RFR: 8263790: C2: new igv_print_immediately() for debugging purpose

[Christian Hagedorn]

On Thu, 18 Mar 2021 10:05:12 GMT, Yi Yang <yyang at openjdk.org> wrote:

> Add a new igv_print_immediately, it prints the current method immediately. This differs from other igv_print* methods, it creates a well-formed and complete ideal graph xml immediately, while others accomplish their ideal graph xml when VM exists (i.e. destructor of `IdealGraphPrinter::_xx_printer`). If VM crashes before VM exit, the ideal graph xml will be ill-formed, this is fairly a common case when debugging another crash.
> 
> Test manually!
> 
> Cheers,
> Yang

I'm not sure if I understand this correctly. Is it just about having an ill-formatted xml file or are you actually having problems opening the graph in the IGV? I've just played around with calling `igv_print()` in gdb from a few places but could open the incomplete xml files in the IGV and have a look at the graphs. Are you seeing this when calling `igv_print()` from certain breakpoints while debugging?

If it's the IGV that has problems opening it, could you maybe provide more information how to reproduce this and/or share the xml file that causes problems?

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PR: https://git.openjdk.java.net/jdk/pull/3071