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<p>Hi everyone,</p>
<p>I am a member of the HSA Foundation tools group, who are
attempting to standardise debugging and profiling interfaces for
heterogeneous systems. <br>
</p>
<p>HSA is a low-level heterogeneous system architecture and software
platform. There are standards describing the architectural
requirements, an LLVM-IR-like intermediate language for portable
HSA applications (HSAIL), and a runtime interface for interacting
with the system. We are currently developing a standard for
debugging HSA applications in a vendor-independent manner. <br>
</p>
<p>By working together with other communities, we are hoping to
extend existing debuggers and standards to support such systems.
To this end, I'm hoping to start a conversation with you all about
how LLDB could be augmented to support heterogeneous debugging,
and to ask for input about the standards we are writing.</p>
<p>To aid these discussions and provide a testbed for ideas, I have
modified LLDB to support debugging HSA programs on AMD's hardware.
My aim for this project is to adapt it to the standard HSA
debugging interface once this is completed, so that it could debug
HSA applications on any vendor's implementation. <br>
</p>
<p>Currently, the changes I have made to LLDB are in no state for
upstreaming to trunk LLDB, as I have made some HSA-specific
alterations to core parts of the code base. My hope is that, aided
by discussion with the community, I can abstract out these
modifications to support the necessary features in an elegant and
extensible manner. This would most likely involve changing the
threading model of LLDB to support groups of threads which run on
different devices and a "some-stop" model by which some thread
groups can continue to execute whilst others are stopped. I plan
on starting work on this soon, but I wonder if anyone else is
already exploring this avenue?</p>
<p>If you would like to examine the code for my LLDB port or try it
out, you can get the code here:
<a class="moz-txt-link-freetext" href="https://github.com/HSAFoundation/HSA-Debugger-LLDB-Source">https://github.com/HSAFoundation/HSA-Debugger-LLDB-Source</a></p>
<p>For our debugging standard, we are currently trying to work out
the best way to express the multiple address spaces of HSA in
DWARF and get an idea of how this is handled by GDB and LLDB. Our
current thinking is to use DW_AT_address_class for pointers types
and DW_op_xdref for variables. I couldn't see anywhere these are
handled in LLDB; is there any ongoing work to add them? Or would
you recommend a different approach?<br>
</p>
<p>Feel free to send me any queries or issues regarding the LLDB
implementation or the HSA standards work.</p>
<p>Thanks,</p>
<p>Simon Brand<br>
</p>
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