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Merge pull request #393 from rust-lang/assume-masks-are-correct

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Assume masks are correct
This commit is contained in:
Caleb Zulawski 2024-02-17 12:04:52 -05:00 committed by GitHub
commit 7348d2da1b
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1 changed files with 15 additions and 3 deletions
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18
crates/core_simd/src/masks.rs
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@ -12,7 +12,7 @@
)]
mod mask_impl;
use crate::simd::{cmp::SimdPartialEq, LaneCount, Simd, SimdCast, SimdElement, SupportedLaneCount};
use crate::simd::{LaneCount, Simd, SimdCast, SimdElement, SupportedLaneCount};
use core::cmp::Ordering;
use core::{fmt, mem};
@ -58,7 +58,16 @@ macro_rules! impl_element {
where
LaneCount<N>: SupportedLaneCount,
{
(value.simd_eq(Simd::splat(0 as _)) | value.simd_eq(Simd::splat(-1 as _))).all()
// We can't use `Simd` directly, because `Simd`'s functions call this function and
// we will end up with an infinite loop.
// Safety: `value` is an integer vector
unsafe {
use core::intrinsics::simd;
let falses: Simd<Self, N> = simd::simd_eq(value, Simd::splat(0 as _));
let trues: Simd<Self, N> = simd::simd_eq(value, Simd::splat(-1 as _));
let valid: Simd<Self, N> = simd::simd_or(falses, trues);
simd::simd_reduce_all(valid)
}
}
#[inline]
@ -174,7 +183,10 @@ where
#[must_use = "method returns a new mask and does not mutate the original value"]
pub unsafe fn from_int_unchecked(value: Simd<T, N>) -> Self {
// Safety: the caller must confirm this invariant
unsafe { Self(mask_impl::Mask::from_int_unchecked(value)) }
unsafe {
core::intrinsics::assume(<T as Sealed>::valid(value));
Self(mask_impl::Mask::from_int_unchecked(value))
}
}
/// Converts a vector of integers to a mask, where 0 represents `false` and -1