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Auto merge of #85828 - scottmcm:raw-eq, r=oli-obk
Stop generating `alloca`s & `memcmp` for simple short array equality
Example:
```rust
pub fn demo(x: [u16; 6], y: [u16; 6]) -> bool { x == y }
```
Before:
```llvm
define zeroext i1 `@_ZN10playground4demo17h48537f7eac23948fE(i96` %0, i96 %1) unnamed_addr #0 {
start:
%y = alloca [6 x i16], align 8
%x = alloca [6 x i16], align 8
%.0..sroa_cast = bitcast [6 x i16]* %x to i96*
store i96 %0, i96* %.0..sroa_cast, align 8
%.0..sroa_cast3 = bitcast [6 x i16]* %y to i96*
store i96 %1, i96* %.0..sroa_cast3, align 8
%_11.i.i.i = bitcast [6 x i16]* %x to i8*
%_14.i.i.i = bitcast [6 x i16]* %y to i8*
%bcmp.i.i.i = call i32 `@bcmp(i8*` nonnull dereferenceable(12) %_11.i.i.i, i8* nonnull dereferenceable(12) %_14.i.i.i, i64 12) #2, !alias.scope !2
%2 = icmp eq i32 %bcmp.i.i.i, 0
ret i1 %2
}
```
```x86
playground::demo: # `@playground::demo`
sub rsp, 32
mov qword ptr [rsp], rdi
mov dword ptr [rsp + 8], esi
mov qword ptr [rsp + 16], rdx
mov dword ptr [rsp + 24], ecx
xor rdi, rdx
xor esi, ecx
or rsi, rdi
sete al
add rsp, 32
ret
```
After:
```llvm
define zeroext i1 `@_ZN4mini4demo17h7a8994aaa314c981E(i96` %0, i96 %1) unnamed_addr #0 {
start:
%2 = icmp eq i96 %0, %1
ret i1 %2
}
```
```x86
_ZN4mini4demo17h7a8994aaa314c981E:
xor rcx, r8
xor edx, r9d
or rdx, rcx
sete al
ret
```- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N] | ||
| where | ||
| A: PartialEq<B>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &[B; N]) -> bool { | ||
| SpecArrayEq::spec_eq(self, other) | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &[B; N]) -> bool { | ||
| SpecArrayEq::spec_ne(self, other) | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<[B]> for [A; N] | ||
| where | ||
| A: PartialEq<B>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &[B]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &[B]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<[A; N]> for [B] | ||
| where | ||
| B: PartialEq<A>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &[A; N]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &[A; N]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<&[B]> for [A; N] | ||
| where | ||
| A: PartialEq<B>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &&[B]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &&[B]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<[A; N]> for &[B] | ||
| where | ||
| B: PartialEq<A>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &[A; N]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &[A; N]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<&mut [B]> for [A; N] | ||
| where | ||
| A: PartialEq<B>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &&mut [B]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &&mut [B]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<A, B, const N: usize> PartialEq<[A; N]> for &mut [B] | ||
| where | ||
| B: PartialEq<A>, | ||
| { | ||
| #[inline] | ||
| fn eq(&self, other: &[A; N]) -> bool { | ||
| self[..] == other[..] | ||
| } | ||
| #[inline] | ||
| fn ne(&self, other: &[A; N]) -> bool { | ||
| self[..] != other[..] | ||
| } | ||
| } | ||
|
|
||
| // NOTE: some less important impls are omitted to reduce code bloat | ||
| // __impl_slice_eq2! { [A; $N], &'b [B; $N] } | ||
| // __impl_slice_eq2! { [A; $N], &'b mut [B; $N] } | ||
|
|
||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl<T: Eq, const N: usize> Eq for [T; N] {} | ||
|
|
||
| trait SpecArrayEq<Other, const N: usize>: Sized { | ||
| fn spec_eq(a: &[Self; N], b: &[Other; N]) -> bool; | ||
| fn spec_ne(a: &[Self; N], b: &[Other; N]) -> bool; | ||
| } | ||
|
|
||
| impl<T: PartialEq<Other>, Other, const N: usize> SpecArrayEq<Other, N> for T { | ||
| default fn spec_eq(a: &[Self; N], b: &[Other; N]) -> bool { | ||
| a[..] == b[..] | ||
| } | ||
| default fn spec_ne(a: &[Self; N], b: &[Other; N]) -> bool { | ||
| a[..] != b[..] | ||
| } | ||
| } | ||
|
|
||
| impl<T: PartialEq<U> + IsRawEqComparable<U>, U, const N: usize> SpecArrayEq<U, N> for T { | ||
| #[cfg(bootstrap)] | ||
| fn spec_eq(a: &[T; N], b: &[U; N]) -> bool { | ||
| a[..] == b[..] | ||
| } | ||
| #[cfg(not(bootstrap))] | ||
| fn spec_eq(a: &[T; N], b: &[U; N]) -> bool { | ||
| // SAFETY: This is why `IsRawEqComparable` is an `unsafe trait`. | ||
| unsafe { | ||
| let b = &*b.as_ptr().cast::<[T; N]>(); | ||
| crate::intrinsics::raw_eq(a, b) | ||
| } | ||
| } | ||
| fn spec_ne(a: &[T; N], b: &[U; N]) -> bool { | ||
| !Self::spec_eq(a, b) | ||
| } | ||
| } | ||
|
|
||
| /// `U` exists on here mostly because `min_specialization` didn't let me | ||
| /// repeat the `T` type parameter in the above specialization, so instead | ||
| /// the `T == U` constraint comes from the impls on this. | ||
| /// # Safety | ||
| /// - Neither `Self` nor `U` has any padding. | ||
| /// - `Self` and `U` have the same layout. | ||
| /// - `Self: PartialEq<U>` is byte-wise (this means no floats, among other things) | ||
| #[rustc_specialization_trait] | ||
| unsafe trait IsRawEqComparable<U> {} | ||
|
|
||
| macro_rules! is_raw_comparable { | ||
| ($($t:ty),+) => {$( | ||
| unsafe impl IsRawEqComparable<$t> for $t {} | ||
| )+}; | ||
| } | ||
| is_raw_comparable!(bool, char, u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize); |
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