bench in-place zip

library/alloc/benches/vec.rs

@@ -1,3 +1,4 @@
+use rand::prelude::*;
 use std::iter::{repeat, FromIterator};
 use test::{black_box, Bencher};
 
@@ -501,6 +502,42 @@ fn bench_in_place_recycle(b: &mut test::Bencher) {
     });
 }
 
+#[bench]
+fn bench_in_place_zip_recycle(b: &mut test::Bencher) {
+    let mut data = vec![0u8; 256];
+    let mut rng = rand::thread_rng();
+    let mut subst = (0..=255u8).collect::<Vec<_>>();
+    subst.shuffle(&mut rng);
+
+    b.iter(|| {
+        let tmp = std::mem::replace(&mut data, Vec::new());
+        let mangled = tmp
+            .into_iter()
+            .zip(subst.iter().copied())
+            .enumerate()
+            .map(|(i, (d, s))| d.wrapping_add(i as u8) ^ s)
+            .collect::<Vec<_>>();
+        assert_eq!(mangled.len(), 256);
+        std::mem::replace(&mut data, black_box(mangled));
+    });
+}
+
+#[bench]
+fn bench_in_place_zip_iter_mut(b: &mut test::Bencher) {
+    let mut data = vec![0u8; 256];
+    let mut rng = rand::thread_rng();
+    let mut subst = (0..=255u8).collect::<Vec<_>>();
+    subst.shuffle(&mut rng);
+
+    b.iter(|| {
+        data.iter_mut().enumerate().for_each(|(i, d)| {
+            *d = d.wrapping_add(i as u8) ^ subst[i];
+        });
+    });
+
+    black_box(data);
+}
+
 #[derive(Clone)]
 struct Droppable(usize);