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Improve documentation

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This commit is contained in:
Caleb Zulawski 2024-06-01 14:17:16 -04:00
parent 86158f581d
commit 9bdc5b2455
2 changed files with 9 additions and 3 deletions
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7
compiler/rustc_codegen_llvm/src/intrinsic.rs
View File

@ -480,10 +480,15 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
}
_ if name.as_str().starts_with("simd_") => {
// Unpack non-power-of-2 #[repr(packed)]
// Unpack non-power-of-2 #[repr(packed, simd)] arguments.
// This gives them the expected layout of a regular #[repr(simd)] vector.
let mut loaded_args = Vec::new();
for (ty, arg) in arg_tys.iter().zip(args) {
loaded_args.push(
// #[repr(packed, simd)] vectors are passed like arrays (as references,
// with reduced alignment and no padding) rather than as immediates.
// We can use a vector load to fix the layout and turn the argument
// into an immediate.
if ty.is_simd()
&& let OperandValue::Ref(place) = arg.val
{

5
tests/ui/simd/repr_packed.rs
View File

@ -36,12 +36,13 @@ fn main() {
check_ty::<f64>();
unsafe {
// powers-of-two have no padding and work as usual
// powers-of-two have no padding and have the same layout as #[repr(simd)]
let x: Simd<f64, 4> =
simd_add(Simd::<f64, 4>([0., 1., 2., 3.]), Simd::<f64, 4>([2., 2., 2., 2.]));
assert_eq!(std::mem::transmute::<_, [f64; 4]>(x), [2., 3., 4., 5.]);
// non-powers-of-two have padding and lesser alignment, but the intrinsic handles it
// non-powers-of-two should have padding (which is removed by #[repr(packed)]),
// but the intrinsic handles it
let x: Simd<f64, 3> = simd_add(Simd::<f64, 3>([0., 1., 2.]), Simd::<f64, 3>([2., 2., 2.]));
let arr: [f64; 3] = x.0;
assert_eq!(arr, [2., 3., 4.]);