Use simd_extract_dyn for extract

 - Remove comments regarding rust-lang/compiler-team#838

Author: sayantn

crates/core_arch/src/macros.rs

@@ -108,11 +108,7 @@ macro_rules! types {
                 // SAFETY: this type is just an overaligned `[T; N]` with
                 // potential padding at the end, so pointer casting to a
                 // `&[T; N]` is safe.
-                //
-                // NOTE: This deliberately doesn't just use `&self.0` because it may soon be banned
-                // see https://github.com/rust-lang/compiler-team/issues/838
                 unsafe { &*(self as *const Self as *const [$elem_type; $len]) }
-
             }
 
             /// Returns a mutable array reference containing the entire SIMD vector.
@@ -121,9 +117,6 @@ macro_rules! types {
                 // SAFETY: this type is just an overaligned `[T; N]` with
                 // potential padding at the end, so pointer casting to a
                 // `&mut [T; N]` is safe.
-                //
-                // NOTE: This deliberately doesn't just use `&mut self.0` because it may soon be banned
-                // see https://github.com/rust-lang/compiler-team/issues/838
                 unsafe { &mut *(self as *mut Self as *mut [$elem_type; $len]) }
             }
         }

crates/core_arch/src/simd.rs

@@ -33,13 +33,9 @@ macro_rules! simd_ty {
                 unsafe { simd_shuffle!(one, one, [0; $len]) }
             }
 
-            /// Extract the element at position `index`.
-            /// `index` is not a constant so this is not efficient!
-            /// Use for testing only.
-            // FIXME: Workaround rust@60637
             #[inline(always)]
             pub(crate) fn extract(&self, index: usize) -> $elem_type {
-                self.as_array()[index]
+                unsafe { $crate::intrinsics::simd::simd_extract_dyn(self, index as u32) }
             }
 
             #[inline]