input values.

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PR: https://git.openjdk.java.net/jdk/pull/8567