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//! Implements methods to read a vector type from a slice.
macro_rules! impl_slice_from_slice {
([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt) => {
impl $id {
/// Instantiates a new vector with the values of the `slice`.
///
/// # Panics
///
/// If `slice.len() < Self::lanes()` or `&slice[0]` is not aligned
/// to an `align_of::<Self>()` boundary.
#[inline]
pub fn from_slice_aligned(slice: &[$elem_ty]) -> Self {
unsafe {
assert!(slice.len() >= $elem_count);
let target_ptr = slice.get_unchecked(0) as *const $elem_ty;
assert_eq!(
target_ptr.align_offset(crate::mem::align_of::<Self>()),
0
);
Self::from_slice_aligned_unchecked(slice)
}
}
/// Instantiates a new vector with the values of the `slice`.
///
/// # Panics
///
/// If `slice.len() < Self::lanes()`.
#[inline]
pub fn from_slice_unaligned(slice: &[$elem_ty]) -> Self {
unsafe {
assert!(slice.len() >= $elem_count);
Self::from_slice_unaligned_unchecked(slice)
}
}
/// Instantiates a new vector with the values of the `slice`.
///
/// # Precondition
///
/// If `slice.len() < Self::lanes()` or `&slice[0]` is not aligned
/// to an `align_of::<Self>()` boundary, the behavior is undefined.
#[inline]
pub unsafe fn from_slice_aligned_unchecked(slice: &[$elem_ty]) -> Self {
debug_assert!(slice.len() >= $elem_count);
let target_ptr = slice.get_unchecked(0) as *const $elem_ty;
debug_assert_eq!(
target_ptr.align_offset(crate::mem::align_of::<Self>()),
0
);
#[cfg_attr(feature = "cargo-clippy", allow(clippy::cast_ptr_alignment))]
*(target_ptr as *const Self)
}
/// Instantiates a new vector with the values of the `slice`.
///
/// # Precondition
///
/// If `slice.len() < Self::lanes()` the behavior is undefined.
#[inline]
pub unsafe fn from_slice_unaligned_unchecked(
slice: &[$elem_ty],
) -> Self {
use crate::mem::size_of;
debug_assert!(slice.len() >= $elem_count);
let target_ptr =
slice.get_unchecked(0) as *const $elem_ty as *const u8;
let mut x = Self::splat(0 as $elem_ty);
let self_ptr = &mut x as *mut Self as *mut u8;
crate::ptr::copy_nonoverlapping(
target_ptr,
self_ptr,
size_of::<Self>(),
);
x
}
}
test_if!{
$test_tt:
paste::item! {
pub mod [<$id _slice_from_slice>] {
use super::*;
use crate::iter::Iterator;
#[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
fn from_slice_unaligned() {
let mut unaligned = [42 as $elem_ty; $id::lanes() + 1];
unaligned[0] = 0 as $elem_ty;
let vec = $id::from_slice_unaligned(&unaligned[1..]);
for (index, &b) in unaligned.iter().enumerate() {
if index == 0 {
assert_eq!(b, 0 as $elem_ty);
} else {
assert_eq!(b, 42 as $elem_ty);
assert_eq!(b, vec.extract(index - 1));
}
}
}
// FIXME: wasm-bindgen-test does not support #[should_panic]
// #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
#[cfg(not(target_arch = "wasm32"))]
#[test]
#[should_panic]
fn from_slice_unaligned_fail() {
let mut unaligned = [42 as $elem_ty; $id::lanes() + 1];
unaligned[0] = 0 as $elem_ty;
// the slice is not large enough => panic
let _vec = $id::from_slice_unaligned(&unaligned[2..]);
}
union A {
data: [$elem_ty; 2 * $id::lanes()],
_vec: $id,
}
#[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
fn from_slice_aligned() {
let mut aligned = A {
data: [0 as $elem_ty; 2 * $id::lanes()],
};
for i in $id::lanes()..(2 * $id::lanes()) {
unsafe {
aligned.data[i] = 42 as $elem_ty;
}
}
let vec =
unsafe { $id::from_slice_aligned(&aligned.data[$id::lanes()..]) };
for (index, &b) in unsafe { aligned.data.iter().enumerate() } {
if index < $id::lanes() {
assert_eq!(b, 0 as $elem_ty);
} else {
assert_eq!(b, 42 as $elem_ty);
assert_eq!(b, vec.extract(index - $id::lanes()));
}
}
}
// FIXME: wasm-bindgen-test does not support #[should_panic]
// #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
#[cfg(not(target_arch = "wasm32"))]
#[test]
#[should_panic]
fn from_slice_aligned_fail_lanes() {
let aligned = A {
data: [0 as $elem_ty; 2 * $id::lanes()],
};
let _vec = unsafe {
$id::from_slice_aligned(&aligned.data[2 * $id::lanes()..])
};
}
// FIXME: wasm-bindgen-test does not support #[should_panic]
// #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
#[cfg(not(target_arch = "wasm32"))]
#[test]
#[should_panic]
fn from_slice_aligned_fail_align() {
unsafe {
let aligned = A {
data: [0 as $elem_ty; 2 * $id::lanes()],
};
// get a pointer to the front of data
let ptr: *const $elem_ty = aligned.data.as_ptr() as *const $elem_ty;
// offset pointer by one element
let ptr = ptr.wrapping_add(1);
if ptr.align_offset(crate::mem::align_of::<$id>()) == 0 {
// the pointer is properly aligned, so from_slice_aligned
// won't fail here (e.g. this can happen for i128x1). So
// we panic to make the "should_fail" test pass:
panic!("ok");
}
// create a slice - this is safe, because the elements
// of the slice exist, are properly initialized, and properly aligned:
let s: &[$elem_ty] = slice::from_raw_parts(ptr, $id::lanes());
// this should always panic because the slice alignment does not match
// the alignment requirements for the vector type:
let _vec = $id::from_slice_aligned(s);
}
}
}
}
}
};
}