Add spin_loop hint for LoongArch

Author: heiher

library/core/src/hint.rs

@@ -301,6 +301,16 @@ pub fn spin_loop() {
         // with support for the v6 feature.
         unsafe { crate::arch::arm::__yield() };
     }
+
+    #[cfg(target_arch = "loongarch32")]
+    {
+        crate::arch::loongarch32::ibar::<0>();
+    }
+
+    #[cfg(target_arch = "loongarch64")]
+    {
+        crate::arch::loongarch64::ibar::<0>();
+    }
 }
 
 /// An identity function that *__hints__* to the compiler to be maximally pessimistic about what