Auto merge of #148425 - matthiaskrgr:rollup-pwibmxt, r=matthiaskrgr

Rollup of 3 pull requests

Successful merges:

 - #146260 (add SliceIndex wrapper types Last and Clamp<Idx>)
 - #148394 (Make explicit that `TypeId`'s layout and size are unstable)
 - #148402 (stdarch subtree update)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

library/core/src/any.rs

@@ -611,6 +611,15 @@ impl dyn Any + Send + Sync {
 /// noting that the hashes and ordering will vary between Rust releases. Beware
 /// of relying on them inside of your code!
 ///
+/// # Layout
+///
+/// Like other [`Rust`-representation][repr-rust] types, `TypeId`'s size and layout are unstable.
+/// In particular, this means that you cannot rely on the size and layout of `TypeId` remaining the
+/// same between Rust releases; they are subject to change without prior notice between Rust
+/// releases.
+///
+/// [repr-rust]: https://doc.rust-lang.org/reference/type-layout.html#r-layout.repr.rust.unspecified
+///
 /// # Danger of Improper Variance
 ///
 /// You might think that subtyping is impossible between two static types,

library/core/src/hint.rs

@@ -271,11 +271,11 @@ pub fn spin_loop() {
     crate::cfg_select! {
         target_arch = "x86" => {
             // SAFETY: the `cfg` attr ensures that we only execute this on x86 targets.
-            unsafe { crate::arch::x86::_mm_pause() }
+            crate::arch::x86::_mm_pause()
         }
         target_arch = "x86_64" => {
             // SAFETY: the `cfg` attr ensures that we only execute this on x86_64 targets.
-            unsafe { crate::arch::x86_64::_mm_pause() }
+            crate::arch::x86_64::_mm_pause()
         }
         target_arch = "riscv32" => crate::arch::riscv32::pause(),
         target_arch = "riscv64" => crate::arch::riscv64::pause(),