llvm dev - Aug 2019 - Live DEBUG_VALUE analysis transfer

Hello,

Looking at the code of Live DEBUG_VALUE analysis which propagates debug
information by inserting new DBG_VALUE instructions to the MIR.

Currently, this pass inserts new DBG_VALUE instructions for register copy,
spill and restore instructions. However, extend instructions such as ARM's
{S|U}XT{B|H} should also have new DBG_VALUE instructions inserted, since
they do kill and define registers.

Is this just a TODO that needs to be implemented, or there is in fact a
reason for this?

Thank you for your time,

Son Tuan Vu
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20190802/88e3ffbf/attachment.html>

> On Aug 1, 2019, at 3:50 PM, Son Tuan VU via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hello,
> 
> Looking at the code of Live DEBUG_VALUE analysis which propagates debug
information by inserting new DBG_VALUE instructions to the MIR.
> 
> Currently, this pass inserts new DBG_VALUE instructions for register copy,
spill and restore instructions. However, extend instructions such as ARM's
{S|U}XT{B|H} should also have new DBG_VALUE instructions inserted, since they do
kill and define registers.
> 
> Is this just a TODO that needs to be implemented, or there is in fact a
reason for this?
> 
Could you post a short example that illustrates the issue? LiveDebugValue's
primary purpose is to propagate DBG_VALUEs across basic block boundaries. Based
on your description I'm not sure whether this wouldn't be a better fit
for a different phase.

-- adrian