[llvm-dev] Function with multi return path?

[TONGARI J via llvm-dev]

2017-06-02 19:51 GMT+08:00 David Chisnall <David.Chisnall at cl.cam.ac.uk>:

> On 2 Jun 2017, at 03:38, TONGARI J via llvm-dev <llvm-dev at lists.llvm.org>
> wrote:
> >
> > I'm aware of the invoke instruction and landingpad. But it's too heavy
> > weight for control flow. It's quite expensive to take the exceptional
> path
> > in C++.
> >
> > What I want is a more lightweight approach, to pass the return address to
> > the callee, and let the callee jump to that address directly.
>
> The best way of implementing this is likely to be to use a custom calling
> convention along with invoke.  The invoke instruction will handle the
> semantics correctly in the IR, but you’ll need to modify the back end to
> understand that it should generate the call site differently and not emit
> unwind tables.
>

A custom calling convention doesn't suffice, there could be more than one
alternate paths. And invoke instruction is also not general enough.
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