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

[Tobias Hartmann]

Hi Christian,

looks good to me too but please use (jio_)snprintf instead of unsafe sprintf.

Small typo: compile.cpp:4605 "set up" -> "sets up"

Best regards,
Tobias

On 07.05.20 20:38, Vladimir Kozlov wrote:
> 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/