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fix(tvix/eval): set up root stack slot in closures & thunks

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Similar to setting up a phantom slot when compiling the root value of
a file, closures and thunks need to have a phantom stack slot for the
root of the expression yielded by their thunk to make all accounting
work correctly.

The tricky thing here is that closures & thunks *escape* their inner
lambda context (that's the point!), so the functions emitting them
need to know both the *inner* slot (to resolve everything correctly
while compiling the slot) and the *outer* slot (to correctly emit
instructions for closing over upvalues).

Change-Id: I62ac58e2f639c4b9e09cc702bdbfd2373e985d7f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6426
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
This commit is contained in:
Vincent Ambo 2022-09-03 03:20:33 +03:00 committed by tazjin
parent 4e24bd56b4
commit 23f248b530
1 changed files with 8 additions and 4 deletions
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12
tvix/eval/src/compiler/mod.rs
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@ -863,8 +863,10 @@ impl Compiler<'_> {
self.end_scope(&node);
}
fn compile_lambda(&mut self, slot: LocalIdx, node: ast::Lambda) {
fn compile_lambda(&mut self, outer_slot: LocalIdx, node: ast::Lambda) {
self.new_context();
let span = self.span_for(&node);
let slot = self.scope_mut().declare_phantom(span);
self.begin_scope();
// Compile the function itself
@ -917,7 +919,7 @@ impl Compiler<'_> {
.push_constant(Value::Blueprint(Rc::new(compiled.lambda)));
self.push_op(OpCode::OpClosure(blueprint_idx), &node);
self.emit_upvalue_data(slot, compiled.scope.upvalues);
self.emit_upvalue_data(outer_slot, compiled.scope.upvalues);
}
fn compile_apply(&mut self, slot: LocalIdx, node: ast::Apply) {
@ -933,12 +935,14 @@ impl Compiler<'_> {
/// Compile an expression into a runtime thunk which should be
/// lazily evaluated when accessed.
// TODO: almost the same as Compiler::compile_lambda; unify?
fn thunk<N, F>(&mut self, slot: LocalIdx, node: &N, content: F)
fn thunk<N, F>(&mut self, outer_slot: LocalIdx, node: &N, content: F)
where
N: AstNode + Clone,
F: FnOnce(&mut Compiler, &N, LocalIdx),
{
self.new_context();
let span = self.span_for(node);
let slot = self.scope_mut().declare_phantom(span);
self.begin_scope();
content(self, node, slot);
self.end_scope(node);
@ -963,7 +967,7 @@ impl Compiler<'_> {
.push_constant(Value::Blueprint(Rc::new(thunk.lambda)));
self.push_op(OpCode::OpThunk(blueprint_idx), node);
self.emit_upvalue_data(slot, thunk.scope.upvalues);
self.emit_upvalue_data(outer_slot, thunk.scope.upvalues);
}
/// Emit the data instructions that the runtime needs to correctly