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//! Implements masked gather and scatters for vectors of pointers
macro_rules! impl_ptr_read {
([$elem_ty:ty; $elem_count:expr]: $id:ident, $mask_ty:ident
| $test_tt:tt) => {
impl<T> $id<T>
where
[T; $elem_count]: sealed::SimdArray,
{
/// Reads selected vector elements from memory.
///
/// Instantiates a new vector by reading the values from `self` for
/// those lanes whose `mask` is `true`, and using the elements of
/// `value` otherwise.
///
/// No memory is accessed for those lanes of `self` whose `mask` is
/// `false`.
///
/// # Safety
///
/// This method is unsafe because it dereferences raw pointers. The
/// pointers must be aligned to `mem::align_of::<T>()`.
#[inline]
pub unsafe fn read<M>(
self,
mask: Simd<[M; $elem_count]>,
value: Simd<[T; $elem_count]>,
) -> Simd<[T; $elem_count]>
where
M: sealed::Mask,
[M; $elem_count]: sealed::SimdArray,
{
use crate::llvm::simd_gather;
Simd(simd_gather(value.0, self.0, mask.0))
}
}
test_if! {
$test_tt:
paste::item! {
mod [<$id _read>] {
use super::*;
#[test]
fn read() {
let mut v = [0_i32; $elem_count];
for i in 0..$elem_count {
v[i] = i as i32;
}
let mut ptr = $id::<i32>::null();
for i in 0..$elem_count {
ptr = ptr.replace(i,
&v[i] as *const i32 as *mut i32
);
}
// all mask elements are true:
let mask = $mask_ty::splat(true);
let def = Simd::<[i32; $elem_count]>::splat(42_i32);
let r: Simd<[i32; $elem_count]> = unsafe {
ptr.read(mask, def)
};
assert_eq!(
r,
Simd::<[i32; $elem_count]>::from_slice_unaligned(
&v
)
);
let mut mask = mask;
for i in 0..$elem_count {
if i % 2 != 0 {
mask = mask.replace(i, false);
}
}
// even mask elements are true, odd ones are false:
let r: Simd<[i32; $elem_count]> = unsafe {
ptr.read(mask, def)
};
let mut e = v;
for i in 0..$elem_count {
if i % 2 != 0 {
e[i] = 42;
}
}
assert_eq!(
r,
Simd::<[i32; $elem_count]>::from_slice_unaligned(
&e
)
);
// all mask elements are false:
let mask = $mask_ty::splat(false);
let def = Simd::<[i32; $elem_count]>::splat(42_i32);
let r: Simd<[i32; $elem_count]> = unsafe {
ptr.read(mask, def) }
;
assert_eq!(r, def);
}
}
}
}
};
}
macro_rules! impl_ptr_write {
([$elem_ty:ty; $elem_count:expr]: $id:ident, $mask_ty:ident
| $test_tt:tt) => {
impl<T> $id<T>
where
[T; $elem_count]: sealed::SimdArray,
{
/// Writes selected vector elements to memory.
///
/// Writes the lanes of `values` for which the mask is `true` to
/// their corresponding memory addresses in `self`.
///
/// No memory is accessed for those lanes of `self` whose `mask` is
/// `false`.
///
/// Overlapping memory addresses of `self` are written to in order
/// from the lest-significant to the most-significant element.
///
/// # Safety
///
/// This method is unsafe because it dereferences raw pointers. The
/// pointers must be aligned to `mem::align_of::<T>()`.
#[inline]
pub unsafe fn write<M>(self, mask: Simd<[M; $elem_count]>, value: Simd<[T; $elem_count]>)
where
M: sealed::Mask,
[M; $elem_count]: sealed::SimdArray,
{
use crate::llvm::simd_scatter;
simd_scatter(value.0, self.0, mask.0)
}
}
test_if! {
$test_tt:
paste::item! {
mod [<$id _write>] {
use super::*;
#[test]
fn write() {
// forty_two = [42, 42, 42, ...]
let forty_two
= Simd::<[i32; $elem_count]>::splat(42_i32);
// This test will write to this array
let mut arr = [0_i32; $elem_count];
for i in 0..$elem_count {
arr[i] = i as i32;
}
// arr = [0, 1, 2, ...]
let mut ptr = $id::<i32>::null();
for i in 0..$elem_count {
ptr = ptr.replace(i, unsafe {
arr.as_ptr().add(i) as *mut i32
});
}
// ptr = [&arr[0], &arr[1], ...]
// write `forty_two` to all elements of `v`
{
let backup = arr;
unsafe {
ptr.write($mask_ty::splat(true), forty_two)
};
assert_eq!(arr, [42_i32; $elem_count]);
arr = backup; // arr = [0, 1, 2, ...]
}
// write 42 to even elements of arr:
{
// set odd elements of the mask to false
let mut mask = $mask_ty::splat(true);
for i in 0..$elem_count {
if i % 2 != 0 {
mask = mask.replace(i, false);
}
}
// mask = [true, false, true, false, ...]
// expected result r = [42, 1, 42, 3, 42, 5, ...]
let mut r = arr;
for i in 0..$elem_count {
if i % 2 == 0 {
r[i] = 42;
}
}
let backup = arr;
unsafe { ptr.write(mask, forty_two) };
assert_eq!(arr, r);
arr = backup; // arr = [0, 1, 2, 3, ...]
}
// write 42 to no elements of arr
{
let backup = arr;
unsafe {
ptr.write($mask_ty::splat(false), forty_two)
};
assert_eq!(arr, backup);
}
}
}
}
}
};
}