perf(css/parser): Improve performance of lexer (#4921)

crates/swc_css_parser/Cargo.toml

@@ -23,7 +23,21 @@ swc_common = { version = "0.18.0", path = "../swc_common" }
 swc_css_ast = { version = "0.93.0", path = "../swc_css_ast" }
 
 [dev-dependencies]
+criterion = "0.3"
 serde = "1.0.127"
 serde_json = "1.0.66"
 swc_css_visit = { version = "0.92.0", path = "../swc_css_visit" }
+swc_node_base = { version = "0.5.0", path = "../swc_node_base" }
 testing = { version = "0.20.0", path = "../testing" }
+
+[[bench]]
+harness = false
+name = "compare"
+
+[[bench]]
+harness = false
+name = "lexer"
+
+[[bench]]
+harness = false
+name = "parser"

crates/swc_css_parser/benches/compare.rs

@@ -0,0 +1,102 @@
+extern crate swc_node_base;
+
+use criterion::{black_box, criterion_group, criterion_main, Bencher, Criterion};
+use swc_common::{input::StringInput, FileName, Span, SyntaxContext, DUMMY_SP};
+use swc_css_ast::Stylesheet;
+use swc_css_parser::{lexer::Lexer, parser::Parser};
+use swc_css_visit::{Fold, FoldWith, VisitMut, VisitMutWith};
+
+static SOURCE: &str = include_str!("files/bootstrap_5_1_3.css");
+
+fn run<F>(b: &mut Bencher, mut op: F)
+where
+    F: FnMut(Stylesheet) -> Stylesheet,
+{
+    let _ = ::testing::run_test(false, |cm, _| {
+        let fm = cm.new_source_file(FileName::Anon, SOURCE.into());
+
+        let lexer = Lexer::new(StringInput::from(&*fm), Default::default());
+        let mut parser = Parser::new(lexer, Default::default());
+        let stylesheet: Stylesheet = parser.parse_all().unwrap();
+
+        b.iter(|| {
+            let stylesheet = stylesheet.clone();
+            let stylesheet = op(stylesheet);
+
+            black_box(stylesheet)
+        });
+
+        Ok(())
+    });
+}
+
+fn bench_cases(c: &mut Criterion) {
+    c.bench_function("css/visitor/compare/clone", |b| run(b, |m: Stylesheet| m));
+
+    c.bench_function("css/visitor/compare/visit_mut_span", |b| {
+        struct RespanVisitMut;
+
+        impl VisitMut for RespanVisitMut {
+            fn visit_mut_span(&mut self, span: &mut Span) {
+                *span = DUMMY_SP;
+            }
+        }
+
+        run(b, |mut m| {
+            m.visit_mut_with(&mut RespanVisitMut);
+
+            m
+        });
+    });
+
+    c.bench_function("css/visitor/compare/visit_mut_span_panic", |b| {
+        struct RespanVisitMut;
+
+        impl VisitMut for RespanVisitMut {
+            fn visit_mut_span(&mut self, span: &mut Span) {
+                if span.ctxt != SyntaxContext::empty() {
+                    panic!()
+                }
+
+                *span = DUMMY_SP;
+            }
+        }
+
+        run(b, |mut m| {
+            m.visit_mut_with(&mut RespanVisitMut);
+
+            m
+        });
+    });
+
+    c.bench_function("css/visitor/compare/fold_span", |b| {
+        struct RespanFold;
+
+        impl Fold for RespanFold {
+            fn fold_span(&mut self, _: Span) -> Span {
+                DUMMY_SP
+            }
+        }
+
+        run(b, |m| m.fold_with(&mut RespanFold));
+    });
+
+    c.bench_function("css/visitor/compare/fold_span_panic", |b| {
+        struct RespanFold;
+
+        impl Fold for RespanFold {
+            fn fold_span(&mut self, s: Span) -> Span {
+                if s.ctxt != SyntaxContext::empty() {
+                    panic!()
+                }
+
+                DUMMY_SP
+            }
+        }
+
+        run(b, |m| m.fold_with(&mut RespanFold));
+    });
+}
+
+criterion_group!(benches, bench_cases);
+criterion_main!(benches);