perf(parser): reorder parse_statement match conditions

For performance reasons, match orders are: 1. plain if check 2. check current token 3. peek token
oxc-project · Dec 4, 2024 · 8599503 · 8599503
1 parent 64f92e9
commit 8599503
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Showing 2 changed files with 15 additions and 7 deletions.
diff --git a/crates/oxc_parser/src/js/expression.rs b/crates/oxc_parser/src/js/expression.rs
@@ -170,8 +170,6 @@ impl<'a> ParserImpl<'a> {
 
         match self.cur_kind() {
             Kind::Ident => self.parse_identifier_expression(), // fast path, keywords are checked at the end
-            // Literal, RegularExpressionLiteral
-            kind if kind.is_literal() => self.parse_literal_expression(),
             // ArrayLiteral
             Kind::LBrack => self.parse_array_expression(),
             // ObjectLiteral
@@ -199,6 +197,8 @@ impl<'a> ParserImpl<'a> {
             Kind::Slash | Kind::SlashEq => self
                 .parse_literal_regexp()
                 .map(|literal| Expression::RegExpLiteral(self.alloc(literal))),
+            // Literal, RegularExpressionLiteral
+            kind if kind.is_literal() => self.parse_literal_expression(),
             // JSXElement, JSXFragment
             Kind::LAngle if self.source_type.is_jsx() => self.parse_jsx_expression(),
             _ => self.parse_identifier_expression(),

diff --git a/crates/oxc_parser/src/js/statement.rs b/crates/oxc_parser/src/js/statement.rs
@@ -87,6 +87,10 @@ impl<'a> ParserImpl<'a> {
             self.eat_decorators()?;
         }
 
+        // For performance reasons, match orders are:
+        // 1. plain if check
+        // 2. check current token
+        // 3. peek token
         match self.cur_kind() {
             Kind::LCurly => self.parse_block_statement(),
             Kind::Semicolon => Ok(self.parse_empty_statement()),
@@ -101,24 +105,28 @@ impl<'a> ParserImpl<'a> {
             Kind::Try => self.parse_try_statement(),
             Kind::Debugger => self.parse_debugger_statement(),
             Kind::Class => self.parse_class_statement(stmt_ctx, start_span),
-            Kind::Import if !matches!(self.peek_kind(), Kind::Dot | Kind::LParen) => {
-                self.parse_import_declaration()
-            }
             Kind::Export => self.parse_export_declaration(),
             // [+Return] ReturnStatement[?Yield, ?Await]
             Kind::Return => self.parse_return_statement(),
             Kind::Var => self.parse_variable_statement(stmt_ctx),
+            // Fast path
+            Kind::Function => self.parse_function_declaration(stmt_ctx),
+            Kind::Let if !self.cur_token().escaped() => self.parse_let(stmt_ctx),
+            Kind::Import if !matches!(self.peek_kind(), Kind::Dot | Kind::LParen) => {
+                self.parse_import_declaration()
+            }
             Kind::Const if !(self.is_ts && self.is_at_enum_declaration()) => {
                 self.parse_variable_statement(stmt_ctx)
             }
-            Kind::Let if !self.cur_token().escaped() => self.parse_let(stmt_ctx),
             Kind::Await
                 if self.peek_kind() == Kind::Using && self.nth_kind(2).is_binding_identifier() =>
             {
                 self.parse_using()
             }
             Kind::Using if self.peek_kind().is_binding_identifier() => self.parse_using(),
-            _ if self.at_function_with_async() => self.parse_function_declaration(stmt_ctx),
+            Kind::Async if self.peek_at(Kind::Function) && !self.peek_token().is_on_new_line => {
+                self.parse_function_declaration(stmt_ctx)
+            }
             _ if self.is_ts && self.at_start_of_ts_declaration() => {
                 self.parse_ts_declaration_statement(start_span)
             }