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feat(tvix/eval): implement tail-calling of __functor attributes

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This implements __functor calling in situations where `OpTailCall` is
used, but not yet for `OpCall`.

For some reason I have not yet figured out, this same implementation
does not work in call_value, which means that it also doesn't yet work
in builtins that apply functions.

Change-Id: I378f9065ac53d4c05166a7d0151acb1f55c91579
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6826
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
This commit is contained in:
Vincent Ambo 2022-09-29 23:58:53 +03:00 committed by clbot
parent c1d8cee215
commit 8336577c41
3 changed files with 39 additions and 19 deletions
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1
tvix/eval/src/tests/tvix_tests/eval-okay-functor-call.exp Normal file
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@ -0,0 +1 @@
42

1
tvix/eval/src/tests/tvix_tests/eval-okay-functor-call.nix Normal file
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@ -0,0 +1 @@
{ x = 21; __functor = self: y: self.x * y; } 2

56
tvix/eval/src/vm.rs
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@ -204,6 +204,42 @@ impl<'o> VM<'o> {
}
}
fn tail_call_value(&mut self, callable: Value) -> EvalResult<()> {
match callable {
Value::Builtin(builtin) => self.call_builtin(builtin),
Value::Thunk(thunk) => self.tail_call_value(thunk.value().clone()),
Value::Closure(closure) => {
let lambda = closure.lambda();
self.observer.observe_tail_call(self.frames.len(), &lambda);
// Replace the current call frames internals with
// that of the tail-called closure.
let mut frame = self.frame_mut();
frame.lambda = lambda;
frame.upvalues = closure.upvalues().clone();
frame.ip = CodeIdx(0); // reset instruction pointer to beginning
Ok(())
}
// Attribute sets with a __functor attribute are callable.
Value::Attrs(ref attrs) => match attrs.select("__functor") {
None => Err(self.error(ErrorKind::NotCallable(callable.type_of()))),
Some(functor) => {
// The functor receives the set itself as its first argument
// and needs to be called with it. However, this call is
// synthetic (i.e. there is no corresponding OpCall for the
// first call in the bytecode.)
self.push(callable.clone());
let primed = self.call_value(functor)?;
self.tail_call_value(primed)
}
},
_ => Err(self.error(ErrorKind::NotCallable(callable.type_of()))),
}
}
/// Execute the given lambda in this VM's context, returning its
/// value after its stack frame completes.
pub fn call(
@ -488,25 +524,7 @@ impl<'o> VM<'o> {
OpCode::OpTailCall => {
let callable = self.pop();
match callable {
Value::Builtin(builtin) => self.call_builtin(builtin)?,
Value::Closure(closure) => {
let lambda = closure.lambda();
self.observer.observe_tail_call(self.frames.len(), &lambda);
// Replace the current call frames
// internals with that of the tail-called
// closure.
let mut frame = self.frame_mut();
frame.lambda = lambda;
frame.upvalues = closure.upvalues().clone();
frame.ip = CodeIdx(0); // reset instruction pointer to beginning
}
_ => return Err(self.error(ErrorKind::NotCallable(callable.type_of()))),
}
self.tail_call_value(callable)?;
}
OpCode::OpGetUpvalue(upv_idx) => {