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

[Jorn Vernee]

On Tue, 15 Feb 2022 20:59:22 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Review comments
>
> 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`](1) that catches these strings. FWIW adding another more nested `ResourceMark` is not possible since some of the GrowableArrays might then be resized in the nested mark which is a bug [(See)](2).

[1]: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/opto/escape.cpp#L96
[2]: https://github.com/openjdk/jdk/blob/master/src/hotspot/share/utilities/growableArray.cpp#L64-L71

-------------

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