[LLVMdev] Interfacing llvm with a precise, relocating GC

[Rafael Espíndola]

On 24 October 2013 17:32, Sanjoy Das <sanjoy at azulsystems.com> wrote:
> Hello llvm-dev!
>
> My colleages and I are currently evaluating llvm's suitability as a
> JIT compiler interfacing with a precise, relocating garbage collector.
> While we couldn't find code or writeups that deal with the issues
> specific to this design goal, it is entirely possible that we may have
> missed something; we would appreciate references to relevant code or
> writeups that people on this list may be aware of.


This would be hard. Currently what we have support for is a non-moving
GC where all the roots are in memory. Adding support for a non-moving
gc with register roots would not be too hard and might be possible to
reuse some of the recent stackmap work.

For a moving GC you would probably have to change how we represent
pointer arithmetic in the selection dag and MI. It would be quiet a
big change. CCIng Andy and Patrick since they might have an idea of
how much work that would be and what the costs and benefits for LLVM
are.

Also to note is that there are plans to move away from selection dag,
so it might be good to sync this work with whatever we end up using
instead.

Cheers,
Rafael