RFR: 8281548: Add escape analysis tracing flag [v4]

[Xin Liu]

On Tue, 15 Feb 2022 21:11:25 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> src/hotspot/share/opto/escape.cpp line 3764:
>> 
>>> 3762:     ss.print("escapes as arg to:");
>>> 3763:     call->dump("", false, &ss);
>>> 3764:     return ss.as_string();
>> 
>> stringStream::as_string will allocate a new string on resource arena. 
>> I think  you should place "ResourceMark rm;" to reclaim that space. 
>> ps: I don't quite understand why not all code of share/opto follow this idiom. maybe it's not an issue.
>
> There is already a `ResourceMark` in [`ConnectionGraph::do_analysis`](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/escape.cpp#L96) that catches these strings. FWIW, I tried adding another more nested `ResourceMark`, but ran into trouble since some of the GrowableArrays might then be resized in the nested mark which is a bug [(See)](https://github.com/openjdk/jdk/blob/master/src/hotspot/share/utilities/growableArray.cpp#L64-L71).

I miss that. you are right!

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PR: https://git.openjdk.java.net/jdk/pull/7428