From 8789184d447eb09e1b0dddc6156ac150d4cbf0d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Donny/=EA=B0=95=EB=8F=99=EC=9C=A4?= <kdy1997.dev@gmail.com>
Date: Mon, 5 Sep 2022 16:05:44 +0900
Subject: [PATCH] perf(es/minifier): Cache the list of bindings for DCE (#5750)

---
 crates/swc_ecma_minifier/src/compress/mod.rs  | 20 ++++++++--------
 .../src/simplify/dce/mod.rs                   | 23 ++++++++++++-------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/crates/swc_ecma_minifier/src/compress/mod.rs b/crates/swc_ecma_minifier/src/compress/mod.rs
index d23b8e8d087..46803b4eb8c 100644
--- a/crates/swc_ecma_minifier/src/compress/mod.rs
+++ b/crates/swc_ecma_minifier/src/compress/mod.rs
@@ -386,19 +386,19 @@ where
         if self.options.unused {
             let _timer = timer!("remove dead code");
 
+            let mut visitor = swc_ecma_transforms_optimization::simplify::dce::dce(
+                swc_ecma_transforms_optimization::simplify::dce::Config {
+                    module_mark: None,
+                    top_level: self.options.top_level(),
+                    top_retain: self.options.top_retain.clone(),
+                },
+                self.marks.unresolved_mark,
+            );
+
             loop {
                 #[cfg(feature = "debug")]
                 let start = n.dump();
 
-                let mut visitor = swc_ecma_transforms_optimization::simplify::dce::dce(
-                    swc_ecma_transforms_optimization::simplify::dce::Config {
-                        module_mark: None,
-                        top_level: self.options.top_level(),
-                        top_retain: self.options.top_retain.clone(),
-                    },
-                    self.marks.unresolved_mark,
-                );
-
                 n.apply(&mut visitor);
 
                 self.changed |= visitor.changed();
@@ -417,6 +417,8 @@ where
                 } else {
                     break;
                 }
+
+                visitor.reset();
             }
         }
 
diff --git a/crates/swc_ecma_transforms_optimization/src/simplify/dce/mod.rs b/crates/swc_ecma_transforms_optimization/src/simplify/dce/mod.rs
index 24f771c6467..de1f0ed1ebf 100644
--- a/crates/swc_ecma_transforms_optimization/src/simplify/dce/mod.rs
+++ b/crates/swc_ecma_transforms_optimization/src/simplify/dce/mod.rs
@@ -39,10 +39,11 @@ pub fn dce(
         config,
         changed: false,
         pass: 0,
-        data: Default::default(),
-        in_block_stmt: false,
         in_fn: false,
+        in_block_stmt: false,
         var_decl_kind: None,
+        data: Default::default(),
+        bindings: Default::default(),
     })
 }
 
@@ -86,6 +87,8 @@ struct TreeShaker {
     var_decl_kind: Option<VarDeclKind>,
 
     data: Arc<Data>,
+
+    bindings: Arc<AHashSet<Id>>,
 }
 
 impl CompilerPass for TreeShaker {
@@ -96,9 +99,6 @@ impl CompilerPass for TreeShaker {
 
 #[derive(Default)]
 struct Data {
-    /// Bindings in the module.
-    bindings: AHashSet<Id>,
-
     used_names: AHashMap<Id, VarInfo>,
 
     /// Variable usage graph
@@ -535,6 +535,7 @@ impl Parallel for TreeShaker {
             expr_ctx: self.expr_ctx.clone(),
             data: self.data.clone(),
             config: self.config.clone(),
+            bindings: self.bindings.clone(),
             ..*self
         }
     }
@@ -606,7 +607,7 @@ impl TreeShaker {
             return false;
         }
 
-        self.data.bindings.contains(&name)
+        self.bindings.contains(&name)
             && self
                 .data
                 .used_names
@@ -795,8 +796,11 @@ impl VisitMut for TreeShaker {
     fn visit_mut_module(&mut self, m: &mut Module) {
         let _tracing = span!(Level::ERROR, "tree-shaker", pass = self.pass).entered();
 
+        if self.bindings.is_empty() {
+            self.bindings = Arc::new(collect_decls(&*m))
+        }
+
         let mut data = Data {
-            bindings: collect_decls(&*m),
             ..Default::default()
         };
 
@@ -822,8 +826,11 @@ impl VisitMut for TreeShaker {
     fn visit_mut_script(&mut self, m: &mut Script) {
         let _tracing = span!(Level::ERROR, "tree-shaker", pass = self.pass).entered();
 
+        if self.bindings.is_empty() {
+            self.bindings = Arc::new(collect_decls(&*m))
+        }
+
         let mut data = Data {
-            bindings: collect_decls(&*m),
             ..Default::default()
         };