feat(es/minifier): Implement rules for optimizing loops (#4157)

crates/swc/Cargo.toml

@@ -96,7 +96,7 @@ optional = true
 version = "2.0.0"
 
 [dev-dependencies]
-rayon = "1"
+rayon = "1.5.1"
 swc_ecma_lints = { version = "0.28.0", path = "../swc_ecma_lints", features = [
   "non_critical_lints",
 ] }

crates/swc/tests/tsc-references/doWhileContinueStatements_es2015.2.minified.js

@@ -1,7 +1,7 @@
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
+for(;;);

crates/swc/tests/tsc-references/doWhileContinueStatements_es5.2.minified.js

@@ -1,7 +1,7 @@
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
+for(;;);

crates/swc/tests/tsc-references/forContinueStatements_es2015.2.minified.js

@@ -1,7 +1,7 @@
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
+for(;;);

crates/swc/tests/tsc-references/forContinueStatements_es5.2.minified.js

@@ -1,7 +1,7 @@
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
+for(;;);

crates/swc/tests/tsc-references/forInContinueStatements_es2015.2.minified.js

@@ -1,7 +1,7 @@
-for(var x in {})continue;
-ONE: for(var x in {})continue ONE;
-TWO: THREE: for(var x in {})continue THREE;
+for(var x in {});
+for(var x in {});
+TWO: for(var x in {});
 FOUR: for(var x in {})FIVE: for(var x in {})continue FOUR;
 for(var x in {})SIX: for(var x in {})continue SIX;
 SEVEN: for(var x in {})for(var x in {})for(var x in {})continue SEVEN;
-EIGHT: for(var x in {})continue EIGHT;
+for(var x in {});

crates/swc/tests/tsc-references/forInContinueStatements_es5.2.minified.js

@@ -1,7 +1,7 @@
-for(var x in {})continue;
-ONE: for(var x in {})continue ONE;
-TWO: THREE: for(var x in {})continue THREE;
+for(var x in {});
+for(var x in {});
+TWO: for(var x in {});
 FOUR: for(var x in {})FIVE: for(var x in {})continue FOUR;
 for(var x in {})SIX: for(var x in {})continue SIX;
 SEVEN: for(var x in {})for(var x in {})for(var x in {})continue SEVEN;
-EIGHT: for(var x in {})continue EIGHT;
+for(var x in {});

crates/swc/tests/tsc-references/parser_breakTarget1_es2015.2.minified.js

@@ -1 +0,0 @@
-target: break target;

crates/swc/tests/tsc-references/parser_breakTarget1_es5.2.minified.js

@@ -1 +0,0 @@
-target: break target;

crates/swc/tests/tsc-references/parser_continueInIterationStatement1_es2015.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement1_es5.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement2_es2015.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement2_es5.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement3_es2015.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement3_es5.2.minified.js

@@ -1 +1 @@
-for(;;)continue;
+for(;;);

crates/swc/tests/tsc-references/parser_continueInIterationStatement4_es2015.2.minified.js

@@ -1 +1 @@
-for(var i in something)continue;
+for(var i in something);

crates/swc/tests/tsc-references/parser_continueInIterationStatement4_es5.2.minified.js

@@ -1 +1 @@
-for(var i in something)continue;
+for(var i in something);

crates/swc/tests/tsc-references/parser_continueLabel_es2015.2.minified.js

@@ -1 +1 @@
-label1: for(var i = 0; i < 1; i++)continue label1;
+for(var i = 0; i < 1; i++);

crates/swc/tests/tsc-references/parser_continueLabel_es5.2.minified.js

@@ -1 +1 @@
-label1: for(var i = 0; i < 1; i++)continue label1;
+for(var i = 0; i < 1; i++);

crates/swc/tests/tsc-references/parser_continueTarget2_es2015.2.minified.js

@@ -1 +1 @@
-target: for(;;)continue target;
+for(;;);

crates/swc/tests/tsc-references/parser_continueTarget2_es5.2.minified.js

@@ -1 +1 @@
-target: for(;;)continue target;
+for(;;);

crates/swc/tests/tsc-references/parser_continueTarget4_es2015.2.minified.js

@@ -1 +1 @@
-target1: target2: for(;;)continue target2;
+target1: for(;;);

crates/swc/tests/tsc-references/parser_continueTarget4_es5.2.minified.js

@@ -1 +1 @@
-target1: target2: for(;;)continue target2;
+target1: for(;;);

crates/swc/tests/tsc-references/whileContinueStatements_es2015.2.minified.js

@@ -1,9 +1,9 @@
-for(;;)continue;
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
-NINE: for(;;)continue NINE;
+for(;;);
+for(;;);

crates/swc/tests/tsc-references/whileContinueStatements_es5.2.minified.js

@@ -1,9 +1,9 @@
-for(;;)continue;
-for(;;)continue;
-ONE: for(;;)continue ONE;
-TWO: THREE: for(;;)continue THREE;
+for(;;);
+for(;;);
+for(;;);
+TWO: for(;;);
 FOUR: for(;;)FIVE: for(;;)continue FOUR;
 for(;;)SIX: for(;;)continue SIX;
 SEVEN: for(;;)for(;;)for(;;)continue SEVEN;
-EIGHT: for(;;)continue EIGHT;
-NINE: for(;;)continue NINE;
+for(;;);
+for(;;);

crates/swc/tests/tsc.rs

@@ -1,8 +1,10 @@
 use std::{
     fs::create_dir_all,
+    panic::{catch_unwind, resume_unwind, AssertUnwindSafe},
     path::{Path, PathBuf},
 };
 
+use rayon::prelude::*;
 use serde::de::DeserializeOwned;
 use swc::{
     config::{Config, IsModule, JscConfig, Options, SourceMapsConfig},
@@ -38,19 +40,33 @@ fn fixture(input: PathBuf) {
         return;
     }
 
-    for (name, opts) in matrix() {
-        let output_dir = Path::new("tests").join("tsc-references");
+    let panics = matrix()
+        .into_par_iter()
+        .filter_map(|(name, opts)| {
+            //
 
-        let _ = create_dir_all(&output_dir);
+            catch_unwind(AssertUnwindSafe(|| {
+                let output_dir = Path::new("tests").join("tsc-references");
 
-        let output_path = output_dir.join(format!(
-            "{}_{}.js",
-            input.file_stem().unwrap().to_str().unwrap(),
-            name
-        ));
+                let _ = create_dir_all(&output_dir);
 
-        compile(&input, &output_path, opts);
+                let output_path = output_dir.join(format!(
+                    "{}_{}.js",
+                    input.file_stem().unwrap().to_str().unwrap(),
+                    name
+                ));
+
+                compile(&input, &output_path, opts);
+            }))
+            .err()
+        })
+        .collect::<Vec<_>>();
+
+    if panics.is_empty() {
+        return;
     }
+
+    resume_unwind(panics.into_iter().next().unwrap());
 }
 
 fn from_json<T>(s: &str) -> T

crates/swc_ecma_minifier/src/compress/pure/dead_code.rs

@@ -1,6 +1,7 @@
-use swc_common::{util::take::Take, DUMMY_SP};
+use swc_common::{util::take::Take, EqIgnoreSpan, DUMMY_SP};
 use swc_ecma_ast::*;
 use swc_ecma_utils::{ExprExt, StmtLike, Value};
+use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 
 use super::Pure;
 use crate::{
@@ -10,6 +11,182 @@ use crate::{
 
 /// Methods related to option `dead_code`.
 impl Pure<'_> {
+    ///  - Removes `L1: break L1`
+    pub(super) fn drop_instant_break(&mut self, s: &mut Stmt) {
+        if let Stmt::Labeled(ls) = s {
+            if let Stmt::Break(BreakStmt {
+                label: Some(label), ..
+            }) = &*ls.body
+            {
+                if label.sym == ls.label.sym {
+                    self.changed = true;
+                    tracing::debug!("Dropping instant break");
+                    s.take();
+                }
+            }
+        }
+    }
+
+    /// # Operations
+    ///
+    ///
+    ///  - Convert if break to conditionals
+    ///
+    /// ```js
+    /// out: {
+    ///     if (foo) break out;
+    ///     console.log("bar");
+    /// }
+    /// ```
+    ///
+    /// =>
+    ///
+    /// ```js
+    /// foo || console.log("bar");
+    /// ```
+    pub(super) fn optimize_labeled_stmt(&mut self, s: &mut Stmt) -> Option<()> {
+        if !self.options.dead_code {
+            return None;
+        }
+
+        if let Stmt::Labeled(ls) = s {
+            if let Stmt::Block(bs) = &mut *ls.body {
+                let first = bs.stmts.first_mut()?;
+
+                if let Stmt::If(IfStmt {
+                    test,
+                    cons,
+                    alt: None,
+                    ..
+                }) = first
+                {
+                    if let Stmt::Break(BreakStmt {
+                        label: Some(label), ..
+                    }) = &**cons
+                    {
+                        if ls.label.sym == label.sym {
+                            self.changed = true;
+                            tracing::debug!("Optimizing labeled stmt with a break to if statement");
+
+                            self.negate(test, true, false);
+                            let test = test.take();
+
+                            let mut cons = bs.take();
+                            cons.stmts.remove(0);
+
+                            *s = Stmt::If(IfStmt {
+                                span: ls.span,
+                                test,
+                                cons: Box::new(Stmt::Block(cons)),
+                                alt: None,
+                            });
+                            return None;
+                        }
+                    }
+                }
+
+                if let Stmt::If(IfStmt {
+                    test,
+                    cons,
+                    alt: Some(alt),
+                    ..
+                }) = first
+                {
+                    if let Stmt::Break(BreakStmt {
+                        label: Some(label), ..
+                    }) = &**alt
+                    {
+                        if ls.label.sym == label.sym {
+                            self.changed = true;
+                            tracing::debug!(
+                                "Optimizing labeled stmt with a break in alt to if statement"
+                            );
+
+                            let test = test.take();
+                            let cons = *cons.take();
+
+                            let mut new_cons = bs.take();
+                            new_cons.stmts[0] = cons;
+
+                            *s = Stmt::If(IfStmt {
+                                span: ls.span,
+                                test,
+                                cons: Box::new(Stmt::Block(new_cons)),
+                                alt: None,
+                            });
+                            return None;
+                        }
+                    }
+                }
+            }
+        }
+
+        None
+    }
+
+    /// Remove the last statement of a loop if it's continue
+    pub(super) fn drop_useless_continue(&mut self, s: &mut Stmt) {
+        match s {
+            Stmt::Labeled(ls) => {
+                let new = self.drop_useless_continue_inner(Some(ls.label.clone()), &mut ls.body);
+                if let Some(new) = new {
+                    *s = new;
+                }
+            }
+
+            _ => {
+                let new = self.drop_useless_continue_inner(None, s);
+                if let Some(new) = new {
+                    *s = new;
+                }
+            }
+        }
+    }
+
+    /// Returns [Some] if the whole statement sohuld be replaced
+    fn drop_useless_continue_inner(
+        &mut self,
+        label: Option<Ident>,
+        loop_stmt: &mut Stmt,
+    ) -> Option<Stmt> {
+        let body = match loop_stmt {
+            Stmt::While(ws) => &mut *ws.body,
+            Stmt::For(fs) => &mut *fs.body,
+            Stmt::ForIn(fs) => &mut *fs.body,
+            Stmt::ForOf(fs) => &mut *fs.body,
+            _ => return None,
+        };
+
+        if let Stmt::Block(b) = body {
+            let last = b.stmts.last_mut()?;
+
+            if let Stmt::Continue(last_cs) = last {
+                match last_cs.label {
+                    Some(_) => {
+                        if label.eq_ignore_span(&last_cs.label) {
+                        } else {
+                            return None;
+                        }
+                    }
+                    None => {}
+                }
+            } else {
+                return None;
+            }
+            self.changed = true;
+            tracing::debug!("Remove useless continue (last stmt of a loop)");
+            b.stmts.remove(b.stmts.len() - 1);
+
+            if let Some(label) = &label {
+                if !contains_label(b, label) {
+                    return Some(loop_stmt.take());
+                }
+            }
+        }
+
+        None
+    }
+
     pub(super) fn drop_unreachable_stmts<T>(&mut self, stmts: &mut Vec<T>)
     where
         T: StmtLike + ModuleItemExt + Take,
@@ -159,3 +336,45 @@ impl Pure<'_> {
         *stmts = new;
     }
 }
+
+fn contains_label<N>(node: &N, label: &Ident) -> bool
+where
+    for<'aa> N: VisitWith<LabelFinder<'aa>>,
+{
+    let mut v = LabelFinder {
+        label,
+        found: false,
+    };
+    node.visit_with(&mut v);
+    v.found
+}
+
+struct LabelFinder<'a> {
+    label: &'a Ident,
+    found: bool,
+}
+impl Visit for LabelFinder<'_> {
+    noop_visit_type!();
+
+    fn visit_break_stmt(&mut self, s: &BreakStmt) {
+        match &s.label {
+            Some(label) => {
+                if label.sym == self.label.sym {
+                    self.found = true;
+                }
+            }
+            None => {}
+        }
+    }
+
+    fn visit_continue_stmt(&mut self, s: &ContinueStmt) {
+        match &s.label {
+            Some(label) => {
+                if label.sym == self.label.sym {
+                    self.found = true;
+                }
+            }
+            None => {}
+        }
+    }
+}

crates/swc_ecma_minifier/src/compress/pure/mod.rs

@@ -598,6 +598,12 @@ impl VisitMut for Pure<'_> {
 
         self.loop_to_for_stmt(s);
 
+        self.drop_instant_break(s);
+
+        self.optimize_labeled_stmt(s);
+
+        self.drop_useless_continue(s);
+
         if let Stmt::Expr(es) = s {
             if es.expr.is_invalid() {
                 *s = Stmt::Empty(EmptyStmt { span: DUMMY_SP });

crates/swc_ecma_minifier/tests/TODO.txt

@@ -518,12 +518,7 @@ keep_names/keep_some_classnames/input.js
 keep_names/keep_some_fnames/input.js
 keep_names/keep_some_fnames_reduce/input.js
 keep_quoted_strict/keep_quoted_strict/input.js
-labels/labels_1/input.js
-labels/labels_2/input.js
 labels/labels_4/input.js
-labels/labels_6/input.js
-labels/labels_7/input.js
-labels/labels_9/input.js
 logical_assignment/assign_in_conditional_part/input.js
 logical_assignment/assignment_in_left_part_2/input.js
 loops/drop_if_else_break_1/input.js

crates/swc_ecma_minifier/tests/golden.txt

@@ -813,10 +813,15 @@ keep_names/keep_classnames/input.js
 keep_names/keep_fnames/input.js
 keep_names/keep_fnames_and_avoid_collisions/input.js
 keep_names/keep_var_fnames/input.js
+labels/labels_1/input.js
 labels/labels_10/input.js
+labels/labels_2/input.js
 labels/labels_3/input.js
 labels/labels_5/input.js
+labels/labels_6/input.js
+labels/labels_7/input.js
 labels/labels_8/input.js
+labels/labels_9/input.js
 logical_assignment/assign_in_conditional_part_reused/input.js
 logical_assignment/assignment_in_left_part/input.js
 logical_assignment/logical_assignment_not_always_happens/input.js

scripts/update-all.sh

@@ -9,9 +9,6 @@ function up(){
 }
 
 up
-up
-up
-up
 
 
 git add -A