feat(tvix/eval): implement OpFinalise instruction r/4667

This instruction finalises the initialisation of deferred upvalues in
closures (and soon, thunks).

The compiler does not yet emit this instruction, some more accounting
is needed for that.

Change-Id: Ic4181b26e19779e206f51e17388559400da5f93a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6337
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs
index d4eb065725..1aaba9b057 100644
--- a/tvix/eval/src/vm.rs
+++ b/tvix/eval/src/vm.rs
@@ -435,6 +435,19 @@ impl VM {
                     }
                 }
 
+                OpCode::OpFinalise(StackIdx(idx)) => {
+                    match &self.stack[self.frame().stack_offset + idx] {
+                        Value::Closure(closure) => closure
+                            .resolve_deferred_upvalues(&self.stack[self.frame().stack_offset..]),
+
+                        v => {
+                            #[cfg(feature = "disassembler")]
+                            drop(tracer);
+                            panic!("compiler error: invalid finaliser value: {}", v);
+                        }
+                    }
+                }
+
                 // Data-carrying operands should never be executed,
                 // that is a critical error in the VM.
                 OpCode::DataLocalIdx(_)