Rollup merge of #41143 - stjepang:optimize-bool-fetch-nand, r=nagisa

Optimize AtomicBool::fetch_nand

This is an attempt to push the PR #40563 to completion.

Benchmark: [source](https://gist.github.com/stjepang/023f5025623f5474184f9f4dfd6379ae)
Improvement:

```
 name  old_ ns/iter  new_ce_ ns/iter  diff ns/iter   diff %
 1t    146,440       89,904                -56,536  -38.61%
 2t    561,456       316,835              -244,621  -43.57%
 4t    2,822,821     1,005,424          -1,817,397  -64.38%
```

r? @eddyb
cc @alexcrichton @nagisa

1 files changed, 14 insertions, 1 deletions

diff --git a/src/libcore/tests/atomic.rs b/src/libcore/tests/atomic.rs
index b6bb5fddf4a..9babe24a985 100644
--- a/src/libcore/tests/atomic.rs
+++ b/src/libcore/tests/atomic.rs
@@ -24,11 +24,24 @@ fn bool_() {
 #[test]
 fn bool_and() {
     let a = AtomicBool::new(true);
-    assert_eq!(a.fetch_and(false, SeqCst),true);
+    assert_eq!(a.fetch_and(false, SeqCst), true);
     assert_eq!(a.load(SeqCst),false);
 }
 
 #[test]
+fn bool_nand() {
+    let a = AtomicBool::new(false);
+    assert_eq!(a.fetch_nand(false, SeqCst), false);
+    assert_eq!(a.load(SeqCst), true);
+    assert_eq!(a.fetch_nand(false, SeqCst), true);
+    assert_eq!(a.load(SeqCst), true);
+    assert_eq!(a.fetch_nand(true, SeqCst), true);
+    assert_eq!(a.load(SeqCst), false);
+    assert_eq!(a.fetch_nand(true, SeqCst), false);
+    assert_eq!(a.load(SeqCst), true);
+}
+
+#[test]
 fn uint_and() {
     let x = AtomicUsize::new(0xf731);
     assert_eq!(x.fetch_and(0x137f, SeqCst), 0xf731);