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feat(minifier): fold for statement (#6450)

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This commit is contained in:
7086cmd 2024-10-11 08:33:23 +00:00
parent 85d93ed713
commit 06ea1216af
2 changed files with 62 additions and 1 deletions
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61
crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs
View file

@ -30,6 +30,7 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
fn enter_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
if let Some(new_stmt) = match stmt {
Statement::IfStatement(if_stmt) => self.try_fold_if(if_stmt, ctx),
Statement::ForStatement(for_stmt) => self.try_fold_for(for_stmt, ctx),
_ => None,
} {
*stmt = new_stmt;
@ -162,6 +163,35 @@ impl<'a> PeepholeRemoveDeadCode {
}
}
fn try_fold_for(
&mut self,
for_stmt: &mut ForStatement<'a>,
ctx: &mut TraverseCtx<'a>,
) -> Option<Statement<'a>> {
let test_boolean =
for_stmt.test.as_ref().map_or(Tri::Unknown, |test| ctx.get_boolean_value(test));
match test_boolean {
Tri::False => {
// Remove the entire `for` statement.
// Check vars in statement
let mut keep_var = KeepVar::new(ctx.ast);
keep_var.visit_statement(&for_stmt.body);
Some(
keep_var
.get_variable_declaration_statement()
.unwrap_or_else(|| ctx.ast.statement_empty(SPAN)),
)
}
Tri::True => {
// Remove the test expression.
for_stmt.test = None;
self.changed = true;
None
}
Tri::Unknown => None,
}
}
/// Try folding conditional expression (?:) if the condition results of the condition is known.
fn try_fold_conditional_expression(
expr: &mut ConditionalExpression<'a>,
@ -229,4 +259,35 @@ mod test {
fold_same("b: { var x = 1; } x = 2;");
fold_same("a: b: { var x = 1; } x = 2;");
}
#[test]
fn test_fold_useless_for() {
fold("for(;false;) { foo() }", "");
fold("for(;void 0;) { foo() }", "");
fold("for(;undefined;) { foo() }", "");
fold("for(;true;) foo() ", "for(;;) foo() ");
fold_same("for(;;) foo()");
fold("for(;false;) { var a = 0; }", "var a");
fold("for(;false;) { const a = 0; }", "");
fold("for(;false;) { let a = 0; }", "");
// Make sure it plays nice with minimizing
fold("for(;false;) { foo(); continue }", "");
// fold("l1:for(;false;) { }", "");
// TODO handle single block statement
fold_same("for(;a;) { foo(); }");
}
#[test]
fn test_minimize_loop_with_constant_condition_vanilla_for() {
fold("for(;true;) foo()", "for(;;) foo()");
fold("for(;0;) foo()", "");
fold("for(;0.0;) foo()", "");
fold("for(;NaN;) foo()", "");
fold("for(;null;) foo()", "");
fold("for(;undefined;) foo()", "");
fold("for(;'';) foo()", "");
}
}

2
tasks/minsize/minsize.snap
View file

@ -22,5 +22,5 @@ Original | Minified | esbuild | Gzip | esbuild
6.69 MB | 2.44 MB | 2.31 MB | 498.88 kB | 488.28 kB | antd.js
10.95 MB | 3.59 MB | 3.49 MB | 913.92 kB | 915.50 kB | typescript.js
10.95 MB | 3.59 MB | 3.49 MB | 913.91 kB | 915.50 kB | typescript.js