diff --git a/crates/core_simd/src/comparisons.rs b/crates/core_simd/src/comparisons.rs
index 988ff857eab5..f3a1954fda22 100644
--- a/crates/core_simd/src/comparisons.rs
+++ b/crates/core_simd/src/comparisons.rs
@@ -1,7 +1,7 @@
 use crate::LanesAtMost32;
 
 macro_rules! implement_mask_ops {
-    { $($vector:ident => $mask:ident ($inner_mask_ty:ident, $inner_ty:ident),)* } => {
+    { $($vector:ident => $mask:ident ($inner_ty:ident),)* } => {
         $(
             impl<const LANES: usize> crate::$vector<LANES>
             where
@@ -12,8 +12,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_eq(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_eq(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_eq(self, other))
                     }
                 }
 
@@ -21,8 +20,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_ne(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_ne(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_ne(self, other))
                     }
                 }
 
@@ -30,8 +28,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_lt(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_lt(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_lt(self, other))
                     }
                 }
 
@@ -39,8 +36,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_gt(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_gt(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_gt(self, other))
                     }
                 }
 
@@ -48,8 +44,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_le(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_le(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_le(self, other))
                     }
                 }
 
@@ -57,8 +52,7 @@ macro_rules! implement_mask_ops {
                 #[inline]
                 pub fn lanes_ge(self, other: Self) -> crate::$mask<LANES> {
                     unsafe {
-                        crate::$inner_mask_ty::from_int_unchecked(crate::intrinsics::simd_ge(self, other))
-                            .into()
+                        crate::$mask::from_int_unchecked(crate::intrinsics::simd_ge(self, other))
                     }
                 }
             }
@@ -67,18 +61,18 @@ macro_rules! implement_mask_ops {
 }
 
 implement_mask_ops! {
-    SimdI8 => Mask8 (SimdMask8, SimdI8),
-    SimdI16 => Mask16 (SimdMask16, SimdI16),
-    SimdI32 => Mask32 (SimdMask32, SimdI32),
-    SimdI64 => Mask64 (SimdMask64, SimdI64),
-    SimdIsize => MaskSize (SimdMaskSize, SimdIsize),
+    SimdI8 => Mask8 (SimdI8),
+    SimdI16 => Mask16 (SimdI16),
+    SimdI32 => Mask32 (SimdI32),
+    SimdI64 => Mask64 (SimdI64),
+    SimdIsize => MaskSize (SimdIsize),
 
-    SimdU8 => Mask8 (SimdMask8, SimdI8),
-    SimdU16 => Mask16 (SimdMask16, SimdI16),
-    SimdU32 => Mask32 (SimdMask32, SimdI32),
-    SimdU64 => Mask64 (SimdMask64, SimdI64),
-    SimdUsize => MaskSize (SimdMaskSize, SimdIsize),
+    SimdU8 => Mask8 (SimdI8),
+    SimdU16 => Mask16 (SimdI16),
+    SimdU32 => Mask32 (SimdI32),
+    SimdU64 => Mask64 (SimdI64),
+    SimdUsize => MaskSize (SimdIsize),
 
-    SimdF32 => Mask32 (SimdMask32, SimdI32),
-    SimdF64 => Mask64 (SimdMask64, SimdI64),
+    SimdF32 => Mask32 (SimdI32),
+    SimdF64 => Mask64 (SimdI64),
 }
diff --git a/crates/core_simd/src/lanes_at_most_32.rs b/crates/core_simd/src/lanes_at_most_32.rs
index 1e2f7e952c62..2fee9ca91891 100644
--- a/crates/core_simd/src/lanes_at_most_32.rs
+++ b/crates/core_simd/src/lanes_at_most_32.rs
@@ -1,4 +1,4 @@
-/// Implemented for bitmask sizes that are supported by the implementation.
+/// Implemented for vectors that are supported by the implementation.
 pub trait LanesAtMost32 {}
 
 macro_rules! impl_for {
@@ -28,5 +28,3 @@ impl_for! { SimdIsize }
 
 impl_for! { SimdF32 }
 impl_for! { SimdF64 }
-
-impl_for! { BitMask }
diff --git a/crates/core_simd/src/masks/bitmask.rs b/crates/core_simd/src/masks/bitmask.rs
index b4d1b6d9557d..32e2ffb86153 100644
--- a/crates/core_simd/src/masks/bitmask.rs
+++ b/crates/core_simd/src/masks/bitmask.rs
@@ -4,14 +4,12 @@ use crate::LanesAtMost32;
 #[derive(Copy, Clone, Debug, PartialOrd, PartialEq, Ord, Eq, Hash)]
 #[repr(transparent)]
 pub struct BitMask<const LANES: usize>(u64)
-where
-    BitMask<LANES>: LanesAtMost32;
 
 impl<const LANES: usize> BitMask<LANES>
 where
     Self: LanesAtMost32,
 {
-    /// Construct a mask by setting all lanes to the given value.
+    #[inline]
     pub fn splat(value: bool) -> Self {
         if value {
             Self(u64::MAX >> (64 - LANES))
@@ -20,23 +18,13 @@ where
         }
     }
 
-    /// Tests the value of the specified lane.
-    ///
-    /// # Panics
-    /// Panics if `lane` is greater than or equal to the number of lanes in the vector.
     #[inline]
-    pub fn test(&self, lane: usize) -> bool {
-        assert!(lane < LANES, "lane index out of range");
+    pub unsafe fn test_unchecked(&self, lane: usize) -> bool {
         (self.0 >> lane) & 0x1 > 0
     }
 
-    /// Sets the value of the specified lane.
-    ///
-    /// # Panics
-    /// Panics if `lane` is greater than or equal to the number of lanes in the vector.
     #[inline]
-    pub fn set(&mut self, lane: usize, value: bool) {
-        assert!(lane < LANES, "lane index out of range");
+    pub unsafe fn set_unchecked(&mut self, lane: usize, value: bool) {
         self.0 ^= ((value ^ self.test(lane)) as u64) << lane
     }
 }
diff --git a/crates/core_simd/src/masks/full_masks.rs b/crates/core_simd/src/masks/full_masks.rs
index 60a6cb5fdbe8..6972a4216b68 100644
--- a/crates/core_simd/src/masks/full_masks.rs
+++ b/crates/core_simd/src/masks/full_masks.rs
@@ -1,18 +1,5 @@
 //! Masks that take up full SIMD vector registers.
 
-/// The error type returned when converting an integer to a mask fails.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub struct TryFromMaskError(());
-
-impl core::fmt::Display for TryFromMaskError {
-    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
-        write!(
-            f,
-            "mask vector must have all bits set or unset in each lane"
-        )
-    }
-}
-
 macro_rules! define_mask {
     {
         $(#[$attr:meta])*
@@ -27,6 +14,8 @@ macro_rules! define_mask {
         where
             crate::$type<LANES>: crate::LanesAtMost32;
 
+        impl_full_mask_reductions! { $name, $type }
+
         impl<const LANES: usize> Copy for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -46,7 +35,6 @@ macro_rules! define_mask {
         where
             crate::$type<LANES>: crate::LanesAtMost32,
         {
-            /// Construct a mask by setting all lanes to the given value.
             pub fn splat(value: bool) -> Self {
                 Self(<crate::$type<LANES>>::splat(
                     if value {
@@ -57,20 +45,12 @@ macro_rules! define_mask {
                 ))
             }
 
-            /// Tests the value of the specified lane.
-            ///
-            /// # Panics
-            /// Panics if `lane` is greater than or equal to the number of lanes in the vector.
             #[inline]
             pub fn test(&self, lane: usize) -> bool {
                 assert!(lane < LANES, "lane index out of range");
                 self.0[lane] == -1
             }
 
-            /// Sets the value of the specified lane.
-            ///
-            /// # Panics
-            /// Panics if `lane` is greater than or equal to the number of lanes in the vector.
             #[inline]
             pub fn set(&mut self, lane: usize, value: bool) {
                 assert!(lane < LANES, "lane index out of range");
@@ -81,56 +61,15 @@ macro_rules! define_mask {
                 }
             }
 
-            /// Converts the mask to the equivalent integer representation, where -1 represents
-            /// "set" and 0 represents "unset".
             #[inline]
             pub fn to_int(self) -> crate::$type<LANES> {
                 self.0
             }
 
-            /// Creates a  mask from the equivalent integer representation, where -1 represents
-            /// "set" and 0 represents "unset".
-            ///
-            /// Each provided lane must be either 0 or -1.
             #[inline]
             pub unsafe fn from_int_unchecked(value: crate::$type<LANES>) -> Self {
                 Self(value)
             }
-
-            /// Creates a mask from the equivalent integer representation, where -1 represents
-            /// "set" and 0 represents "unset".
-            ///
-            /// # Panics
-            /// Panics if any lane is not 0 or -1.
-            #[inline]
-            pub fn from_int(value: crate::$type<LANES>) -> Self {
-                use core::convert::TryInto;
-                value.try_into().unwrap()
-            }
-        }
-
-        impl<const LANES: usize> core::convert::From<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            fn from(value: bool) -> Self {
-                Self::splat(value)
-            }
-        }
-
-        impl<const LANES: usize> core::convert::TryFrom<crate::$type<LANES>> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Error = TryFromMaskError;
-            fn try_from(value: crate::$type<LANES>) -> Result<Self, Self::Error> {
-                let valid = (value.lanes_eq(crate::$type::<LANES>::splat(0)) | value.lanes_eq(crate::$type::<LANES>::splat(-1))).all();
-                if valid {
-                    Ok(Self(value))
-                } else {
-                    Err(TryFromMaskError(()))
-                }
-            }
         }
 
         impl<const LANES: usize> core::convert::From<$name<LANES>> for crate::$type<LANES>
@@ -142,36 +81,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::convert::From<crate::BitMask<LANES>> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-            crate::BitMask<LANES>: crate::LanesAtMost32,
-        {
-            fn from(value: crate::BitMask<LANES>) -> Self {
-                // TODO use an intrinsic to do this efficiently (with LLVM's sext instruction)
-                let mut mask = Self::splat(false);
-                for lane in 0..LANES {
-                    mask.set(lane, value.test(lane));
-                }
-                mask
-            }
-        }
-
-        impl<const LANES: usize> core::convert::From<$name<LANES>> for crate::BitMask<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-            crate::BitMask<LANES>: crate::LanesAtMost32,
-        {
-            fn from(value: $name<$lanes>) -> Self {
-                // TODO use an intrinsic to do this efficiently (with LLVM's trunc instruction)
-                let mut mask = Self::splat(false);
-                for lane in 0..LANES {
-                    mask.set(lane, value.test(lane));
-                }
-                mask
-            }
-        }
-
         impl<const LANES: usize> core::fmt::Debug for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -230,28 +139,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::ops::BitAnd<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = Self;
-            #[inline]
-            fn bitand(self, rhs: bool) -> Self {
-                self & Self::splat(rhs)
-            }
-        }
-
-        impl<const LANES: usize> core::ops::BitAnd<$name<LANES>> for bool
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = $name<LANES>;
-            #[inline]
-            fn bitand(self, rhs: $name<LANES>) -> $name<LANES> {
-                $name::<LANES>::splat(self) & rhs
-            }
-        }
-
         impl<const LANES: usize> core::ops::BitOr for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -263,28 +150,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::ops::BitOr<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = Self;
-            #[inline]
-            fn bitor(self, rhs: bool) -> Self {
-                self | Self::splat(rhs)
-            }
-        }
-
-        impl<const LANES: usize> core::ops::BitOr<$name<LANES>> for bool
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = $name<LANES>;
-            #[inline]
-            fn bitor(self, rhs: $name<LANES>) -> $name<LANES> {
-                $name::<LANES>::splat(self) | rhs
-            }
-        }
-
         impl<const LANES: usize> core::ops::BitXor for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -296,28 +161,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::ops::BitXor<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = Self;
-            #[inline]
-            fn bitxor(self, rhs: bool) -> Self::Output {
-                self ^ Self::splat(rhs)
-            }
-        }
-
-        impl<const LANES: usize> core::ops::BitXor<$name<LANES>> for bool
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            type Output = $name<LANES>;
-            #[inline]
-            fn bitxor(self, rhs: $name<LANES>) -> Self::Output {
-                $name::<LANES>::splat(self) ^ rhs
-            }
-        }
-
         impl<const LANES: usize> core::ops::Not for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -339,16 +182,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::ops::BitAndAssign<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            #[inline]
-            fn bitand_assign(&mut self, rhs: bool) {
-                *self &= Self::splat(rhs);
-            }
-        }
-
         impl<const LANES: usize> core::ops::BitOrAssign for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -359,16 +192,6 @@ macro_rules! define_mask {
             }
         }
 
-        impl<const LANES: usize> core::ops::BitOrAssign<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            #[inline]
-            fn bitor_assign(&mut self, rhs: bool) {
-                *self |= Self::splat(rhs);
-            }
-        }
-
         impl<const LANES: usize> core::ops::BitXorAssign for $name<LANES>
         where
             crate::$type<LANES>: crate::LanesAtMost32,
@@ -378,47 +201,35 @@ macro_rules! define_mask {
                 self.0 ^= rhs.0;
             }
         }
-
-        impl<const LANES: usize> core::ops::BitXorAssign<bool> for $name<LANES>
-        where
-            crate::$type<LANES>: crate::LanesAtMost32,
-        {
-            #[inline]
-            fn bitxor_assign(&mut self, rhs: bool) {
-                *self ^= Self::splat(rhs);
-            }
-        }
-
-        impl_full_mask_reductions! { $name, $type }
     }
 }
 
 define_mask! {
     /// A mask equivalent to [SimdI8](crate::SimdI8), where all bits in the lane must be either set
     /// or unset.
-    struct SimdMask8<const LANES: usize>(crate::SimdI8<LANES>);
+    struct Mask8<const LANES: usize>(crate::SimdI8<LANES>);
 }
 
 define_mask! {
     /// A mask equivalent to [SimdI16](crate::SimdI16), where all bits in the lane must be either set
     /// or unset.
-    struct SimdMask16<const LANES: usize>(crate::SimdI16<LANES>);
+    struct Mask16<const LANES: usize>(crate::SimdI16<LANES>);
 }
 
 define_mask! {
     /// A mask equivalent to [SimdI32](crate::SimdI32), where all bits in the lane must be either set
     /// or unset.
-    struct SimdMask32<const LANES: usize>(crate::SimdI32<LANES>);
+    struct Mask32<const LANES: usize>(crate::SimdI32<LANES>);
 }
 
 define_mask! {
     /// A mask equivalent to [SimdI64](crate::SimdI64), where all bits in the lane must be either set
     /// or unset.
-    struct SimdMask64<const LANES: usize>(crate::SimdI64<LANES>);
+    struct Mask64<const LANES: usize>(crate::SimdI64<LANES>);
 }
 
 define_mask! {
     /// A mask equivalent to [SimdIsize](crate::SimdIsize), where all bits in the lane must be either set
     /// or unset.
-    struct SimdMaskSize<const LANES: usize>(crate::SimdIsize<LANES>);
+    struct MaskSize<const LANES: usize>(crate::SimdIsize<LANES>);
 }
diff --git a/crates/core_simd/src/masks/mod.rs b/crates/core_simd/src/masks/mod.rs
index c394c7003a35..fbb934b96424 100644
--- a/crates/core_simd/src/masks/mod.rs
+++ b/crates/core_simd/src/masks/mod.rs
@@ -1,25 +1,24 @@
 //! Types and traits associated with masking lanes of vectors.
+//! Types representing
 #![allow(non_camel_case_types)]
 
-mod full_masks;
-pub use full_masks::*;
-
-mod bitmask;
-pub use bitmask::*;
+#[cfg_attr(not(all(target_arch = "x86_64", target_feature = "avx512f")), path = "full_masks.rs")]
+#[cfg_attr(all(target_arch = "x86_64", target_feature = "avx512f"), path = "bitmask.rs")]
+mod mask_impl;
 
 use crate::{LanesAtMost32, SimdI16, SimdI32, SimdI64, SimdI8, SimdIsize};
 
 macro_rules! define_opaque_mask {
     {
         $(#[$attr:meta])*
-        struct $name:ident<const $lanes:ident: usize>($inner_ty:ident<$lanes2:ident>);
+        struct $name:ident<const $lanes:ident: usize>($inner_ty:ty);
         @bits $bits_ty:ident
     } => {
         $(#[$attr])*
         #[allow(non_camel_case_types)]
-        pub struct $name<const LANES: usize>($inner_ty<LANES>) where $bits_ty<LANES>: LanesAtMost32;
+        pub struct $name<const LANES: usize>($inner_ty) where $bits_ty<LANES>: LanesAtMost32;
 
-        impl_opaque_mask_reductions! { $name, $inner_ty, $bits_ty }
+        impl_opaque_mask_reductions! { $name, $bits_ty }
 
         impl<const LANES: usize> $name<LANES>
         where
@@ -27,7 +26,7 @@ macro_rules! define_opaque_mask {
         {
             /// Construct a mask by setting all lanes to the given value.
             pub fn splat(value: bool) -> Self {
-                Self(<$inner_ty<LANES>>::splat(value))
+                Self(<$inner_ty>::splat(value))
             }
 
             /// Converts an array to a SIMD vector.
@@ -52,6 +51,16 @@ macro_rules! define_opaque_mask {
                 array
             }
 
+            /// Converts a vector of integers to a mask, where 0 represents `false` and -1
+            /// represents `true`.
+            ///
+            /// # Safety
+            /// All lanes must be either 0 or -1.
+            #[inline]
+            pub unsafe fn from_int_unchecked(value: $bits_ty<LANES>) -> Self {
+                Self(<$inner_ty>::from_int_unchecked(value))
+            }
+
             /// Tests the value of the specified lane.
             ///
             /// # Panics
@@ -71,44 +80,6 @@ macro_rules! define_opaque_mask {
             }
         }
 
-        impl<const LANES: usize> From<BitMask<LANES>> for $name<LANES>
-        where
-            $bits_ty<LANES>: LanesAtMost32,
-            BitMask<LANES>: LanesAtMost32,
-        {
-            fn from(value: BitMask<LANES>) -> Self {
-                Self(value.into())
-            }
-        }
-
-        impl<const LANES: usize> From<$name<LANES>> for crate::BitMask<LANES>
-        where
-            $bits_ty<LANES>: LanesAtMost32,
-            BitMask<LANES>: LanesAtMost32,
-        {
-            fn from(value: $name<LANES>) -> Self {
-                value.0.into()
-            }
-        }
-
-        impl<const LANES: usize> From<$inner_ty<LANES>> for $name<LANES>
-        where
-            $bits_ty<LANES>: LanesAtMost32,
-        {
-            fn from(value: $inner_ty<LANES>) -> Self {
-                Self(value)
-            }
-        }
-
-        impl<const LANES: usize> From<$name<LANES>> for $inner_ty<LANES>
-        where
-            $bits_ty<LANES>: LanesAtMost32,
-        {
-            fn from(value: $name<LANES>) -> Self {
-                value.0
-            }
-        }
-
         // vector/array conversion
         impl<const LANES: usize> From<[bool; LANES]> for $name<LANES>
         where
@@ -130,7 +101,7 @@ macro_rules! define_opaque_mask {
 
         impl<const LANES: usize> Copy for $name<LANES>
         where
-            $inner_ty<LANES>: Copy,
+            $inner_ty: Copy,
             $bits_ty<LANES>: LanesAtMost32,
         {}
 
@@ -359,7 +330,7 @@ define_opaque_mask! {
     /// Mask for vectors with `LANES` 8-bit elements.
     ///
     /// The layout of this type is unspecified.
-    struct Mask8<const LANES: usize>(SimdMask8<LANES>);
+    struct Mask8<const LANES: usize>(mask_impl::Mask8<LANES>);
     @bits SimdI8
 }
 
@@ -367,7 +338,7 @@ define_opaque_mask! {
     /// Mask for vectors with `LANES` 16-bit elements.
     ///
     /// The layout of this type is unspecified.
-    struct Mask16<const LANES: usize>(SimdMask16<LANES>);
+    struct Mask16<const LANES: usize>(mask_impl::Mask16<LANES>);
     @bits SimdI16
 }
 
@@ -375,7 +346,7 @@ define_opaque_mask! {
     /// Mask for vectors with `LANES` 32-bit elements.
     ///
     /// The layout of this type is unspecified.
-    struct Mask32<const LANES: usize>(SimdMask32<LANES>);
+    struct Mask32<const LANES: usize>(mask_impl::Mask32<LANES>);
     @bits SimdI32
 }
 
@@ -383,7 +354,7 @@ define_opaque_mask! {
     /// Mask for vectors with `LANES` 64-bit elements.
     ///
     /// The layout of this type is unspecified.
-    struct Mask64<const LANES: usize>(SimdMask64<LANES>);
+    struct Mask64<const LANES: usize>(mask_impl::Mask64<LANES>);
     @bits SimdI64
 }
 
@@ -391,7 +362,7 @@ define_opaque_mask! {
     /// Mask for vectors with `LANES` pointer-width elements.
     ///
     /// The layout of this type is unspecified.
-    struct MaskSize<const LANES: usize>(SimdMaskSize<LANES>);
+    struct MaskSize<const LANES: usize>(mask_impl::MaskSize<LANES>);
     @bits SimdIsize
 }
 
diff --git a/crates/core_simd/src/reduction.rs b/crates/core_simd/src/reduction.rs
index 382d366dd3d1..2d4f1bca2647 100644
--- a/crates/core_simd/src/reduction.rs
+++ b/crates/core_simd/src/reduction.rs
@@ -103,18 +103,16 @@ macro_rules! impl_float_reductions {
 }
 
 macro_rules! impl_full_mask_reductions {
-    { $name:ident, $inner:ident } => {
-        impl<const LANES: usize> crate::$name<LANES>
+    { $name:ident, $bits_ty:ident } => {
+        impl<const LANES: usize> $name<LANES>
         where
-            crate::$inner<LANES>: crate::LanesAtMost32
+            crate::$bits_ty<LANES>: crate::LanesAtMost32
         {
-            /// Returns true if any lane is set, or false otherwise.
             #[inline]
             pub fn any(self) -> bool {
                 unsafe { crate::intrinsics::simd_reduce_any(self.to_int()) }
             }
 
-            /// Returns true if all lanes are set, or false otherwise.
             #[inline]
             pub fn all(self) -> bool {
                 unsafe { crate::intrinsics::simd_reduce_all(self.to_int()) }
@@ -124,10 +122,10 @@ macro_rules! impl_full_mask_reductions {
 }
 
 macro_rules! impl_opaque_mask_reductions {
-    { $name:ident, $inner:ident, $bits_ty:ident } => {
+    { $name:ident, $bits_ty:ident } => {
         impl<const LANES: usize> $name<LANES>
         where
-            $bits_ty<LANES>: crate::LanesAtMost32
+            crate::$bits_ty<LANES>: crate::LanesAtMost32
         {
             /// Returns true if any lane is set, or false otherwise.
             #[inline]
@@ -143,20 +141,3 @@ macro_rules! impl_opaque_mask_reductions {
         }
     }
 }
-
-impl<const LANES: usize> crate::BitMask<LANES>
-where
-    crate::BitMask<LANES>: crate::LanesAtMost32,
-{
-    /// Returns true if any lane is set, or false otherwise.
-    #[inline]
-    pub fn any(self) -> bool {
-        self != Self::splat(false)
-    }
-
-    /// Returns true if all lanes are set, or false otherwise.
-    #[inline]
-    pub fn all(self) -> bool {
-        self == Self::splat(true)
-    }
-}
diff --git a/crates/core_simd/tests/masks.rs b/crates/core_simd/tests/masks.rs
index 59da77de622b..6c3993e39a93 100644
--- a/crates/core_simd/tests/masks.rs
+++ b/crates/core_simd/tests/masks.rs
@@ -1,30 +1,9 @@
-use core::convert::TryFrom;
-use core_simd::{BitMask, Mask8, SimdI8, SimdMask8};
-
 #[cfg(target_arch = "wasm32")]
 use wasm_bindgen_test::*;
 
 #[cfg(target_arch = "wasm32")]
 wasm_bindgen_test_configure!(run_in_browser);
 
-#[test]
-#[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
-fn mask_format_round_trip() {
-    let ints = SimdI8::from_array([-1, 0, 0, -1]);
-
-    let simd_mask = SimdMask8::try_from(ints).unwrap();
-
-    let bitmask = BitMask::from(simd_mask);
-
-    let opaque_mask = Mask8::from(bitmask);
-
-    let simd_mask_returned = SimdMask8::from(opaque_mask);
-
-    let ints_returned = SimdI8::from(simd_mask_returned);
-
-    assert_eq!(ints_returned, ints);
-}
-
 macro_rules! test_mask_api {
     { $name:ident } => {
         #[allow(non_snake_case)]
@@ -83,6 +62,4 @@ macro_rules! test_mask_api {
 
 mod mask_api {
     test_mask_api! { Mask8 }
-    test_mask_api! { SimdMask8 }
-    test_mask_api! { BitMask }
 }
diff --git a/crates/test_helpers/src/lib.rs b/crates/test_helpers/src/lib.rs
index 9e8790842b49..8b56877967cb 100644
--- a/crates/test_helpers/src/lib.rs
+++ b/crates/test_helpers/src/lib.rs
@@ -281,7 +281,6 @@ macro_rules! test_lanes {
                     core_simd::SimdIsize<$lanes>: core_simd::LanesAtMost32,
                     core_simd::SimdF32<$lanes>: core_simd::LanesAtMost32,
                     core_simd::SimdF64<$lanes>: core_simd::LanesAtMost32,
-                    core_simd::BitMask<$lanes>: core_simd::LanesAtMost32,
                 $body
 
                 #[cfg(target_arch = "wasm32")]
@@ -351,7 +350,6 @@ macro_rules! test_lanes_panic {
                     core_simd::SimdIsize<$lanes>: core_simd::LanesAtMost32,
                     core_simd::SimdF32<$lanes>: core_simd::LanesAtMost32,
                     core_simd::SimdF64<$lanes>: core_simd::LanesAtMost32,
-                    core_simd::BitMask<$lanes>: core_simd::LanesAtMost32,
                 $body
 
                 #[test]