1 files changed, 124 insertions, 0 deletions
diff --git a/third_party/rust/packed_simd/src/api/from/from_array.rs b/third_party/rust/packed_simd/src/api/from/from_array.rs
new file mode 100644
index 0000000000..5c7801ddaf
--- /dev/null
+++ b/third_party/rust/packed_simd/src/api/from/from_array.rs
@@ -0,0 +1,124 @@
+//! Implements `From<[T; N]>` and `Into<[T; N]>` for vector types.
+
+macro_rules! impl_from_array {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt
+     | ($non_default_array:expr, $non_default_vec:expr)) => {
+        impl From<[$elem_ty; $elem_count]> for $id {
+            #[inline]
+            fn from(array: [$elem_ty; $elem_count]) -> Self {
+                union U {
+                    array: [$elem_ty; $elem_count],
+                    vec: $id,
+                }
+                unsafe { U { array }.vec }
+            }
+        }
+
+        impl From<$id> for [$elem_ty; $elem_count] {
+            #[inline]
+            fn from(vec: $id) -> Self {
+                union U {
+                    array: [$elem_ty; $elem_count],
+                    vec: $id,
+                }
+                unsafe { U { vec }.array }
+            }
+        }
+
+        // FIXME: `Into::into` is not inline, but due to
+        // the blanket impl in `std`, which is not
+        // marked `default`, we cannot override it here with
+        // specialization.
+        /*
+        impl Into<[$elem_ty; $elem_count]> for $id {
+            #[inline]
+            fn into(self) -> [$elem_ty; $elem_count] {
+                union U {
+                    array: [$elem_ty; $elem_count],
+                    vec: $id,
+                }
+                unsafe { U { vec: self }.array }
+            }
+        }
+
+        impl Into<$id> for [$elem_ty; $elem_count] {
+            #[inline]
+            fn into(self) -> $id {
+                union U {
+                    array: [$elem_ty; $elem_count],
+                    vec: $id,
+                }
+                unsafe { U { array: self }.vec }
+            }
+        }
+        */
+
+        test_if! {
+            $test_tt:
+            paste::item! {
+                // Comparisons use integer casts within mantissa^1 range.
+                #[allow(clippy::float_cmp)]
+                mod [<$id _from>] {
+                    use super::*;
+                    #[test]
+                    #[cfg_attr(miri, ignore)]
+                    fn array() {
+                        let vec: $id = Default::default();
+
+                        // FIXME: Workaround for arrays with more than 32
+                        // elements.
+                        //
+                        // Safe because we never take a reference to any
+                        // uninitialized element.
+                        union W {
+                            array: [$elem_ty; $elem_count],
+                            other: ()
+                        }
+                        let mut array = W { other: () };
+                        for i in 0..$elem_count {
+                            let default: $elem_ty = Default::default();
+                            // note: array.other is the active member and
+                            // initialized so we can take a reference to it:
+                            let p = unsafe {
+                                &mut array.other as *mut () as *mut $elem_ty
+                            };
+                            // note: default is a valid bit-pattern for
+                            // $elem_ty:
+                            unsafe {
+                                crate::ptr::write(p.wrapping_add(i), default)
+                            };
+                        }
+                        // note: the array variant of the union is properly
+                        // initialized:
+                        let mut array = unsafe {
+                            array.array
+                        };
+
+                        array[0] = $non_default_array;
+                        let vec = vec.replace(0, $non_default_vec);
+
+                        let vec_from_array = $id::from(array);
+                        assert_eq!(vec_from_array, vec);
+                        let array_from_vec
+                            = <[$elem_ty; $elem_count]>::from(vec);
+                        // FIXME: Workaround for arrays with more than 32
+                        // elements.
+                        for i in 0..$elem_count {
+                            assert_eq!(array_from_vec[i], array[i]);
+                        }
+
+                        let vec_from_into_array: $id = array.into();
+                        assert_eq!(vec_from_into_array, vec);
+                        let array_from_into_vec: [$elem_ty; $elem_count]
+                            = vec.into();
+                        // FIXME: Workaround for arrays with more than 32
+                        // elements.
+                        for i in 0..$elem_count {
+                            assert_eq!(array_from_into_vec[i], array[i]);
+                        }
+                    }
+                }
+            }
+        }
+    };
+}