Add VecDeque::extend TrustedLen benchmark

Author: paolobarbolini

library/alloc/benches/vec_deque.rs

@@ -91,3 +91,35 @@ fn bench_extend_vec(b: &mut Bencher) {
         ring.extend(black_box(input));
     });
 }
+
+#[bench]
+fn bench_extend_trustedlen(b: &mut Bencher) {
+    let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
+
+    b.iter(|| {
+        ring.clear();
+        ring.extend(black_box(0..512));
+    });
+}
+
+#[bench]
+fn bench_extend_chained_trustedlen(b: &mut Bencher) {
+    let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
+
+    b.iter(|| {
+        ring.clear();
+        ring.extend(black_box((0..256).chain(768..1024)));
+    });
+}
+
+#[bench]
+fn bench_extend_chained_bytes(b: &mut Bencher) {
+    let mut ring: VecDeque<u16> = VecDeque::with_capacity(1000);
+    let input1: &[u16] = &[128; 256];
+    let input2: &[u16] = &[255; 256];
+
+    b.iter(|| {
+        ring.clear();
+        ring.extend(black_box(input1.iter().chain(input2.iter())));
+    });
+}