build(rust): vendor rnix parser crate

third_party/crates/countme-3.0.1/examples/bench_single_thread.rs

@@ -0,0 +1,77 @@
+use countme::{get, Count};
+
+#[derive(Default)]
+struct Foo {
+    _c: Count<Self>,
+}
+
+#[derive(Default)]
+struct Bar {
+    _c: Count<Self>,
+    _x: i32,
+}
+
+mod deeply {
+    pub(crate) mod nested {
+        pub(crate) mod module {
+            use countme::Count;
+
+            #[derive(Default)]
+            pub(crate) struct Quux {
+                _c: Count<Self>,
+            }
+        }
+    }
+}
+
+fn main() {
+    countme::enable(true);
+    let t = std::time::Instant::now();
+    let n = 6;
+    let m = 2_000_000;
+
+    for _ in 0..n {
+        for _ in 0..m {
+            Foo::default();
+        }
+
+        let mut xs = Vec::with_capacity(m);
+        for _ in 0..m {
+            xs.push(Bar::default())
+        }
+
+        for _ in 0..m {
+            deeply::nested::module::Quux::default();
+        }
+
+        let fs = [
+            || drop(Foo::default()),
+            || drop(Bar::default()),
+            || drop(deeply::nested::module::Quux::default()),
+            || {
+                #[derive(Default)]
+                struct Local(Count<Self>);
+
+                Local::default();
+            },
+        ];
+        for i in 0..m {
+            fs[i % 4]();
+        }
+    }
+
+    let foo = get::<Foo>();
+    assert_eq!(foo.total, m * n + (m * n / 4));
+    assert_eq!(foo.max_live, 1);
+    assert_eq!(foo.live, 0);
+
+    let bar = get::<Bar>();
+    assert_eq!(bar.total, m * n + (m * n / 4));
+
+    // FIXME: why +1? This seems like a bug
+    // overreporting by 1 is not significant, but anyway
+    assert_eq!(bar.max_live, m + 1);
+    assert_eq!(bar.live, 0);
+
+    println!("{:?}", t.elapsed());
+}