Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

refactor(minifier): move compress block to dce #6468

Merged
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
56 changes: 53 additions & 3 deletions crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,10 @@ impl<'a> Traverse<'a> for PeepholeRemoveDeadCode {
}
}

fn exit_statement(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
self.compress_block(stmt, ctx);
}

fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
if stmts.iter().any(|stmt| matches!(stmt, Statement::EmptyStatement(_))) {
stmts.retain(|stmt| !matches!(stmt, Statement::EmptyStatement(_)));
Expand Down Expand Up @@ -128,6 +132,27 @@ impl<'a> PeepholeRemoveDeadCode {
}
}

/// Remove block from single line blocks
/// `{ block } -> block`
fn compress_block(&mut self, stmt: &mut Statement<'a>, ctx: &mut TraverseCtx<'a>) {
if let Statement::BlockStatement(block) = stmt {
// Avoid compressing `if (x) { var x = 1 }` to `if (x) var x = 1` due to different
// semantics according to AnnexB, which lead to different semantics.
if block.body.len() == 1 && !block.body[0].is_declaration() {
*stmt = block.body.remove(0);
self.compress_block(stmt, ctx);
self.changed = true;
return;
}
if block.body.len() == 0
&& (ctx.parent().is_block_statement() || ctx.parent().is_program())
{
// Remove the block if it is empty and the parent is a block statement.
*stmt = ctx.ast.statement_empty(SPAN);
}
}
}

fn try_fold_if(
&mut self,
if_stmt: &mut IfStatement<'a>,
Expand Down Expand Up @@ -264,6 +289,34 @@ mod test {
test(js, expected);
}

#[test]
fn test_fold_block() {
fold("{{foo()}}", "foo()");
fold("{foo();{}}", "foo()");
fold("{{foo()}{}}", "foo()");
// fold("{{foo()}{bar()}}", "foo();bar()");
fold("{if(false)foo(); {bar()}}", "bar()");
fold("{if(false)if(false)if(false)foo(); {bar()}}", "bar()");

fold("{'hi'}", "");
// fold("{x==3}", "");
// fold("{`hello ${foo}`}", "");
// fold("{ (function(){x++}) }", "");
// fold_same("function f(){return;}");
// fold("function f(){return 3;}", "function f(){return 3}");
// fold_same("function f(){if(x)return; x=3; return; }");
// fold("{x=3;;;y=2;;;}", "x=3;y=2");

// Cases to test for empty block.
// fold("while(x()){x}", "while(x());");
// fold("while(x()){x()}", "while(x())x()");
// fold("for(x=0;x<100;x++){x}", "for(x=0;x<100;x++);");
// fold("for(x in y){x}", "for(x in y);");
// fold("for (x of y) {x}", "for(x of y);");
// fold_same("for (let x = 1; x <10; x++ ) {}");
// fold_same("for (var x = 1; x <10; x++ ) {}");
}

#[test]
#[ignore]
fn test_remove_no_op_labelled_statement() {
Expand Down Expand Up @@ -300,9 +353,6 @@ mod test {
fold("for(;false;) { foo(); continue }", "");

// fold("l1:for(;false;) { }", "");

// TODO handle single block statement
fold_same("for(;a;) { foo(); }");
}

#[test]
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -33,11 +33,6 @@ impl<'a> CompressorPass<'a> for PeepholeSubstituteAlternateSyntax {
}

impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
fn enter_statement(&mut self, stmt: &mut Statement<'a>, _ctx: &mut TraverseCtx<'a>) {
self.compress_block(stmt);
// self.compress_while(stmt);
}

fn exit_return_statement(
&mut self,
stmt: &mut ReturnStatement<'a>,
Expand Down Expand Up @@ -161,20 +156,6 @@ impl<'a> PeepholeSubstituteAlternateSyntax {

/* Statements */

/// Remove block from single line blocks
/// `{ block } -> block`
fn compress_block(&mut self, stmt: &mut Statement<'a>) {
if let Statement::BlockStatement(block) = stmt {
// Avoid compressing `if (x) { var x = 1 }` to `if (x) var x = 1` due to different
// semantics according to AnnexB, which lead to different semantics.
if block.body.len() == 1 && !block.body[0].is_declaration() {
*stmt = block.body.remove(0);
self.compress_block(stmt);
self.changed = true;
}
}
}

// /// Transforms `while(expr)` to `for(;expr;)`
// fn compress_while(&mut self, stmt: &mut Statement<'a>) {
// let Statement::WhileStatement(while_stmt) = stmt else { return };
Expand Down Expand Up @@ -531,7 +512,8 @@ mod test {
test("function f(){return void 0;}", "function f(){return}");
test("function f(){return void foo();}", "function f(){return void foo()}");
test("function f(){return undefined;}", "function f(){return}");
test("function f(){if(a()){return undefined;}}", "function f(){if(a())return}");
// Here we handle the block in dce.
test("function f(){if(a()){return undefined;}}", "function f(){if(a()){return}}");
}

#[test]
Expand Down
50 changes: 25 additions & 25 deletions crates/oxc_minifier/tests/ast_passes/dead_code_elimination.rs
Original file line number Diff line number Diff line change
Expand Up @@ -18,57 +18,57 @@ fn test_same(source_text: &str) {

#[test]
fn dce_if_statement() {
test("if (true) { foo }", "{ foo }");
test("if (true) { foo } else { bar }", "{ foo }");
test("if (false) { foo } else { bar }", "{ bar }");
test("if (true) { foo }", "foo");
test("if (true) { foo } else { bar }", "foo");
test("if (false) { foo } else { bar }", "bar");

test("if (xxx) { foo } else if (false) { bar }", "if (xxx) { foo }");
test("if (xxx) { foo } else if (false) { bar } else { baz }", "if (xxx) { foo } else { baz }");
test("if (xxx) { foo } else if (false) { bar } else if (false) { baz }", "if (xxx) { foo }");
test("if (xxx) { foo } else if (false) { bar }", "if (xxx) foo");
test("if (xxx) { foo } else if (false) { bar } else { baz }", "if (xxx) foo; else baz");
test("if (xxx) { foo } else if (false) { bar } else if (false) { baz }", "if (xxx) foo");
test(
"if (xxx) { foo } else if (false) { bar } else if (false) { baz } else { quaz }",
"if (xxx) { foo } else { quaz }",
"if (xxx) foo; else quaz",
);
test(
"if (xxx) { foo } else if (true) { bar } else if (false) { baz }",
"if (xxx) { foo } else { bar }",
"if (xxx) foo; else bar",
);
test(
"if (xxx) { foo } else if (false) { bar } else if (true) { baz }",
"if (xxx) { foo } else { baz }",
"if (xxx) foo; else baz",
);
test(
"if (xxx) { foo } else if (true) { bar } else if (true) { baz }",
"if (xxx) { foo } else { bar }",
"if (xxx) foo; else bar",
);
test(
"if (xxx) { foo } else if (false) { var a; var b; } else if (false) { var c; var d; }",
"if (xxx) { foo } else var c, d;",
"if (xxx) foo; else var c, d;",
);

test("if (!false) { foo }", "{ foo }");
test("if (!true) { foo } else { bar }", "{ bar }");
test("if (!false) { foo }", "foo");
test("if (!true) { foo } else { bar }", "bar");

test("if (!false && xxx) { foo }", "if (xxx) { foo; }");
test("if (!true && yyy) { foo } else { bar }", "{ bar }");
test("if (!false && xxx) { foo }", "if (xxx) foo");
test("if (!true && yyy) { foo } else { bar }", "bar");

test("if (true || xxx) { foo }", "{ foo }");
test("if (false || xxx) { foo }", "if (xxx) { foo }");
test("if (true || xxx) { foo }", "foo");
test("if (false || xxx) { foo }", "if (xxx) foo");

test("if ('production' == 'production') { foo } else { bar }", "{ foo }");
test("if ('development' == 'production') { foo } else { bar }", "{ bar }");
test("if ('production' == 'production') { foo } else { bar }", "foo");
test("if ('development' == 'production') { foo } else { bar }", "bar");

test("if ('production' === 'production') { foo } else { bar }", "{ foo }");
test("if ('development' === 'production') { foo } else { bar }", "{ bar }");
test("if ('production' === 'production') { foo } else { bar }", "foo");
test("if ('development' === 'production') { foo } else { bar }", "bar");

// Shadowed `undefined` as a variable should not be erased.
// This is a rollup test.
test_same("function foo(undefined) { if (!undefined) { } }");

test("function foo() { if (undefined) { bar } }", "function foo() { }");
test_same("function foo() { { bar } }");
test("function foo() { { bar } }", "function foo() { bar }");

test("if (true) { foo; } if (true) { foo; }", "{ foo; } { foo; }");
test("if (true) { foo; } if (true) { foo; }", "foo; foo;");

test(
"
Expand All @@ -83,11 +83,11 @@ fn dce_if_statement() {
// nested expression
test(
"const a = { fn: function() { if (true) { foo; } } }",
"const a = { fn: function() { { foo; } } }",
"const a = { fn: function() { foo; } }",
);

// parenthesized
test("if (!!(false)) { REMOVE; } else { KEEP; }", "{ KEEP }");
test("if (!!(false)) { REMOVE; } else { KEEP; }", "KEEP");

// typeof
test("if (typeof 1 !== 'number') { REMOVE; }", "");
Expand Down