Allow memcmp
for more array comparisons
This way comparing `[NonZeroU8; 8]` is just as fast as comparing `[u8; 8]`.
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parent
f0448f44bc
commit
24affba02e
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@ -1,3 +1,6 @@
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use crate::num::{NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize};
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use crate::num::{NonZeroU128, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize};
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#[stable(feature = "rust1", since = "1.0.0")]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]
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impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]
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where
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where
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@ -124,7 +127,7 @@ impl<T: PartialEq<Other>, Other, const N: usize> SpecArrayEq<Other, N> for T {
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}
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}
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}
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}
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impl<T: PartialEq<U> + IsRawEqComparable<U>, U, const N: usize> SpecArrayEq<U, N> for T {
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impl<T: IsRawEqComparable<U>, U, const N: usize> SpecArrayEq<U, N> for T {
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fn spec_eq(a: &[T; N], b: &[U; N]) -> bool {
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fn spec_eq(a: &[T; N], b: &[U; N]) -> bool {
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// SAFETY: This is why `IsRawEqComparable` is an `unsafe trait`.
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// SAFETY: This is why `IsRawEqComparable` is an `unsafe trait`.
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unsafe {
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unsafe {
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@ -145,11 +148,52 @@ impl<T: PartialEq<U> + IsRawEqComparable<U>, U, const N: usize> SpecArrayEq<U, N
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/// - `Self` and `U` have the same layout.
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/// - `Self` and `U` have the same layout.
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/// - `Self: PartialEq<U>` is byte-wise (this means no floats, among other things)
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/// - `Self: PartialEq<U>` is byte-wise (this means no floats, among other things)
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#[rustc_specialization_trait]
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#[rustc_specialization_trait]
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unsafe trait IsRawEqComparable<U> {}
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unsafe trait IsRawEqComparable<U>: PartialEq<U> {}
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macro_rules! is_raw_comparable {
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macro_rules! is_raw_eq_comparable {
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($($t:ty),+) => {$(
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($($t:ty),+ $(,)?) => {$(
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unsafe impl IsRawEqComparable<$t> for $t {}
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unsafe impl IsRawEqComparable<$t> for $t {}
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)+};
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)+};
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}
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}
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is_raw_comparable!(bool, char, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
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// SAFETY: All the ordinary integer types allow all bit patterns as distinct values
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is_raw_eq_comparable!(u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize);
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// SAFETY: bool and char have *niches*, but no *padding*, so this is sound
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is_raw_eq_comparable!(bool, char);
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// SAFETY: Similarly, the non-zero types have a niche, but no undef,
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// and they compare like their underlying numeric type.
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is_raw_eq_comparable!(
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NonZeroU8,
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NonZeroU16,
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NonZeroU32,
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NonZeroU64,
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NonZeroU128,
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NonZeroUsize,
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NonZeroI8,
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NonZeroI16,
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NonZeroI32,
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NonZeroI64,
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NonZeroI128,
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NonZeroIsize,
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);
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// SAFETY: The NonZero types have the "null" optimization guaranteed, and thus
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// are also safe to equality-compare bitwise inside an `Option`.
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// The way `PartialOrd` is defined for `Option` means that this wouldn't work
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// for `<` or `>` on the signed types, but since we only do `==` it's fine.
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is_raw_eq_comparable!(
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Option<NonZeroU8>,
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Option<NonZeroU16>,
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Option<NonZeroU32>,
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Option<NonZeroU64>,
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Option<NonZeroU128>,
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Option<NonZeroUsize>,
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Option<NonZeroI8>,
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Option<NonZeroI16>,
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Option<NonZeroI32>,
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Option<NonZeroI64>,
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Option<NonZeroI128>,
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Option<NonZeroIsize>,
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);
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