[LLVMdev] Proposal: stack/context switching within a thread

[Lacey, Mark]

I'm very interested in seeing support for stack/context switching in LLVM, if only for prototyping language ideas. I'm particularly interested in mechanisms that would make it possible to implement full asymmetric coroutines as described in "Revisiting Coroutines" (Moura & Ierusalimschy, Feb 2009 TOPLAS). From skimming the thread and looking at the llvm-stack-switch wiki, it looks like you're headed more in the direction of symmetric coroutines.

I've read that there is a Lua JIT based on LLVM, but haven't looked into the details of how coroutines are implemented there.

In skimming through this thread I see some apparent requirements that I would hope could be avoided - e.g. the existence of mmap, any memory allocation going on "under the covers", or a requirement that a front-end do CPS conversion - it looks like later email has made this same point, so perhaps this is not being considered any longer.

One thing I don't think I've seen mentioned so far is the interplay between swapcontext() and register allocation - I would hope a high performance implementation would exist that would only result in registers that are currently live being saved/restored at these points, not just a general save/restore of register state.

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