Merge pull request rust-lang#4469 from Patrick-6/add-spinloop-hints

Add std::hint::spin_loop() to tests

Author: RalfJung

src/tools/miri/tests/pass/0weak_memory_consistency.rs

@@ -41,7 +41,15 @@ fn static_atomic_bool(val: bool) -> &'static AtomicBool {
 }
 
 /// Spins until it acquires a pre-determined value.
-fn loads_value(loc: &AtomicI32, ord: Ordering, val: i32) -> i32 {
+fn spin_until_i32(loc: &AtomicI32, ord: Ordering, val: i32) -> i32 {
+    while loc.load(ord) != val {
+        std::hint::spin_loop();
+    }
+    val
+}
+
+/// Spins until it acquires a pre-determined boolean.
+fn spin_until_bool(loc: &AtomicBool, ord: Ordering, val: bool) -> bool {
     while loc.load(ord) != val {
         std::hint::spin_loop();
     }
@@ -65,7 +73,7 @@ fn test_corr() {
     }); //                                           |                    |
     #[rustfmt::skip] //                              |synchronizes-with   |happens-before
     let j3 = spawn(move || { //                      |                    |
-        loads_value(&y, Acquire, 1); // <------------+                    |
+        spin_until_i32(&y, Acquire, 1); // <---------+                    |
         x.load(Relaxed) // <----------------------------------------------+
         // The two reads on x are ordered by hb, so they cannot observe values
         // differently from the modification order. If the first read observed
@@ -90,12 +98,12 @@ fn test_wrc() {
     }); //                                           |                     |
     #[rustfmt::skip] //                              |synchronizes-with    |
     let j2 = spawn(move || { //                      |                     |
-        loads_value(&x, Acquire, 1); // <------------+                     |
+        spin_until_i32(&x, Acquire, 1); // <---------+                     |
         y.store(1, Release); // ---------------------+                     |happens-before
     }); //                                           |                     |
     #[rustfmt::skip] //                              |synchronizes-with    |
     let j3 = spawn(move || { //                      |                     |
-        loads_value(&y, Acquire, 1); // <------------+                     |
+        spin_until_i32(&y, Acquire, 1); // <---------+                     |
         x.load(Relaxed) // <-----------------------------------------------+
     });
 
@@ -121,7 +129,7 @@ fn test_message_passing() {
     #[rustfmt::skip] //                              |synchronizes-with  | happens-before
     let j2 = spawn(move || { //                      |                   |
         let x = x; // avoid field capturing          |                   |
-        loads_value(&y, Acquire, 1); // <------------+                   |
+        spin_until_i32(&y, Acquire, 1); // <---------+                   |
         unsafe { *x.0 } // <---------------------------------------------+
     });
 
@@ -216,12 +224,12 @@ fn test_sync_through_rmw_and_fences() {
     let go = static_atomic_bool(false);
 
     let t1 = spawn(move || {
-        while !go.load(Relaxed) {}
+        spin_until_bool(go, Relaxed, true);
         rdmw(y, x, z)
     });
 
     let t2 = spawn(move || {
-        while !go.load(Relaxed) {}
+        spin_until_bool(go, Relaxed, true);
         rdmw(z, x, y)
     });
 

src/tools/miri/tests/pass/0weak_memory_consistency_sc.rs

@@ -20,7 +20,15 @@ fn static_atomic_bool(val: bool) -> &'static AtomicBool {
 }
 
 /// Spins until it acquires a pre-determined value.
-fn loads_value(loc: &AtomicI32, ord: Ordering, val: i32) -> i32 {
+fn spin_until_i32(loc: &AtomicI32, ord: Ordering, val: i32) -> i32 {
+    while loc.load(ord) != val {
+        std::hint::spin_loop();
+    }
+    val
+}
+
+/// Spins until it acquires a pre-determined boolean.
+fn spin_until_bool(loc: &AtomicBool, ord: Ordering, val: bool) -> bool {
     while loc.load(ord) != val {
         std::hint::spin_loop();
     }
@@ -60,11 +68,11 @@ fn test_iriw_sc_rlx() {
     let a = spawn(move || x.store(true, Relaxed));
     let b = spawn(move || y.store(true, Relaxed));
     let c = spawn(move || {
-        while !x.load(SeqCst) {}
+        spin_until_bool(x, SeqCst, true);
         y.load(SeqCst)
     });
     let d = spawn(move || {
-        while !y.load(SeqCst) {}
+        spin_until_bool(y, SeqCst, true);
         x.load(SeqCst)
     });
 
@@ -136,7 +144,7 @@ fn test_cpp20_rwc_syncs() {
     });
 
     let j2 = spawn(move || {
-        loads_value(&x, Relaxed, 1);
+        spin_until_i32(&x, Relaxed, 1);
         fence(SeqCst);
         y.load(Relaxed)
     });

src/tools/miri/tests/pass/weak_memory/weak.rs

@@ -24,7 +24,7 @@ fn static_atomic(val: usize) -> &'static AtomicUsize {
 }
 
 // Spins until it reads the given value
-fn reads_value(loc: &AtomicUsize, val: usize) -> usize {
+fn spin_until(loc: &AtomicUsize, val: usize) -> usize {
     while loc.load(Relaxed) != val {
         std::hint::spin_loop();
     }
@@ -85,7 +85,7 @@ fn initialization_write(add_fence: bool) -> bool {
     });
 
     let j2 = spawn(move || {
-        reads_value(wait, 1);
+        spin_until(wait, 1);
         if add_fence {
             fence(AcqRel);
         }
@@ -119,12 +119,12 @@ fn faa_replaced_by_load() -> bool {
     let go = static_atomic(0);
 
     let t1 = spawn(move || {
-        while go.load(Relaxed) == 0 {}
+        spin_until(go, 1);
         rdmw(y, x, z)
     });
 
     let t2 = spawn(move || {
-        while go.load(Relaxed) == 0 {}
+        spin_until(go, 1);
         rdmw(z, x, y)
     });