Improve optimizer (swc-project#660)

Although it's quite naive at the moment, I added two optimization passes.

 - dead code elimination (Closes swc-project#607)
 - inlining

common/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "swc_common"
-version = "0.5.2"
+version = "0.5.3"
 authors = ["강동윤 <[email protected]>"]
 license = "Apache-2.0/MIT"
 repository = "https://github.com/swc-project/swc.git"

common/src/fold/and_then.rs

@@ -1,5 +1,9 @@
 use super::{Fold, FoldWith, Visit, VisitWith};
-use crate::util::move_map::MoveMap;
+use crate::{
+    pass::{CompilerPass, Repeated, RepeatedPass},
+    util::move_map::MoveMap,
+};
+use std::borrow::Cow;
 
 #[macro_export]
 macro_rules! chain {
@@ -90,3 +94,35 @@ where
         self.second.visit(node);
     }
 }
+
+impl<A, B> CompilerPass for AndThen<A, B>
+where
+    A: CompilerPass,
+    B: CompilerPass,
+{
+    fn name() -> Cow<'static, str> {
+        format!("{} -> {}", A::name(), B::name()).into()
+    }
+}
+
+impl<A, B, At> RepeatedPass<At> for AndThen<A, B>
+where
+    A: RepeatedPass<At>,
+    B: RepeatedPass<At>,
+{
+}
+
+impl<A, B> Repeated for AndThen<A, B>
+where
+    A: Repeated,
+    B: Repeated,
+{
+    fn changed(&self) -> bool {
+        self.first.changed() || self.second.changed()
+    }
+
+    fn reset(&mut self) {
+        self.first.reset();
+        self.second.reset();
+    }
+}

common/src/lib.rs

@@ -24,6 +24,7 @@ pub mod fold;
 pub mod input;
 pub mod iter;
 pub mod macros;
+pub mod pass;
 mod pos;
 mod rustc_data_structures;
 pub mod serializer;

common/src/pass.rs

@@ -0,0 +1,85 @@
+use crate::{Fold, FoldWith};
+use serde::export::PhantomData;
+use std::borrow::Cow;
+
+pub trait CompilerPass {
+    /// Name should follow hyphen-case
+    ///
+    /// TODO: timing
+    fn name() -> Cow<'static, str>;
+}
+
+pub trait Repeated: CompilerPass {
+    /// Should run again?
+    fn changed(&self) -> bool;
+
+    /// Reset.
+    fn reset(&mut self);
+}
+
+pub trait RepeatedPass<At>: Repeated + CompilerPass {}
+
+impl<T, P> RepeatedPass<T> for P where P: CompilerPass + Repeated {}
+
+#[derive(Debug, Copy, Clone)]
+pub struct Repeat<P, At>
+where
+    P: RepeatedPass<At>,
+{
+    pass: P,
+    at: PhantomData<At>,
+}
+
+impl<P, At> Repeat<P, At>
+where
+    P: RepeatedPass<At>,
+{
+    pub fn new(pass: P) -> Self {
+        Self {
+            pass,
+            at: PhantomData,
+        }
+    }
+}
+
+impl<P, At> CompilerPass for Repeat<P, At>
+where
+    P: RepeatedPass<At>,
+{
+    fn name() -> Cow<'static, str> {
+        format!("Repeat({})", P::name()).into()
+    }
+}
+
+impl<P, At> Repeated for Repeat<P, At>
+where
+    P: RepeatedPass<At>,
+{
+    fn changed(&self) -> bool {
+        self.pass.changed()
+    }
+
+    fn reset(&mut self) {
+        self.pass.reset()
+    }
+}
+
+#[cfg(feature = "fold")]
+impl<P, At> Fold<At> for Repeat<P, At>
+where
+    At: FoldWith<Self> + FoldWith<P>,
+    P: RepeatedPass<At>,
+{
+    fn fold(&mut self, mut node: At) -> At {
+        loop {
+            self.pass.reset();
+            node = node.fold_with(&mut self.pass);
+
+            if !self.pass.changed() {
+                break;
+            }
+        }
+
+        node
+    }
+}

ecmascript/parser/Cargo.toml

@@ -22,7 +22,7 @@ swc_ecma_ast = { version = "0.17.0", path ="../ast" }
 swc_ecma_parser_macros = { version = "0.4", path ="./macros" }
 enum_kind = { version = "0.2", path ="../../macros/enum_kind" }
 unicode-xid = "0.2"
-log = { version = "0.4", features = ["release_max_level_debug"] }
+log = "0.4"
 either = { version = "1.4" }
 serde = { version = "1", features = ["derive"] }
 smallvec = "1"

ecmascript/transforms/Cargo.toml

@@ -30,6 +30,7 @@ arrayvec = "0.5.1"
 serde_json = "1"
 smallvec = "1"
 is-macro = "0.1"
+log = "0.4.8"
 
 [dev-dependencies]
 testing = { version = "0.5", path ="../../testing" }

ecmascript/transforms/src/compat/es2015/regenerator/case.rs

@@ -49,7 +49,7 @@ pub(super) struct CaseHandler<'a> {
     listing_len: usize,
 
     /// A sparse array whose keys correspond to locations in this.listing
-    /// that have been marked as branch/jump targets.
+    /// that have been marked as stmt/jump targets.
     marked: Vec<Loc>,
 
     leaps: LeapManager,

ecmascript/transforms/src/fixer.rs

@@ -149,6 +149,24 @@ impl Fold<Stmt> for Fixer {
     }
 }
 
+impl Fold<IfStmt> for Fixer {
+    fn fold(&mut self, node: IfStmt) -> IfStmt {
+        let node: IfStmt = node.fold_children(self);
+
+        match *node.cons {
+            Stmt::If(..) => IfStmt {
+                cons: box Stmt::Block(BlockStmt {
+                    span: node.cons.span(),
+                    stmts: vec![*node.cons],
+                }),
+                ..node
+            },
+
+            _ => node,
+        }
+    }
+}
+
 macro_rules! context_fn_args {
     ($T:tt, $is_new:expr) => {
         impl Fold<$T> for Fixer {
@@ -510,6 +528,17 @@ impl Fold<Expr> for Fixer {
                     }
 
                     e @ Expr::Seq(..)
+                    | e @ Expr::Update(..)
+                    | e
+                    @
+                    Expr::Unary(UnaryExpr {
+                        op: op!("delete"), ..
+                    })
+                    | e
+                    @
+                    Expr::Unary(UnaryExpr {
+                        op: op!("void"), ..
+                    })
                     | e @ Expr::Yield(..)
                     | e @ Expr::Cond(..)
                     | e @ Expr::Assign(..)
@@ -1039,4 +1068,6 @@ var store = global[SHARED] || (global[SHARED] = {});
     foo: 1
 });"
     );
+
+    test_fixer!(void_and_bin, "(void 0) * 2", "(void 0) * 2");
 }

ecmascript/transforms/src/optimization.rs

@@ -1,9 +1,5 @@
-pub use self::{
-    inline_globals::InlineGlobals,
-    json_parse::JsonParse,
-    simplify::{expr_simplifier, simplifier},
-};
+pub use self::{inline_globals::InlineGlobals, json_parse::JsonParse, simplify::simplifier};
 
 mod inline_globals;
 mod json_parse;
-mod simplify;
+pub mod simplify;