#265: Move comparisons to traits

A simpler variant of #206.

* Comparisons are moved to `SimdPartialEq`, `SimdPartialOrd`, and `SimdOrd`.  The function names are prefixed with `simd_` to disambiguate from the regular `PartialEq` etc functions.  With the functions on traits instead of `Simd` directly, shadowing the function names doesn't work very well.
* Floating point `Ord`-like functions are put into a `SimdFloat` trait.  The intention is that eventually (some time after this PR) all floating point functions will be moved from `Simd` to `SimdFloat`, and the same goes for future `SimdInt`/`SimdUint` traits.

crates/core_simd/src/eq.rs

@@ -0,0 +1,73 @@
+use crate::simd::{intrinsics, LaneCount, Mask, Simd, SimdElement, SupportedLaneCount};
+
+/// Parallel `PartialEq`.
+pub trait SimdPartialEq {
+    /// The mask type returned by each comparison.
+    type Mask;
+
+    /// Test if each lane is equal to the corresponding lane in `other`.
+    #[must_use = "method returns a new mask and does not mutate the original value"]
+    fn simd_eq(self, other: Self) -> Self::Mask;
+
+    /// Test if each lane is equal to the corresponding lane in `other`.
+    #[must_use = "method returns a new mask and does not mutate the original value"]
+    fn simd_ne(self, other: Self) -> Self::Mask;
+}
+
+macro_rules! impl_number {
+    { $($number:ty),* } => {
+        $(
+        impl<const LANES: usize> SimdPartialEq for Simd<$number, LANES>
+        where
+            LaneCount<LANES>: SupportedLaneCount,
+        {
+            type Mask = Mask<<$number as SimdElement>::Mask, LANES>;
+
+            #[inline]
+            fn simd_eq(self, other: Self) -> Self::Mask {
+                // Safety: `self` is a vector, and the result of the comparison
+                // is always a valid mask.
+                unsafe { Mask::from_int_unchecked(intrinsics::simd_eq(self, other)) }
+            }
+
+            #[inline]
+            fn simd_ne(self, other: Self) -> Self::Mask {
+                // Safety: `self` is a vector, and the result of the comparison
+                // is always a valid mask.
+                unsafe { Mask::from_int_unchecked(intrinsics::simd_ne(self, other)) }
+            }
+        }
+        )*
+    }
+}
+
+impl_number! { f32, f64, u8, u16, u32, u64, usize, i8, i16, i32, i64, isize }
+
+macro_rules! impl_mask {
+    { $($integer:ty),* } => {
+        $(
+        impl<const LANES: usize> SimdPartialEq for Mask<$integer, LANES>
+        where
+            LaneCount<LANES>: SupportedLaneCount,
+        {
+            type Mask = Self;
+
+            #[inline]
+            fn simd_eq(self, other: Self) -> Self::Mask {
+                // Safety: `self` is a vector, and the result of the comparison
+                // is always a valid mask.
+                unsafe { Self::from_int_unchecked(intrinsics::simd_eq(self.to_int(), other.to_int())) }
+            }
+
+            #[inline]
+            fn simd_ne(self, other: Self) -> Self::Mask {
+                // Safety: `self` is a vector, and the result of the comparison
+                // is always a valid mask.
+                unsafe { Self::from_int_unchecked(intrinsics::simd_ne(self.to_int(), other.to_int())) }
+            }
+        }
+        )*
+    }
+}
+
+impl_mask! { i8, i16, i32, i64, isize }

crates/core_simd/src/masks.rs

@@ -15,7 +15,7 @@ mod mask_impl;
 mod to_bitmask;
 pub use to_bitmask::ToBitMask;
 
-use crate::simd::{intrinsics, LaneCount, Simd, SimdElement, SupportedLaneCount};
+use crate::simd::{intrinsics, LaneCount, Simd, SimdElement, SimdPartialEq, SupportedLaneCount};
 use core::cmp::Ordering;
 use core::{fmt, mem};
 
@@ -56,7 +56,7 @@ macro_rules! impl_element {
             where
                 LaneCount<LANES>: SupportedLaneCount,
             {
-                (value.lanes_eq(Simd::splat(0)) | value.lanes_eq(Simd::splat(-1))).all()
+                (value.simd_eq(Simd::splat(0 as _)) | value.simd_eq(Simd::splat(-1 as _))).all()
             }
 
             fn eq(self, other: Self) -> bool { self == other }

crates/core_simd/src/mod.rs

@@ -9,13 +9,14 @@ pub(crate) mod intrinsics;
 #[cfg(feature = "generic_const_exprs")]
 mod to_bytes;
 
-mod comparisons;
+mod eq;
 mod fmt;
 mod iter;
 mod lane_count;
 mod masks;
 mod math;
 mod ops;
+mod ord;
 mod round;
 mod select;
 mod vector;
@@ -25,8 +26,10 @@ mod vendor;
 pub mod simd {
     pub(crate) use crate::core_simd::intrinsics;
 
+    pub use crate::core_simd::eq::*;
     pub use crate::core_simd::lane_count::{LaneCount, SupportedLaneCount};
     pub use crate::core_simd::masks::*;
+    pub use crate::core_simd::ord::*;
     pub use crate::core_simd::swizzle::*;
     pub use crate::core_simd::vector::*;
 }

crates/core_simd/src/ops.rs

@@ -1,4 +1,4 @@
-use crate::simd::{LaneCount, Simd, SimdElement, SupportedLaneCount};
+use crate::simd::{LaneCount, Simd, SimdElement, SimdPartialEq, SupportedLaneCount};
 use core::ops::{Add, Mul};
 use core::ops::{BitAnd, BitOr, BitXor};
 use core::ops::{Div, Rem, Sub};
@@ -74,18 +74,18 @@ macro_rules! int_divrem_guard {
             $simd_call:ident
         },
         $int:ident ) => {
-        if $rhs.lanes_eq(Simd::splat(0)).any() {
+        if $rhs.simd_eq(Simd::splat(0 as _)).any() {
             panic!($zero);
         } else {
             // Prevent otherwise-UB overflow on the MIN / -1 case.
             let rhs = if <$int>::MIN != 0 {
                 // This should, at worst, optimize to a few branchless logical ops
                 // Ideally, this entire conditional should evaporate
                 // Fire LLVM and implement those manually if it doesn't get the hint
-                ($lhs.lanes_eq(Simd::splat(<$int>::MIN))
+                ($lhs.simd_eq(Simd::splat(<$int>::MIN))
                 // type inference can break here, so cut an SInt to size
-                & $rhs.lanes_eq(Simd::splat(-1i64 as _)))
-                .select(Simd::splat(1), $rhs)
+                & $rhs.simd_eq(Simd::splat(-1i64 as _)))
+                .select(Simd::splat(1 as _), $rhs)
             } else {
                 // Nice base case to make it easy to const-fold away the other branch.
                 $rhs