[m-rev.] for post-commit review: Match output arguments correctly?for mutually recursive code

Paul Bone paul at bone.id.au
Wed Apr 12 10:26:01 AEST 2017

On Wed, Apr 12, 2017 at 10:19:21AM +1000, Zoltan Somogyi wrote:
> I don't think ignoring the remaining arguments in the OutputVars0 = [] case
> is right. If the caller's output arguments are X, Y and Z, and the callee's are
> X, Y, Z and W, then I don't think we want to consider the call to be a tail call.
> The code we would generate for a tail call for e.g. the LLDS backend may do
> the right thing, but it would do so only by accident, and I don't think we
> want to rely on accidents.
> I think requiring the caller and callee to have the *same* sequence of
> output arguments is safer, and it can be done with simpler code.
> That is why I am committing the attached diff.

Okay, I didn't know how much this could be relied on, we havn't changed the
calling conventions before (to my knowledge) so I assumed they were pretty
stable.  I agree that it is possible they could change or new optimisations
could be added and that would cause problems.


Paul Bone

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