Rollup merge of rust-lang#59239 - gnzlbg:fix_spin_loop, r=nagisa

Remove inline assembly from hint::spin_loop

This PR removes the inline assembly which was not required since these
instructions are available in core::arch, and extends support of
the spin_loop hint to arm targets with the v6 feature which also
support the yield instruction.

Author: Centril

src/libcore/hint.rs

@@ -2,7 +2,7 @@
 
 //! Hints to compiler that affects how code should be emitted or optimized.
 
-use intrinsics;
+use {arch, intrinsics};
 
 /// Informs the compiler that this point in the code is not reachable, enabling
 /// further optimizations.
@@ -62,13 +62,32 @@ pub unsafe fn unreachable_unchecked() -> ! {
 #[inline]
 #[unstable(feature = "renamed_spin_loop", issue = "55002")]
 pub fn spin_loop() {
-    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-    unsafe {
-        asm!("pause" ::: "memory" : "volatile");
+    #[cfg(
+        all(
+            any(target_arch = "x86", target_arch = "x86_64"),
+            target_feature = "sse2"
+        )
+    )] {
+        #[cfg(target_arch = "x86")] {
+            unsafe { arch::x86::_mm_pause() };
+        }
+
+        #[cfg(target_arch = "x86_64")] {
+            unsafe { arch::x86_64::_mm_pause() };
+        }
     }
 
-    #[cfg(target_arch = "aarch64")]
-    unsafe {
-        asm!("yield" ::: "memory" : "volatile");
+    #[cfg(
+        any(
+            target_arch = "aarch64",
+            all(target_arch = "arm", target_feature = "v6")
+        )
+    )] {
+        #[cfg(target_arch = "aarch64")] {
+            unsafe { arch::aarch64::__yield() };
+        }
+        #[cfg(target_arch = "arm")] {
+            unsafe { arch::arm::__yield() };
+        }
     }
 }