--- atomic.orig/src/lib.rs
+++ atomic/src/lib.rs
@@ -500,4 +500,8 @@
     }
 
+    // on 32-bit x86 64 bit atomics exist, but they can't be used to implement
+    // atomic<i64> because AtomicI64 has a greater alignment requirement than
+    // i64.
+    #[cfg(any(feature = "fallback",all(target_has_atomic = "64",not(target_arch = "x86"))))]
     #[test]
     fn atomic_i64() {
@@ -523,4 +527,5 @@
     }
 
+    #[cfg(any(feature = "fallback",all(feature = "nightly", target_has_atomic = "128")))]
     #[test]
     fn atomic_i128() {
@@ -631,4 +636,8 @@
     }
 
+    // on 32-bit x86 64 bit atomics exist, but they can't be used to implement
+    // atomic<u64> because AtomicU64 has a greater alignment requirement than
+    // u64.
+    #[cfg(any(feature = "fallback",all(target_has_atomic = "64",not(target_arch = "x86"))))]
     #[test]
     fn atomic_u64() {
@@ -654,4 +663,5 @@
     }
 
+    #[cfg(any(feature = "fallback",all(feature = "nightly", target_has_atomic = "128")))]
     #[test]
     fn atomic_u128() {
@@ -696,4 +706,5 @@
     }
 
+    #[cfg(feature = "fallback")]
     #[test]
     fn atomic_foo() {
@@ -715,4 +726,5 @@
     }
 
+    #[cfg(feature = "fallback")]
     #[test]
     fn atomic_bar() {