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feat(minifier): use remove_unused_expression in try_fold_sequence_expression in remove_dead_code #9467

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Merged
graphite-app merged 1 commit into from
Mar 1, 2025
Merged

feat(minifier): use remove_unused_expression in try_fold_sequence_expression in remove_dead_code #9467

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8 changes: 4 additions & 4 deletions crates/oxc_minifier/src/peephole/fold_constants.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1212,7 +1212,7 @@ mod test {
#[test]
fn test_fold_logical_op() {
fold("x = true && x", "x = x");
fold("x = [foo()] && x", "x = ([foo()],x)");
fold("x = [foo()] && x", "x = (foo(),x)");

fold("x = false && x", "x = !1");
fold("x = true || x", "x = !0");
Expand Down Expand Up @@ -1240,7 +1240,7 @@ mod test {
fold("x = foo() || true && bar()", "x = foo() || bar()");
fold("x = foo() || false && bar()", "x = foo() || !1");
fold("x = foo() && false && bar()", "x = foo() && !1");
fold("x = foo() && false || bar()", "x = (foo() && !1, bar())");
fold("x = foo() && false || bar()", "x = (foo(), bar())");
fold("x = foo() || false || bar()", "x = foo() || bar()");
fold("x = foo() && true && bar()", "x = foo() && bar()");
fold("x = foo() || true || bar()", "x = foo() || !0");
Expand Down Expand Up @@ -1280,15 +1280,15 @@ mod test {
fn test_fold_logical_op2() {
fold("x = function(){} && x", "x=x");
fold("x = true && function(){}", "x=function(){}");
fold("x = [(function(){alert(x)})()] && x", "x=([function(){alert(x)}()],x)");
fold("x = [(function(){alert(x)})()] && x", "x=(function(){alert(x)}(),x)");
}

#[test]
fn test_fold_nullish_coalesce() {
// fold if left is null/undefined
fold("null ?? 1", "1");
fold("undefined ?? false", "!1");
fold("(a(), null) ?? 1", "(a(), null, 1)");
fold("(a(), null) ?? 1", "(a(), 1)");

fold("x = [foo()] ?? x", "x = [foo()]");

Expand Down
79 changes: 39 additions & 40 deletions crates/oxc_minifier/src/peephole/remove_dead_code.rs
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Expand Up @@ -2,6 +2,7 @@ use oxc_allocator::Vec;
use oxc_ast::ast::*;
use oxc_ast_visit::Visit;
use oxc_ecmascript::{constant_evaluation::ConstantEvaluation, side_effects::MayHaveSideEffects};
use oxc_span::GetSpan;
use oxc_traverse::Ancestor;

use crate::{ctx::Ctx, keep_var::KeepVar};
Expand Down Expand Up @@ -39,7 +40,7 @@ impl<'a, 'b> PeepholeOptimizations {
if let Some(folded_expr) = match expr {
Expression::ConditionalExpression(e) => self.try_fold_conditional_expression(e, ctx),
Expression::SequenceExpression(sequence_expression) => {
Self::try_fold_sequence_expression(sequence_expression, ctx)
self.try_fold_sequence_expression(sequence_expression, ctx)
}
_ => None,
} {
Expand Down Expand Up @@ -381,60 +382,49 @@ impl<'a, 'b> PeepholeOptimizations {
}

fn try_fold_sequence_expression(
&mut self,
sequence_expr: &mut SequenceExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let should_keep_as_sequence_expr = matches!(
ctx.parent(),
Ancestor::CallExpressionCallee(_) | Ancestor::TaggedTemplateExpressionTag(_)
);

if should_keep_as_sequence_expr && sequence_expr.expressions.len() == 2 {
if should_keep_as_sequence_expr
&& sequence_expr.expressions.len() == 2
&& sequence_expr.expressions.first().unwrap().is_number_0()
{
return None;
}

let (should_fold, new_len) = sequence_expr.expressions.iter().enumerate().fold(
(false, 0),
|(mut should_fold, mut new_len), (i, expr)| {
if i == sequence_expr.expressions.len() - 1 || expr.may_have_side_effects(&ctx) {
new_len += 1;
} else {
should_fold = true;
}
(should_fold, new_len)
},
);

if new_len == 0 {
return Some(ctx.ast.expression_null_literal(sequence_expr.span));
}

if should_fold {
let mut new_exprs = ctx.ast.vec_with_capacity(new_len);
let len = sequence_expr.expressions.len();
for (i, expr) in sequence_expr.expressions.iter_mut().enumerate() {
if i == len - 1 || expr.may_have_side_effects(&ctx) {
new_exprs.push(ctx.ast.move_expression(expr));
let old_len = sequence_expr.expressions.len();
let mut i = 0;
sequence_expr.expressions.retain_mut(|e| {
i += 1;
if should_keep_as_sequence_expr && i == old_len - 1 {
if self.remove_unused_expression(e, ctx) {
*e = ctx.ast.expression_numeric_literal(
e.span(),
0.0,
None,
NumberBase::Decimal,
);
self.mark_current_function_as_changed();
}
return true;
}

if should_keep_as_sequence_expr && new_exprs.len() == 1 {
let number = ctx.ast.expression_numeric_literal(
sequence_expr.span,
1.0,
None,
NumberBase::Decimal,
);
new_exprs.insert(0, number);
}

if new_exprs.len() == 1 {
return Some(new_exprs.pop().unwrap());
if i == old_len {
return true;
}

return Some(ctx.ast.expression_sequence(sequence_expr.span, new_exprs));
!self.remove_unused_expression(e, ctx)
});
if sequence_expr.expressions.len() == 1 {
return Some(sequence_expr.expressions.pop().unwrap());
}

if sequence_expr.expressions.len() != old_len {
self.mark_current_function_as_changed();
}
None
}
}
Expand Down Expand Up @@ -607,6 +597,15 @@ mod test {
test("while(true) { return a; unreachable;}", "for(;;) return a");
}

#[test]
fn remove_unused_expressions_in_sequence() {
test("true, foo();", "foo();");
test("(true, foo)();", "(0, foo)();");
test("(true, true, foo)();", "(0, foo)();");
test("var foo; (true, foo)();", "var foo; (0, foo)();");
test("var foo; (true, true, foo)();", "var foo; (0, foo)();");
}

#[test]
fn remove_unused_expressions_in_for() {
test(
Expand Down
14 changes: 7 additions & 7 deletions crates/oxc_minifier/tests/peephole/mod.rs
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Expand Up @@ -57,7 +57,7 @@ fn integration() {
}
console.log(c, d);
",
"if ((() => console.log('effect'))(), !1) for (var c = 1, c; unknownGlobal; unknownGlobal) var d;
"if (console.log('effect'), !1) for (var c = 1, c; unknownGlobal; unknownGlobal) var d;
console.log(c, d);
",
);
Expand All @@ -74,8 +74,8 @@ fn fold() {

#[test] // https://github.com/oxc-project/oxc/issues/4341
fn tagged_template() {
test_same("(1, o.f)()");
test_same("(1, o.f)``");
test("(1, o.f)()", "(0, o.f)()");
test("(1, o.f)``", "(0, o.f)``");
test_same("(!0 && o.f)()");
test_same("(!0 && o.f)``");
test("(!0 ? o.f : !1)()", "(0 ? !1: o.f)()");
Expand All @@ -91,10 +91,10 @@ fn eval() {
test_same("(!0 && eval)(x)");
test_same("(1 ? eval : 2)(x)");
test_same("(1 ? eval : 2)?.(x)");
test_same("(1, eval)(x)");
test_same("(1, eval)?.(x)");
test_same("(3, eval)(x)");
test_same("(4, eval)?.(x)");
test("(1, eval)(x)", "(0, eval)(x)");
test("(1, eval)?.(x)", "(0, eval)?.(x)");
test("(3, eval)(x)", "(0, eval)(x)");
test("(4, eval)?.(x)", "(0, eval)?.(x)");
test_same("(eval)(x)");
test_same("(eval)?.(x)");
test_same("eval(x)");
Expand Down
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