[15] RFR(M): 8244207: Simplify usage of Compile::print_method() when debugging with gdb and enable its use with rr

[Vladimir Kozlov]

Looks good.

Thanks,
Vladimir

On 5/7/20 5:09 AM, Christian Hagedorn wrote:
> Hi
> 
> Please review the following debugging enhancement:
> https://bugs.openjdk.java.net/browse/JDK-8244207
> http://cr.openjdk.java.net/~chagedorn/8244207/webrev.00/
> 
> This enhancement simplifies the usage for printing the ideal graph for visualization with the Ideal Graph Visualizer 
> when debugging with gdb and enables graph printing with rr [1].
> 
> Instead of calling Compile::current()->print_method(PHASE_X, y, z) from gdb, one can now just call igv_print() or 
> igv_print(phase_name) with a custom phase name. There are multiple options depending on where the graph should be 
> printed to (file or over network/locally to an opened Ideal Graph Visualizer). When choosing file, the output is always 
> printed to a file named custom_debug.xml. I think the flexibility to choose another file name is not really required 
> since it's only used while debugging. These new igv_print() methods can also be called from gdb without setting any 
> flags required for the usual calls to Compile::current()->print_method(PHASE_X, y, z) to work.
> 
> The standard Compile::current()->print_method(PHASE_X, y, z) call does not work while debugging a program trace with rr 
> (and is probably also problematic with related replay tools). The call gets stuck somewhere. rr allows to alter some 
> data at a breakpoint but as soon as execution continues on the replayed trace, the modifications are undone (except for 
> file writes). This enhancement also addresses this such that the new igv_print() methods can be used with rr. However, 
> when printing to a file is chosen, igv_print() will overwrite custom_debug.xml again at the next execution stop. To 
> avoid that I added additional rr-specific igv_append() and igv_append(phase_name) methods that simply append a graph to 
> the existing custom_debug.xml file without setting up a file header again. This allows all printed graphs to be kept in 
> one file which makes it easier to navigate through them.
> 
> Thank you!
> 
> Best regards,
> Christian
> 
> 
> [1] https://rr-project.org/