new llvm IR callbr instruction useful for proc-point splitting?

Kavon Farvardin kavon at
Wed Dec 4 19:31:46 UTC 2019

Hi Ben,
The Wiki now has a link to the Google Doc that Michal and I were working on to
compile all of the notes into one place.
The key progress made on this front has been in evaluating the trade-offs of the
design space being considered by GHC, but tested within Manticore.
I'm drafting a message today for the LLVM mailing list regarding one of our
first options: defining a GHC ABI to redefine which stack-pointer register is
Once we have additional answers to the question "how much effort is it to add a
GHC ABI to LLVM?", we can then then start a discussion on whether GHC wants to
change instead by moving to a native stack-pointer register (to take advantage
of existing debugging and profiling tools, etc).
Ideally, we would then make a decision on which option to take and someone
(perhaps a GSoC student with mentorship from myself and others) with spare time
can work on it.
On Wed, 2019-12-04 at 11:38 -0500, Ben Gamari wrote:
> Kavon Farvardin <kavon at> writes:
> Yes, callbr is part of the discussion on removing proc-point splitting! Soon
> there will be an announcement about a new working group dedicated to
> LLVMissues such as this one on this mailing list. Anyone interested is welcome
> tojoin our meetings.We're currently gathering our notes together first, but
> you can have a look herefor a preview: 
> Hi Kavon,
> What ever happened to this? It came up during the GHC call and werealized that
> none of us knew what the state of the proposal was. Isthis Wiki page still
> reflective of the current state of play?
> Cheers,
> - Ben
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