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refactor(tvix/eval): clean up logic in Compiler::end_scope

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The condition here was extremely hard to read prior to this change.

As the locals vector is now guaranteed to never be empty (there is
always at least a phantom for the current chunk's root expression),
the logic here can be simplified to just dropping tailing locals
entries while their depth matches that of the scope being closed.

Change-Id: I24973e23bc2ad25e62ece64ab4d8624e6e274c16
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6427
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
This commit is contained in:
Vincent Ambo 2022-09-03 03:40:53 +03:00 committed by tazjin
parent 23f248b530
commit 0af1df4be2
1 changed files with 3 additions and 5 deletions
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8
tvix/eval/src/compiler/mod.rs
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@ -1053,8 +1053,6 @@ impl Compiler<'_> {
let depth = self.scope().scope_depth;
self.scope_mut().unpoison(depth);
self.scope_mut().scope_depth -= 1;
// When ending a scope, all corresponding locals need to be
// removed, but the value of the body needs to remain on the
// stack. This is implemented by a separate instruction.
@ -1062,9 +1060,7 @@ impl Compiler<'_> {
// TL;DR - iterate from the back while things belonging to the
// ended scope still exist.
while !self.scope().locals.is_empty()
&& self.scope().locals[self.scope().locals.len() - 1].above(self.scope().scope_depth)
{
while self.scope().locals.last().unwrap().depth == depth {
if let Some(local) = self.scope_mut().locals.pop() {
// pop the local from the stack if it was actually
// initialised
@ -1085,6 +1081,8 @@ impl Compiler<'_> {
if pops > 0 {
self.push_op(OpCode::OpCloseScope(Count(pops)), node);
}
self.scope_mut().scope_depth -= 1;
}
/// Open a new lambda context within which to compile a function,