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refactor(minifier): remove unused reference #13568

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29 changes: 23 additions & 6 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 @@ -8,7 +8,7 @@ use oxc_ecmascript::{
use oxc_span::GetSpan;
use oxc_syntax::operator::{BinaryOperator, LogicalOperator};

use crate::ctx::Ctx;
use crate::{ctx::Ctx, peephole::DeleteCode};

use super::PeepholeOptimizations;

Expand All @@ -30,6 +30,7 @@ impl<'a> PeepholeOptimizations {
_ if e.may_have_side_effects(ctx) => {}
_ => {
if let Some(changed) = e.evaluate_value(ctx).map(|v| ctx.value_to_expr(e.span, v)) {
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand All @@ -44,6 +45,7 @@ impl<'a> PeepholeOptimizations {
return;
}
if let Some(changed) = e.evaluate_value(ctx).map(|value| ctx.value_to_expr(e.span, value)) {
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand All @@ -56,6 +58,7 @@ impl<'a> PeepholeOptimizations {
return;
}
if let Some(changed) = e.evaluate_value(ctx).map(|value| ctx.value_to_expr(e.span, value)) {
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand All @@ -67,6 +70,7 @@ impl<'a> PeepholeOptimizations {
LogicalOperator::And | LogicalOperator::Or => Self::try_fold_and_or(e, ctx),
LogicalOperator::Coalesce => Self::try_fold_coalesce(e, ctx),
} {
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand Down Expand Up @@ -94,6 +98,7 @@ impl<'a> PeepholeOptimizations {
if let Some(changed) = (ty.is_null() || ty.is_undefined())
.then(|| ctx.value_to_expr(e.span, ConstantValue::Undefined))
{
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand Down Expand Up @@ -334,6 +339,7 @@ impl<'a> PeepholeOptimizations {
BinaryOperator::In => None,
};
if let Some(changed) = changed {
expr.delete(ctx);
*expr = changed;
ctx.state.changed = true;
}
Expand Down Expand Up @@ -541,19 +547,24 @@ impl<'a> PeepholeOptimizations {
if let Some(n) = arg.evaluate_value_to_number(ctx) {
n
} else {
*expr = ctx.ast.expression_unary(
let new_expr = ctx.ast.expression_unary(
e.span,
UnaryOperator::UnaryPlus,
ctx.ast.expression_string_literal(n.span, n.value, n.raw),
);

expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
return;
}
}
e if e.is_void_0() => f64::NAN,
_ => return,
});
*expr = ctx.value_to_expr(e.span, value);
let new_expr = ctx.value_to_expr(e.span, value);
expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
}

Expand All @@ -575,7 +586,9 @@ impl<'a> PeepholeOptimizations {
e.operator,
BinaryOperator::StrictEquality | BinaryOperator::Equality
);
*expr = ctx.ast.expression_boolean_literal(e.span, b);
let new_expr = ctx.ast.expression_boolean_literal(e.span, b);
expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
return;
}
Expand All @@ -591,11 +604,13 @@ impl<'a> PeepholeOptimizations {
let right_ty = e.right.value_type(ctx);

if !right_ty.is_undetermined() && right_ty != ValueType::String {
*expr = ctx.ast.expression_boolean_literal(
let new_expr = ctx.ast.expression_boolean_literal(
e.span,
e.operator == BinaryOperator::Inequality
|| e.operator == BinaryOperator::StrictInequality,
);
expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
return;
}
Expand All @@ -612,11 +627,13 @@ impl<'a> PeepholeOptimizations {
| "function"
| "unknown" // IE
) {
*expr = ctx.ast.expression_boolean_literal(
let new_expr = ctx.ast.expression_boolean_literal(
e.span,
e.operator == BinaryOperator::Inequality
|| e.operator == BinaryOperator::StrictInequality,
);
expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
}
}
Expand Down
6 changes: 4 additions & 2 deletions crates/oxc_minifier/src/peephole/inline.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use oxc_traverse::Ancestor;

use crate::ctx::Ctx;

use super::PeepholeOptimizations;
use super::{DeleteCode, PeepholeOptimizations};

impl<'a> PeepholeOptimizations {
pub fn init_symbol_value(decl: &VariableDeclarator<'a>, ctx: &mut Ctx<'a, '_>) {
Expand Down Expand Up @@ -45,7 +45,9 @@ impl<'a> PeepholeOptimizations {
ConstantValue::Boolean(_) | ConstantValue::Undefined | ConstantValue::Null => true,
}
{
*expr = ctx.value_to_expr(expr.span(), cv.clone());
let new_expr = ctx.value_to_expr(expr.span(), cv.clone());
expr.delete(ctx);
*expr = new_expr;
ctx.state.changed = true;
}
}
Expand Down
7 changes: 5 additions & 2 deletions crates/oxc_minifier/src/peephole/minimize_conditional_expression.rs
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Expand Up @@ -7,7 +7,7 @@ use oxc_ecmascript::{
use oxc_span::{ContentEq, GetSpan};
use oxc_syntax::es_target::ESTarget;

use crate::ctx::Ctx;
use crate::{ctx::Ctx, peephole::DeleteCode};

use super::PeepholeOptimizations;

Expand Down Expand Up @@ -244,6 +244,7 @@ impl<'a> PeepholeOptimizations {
if matches!(consequent.arguments[0], Argument::SpreadElement(_))
&& matches!(alternate.arguments[0], Argument::SpreadElement(_))
{
alternate.callee.delete(ctx);
let callee = consequent.callee.take_in(ctx.ast);
let consequent_first_arg = {
let Argument::SpreadElement(el) = &mut consequent.arguments[0] else {
Expand Down Expand Up @@ -273,8 +274,8 @@ impl<'a> PeepholeOptimizations {
if !matches!(consequent.arguments[0], Argument::SpreadElement(_))
&& !matches!(alternate.arguments[0], Argument::SpreadElement(_))
{
alternate.callee.delete(ctx);
let callee = consequent.callee.take_in(ctx.ast);

let consequent_first_arg =
consequent.arguments[0].to_expression_mut().take_in(ctx.ast);
let alternate_first_arg =
Expand Down Expand Up @@ -339,8 +340,10 @@ impl<'a> PeepholeOptimizations {
value_expr.take_in(ctx.ast),
LogicalOperator::Coalesce,
if is_negate {
expr.consequent.delete(ctx);
expr.alternate.take_in(ctx.ast)
} else {
expr.alternate.delete(ctx);
expr.consequent.take_in(ctx.ast)
},
));
Expand Down
15 changes: 11 additions & 4 deletions crates/oxc_minifier/src/peephole/minimize_conditions.rs
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Expand Up @@ -10,7 +10,7 @@ use oxc_syntax::es_target::ESTarget;

use crate::ctx::Ctx;

use super::PeepholeOptimizations;
use super::{DeleteCode, PeepholeOptimizations};

/// Minimize Conditions
///
Expand Down Expand Up @@ -108,6 +108,8 @@ impl<'a> PeepholeOptimizations {
BinaryOperator::Equality => {}
_ => return,
}
e.left.delete(ctx);
e.right.delete(ctx);
*expr = if b {
e.left.take_in(ctx.ast)
} else {
Expand All @@ -130,6 +132,7 @@ impl<'a> PeepholeOptimizations {
return;
}
if let Some(ConstantValue::Boolean(left_bool)) = e.left.evaluate_value(ctx) {
e.left.delete(ctx);
e.left = ctx.ast.expression_numeric_literal(
e.left.span(),
if left_bool { 1.0 } else { 0.0 },
Expand All @@ -140,6 +143,7 @@ impl<'a> PeepholeOptimizations {
return;
}
if let Some(ConstantValue::Boolean(right_bool)) = e.right.evaluate_value(ctx) {
e.right.delete(ctx);
e.right = ctx.ast.expression_numeric_literal(
e.right.span(),
if right_bool { 1.0 } else { 0.0 },
Expand Down Expand Up @@ -206,7 +210,9 @@ impl<'a> PeepholeOptimizations {

let new_op = logical_expr.operator.to_assignment_operator();
expr.operator = new_op;
expr.right = logical_expr.right.take_in(ctx.ast);
let new_expr = logical_expr.right.take_in(ctx.ast);
expr.right.delete(ctx);
expr.right = new_expr;
ctx.state.changed = true;
}

Expand All @@ -226,9 +232,10 @@ impl<'a> PeepholeOptimizations {
}

Self::mark_assignment_target_as_read(&expr.left, ctx);

let new_expr = binary_expr.right.take_in(ctx.ast);
expr.right.delete(ctx);
expr.operator = new_op;
expr.right = binary_expr.right.take_in(ctx.ast);
expr.right = new_expr;
ctx.state.changed = true;
}

Expand Down
7 changes: 4 additions & 3 deletions crates/oxc_minifier/src/peephole/minimize_logical_expression.rs
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Expand Up @@ -4,7 +4,7 @@ use oxc_semantic::ReferenceFlags;
use oxc_span::{ContentEq, GetSpan};
use oxc_syntax::es_target::ESTarget;

use crate::ctx::Ctx;
use crate::{ctx::Ctx, peephole::DeleteCode};

use super::PeepholeOptimizations;

Expand Down Expand Up @@ -32,7 +32,7 @@ impl<'a> PeepholeOptimizations {
/// - `document.all == null` is `true`
fn try_compress_is_null_or_undefined(
expr: &mut LogicalExpression<'a>,
ctx: &Ctx<'a, '_>,
ctx: &mut Ctx<'a, '_>,
) -> Option<Expression<'a>> {
let op = expr.operator;
let target_ops = match op {
Expand Down Expand Up @@ -78,7 +78,7 @@ impl<'a> PeepholeOptimizations {
right: &mut Expression<'a>,
span: Span,
(find_op, replace_op): (BinaryOperator, BinaryOperator),
ctx: &Ctx<'a, '_>,
ctx: &mut Ctx<'a, '_>,
) -> Option<Expression<'a>> {
enum LeftPairValueResult {
Null(Span),
Expand Down Expand Up @@ -136,6 +136,7 @@ impl<'a> PeepholeOptimizations {
if left_id_name != right_id.name {
return None;
}
right_id.delete(ctx);

let null_expr_span = match left_value {
LeftPairValueResult::Null(span) => span,
Expand Down
7 changes: 4 additions & 3 deletions crates/oxc_minifier/src/peephole/minimize_statements.rs
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Expand Up @@ -13,7 +13,7 @@ use oxc_traverse::Ancestor;

use crate::{ctx::Ctx, keep_var::KeepVar};

use super::PeepholeOptimizations;
use super::{DeleteCode, PeepholeOptimizations};

impl<'a> PeepholeOptimizations {
/// `mangleStmts`: <https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_parser.go#L8788>
Expand Down Expand Up @@ -1099,7 +1099,7 @@ impl<'a> PeepholeOptimizations {
fn substitute_single_use_symbol_in_statement(
expr_in_stmt: &mut Expression<'a>,
stmts: &mut Vec<'a, Statement<'a>>,
ctx: &Ctx<'a, '_>,
ctx: &mut Ctx<'a, '_>,
) -> bool {
// TODO: we should skip this compression when direct eval exists
// because the code inside eval may reference the variable
Expand Down Expand Up @@ -1183,11 +1183,12 @@ impl<'a> PeepholeOptimizations {
search_for: &str,
replacement: &mut Expression<'a>,
replacement_has_side_effect: bool,
ctx: &Ctx<'a, '_>,
ctx: &mut Ctx<'a, '_>,
) -> Option<bool> {
match target_expr {
Expression::Identifier(id) => {
if id.name == search_for {
target_expr.delete(ctx);
*target_expr = replacement.take_in(ctx.ast);
return Some(true);
}
Expand Down
79 changes: 68 additions & 11 deletions crates/oxc_minifier/src/peephole/mod.rs
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Expand Up @@ -111,18 +111,18 @@ impl<'a> Traverse<'a, MinifierState<'a>> for PeepholeOptimizations {
ctx.state.changed = false;
}

fn exit_program(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
fn exit_program(&mut self, _program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) {
self.changed = ctx.state.changed;
if self.changed {
// Remove unused references by visiting the AST again and diff the collected references.
let refs_before =
ctx.scoping().resolved_references().flatten().copied().collect::<FxHashSet<_>>();
let mut counter = ReferencesCounter::default();
counter.visit_program(program);
for reference_id_to_remove in refs_before.difference(&counter.refs) {
ctx.scoping_mut().delete_reference(*reference_id_to_remove);
}
}
// if self.changed {
// Remove unused references by visiting the AST again and diff the collected references.
// let refs_before =
// ctx.scoping().resolved_references().flatten().copied().collect::<FxHashSet<_>>();
// let mut counter = ReferencesCounter::default();
// counter.visit_program(program);
// for reference_id_to_remove in refs_before.difference(&counter.refs) {
// ctx.scoping_mut().delete_reference(*reference_id_to_remove);
// }
// }
}

fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
Expand Down Expand Up @@ -521,3 +521,60 @@ impl<'a> Visit<'a> for ReferencesCounter {
self.refs.insert(reference_id);
}
}

pub trait DeleteCode<'a, 'b> {
fn delete(&self, _ctx: &mut Ctx<'a, 'b>) {}
}

impl<'a> DeleteCode<'a, '_> for IdentifierReference<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_identifier_reference(self);
}
}

impl<'a> DeleteCode<'a, '_> for ExpressionStatement<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_expression_statement(self);
}
}

impl<'a> DeleteCode<'a, '_> for Statement<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_statement(self);
}
}

impl<'a> DeleteCode<'a, '_> for Expression<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_expression(self);
}
}

impl<'a> DeleteCode<'a, '_> for AssignmentTarget<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_assignment_target(self);
}
}

impl<'a> DeleteCode<'a, '_> for SimpleAssignmentTarget<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_simple_assignment_target(self);
}
}

impl<'a> DeleteCode<'a, '_> for IfStatement<'a> {
fn delete(&self, ctx: &mut Ctx<'a, '_>) {
ReferencesRemover { ctx }.visit_if_statement(self);
}
}

struct ReferencesRemover<'a, 'b, 'c> {
ctx: &'c mut Ctx<'a, 'b>,
}

impl<'a> Visit<'a> for ReferencesRemover<'a, '_, '_> {
fn visit_identifier_reference(&mut self, it: &IdentifierReference<'a>) {
let reference_id = it.reference_id();
self.ctx.scoping_mut().delete_reference(reference_id);
}
}
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