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fix(minifier): don't inline single use variables that are not literals to for statement initializers #13769

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merged 1 commit into from
Sep 15, 2025
Merged

fix(minifier): don't inline single use variables that are not literals to for statement initializers #13769

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54 changes: 42 additions & 12 deletions crates/oxc_minifier/src/peephole/minimize_statements.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -384,8 +384,12 @@ impl<'a> PeepholeOptimizations {
if let Some(first_decl) = var_decl.declarations.first_mut()
&& let Some(first_decl_init) = first_decl.init.as_mut()
{
let changed =
Self::substitute_single_use_symbol_in_statement(first_decl_init, result, ctx);
let changed = Self::substitute_single_use_symbol_in_statement(
first_decl_init,
result,
ctx,
false,
);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -433,8 +437,12 @@ impl<'a> PeepholeOptimizations {

ctx: &mut Ctx<'a, '_>,
) {
let changed =
Self::substitute_single_use_symbol_in_statement(&mut expr_stmt.expression, result, ctx);
let changed = Self::substitute_single_use_symbol_in_statement(
&mut expr_stmt.expression,
result,
ctx,
false,
);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -562,6 +570,7 @@ impl<'a> PeepholeOptimizations {
&mut switch_stmt.discriminant,
result,
ctx,
false,
);
if changed {
ctx.state.changed = true;
Expand All @@ -588,7 +597,7 @@ impl<'a> PeepholeOptimizations {
ctx: &mut Ctx<'a, '_>,
) -> ControlFlow<()> {
let changed =
Self::substitute_single_use_symbol_in_statement(&mut if_stmt.test, result, ctx);
Self::substitute_single_use_symbol_in_statement(&mut if_stmt.test, result, ctx, false);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -747,8 +756,12 @@ impl<'a> PeepholeOptimizations {
ctx: &mut Ctx<'a, '_>,
) {
if let Some(ret_argument_expr) = &mut ret_stmt.argument {
let changed =
Self::substitute_single_use_symbol_in_statement(ret_argument_expr, result, ctx);
let changed = Self::substitute_single_use_symbol_in_statement(
ret_argument_expr,
result,
ctx,
false,
);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -799,8 +812,12 @@ impl<'a> PeepholeOptimizations {

ctx: &mut Ctx<'a, '_>,
) {
let changed =
Self::substitute_single_use_symbol_in_statement(&mut throw_stmt.argument, result, ctx);
let changed = Self::substitute_single_use_symbol_in_statement(
&mut throw_stmt.argument,
result,
ctx,
false,
);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -830,10 +847,12 @@ impl<'a> PeepholeOptimizations {
if let Some(first_decl) = var_decl.declarations.first_mut()
&& let Some(first_decl_init) = first_decl.init.as_mut()
{
let is_block_scoped_decl = !first_decl.kind.is_var();
let changed = Self::substitute_single_use_symbol_in_statement(
first_decl_init,
result,
ctx,
is_block_scoped_decl,
);
if changed {
ctx.state.changed = true;
Expand All @@ -843,7 +862,7 @@ impl<'a> PeepholeOptimizations {
match_expression!(ForStatementInit) => {
let init = init.to_expression_mut();
let changed =
Self::substitute_single_use_symbol_in_statement(init, result, ctx);
Self::substitute_single_use_symbol_in_statement(init, result, ctx, false);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -922,10 +941,12 @@ impl<'a> PeepholeOptimizations {
// That is evaluated before the right hand side is evaluated. So, in that case, skip the single use substitution.
if !matches!(&for_in_stmt.left, ForStatementLeft::VariableDeclaration(var_decl) if var_decl.has_init())
{
let is_block_scoped_decl = matches!(&for_in_stmt.left, ForStatementLeft::VariableDeclaration(var_decl) if !var_decl.kind.is_var());
let changed = Self::substitute_single_use_symbol_in_statement(
&mut for_in_stmt.right,
result,
ctx,
is_block_scoped_decl,
);
if changed {
ctx.state.changed = true;
Expand Down Expand Up @@ -1005,8 +1026,13 @@ impl<'a> PeepholeOptimizations {
result: &mut Vec<'a, Statement<'a>>,
ctx: &mut Ctx<'a, '_>,
) {
let changed =
Self::substitute_single_use_symbol_in_statement(&mut for_of_stmt.right, result, ctx);
let is_block_scoped_decl = matches!(&for_of_stmt.left, ForStatementLeft::VariableDeclaration(var_decl) if !var_decl.kind.is_var());
let changed = Self::substitute_single_use_symbol_in_statement(
&mut for_of_stmt.right,
result,
ctx,
is_block_scoped_decl,
);
if changed {
ctx.state.changed = true;
}
Expand Down Expand Up @@ -1100,6 +1126,7 @@ impl<'a> PeepholeOptimizations {
expr_in_stmt: &mut Expression<'a>,
stmts: &mut Vec<'a, Statement<'a>>,
ctx: &Ctx<'a, '_>,
non_scoped_literal_only: bool,
) -> bool {
// TODO: we should skip this compression when direct eval exists
// because the code inside eval may reference the variable
Expand Down Expand Up @@ -1139,6 +1166,9 @@ impl<'a> PeepholeOptimizations {
{
return true;
}
if non_scoped_literal_only && !prev_decl_init.is_literal_value(false, ctx) {
return true;
}
let replaced = Self::substitute_single_use_symbol_in_expression(
expr_in_stmt,
&prev_decl_id.name,
Expand Down
45 changes: 41 additions & 4 deletions crates/oxc_minifier/tests/peephole/inline_single_use_variable.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -156,17 +156,46 @@ fn test_inline_single_use_variable() {
);

test(
"function wrapper() { var x = foo; for (var i = x; i < 10; i++) console.log(i) }",
"function wrapper() { for (var i = foo; i < 10; i++) console.log(i) }",
"function wrapper() { var x = 1; for (var i = x; i < 10; i++) console.log(i) }",
"function wrapper() { for (var i = 1; i < 10; i++) console.log(i) }",
);
test(
"function wrapper() { var i, x = foo; for (i = x; i < 10; i++) console.log(i) }",
"function wrapper() { var i; for (i = foo; i < 10; i++) console.log(i) }",
"function wrapper() { var x = 1; for (let i = x; i < 10; i++) console.log(i) }",
"function wrapper() { for (let i = 1; i < 10; i++) console.log(i) }",
);
test(
"function wrapper() { var x = function () { return console.log(i), 1 }; for (let i = x(); i < 10; i++) console.log(i) }",
"function wrapper() { var x = function () { return console.log(i), 1 }; for (let i = x(); i < 10; i++) console.log(i) }",
);
// this is fine because `let j` inside the block cannot be referenced from `var i = j`
test(
"function wrapper() { var x = j; for (var i = x; i < 10; i++) { let j; console.log(i) } }",
"function wrapper() { for (var i = j; i < 10; i++) { let j; console.log(i) } }",
);
test(
"function wrapper() { var i, x = 1; for (i = x; i < 10; i++) console.log(i) }",
"function wrapper() { var i; for (i = 1; i < 10; i++) console.log(i) }",
);
test(
"function wrapper() { var x = i; for (var i = x; i < 10; i++) console.log(i) }",
"function wrapper() { for (var i = i; i < 10; i++) console.log(i) }",
);
test(
"function wrapper() { var x = i; for (let i = x; i < 10; i++) console.log(i) }",
"function wrapper() { var x = i; for (let i = x; i < 10; i++) console.log(i) }",
);
test(
"function wrapper() { var x = {}; for (var a in x) console.log(a) }",
"function wrapper() { for (var a in {}) console.log(a) }",
);
test(
"function wrapper() { var x = a; for (var a in x) console.log(a) }",
"function wrapper() { for (var a in a) console.log(a) }",
);
test(
"function wrapper() { var x = a; for (let a in x) console.log(a) }",
"function wrapper() { var x = a; for (let a in x) console.log(a) }",
);
test(
"function wrapper() { var x = {}; for (var a = 0 in x) console.log(a) }",
"function wrapper() { var x = {}; for (var a = 0 in x) console.log(a) }",
Expand All @@ -175,6 +204,14 @@ fn test_inline_single_use_variable() {
"function wrapper() { var x = []; for (var a of x) console.log(a) }",
"function wrapper() { for (var a of []) console.log(a) }",
);
test(
"function wrapper() { var x = a; for (var a of x) console.log(a) }",
"function wrapper() { for (var a of a) console.log(a) }",
);
test(
"function wrapper() { var x = a; for (let a of x) console.log(a) }",
"function wrapper() { var x = a; for (let a of x) console.log(a) }",
);
}

#[test]
Expand Down
4 changes: 2 additions & 2 deletions tasks/track_memory_allocations/allocs_minifier.snap
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Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
File | File size || Sys allocs | Sys reallocs || Arena allocs | Arena reallocs | Arena bytes
-------------------------------------------------------------------------------------------------------------------------------------------
checker.ts | 2.92 MB || 84058 | 14190 || 153533 | 29395 | 5.615 MB
checker.ts | 2.92 MB || 84073 | 14190 || 153691 | 29463 | 5.625 MB

cal.com.tsx | 1.06 MB || 40525 | 3033 || 37074 | 4733 | 1.654 MB

RadixUIAdoptionSection.jsx | 2.52 kB || 82 | 8 || 30 | 6 | 992 B

pdf.mjs | 567.30 kB || 19572 | 2900 || 47384 | 7770 | 1.623 MB
pdf.mjs | 567.30 kB || 19576 | 2900 || 47400 | 7781 | 1.624 MB

antd.js | 6.69 MB || 99854 | 13518 || 331725 | 70117 | 17.407 MB

Expand Down
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