[LLVMdev] Correlating stack map with call frames.

[Paweł Batko]

Hi all,

I'm writing a GC plugin, targeting x86_64. I'm stuck on handling stack
maps. I generate assembly for them like in the documentation:
http://llvm.org/docs/GarbageCollection.html#emitting-assembly-code-gcmetadataprinter
and now I'm trying to figure out the best way to correlate stack maps with
call frames.
I have an idea to put a label before every stack map entry and then put the
address of this label within well known offset from the function. Then,
while walking the call stack and having function address I could retrieve
relevant stack map entry..
My current approach to generating the label for stack map entries looks
like this:
  MCSymbol *ala = AP.OutContext.GetOrCreateSymbol(StringRef("ala"));
  OS.EmitLabel(ala);
But then, I don't know how to emit the address of the label near the
function. I mean, I think I'd use something like this
'OS.EmitSymbolValue(ala, 4)', but I'm not sure where I should hook into to
achieve this.

Note that I'm fairly new to LLVM and the approach I described above does
not necessarily make much sense. I'd pleased to hear the proper way to
handle stack maps.

Regards,
Paweł
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