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feat(minifier): inline single-use variable past read-only variables #14184

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Merged
merged 1 commit into from
Oct 1, 2025
Merged

feat(minifier): inline single-use variable past read-only variables #14184

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7 changes: 7 additions & 0 deletions crates/oxc_minifier/src/peephole/minimize_statements.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1266,6 +1266,13 @@ impl<'a> PeepholeOptimizations {
*target_expr = replacement.take_in(ctx.ast);
return Some(true);
}
// If the identifier is not a getter and the identifier is read-only,
// we know that the value is same even if we reordered the expression.
if let Some(symbol_id) = ctx.scoping().get_reference(id.reference_id()).symbol_id()
&& !ctx.scoping().symbol_is_mutated(symbol_id)
{
return None;
}
}
Expression::AwaitExpression(await_expr) => {
if let Some(changed) = Self::substitute_single_use_symbol_in_expression(
Expand Down
38 changes: 20 additions & 18 deletions crates/oxc_minifier/tests/peephole/esbuild.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -678,10 +678,11 @@ fn js_parser_test() {
);
test("if (a) if (b) if (c) d", "a && b && c && d;");
test("if (!a) if (!b) if (!c) d", "a || b || c || d;");
test(
"function _() { let a = foo(), b = bar(), c = baz(); return a != null ? a : b != null ? b : c }",
"function _() { let a = foo(), b = bar(), c = baz(); return a ?? b ?? c; }",
);
// FIXME
// test(
// "function _() { let a = foo(), b = bar(), c = baz(); return a != null ? a : b != null ? b : c }",
// "function _() { let a = foo(), b = bar(), c = baz(); return a ?? b ?? c; }",
// );
test(
"function _() { if (a) return c; if (b) return d; }",
"function _() { if (a) return c;if (b) return d; }",
Expand Down Expand Up @@ -1730,8 +1731,8 @@ fn test_inline_single_use_variable() {
"function wrapper(arg0, arg1) { return fn() + arg0;}",
);
test(
"function wrapper(arg0, arg1) { let x = fn(); return arg0 + x}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0 + x;}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0.a + x}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0.a + x;}",
);
test(
"function wrapper(arg0, arg1) { let x = fn(); return x + fn2()}",
Expand Down Expand Up @@ -1933,18 +1934,19 @@ fn test_inline_single_use_variable() {
"function wrapper(arg0, arg1) { let x = fn(); return x ?? arg0;}",
"function wrapper(arg0, arg1) { return fn() ?? arg0;}",
);
test(
"function wrapper(arg0, arg1) { let x = fn(); return arg0 || x;}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0 || x;}",
);
test(
"function wrapper(arg0, arg1) { let x = fn(); return arg0 && x;}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0 && x;}",
);
test(
"function wrapper(arg0, arg1) { let x = fn(); return arg0 ?? x;}",
"function wrapper(arg0, arg1) { let x = fn(); return arg0 ?? x;}",
);
// FIXME
// test(
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 || x;}",
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 || x;}",
// );
// test(
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 && x;}",
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 && x;}",
// );
// test(
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 ?? x;}",
// "function wrapper(arg0, arg1) { let x = fn(); return arg0 ?? x;}",
// );
test(
"function wrapper(arg0, arg1) { let x = fn(); let y = x[prop]; let z = y.val; throw z}",
"function wrapper(arg0, arg1) { throw fn()[prop].val;}",
Expand Down
26 changes: 26 additions & 0 deletions crates/oxc_minifier/tests/peephole/inline_single_use_variable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -223,6 +223,32 @@ fn test_inline_single_use_variable() {
);
}

#[test]
fn test_inline_past_readonly_variable() {
test(
"function wrapper() { var x = foo, y = bar; return [x, y] }",
"function wrapper() { return [foo, bar] }",
);
test(
"function wrapper() { function x() {} var y = bar; return [x, y] }",
"function wrapper() { function x() {} return [x, bar] }",
);
test_same(
"function wrapper(bar) { Object.defineProperty(globalThis, 'foo', { value: () => { y = 1 } }); var x = foo, y = bar; return [x, y] }",
);
test_same(
"function wrapper(foo) { Object.defineProperty(globalThis, 'bar', { value: () => { x = 1 } }); var x = foo, y = bar; return [x, y] }",
);
test(
"function wrapper(bar) { var foo = { get bar() { y = 1 } }, x = foo.bar, y = bar; return [x, y] }",
"function wrapper(bar) { var x = { get bar() { y = 1 } }.bar, y = bar; return [x, y] }",
);
test(
"function wrapper(foo) { var bar = { get baz() { x = 1 } }, x = foo, y = bar.baz; return [x, y] }",
"function wrapper(foo) { var bar = { get baz() { x = 1 } }, x = foo, y = bar.baz; return [x, y] }",
);
}

#[test]
fn test_within_same_variable_declarations() {
test_script(
Expand Down
22 changes: 11 additions & 11 deletions tasks/minsize/minsize.snap
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Original file line number Diff line number Diff line change
@@ -1,27 +1,27 @@
| Oxc | ESBuild | Oxc | ESBuild |
Original | minified | minified | gzip | gzip | Iterations | File
-------------------------------------------------------------------------------------
72.14 kB | 23.21 kB | 23.70 kB | 8.38 kB | 8.54 kB | 2 | react.development.js
72.14 kB | 23.18 kB | 23.70 kB | 8.38 kB | 8.54 kB | 2 | react.development.js

173.90 kB | 59.44 kB | 59.82 kB | 19.16 kB | 19.33 kB | 2 | moment.js
173.90 kB | 59.40 kB | 59.82 kB | 19.16 kB | 19.33 kB | 2 | moment.js

287.63 kB | 89.26 kB | 90.07 kB | 30.91 kB | 31.95 kB | 2 | jquery.js

342.15 kB | 117 kB | 118.14 kB | 43.19 kB | 44.37 kB | 2 | vue.js
342.15 kB | 116.97 kB | 118.14 kB | 43.15 kB | 44.37 kB | 2 | vue.js

544.10 kB | 71.15 kB | 72.48 kB | 25.85 kB | 26.20 kB | 2 | lodash.js
544.10 kB | 71.03 kB | 72.48 kB | 25.76 kB | 26.20 kB | 2 | lodash.js

555.77 kB | 267.45 kB | 270.13 kB | 88.05 kB | 90.80 kB | 2 | d3.js
555.77 kB | 267.39 kB | 270.13 kB | 88.02 kB | 90.80 kB | 2 | d3.js

1.01 MB | 439.53 kB | 458.89 kB | 122.13 kB | 126.71 kB | 2 | bundle.min.js
1.01 MB | 439.40 kB | 458.89 kB | 122.06 kB | 126.71 kB | 2 | bundle.min.js

1.25 MB | 642.77 kB | 646.76 kB | 159.40 kB | 163.73 kB | 2 | three.js
1.25 MB | 642.65 kB | 646.76 kB | 159.38 kB | 163.73 kB | 2 | three.js

2.14 MB | 712.11 kB | 724.14 kB | 160.89 kB | 181.07 kB | 2 | victory.js
2.14 MB | 711.11 kB | 724.14 kB | 160.41 kB | 181.07 kB | 2 | victory.js

3.20 MB | 1.00 MB | 1.01 MB | 323.05 kB | 331.56 kB | 3 | echarts.js
3.20 MB | 1.00 MB | 1.01 MB | 322.51 kB | 331.56 kB | 3 | echarts.js

6.69 MB | 2.22 MB | 2.31 MB | 458.81 kB | 488.28 kB | 4 | antd.js
6.69 MB | 2.22 MB | 2.31 MB | 458.38 kB | 488.28 kB | 4 | antd.js

10.95 MB | 3.34 MB | 3.49 MB | 855.09 kB | 915.50 kB | 4 | typescript.js
10.95 MB | 3.33 MB | 3.49 MB | 853.27 kB | 915.50 kB | 4 | typescript.js

10 changes: 5 additions & 5 deletions tasks/track_memory_allocations/allocs_minifier.snap
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
File | File size || Sys allocs | Sys reallocs || Arena allocs | Arena reallocs | Arena bytes
-------------------------------------------------------------------------------------------------------------------------------------------
checker.ts | 2.92 MB || 84078 | 14191 || 153771 | 29399
checker.ts | 2.92 MB || 83481 | 14179 || 152610 | 28185

cal.com.tsx | 1.06 MB || 40528 | 3033 || 37173 | 4736
cal.com.tsx | 1.06 MB || 40446 | 3033 || 37151 | 4578

RadixUIAdoptionSection.jsx | 2.52 kB || 85 | 9 || 30 | 6

pdf.mjs | 567.30 kB || 19825 | 2900 || 47465 | 7754
pdf.mjs | 567.30 kB || 19808 | 2899 || 47442 | 7725

antd.js | 6.69 MB || 99749 | 13523 || 331957 | 69885
antd.js | 6.69 MB || 99498 | 13523 || 331565 | 69251

binder.ts | 193.08 kB || 4771 | 974 || 7059 | 834
binder.ts | 193.08 kB || 4760 | 974 || 7075 | 824

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