[llvm-dev] Passing on stack pointers to statepoint GC intrinsic

[Jake Hughes via llvm-dev]

Hi,

I'm trying to use the statepoint intrinsic to record roots for garbage
collection at safepoints. I'm using the "statepoint-example" GCStrategy and
the RewriteStatepointsForGC pass to insert the statepoint relocation
sequences at function invocations.

My language allows for function locals which could be GC pointers and are
represented in the IR with allocas. The RS4GC pass doesn't include these in
the gc pointer list. 

If I've understood the documentation correctly, I need to include these
allocas in the gc pointer operand list myself. I'm not sure how to tackle
this though. Specifically my questions are:

Do I need to include these pointer values in the deopt param list as well? 

Should I be extending RS4GC to do this myself, or is there builtin
functionality somewhere which I am missing? 

Are there any examples of this being done? 

The documentation states w.r.t recording on stack regions that "This
alternate form is not well execised ... the RS4GC pass does not do anything
for allocas today." [1] I infer from this that there must be a preferred way
for dealing with on stack regions, if so, what would that be? 

Thanks very much for your time,

Jake

[1] https://llvm.org/docs/Statepoints.html#recording-on-stack-regions