perf(es/minifier): Remove needless operations for char freq analysis (#…

…8222)

**Description:**

This skips a string search operation, which is quite costly, without affecting the output.

crates/swc_bundler/src/hash.rs

@@ -126,4 +126,8 @@ impl WriteJs for &mut Hasher<'_> {
     fn commit_pending_semi(&mut self) -> io::Result<()> {
         Ok(())
     }
+
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        true
+    }
 }

crates/swc_ecma_codegen/src/lib.rs

@@ -2170,10 +2170,17 @@ where
         // TODO: span
 
         if self.cfg.ascii_only {
-            self.wr.write_symbol(
-                DUMMY_SP,
-                &get_ascii_only_ident(&handle_invalid_unicodes(&ident.sym), self.cfg.target),
-            )?;
+            if self.wr.can_ignore_invalid_unicodes() {
+                self.wr
+                    .write_symbol(DUMMY_SP, &get_ascii_only_ident(&ident.sym, self.cfg.target))?;
+            } else {
+                self.wr.write_symbol(
+                    DUMMY_SP,
+                    &get_ascii_only_ident(&handle_invalid_unicodes(&ident.sym), self.cfg.target),
+                )?;
+            }
+        } else if self.wr.can_ignore_invalid_unicodes() {
+            self.wr.write_symbol(DUMMY_SP, &ident.sym)?;
         } else {
             self.wr
                 .write_symbol(DUMMY_SP, &handle_invalid_unicodes(&ident.sym))?;

crates/swc_ecma_codegen/src/text_writer.rs

@@ -42,6 +42,14 @@ pub trait WriteJs {
     fn add_srcmap(&mut self, pos: BytePos) -> Result;
 
     fn commit_pending_semi(&mut self) -> Result;
+
+    /// If true, the code generator will skip **modification** of invalid
+    /// unicode characters.
+    ///
+    /// Defaults to `false``
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        false
+    }
 }
 
 impl<W> WriteJs for Box<W>
@@ -136,6 +144,11 @@ where
     fn commit_pending_semi(&mut self) -> Result {
         (**self).commit_pending_semi()
     }
+
+    #[inline(always)]
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        (**self).can_ignore_invalid_unicodes()
+    }
 }
 
 impl<W> WriteJs for &'_ mut W
@@ -227,7 +240,13 @@ where
         (**self).add_srcmap(pos)
     }
 
+    #[inline(always)]
     fn commit_pending_semi(&mut self) -> Result {
         (**self).commit_pending_semi()
     }
+
+    #[inline(always)]
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        (**self).can_ignore_invalid_unicodes()
+    }
 }

crates/swc_ecma_codegen/src/text_writer/basic_impl.rs

@@ -297,6 +297,11 @@ impl<'a, W: Write> WriteJs for JsWriter<'a, W> {
     fn commit_pending_semi(&mut self) -> Result {
         Ok(())
     }
+
+    #[inline(always)]
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        false
+    }
 }
 
 #[derive(Debug)]

crates/swc_ecma_codegen/src/text_writer/semicolon.rs

@@ -97,4 +97,9 @@ impl<W: WriteJs> WriteJs for OmitTrailingSemi<W> {
         }
         Ok(())
     }
+
+    #[inline(always)]
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        self.inner.can_ignore_invalid_unicodes()
+    }
 }

crates/swc_ecma_minifier/src/util/base54.rs

@@ -178,6 +178,11 @@ impl WriteJs for CharFreq {
     fn commit_pending_semi(&mut self) -> io::Result<()> {
         Ok(())
     }
+
+    #[inline(always)]
+    fn can_ignore_invalid_unicodes(&mut self) -> bool {
+        true
+    }
 }
 
 impl CharFreq {