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Fix: Check non-exhaustible conditional returns using a goto mechanism #75

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Fix: Check non-exhaustible conditional returns using a goto mechanism #75

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affc160
add SimpleLine::Goto and refactor the inlining mechanism for it
divyaranjan1905 Oct 16, 2025
4af51f1
add Line::Goto and process SimpleLine::Goto during intermediate compi…
divyaranjan1905 Oct 16, 2025
cdb9346
fmt
TomWambsgans Oct 16, 2025
8cfefb2
chore: typo
divyaranjan1905 Oct 16, 2025
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77 changes: 58 additions & 19 deletions crates/lean_compiler/src/a_simplify_lang.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -148,6 +148,9 @@ pub enum SimpleLine {
LocationReport {
location: SourceLineNumber,
},
Goto {
label: String,
},
}

pub fn simplify_program(mut program: Program) -> SimpleProgram {
Expand Down Expand Up @@ -690,6 +693,11 @@ fn simplify_lines(
location: *location,
});
}
Line::Goto { label } => {
res.push(SimpleLine::Goto {
label: label.clone(),
});
}
}
}

Expand Down Expand Up @@ -898,7 +906,7 @@ pub fn find_variable_usage(lines: &[Line]) -> (BTreeSet<Var>, BTreeSet<Var>) {
on_new_expr(index, &internal_vars, &mut external_vars);
on_new_expr(value, &internal_vars, &mut external_vars);
}
Line::Panic | Line::Break | Line::LocationReport { .. } => {}
Line::Panic | Line::Break | Line::LocationReport { .. } | Line::Goto { .. } => {}
}
}

Expand Down Expand Up @@ -943,6 +951,7 @@ pub fn inline_lines(
args: &BTreeMap<Var, SimpleExpr>,
res: &[Var],
inlining_count: usize,
epilogue_label: Option<String>,
) {
let inline_condition = |condition: &mut Boolean| {
let (Boolean::Equal { left, right } | Boolean::Different { left, right }) = condition;
Expand All @@ -964,7 +973,13 @@ pub fn inline_lines(
Line::Match { value, arms } => {
inline_expr(value, args, inlining_count);
for (_, statements) in arms {
inline_lines(statements, args, res, inlining_count);
inline_lines(
statements,
args,
res,
inlining_count,
epilogue_label.clone(),
);
}
}
Line::Assignment { var, value } => {
Expand All @@ -978,8 +993,20 @@ pub fn inline_lines(
} => {
inline_condition(condition);

inline_lines(then_branch, args, res, inlining_count);
inline_lines(else_branch, args, res, inlining_count);
inline_lines(
then_branch,
args,
res,
inlining_count,
epilogue_label.clone(),
);
inline_lines(
else_branch,
args,
res,
inlining_count,
epilogue_label.clone(),
);
}
Line::FunctionCall {
args: func_args,
Expand All @@ -1002,16 +1029,22 @@ pub fn inline_lines(
for expr in return_data.iter_mut() {
inline_expr(expr, args, inlining_count);
}
lines_to_replace.push((
i,
res.iter()
.zip(return_data)
.map(|(res_var, expr)| Line::Assignment {
var: res_var.clone(),
value: expr.clone(),
})
.collect::<Vec<_>>(),
));

let mut replacement_lines = res
.iter()
.zip(return_data)
.map(|(res_var, expr)| Line::Assignment {
var: res_var.clone(),
value: expr.clone(),
})
.collect::<Vec<_>>();

if let Some(label) = &epilogue_label {
replacement_lines.push(Line::Goto {
label: label.clone(),
});
}
lines_to_replace.push((i, replacement_lines));
}
Line::MAlloc { var, size, .. } => {
inline_expr(size, args, inlining_count);
Expand Down Expand Up @@ -1048,7 +1081,7 @@ pub fn inline_lines(
rev: _,
unroll: _,
} => {
inline_lines(body, args, res, inlining_count);
inline_lines(body, args, res, inlining_count, epilogue_label.clone());
inline_internal_var(iterator);
inline_expr(start, args, inlining_count);
inline_expr(end, args, inlining_count);
Expand All @@ -1062,7 +1095,7 @@ pub fn inline_lines(
inline_expr(index, args, inlining_count);
inline_expr(value, args, inlining_count);
}
Line::Panic | Line::Break | Line::LocationReport { .. } => {}
Line::Panic | Line::Goto { .. } | Line::Break | Line::LocationReport { .. } => {}
}
}
for (i, new_lines) in lines_to_replace.into_iter().rev() {
Expand Down Expand Up @@ -1531,7 +1564,7 @@ fn replace_vars_for_unroll(
Line::CounterHint { var } => {
*var = format!("@unrolled_{unroll_index}_{iterator_value}_{var}");
}
Line::Break | Line::Panic | Line::LocationReport { .. } => {}
Line::Break | Line::Panic | Line::LocationReport { .. } | Line::Goto { .. } => {}
}
}
}
Expand Down Expand Up @@ -1652,12 +1685,14 @@ fn handle_inlined_functions_helper(
.zip(&simplified_args)
.map(|((var, _), expr)| (var.clone(), expr.clone()))
.collect::<BTreeMap<_, _>>();
let epilogue_label = format!("@inline_epilogue_{}", total_inlined_counter.0);
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@TomWambsgans TomWambsgans Oct 16, 2025

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This idea of "epilogue_label" looks promising. Currently you always put an epilogue_label when inlining but in some cases, when there is no instructions after the RETURN this is unnecessary (we can call such RETURNs "final"). But detecting it is not trivial. We would somehow need to peek at the following of the code (what comes after the RETURN), to see if it's terminal or not, if that makes sense

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@divyaranjan1905 divyaranjan1905 Oct 16, 2025

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I agree, you don't need to always put the label. But yeah finding where you don't need to is quite difficult. We'll need to have some context of what is final in the remainder of the scope.

let mut func_body = func.body.clone();
inline_lines(
&mut func_body,
&inlined_args,
return_data,
total_inlined_counter.next(),
Some(epilogue_label.clone()),
);
inlined_lines.extend(func_body);

Expand Down Expand Up @@ -1921,7 +1956,8 @@ fn get_function_called(lines: &[Line], function_called: &mut Vec<String>) {
| Line::MAlloc { .. }
| Line::Panic
| Line::Break
| Line::LocationReport { .. } => {}
| Line::LocationReport { .. }
| Line::Goto { .. } => {}
}
}
}
Expand Down Expand Up @@ -2025,7 +2061,7 @@ fn replace_vars_by_const_in_lines(lines: &mut [Line], map: &BTreeMap<Var, F>) {
assert!(!map.contains_key(var), "Variable {var} is a constant");
replace_vars_by_const_in_expr(size, map);
}
Line::Panic | Line::Break | Line::LocationReport { .. } => {}
Line::Panic | Line::Break | Line::LocationReport { .. } | Line::Goto { .. } => {}
}
}
}
Expand Down Expand Up @@ -2213,6 +2249,9 @@ impl SimpleLine {
}
Self::Panic => "panic".to_string(),
Self::LocationReport { .. } => Default::default(),
Self::Goto { label } => {
format!("goto_{}", label)
}
};
format!("{spaces}{line_str}")
}
Expand Down
15 changes: 14 additions & 1 deletion crates/lean_compiler/src/b_compile_intermediate.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -597,6 +597,18 @@ fn compile_lines(
location: *location,
});
}
SimpleLine::Goto { label } => {
let goto_label = Label::Custom(label.clone());
instructions.push(IntermediateInstruction::Jump {
dest: IntermediateValue::label(goto_label.clone()),
updated_fp: None,
});

let remaining =
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@TomWambsgans TomWambsgans Oct 16, 2025

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After a GOTO intuitively there should not remain any lines to compile? So we could simply assert lines[i + 1..].is_empty() instead of compiling it? Or maybe am I missing some case?

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@divyaranjan1905 divyaranjan1905 Oct 16, 2025

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I think one cannot assert that lines[i + 1..] is empty after a GOTO. There are valid cases where lines exist after a GOTO, and those lines need to be compiled and registered with the epilogue label.

compile_lines(&lines[i + 1..], compiler, final_jump, declared_vars)?;
compiler.bytecode.insert(goto_label, remaining);
return Ok(instructions);
}
}
}

Expand Down Expand Up @@ -795,7 +807,8 @@ fn find_internal_vars(lines: &[SimpleLine]) -> BTreeSet<Var> {
| SimpleLine::Print { .. }
| SimpleLine::FunctionRet { .. }
| SimpleLine::Precompile { .. }
| SimpleLine::LocationReport { .. } => {}
| SimpleLine::LocationReport { .. }
| SimpleLine::Goto { .. } => {}
}
}
internal_vars
Expand Down
6 changes: 6 additions & 0 deletions crates/lean_compiler/src/lang.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -366,6 +366,9 @@ pub enum Line {
LocationReport {
location: SourceLineNumber,
},
Goto {
label: String,
},
}
impl Display for Expression {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
Expand Down Expand Up @@ -561,6 +564,9 @@ impl Line {
}
Self::Break => "break".to_string(),
Self::Panic => "panic".to_string(),
Self::Goto { label } => {
format!("goto_{}", label)
}
};
format!("{spaces}{line_str}")
}
Expand Down
35 changes: 18 additions & 17 deletions crates/lean_compiler/tests/test_compiler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -438,23 +438,24 @@ fn test_match() {
compile_and_run(program, &[], &[], DEFAULT_NO_VEC_RUNTIME_MEMORY, false);
}

// #[test]
// fn inline_bug_mre() {
// let program = r#"
// fn main() {
// boolean(0);
// return;
// }

// fn boolean(a) inline -> 1 {
// if a == 0 {
// return 0;
// }
// return 1;
// }
// "#;
// compile_and_run(program, &[], &[]);
// }
#[test]
fn inline_bug_mre() {
let program = r#"
fn main() {
x = boolean(0);
return;
}

fn boolean(a) inline -> 1 {
if a == 0 {
return 0;
}
retur3n 1;
}
"#;

compile_and_run(program, &[], &[], DEFAULT_NO_VEC_RUNTIME_MEMORY, false);
}

#[test]
fn test_const_functions_calling_const_functions() {
Expand Down
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