ghci: support foreign import prim

The only thing to my knowledge which GHCi doesn't support is the foreign import prim calling convention.

It would be good to be able to support this calling convention if possible (perhaps by performing the call via a wrapper or the like).

cc @luite

changed milestone to %9.6.1

added needs triage label

sounds like a good idea, perhaps something similar to the unboxed tuples where the bytecode contains the data of where to move the arguments

added GHCi Pnormal Tfeature request labels and removed needs triage label

assigned to @luite

This is in progress.

I got it working for with a new PRIMCALL bytecode instruction, including for calls that return a tuple.

I still need to do more testing, add tests and do some cleanups. Hopefully an MR will follow soon.

well I spent half of ICFP debugging this but it seems to actually work now

MR in !9026 (closed)

Feature complete if CI passes, needs a bit more cleanup and somewhat more comprehensive testcase

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