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feat(minifier): fold constants if the folded expression is shorter than the original one #9008

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feat(minifier): fold constants if the folded expression is shorter than the original one #9008

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feat(minifier): fold constants if the folded expression is shorter th…
sapphi-red Feb 10, 2025
f7de886
make conformance pass
sapphi-red Feb 10, 2025
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2 changes: 1 addition & 1 deletion crates/oxc_codegen/src/gen.rs
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Expand Up @@ -1345,7 +1345,7 @@ impl Gen for RegExpLiteral<'_> {
fn gen(&self, p: &mut Codegen, _ctx: Context) {
p.add_source_mapping(self.span);
let last = p.last_byte();
let pattern_text = self.regex.pattern.source_text(p.source_text);
let pattern_text = self.regex.pattern.to_string();
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@sapphi-red sapphi-red Feb 10, 2025

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Because I'm not calling CodeGen::build in count_char_when_printing, self.regex.pattern.source_text(p.source_text) errors due to CodeGen::source_text being an empty string.

let mut cg = Codegen::new()
    .with_options(CodegenOptions { minify: true, ..CodegenOptions::default() });
cg.print_expression(expr);
cg.into_source_text().len()

// Avoid forming a single-line comment or "</script" sequence
if last == Some(b'/')
|| (last == Some(b'<') && pattern_text.cow_to_ascii_lowercase().starts_with("script"))
Expand Down
6 changes: 5 additions & 1 deletion crates/oxc_ecmascript/src/constant_evaluation/mod.rs
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Expand Up @@ -374,7 +374,11 @@ pub trait ConstantEvaluation<'a>: MayHaveSideEffects {
}
None
}
_ => None,
BinaryOperator::In
| BinaryOperator::Equality
| BinaryOperator::Inequality
| BinaryOperator::StrictEquality
| BinaryOperator::StrictInequality => None,
}
}

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113 changes: 22 additions & 91 deletions crates/oxc_minifier/src/peephole/fold_constants.rs
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@@ -1,4 +1,5 @@
use oxc_ast::ast::*;
use oxc_codegen::{Codegen, CodegenOptions};
use oxc_ecmascript::{
constant_evaluation::{ConstantEvaluation, ConstantValue, ValueType},
side_effects::MayHaveSideEffects,
Expand All @@ -19,8 +20,9 @@ impl<'a> PeepholeOptimizations {
///
/// <https://github.com/google/closure-compiler/blob/v20240609/src/com/google/javascript/jscomp/PeepholeFoldConstants.java>
pub fn fold_constants_exit_expression(&mut self, expr: &mut Expression<'a>, ctx: Ctx<'a, '_>) {
let current_len = Self::count_char_when_printing(expr);
if let Some(folded_expr) = match expr {
Expression::BinaryExpression(e) => Self::try_fold_binary_expr(e, ctx)
Expression::BinaryExpression(e) => Self::try_fold_binary_expr(e, current_len, ctx)
.or_else(|| Self::try_fold_binary_typeof_comparison(e, ctx)),
Expression::UnaryExpression(e) => Self::try_fold_unary_expr(e, ctx),
Expression::StaticMemberExpression(e) => Self::try_fold_static_member_expr(e, ctx),
Expand Down Expand Up @@ -202,25 +204,15 @@ impl<'a> PeepholeOptimizations {
}
}

fn extract_numeric_values(e: &BinaryExpression<'a>) -> Option<(f64, f64)> {
if let (Expression::NumericLiteral(left), Expression::NumericLiteral(right)) =
(&e.left, &e.right)
{
return Some((left.value, right.value));
}
None
}

#[expect(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
fn try_fold_binary_expr(
e: &mut BinaryExpression<'a>,
current_len: usize,
ctx: Ctx<'a, '_>,
) -> Option<Expression<'a>> {
// TODO: tryReduceOperandsForOp

// https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_ast_helpers.go#L1136
// https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_ast_helpers.go#L1222
let span = e.span;
match e.operator {
BinaryOperator::Equality
| BinaryOperator::Inequality
Expand All @@ -234,80 +226,19 @@ impl<'a> PeepholeOptimizations {
ctx.eval_binary(e).or_else(|| Self::try_fold_left_child_op(e, ctx))
}
BinaryOperator::Addition => Self::try_fold_add(e, ctx),
BinaryOperator::Subtraction => {
// Subtraction of small-ish integers can definitely be folded without issues
Self::extract_numeric_values(e)
.filter(|(left, right)| {
left.is_nan()
|| left.is_finite()
|| right.is_nan()
|| right.is_finite()
|| (left.fract() == 0.0
&& right.fract() == 0.0
&& (left.abs() as usize) <= 0xFFFF_FFFF
&& (right.abs() as usize) <= 0xFFFF_FFFF)
})
.and_then(|_| ctx.eval_binary(e))
_ => {
let folded_expr = ctx.eval_binary(e)?;
let folded_len = Self::count_char_when_printing(&folded_expr);
(folded_len <= current_len).then_some(folded_expr)
}
BinaryOperator::Multiplication
| BinaryOperator::Exponential
| BinaryOperator::Remainder => Self::extract_numeric_values(e)
.filter(|(left, right)| {
*left == 0.0
|| left.is_nan()
|| left.is_infinite()
|| *right == 0.0
|| right.is_nan()
|| right.is_infinite()
})
.and_then(|_| ctx.eval_binary(e)),
BinaryOperator::Division => Self::extract_numeric_values(e)
.filter(|(_, right)| *right == 0.0 || right.is_nan() || right.is_infinite())
.and_then(|_| ctx.eval_binary(e)),
BinaryOperator::ShiftLeft => {
if let Some((left, right)) = Self::extract_numeric_values(e) {
let result = ctx.eval_binary_expression(e)?.into_number()?;
let left_len = Self::approximate_printed_int_char_count(left);
let right_len = Self::approximate_printed_int_char_count(right);
let result_len = Self::approximate_printed_int_char_count(result);
if result_len <= left_len + 2 + right_len {
return Some(ctx.value_to_expr(span, ConstantValue::Number(result)));
}
}
None
}
BinaryOperator::ShiftRightZeroFill => {
if let Some((left, right)) = Self::extract_numeric_values(e) {
let result = ctx.eval_binary_expression(e)?.into_number()?;
let left_len = Self::approximate_printed_int_char_count(left);
let right_len = Self::approximate_printed_int_char_count(right);
let result_len = Self::approximate_printed_int_char_count(result);
if result_len <= left_len + 3 + right_len {
return Some(ctx.value_to_expr(span, ConstantValue::Number(result)));
}
}
None
}
BinaryOperator::ShiftRight | BinaryOperator::Instanceof => ctx.eval_binary(e),
BinaryOperator::In => None,
}
}

// https://github.com/evanw/esbuild/blob/v0.24.2/internal/js_ast/js_ast_helpers.go#L1128
#[expect(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
#[must_use]
fn approximate_printed_int_char_count(value: f64) -> usize {
let mut count = if value.is_infinite() {
"Infinity".len()
} else if value.is_nan() {
"NaN".len()
} else {
1 + 0.max(value.abs().log10().floor() as usize)
};
if value.is_sign_negative() {
count += 1;
}
count
fn count_char_when_printing(expr: &Expression) -> usize {
let mut cg = Codegen::new()
.with_options(CodegenOptions { minify: true, ..CodegenOptions::default() });
cg.print_expression(expr);
cg.into_source_text().len()
}

// Simplified version of `tryFoldAdd` from closure compiler.
Expand Down Expand Up @@ -1614,7 +1545,7 @@ mod test {

#[test]
fn test_fold_multiply() {
fold_same("x = 2.25 * 3");
fold("x = 2.25 * 3", "x = 6.75");
fold_same("z = x * y");
fold_same("x = y * 5");
// test("x = null * undefined", "x = NaN");
Expand All @@ -1631,28 +1562,28 @@ mod test {
fold("x = Infinity / 0", "x = Infinity");
fold("x = 1 / 0", "x = Infinity");
fold("x = 0 / 0", "x = NaN");
fold_same("x = 2 / 4");
fold("x = 2 / 4", "x = .5");
fold_same("x = y / 2 / 4");
}

#[test]
fn test_fold_remainder() {
fold_same("x = 3 % 2");
fold_same("x = 3 % -2");
fold_same("x = -1 % 3");
fold("x = 3 % 2", "x = 1");
fold("x = 3 % -2", "x = 1");
fold("x = -1 % 3", "x = -1");
fold("x = 1 % 0", "x = NaN");
fold("x = 0 % 0", "x = NaN");
}

#[test]
fn test_fold_exponential() {
fold_same("x = 2 ** 3");
fold_same("x = 2 ** -3");
fold("x = 2 ** 3", "x = 8");
fold("x = 2 ** -3", "x = .125");
fold_same("x = 2 ** 55");
fold_same("x = 3 ** -1");
fold_same("x = (-1) ** 0.5");
fold("x = (-1) ** 0.5", "x = NaN");
fold("x = (-0) ** 3", "x = -0");
fold_same("x = null ** 0");
fold("x = null ** 0", "x = 1");
}

#[test]
Expand Down
27 changes: 14 additions & 13 deletions crates/oxc_minifier/src/peephole/replace_known_methods.rs
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Expand Up @@ -1813,19 +1813,20 @@ mod test {

#[test]
fn test_fold_pow() {
test("Math.pow(2, 3)", "2 ** 3");
test("Math.pow(a, 3)", "a ** 3");
test("Math.pow(2, b)", "2 ** b");
test("Math.pow(a, b)", "a ** +b");
test("Math.pow(2n, 3n)", "2n ** +3n"); // errors both before and after
test("Math.pow(a + b, c)", "(a + b) ** +c");
test_same("Math.pow()");
test_same("Math.pow(1)");
test_same("Math.pow(...a, 1)");
test_same("Math.pow(1, ...a)");
test_same("Math.pow(1, 2, 3)");
test_es2015("Math.pow(2, 3)", "Math.pow(2, 3)");
test_same("Unknown.pow(1, 2)");
test_value("Math.pow(2, 3)", "8");
test_value("Math.pow(a, 3)", "a ** 3");
test_value("Math.pow(2, b)", "2 ** b");
test_value("Math.pow(a, b)", "a ** +b");
test_value("Math.pow(2n, 3n)", "2n ** +3n"); // errors both before and after
test_value("Math.pow(a + b, c)", "(a + b) ** +c");
test_same_value("Math.pow()");
test_same_value("Math.pow(1)");
test_same_value("Math.pow(...a, 1)");
test_same_value("Math.pow(1, ...a)");
test_same_value("Math.pow(1, 2, 3)");
test_es2015("x = Math.pow(2, 3)", "x = Math.pow(2, 3)"); // NOTE: can fold to 8
test_es2015("x = Math.pow(a, 3)", "x = Math.pow(a, 3)");
test_same_value("Unknown.pow(1, 2)");
}

#[test]
Expand Down
8 changes: 4 additions & 4 deletions crates/oxc_minifier/tests/peephole/esbuild.rs
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Expand Up @@ -907,10 +907,10 @@ fn constant_evaluation_test() {
test("x = +{valueOf:()=>1}", "x = +{ valueOf: () => 1 };");
test("x = 3 + 6", "x = 9;");
test("x = 3 - 6", "x = -3;");
test("x = 3 * 6", "x = 3 * 6;");
test("x = 3 / 6", "x = 3 / 6;");
test("x = 3 % 6", "x = 3 % 6;");
test("x = 3 ** 6", "x = 3 ** 6;");
test("x = 3 * 6", "x = 18;");
test("x = 3 / 6", "x = .5;");
test("x = 3 % 6", "x = 3;");
test("x = 3 ** 6", "x = 729;");
test("x = 0 / 0", "x = NaN;");
test("x = 123 / 0", "x = Infinity;");
test("x = 123 / -0", "x = -Infinity;");
Expand Down
10 changes: 5 additions & 5 deletions tasks/minsize/minsize.snap
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Expand Up @@ -3,23 +3,23 @@ Original | minified | minified | gzip | gzip | Fixture
-------------------------------------------------------------------------------------
72.14 kB | 23.49 kB | 23.70 kB | 8.47 kB | 8.54 kB | react.development.js

173.90 kB | 59.53 kB | 59.82 kB | 19.18 kB | 19.33 kB | moment.js
173.90 kB | 59.51 kB | 59.82 kB | 19.18 kB | 19.33 kB | moment.js

287.63 kB | 89.34 kB | 90.07 kB | 30.95 kB | 31.95 kB | jquery.js

342.15 kB | 117.25 kB | 118.14 kB | 43.31 kB | 44.37 kB | vue.js

544.10 kB | 71.38 kB | 72.48 kB | 25.85 kB | 26.20 kB | lodash.js

555.77 kB | 270.83 kB | 270.13 kB | 88.26 kB | 90.80 kB | d3.js
555.77 kB | 270.83 kB | 270.13 kB | 88.27 kB | 90.80 kB | d3.js

1.01 MB | 440.17 kB | 458.89 kB | 122.38 kB | 126.71 kB | bundle.min.js
1.01 MB | 440.17 kB | 458.89 kB | 122.37 kB | 126.71 kB | bundle.min.js

1.25 MB | 647.05 kB | 646.76 kB | 160.27 kB | 163.73 kB | three.js
1.25 MB | 647.04 kB | 646.76 kB | 160.27 kB | 163.73 kB | three.js

2.14 MB | 716.14 kB | 724.14 kB | 161.79 kB | 181.07 kB | victory.js

3.20 MB | 1.01 MB | 1.01 MB | 324.15 kB | 331.56 kB | echarts.js
3.20 MB | 1.01 MB | 1.01 MB | 324.14 kB | 331.56 kB | echarts.js

6.69 MB | 2.28 MB | 2.31 MB | 466.12 kB | 488.28 kB | antd.js

Expand Down