From 26872310f60d4de40e717cd30e7bf856bad3edba 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, 20 Jan 2025 07:58:42 +0900
Subject: [PATCH] perf(es/minifier): Do heavy operation only if required
 (#9902)

**Description:**

In `store_var_for_inlining`, we had called `inline_with_multi_replacer` needlessly. This PR fixes it.
---
 .changeset/old-foxes-train.md                      |  6 ++++++
 .../src/compress/optimize/inline.rs                | 14 +++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/old-foxes-train.md

diff --git a/.changeset/old-foxes-train.md b/.changeset/old-foxes-train.md
new file mode 100644
index 000000000000..198fd65d24d5
--- /dev/null
+++ b/.changeset/old-foxes-train.md
@@ -0,0 +1,6 @@
+---
+swc_ecma_minifier: minor
+swc_core: minor
+---
+
+perf(es/minifier): Do heavy operation only if required
diff --git a/crates/swc_ecma_minifier/src/compress/optimize/inline.rs b/crates/swc_ecma_minifier/src/compress/optimize/inline.rs
index 8d976d002b3c..c541affbf9d2 100644
--- a/crates/swc_ecma_minifier/src/compress/optimize/inline.rs
+++ b/crates/swc_ecma_minifier/src/compress/optimize/inline.rs
@@ -89,7 +89,7 @@ impl Optimizer<'_> {
             let is_inline_enabled =
                 self.options.reduce_vars || self.options.collapse_vars || self.options.inline != 0;
 
-            self.vars.inline_with_multi_replacer(init);
+            let mut inlined_into_init = false;
 
             let id = ident.to_id();
 
@@ -107,6 +107,9 @@ impl Optimizer<'_> {
                 && !usage.used_as_ref
             {
                 if let Expr::Array(arr) = init {
+                    self.vars.inline_with_multi_replacer(arr);
+                    inlined_into_init = true;
+
                     if arr.elems.len() < 32
                         && arr.elems.iter().all(|e| match e {
                             Some(ExprOrSpread { spread: None, expr }) => match &**expr {
@@ -257,6 +260,11 @@ impl Optimizer<'_> {
                     _ => false,
                 }
             {
+                if !inlined_into_init {
+                    inlined_into_init = true;
+                    self.vars.inline_with_multi_replacer(init);
+                }
+
                 self.mode.store(id.clone(), &*init);
 
                 let VarUsageInfo {
@@ -498,6 +506,10 @@ impl Optimizer<'_> {
                     return;
                 }
 
+                if !inlined_into_init {
+                    self.vars.inline_with_multi_replacer(init);
+                }
+
                 report_change!(
                     "inline: Decided to inline var '{}' because it's used only once",
                     ident