Merge pull request #360 from rust-lang/shift-scalar

Add scalar shifts

crates/core_simd/src/ops.rs

@@ -6,6 +6,7 @@ use core::ops::{Shl, Shr};
 
 mod assign;
 mod deref;
+mod shift_scalar;
 mod unary;
 
 impl<I, T, const LANES: usize> core::ops::Index<I> for Simd<T, LANES>

crates/core_simd/src/ops/shift_scalar.rs

@@ -0,0 +1,58 @@
+// Shift operations uniquely typically only have a scalar on the right-hand side.
+// Here, we implement shifts for scalar RHS arguments.
+
+use crate::simd::{LaneCount, Simd, SupportedLaneCount};
+
+macro_rules! impl_splatted_shifts {
+    { impl $trait:ident :: $trait_fn:ident for $ty:ty } => {
+        impl<const N: usize> core::ops::$trait<$ty> for Simd<$ty, N>
+        where
+            LaneCount<N>: SupportedLaneCount,
+        {
+            type Output = Self;
+            fn $trait_fn(self, rhs: $ty) -> Self::Output {
+                self.$trait_fn(Simd::splat(rhs))
+            }
+        }
+
+        impl<const N: usize> core::ops::$trait<&$ty> for Simd<$ty, N>
+        where
+            LaneCount<N>: SupportedLaneCount,
+        {
+            type Output = Self;
+            fn $trait_fn(self, rhs: &$ty) -> Self::Output {
+                self.$trait_fn(Simd::splat(*rhs))
+            }
+        }
+
+        impl<'lhs, const N: usize> core::ops::$trait<$ty> for &'lhs Simd<$ty, N>
+        where
+            LaneCount<N>: SupportedLaneCount,
+        {
+            type Output = Simd<$ty, N>;
+            fn $trait_fn(self, rhs: $ty) -> Self::Output {
+                self.$trait_fn(Simd::splat(rhs))
+            }
+        }
+
+        impl<'lhs, const N: usize> core::ops::$trait<&$ty> for &'lhs Simd<$ty, N>
+        where
+            LaneCount<N>: SupportedLaneCount,
+        {
+            type Output = Simd<$ty, N>;
+            fn $trait_fn(self, rhs: &$ty) -> Self::Output {
+                self.$trait_fn(Simd::splat(*rhs))
+            }
+        }
+    };
+    { $($ty:ty),* } => {
+        $(
+        impl_splatted_shifts! { impl Shl::shl for $ty }
+        impl_splatted_shifts! { impl Shr::shr for $ty }
+        )*
+    }
+}
+
+// In the past there were inference issues when generically splatting arguments.
+// Enumerate them instead.
+impl_splatted_shifts! { i8, i16, i32, i64, isize, u8, u16, u32, u64, usize }

crates/core_simd/tests/ops_macros.rs

@@ -94,6 +94,36 @@ macro_rules! impl_binary_checked_op_test {
 macro_rules! impl_common_integer_tests {
     { $vector:ident, $scalar:ident } => {
         test_helpers::test_lanes! {
+            fn shr<const LANES: usize>() {
+                use core::ops::Shr;
+                let shr = |x: $scalar, y: $scalar| x.wrapping_shr(y as _);
+                test_helpers::test_binary_elementwise(
+                    &<$vector::<LANES> as Shr<$vector::<LANES>>>::shr,
+                    &shr,
+                    &|_, _| true,
+                );
+                test_helpers::test_binary_scalar_rhs_elementwise(
+                    &<$vector::<LANES> as Shr<$scalar>>::shr,
+                    &shr,
+                    &|_, _| true,
+                );
+            }
+
+            fn shl<const LANES: usize>() {
+                use core::ops::Shl;
+                let shl = |x: $scalar, y: $scalar| x.wrapping_shl(y as _);
+                test_helpers::test_binary_elementwise(
+                    &<$vector::<LANES> as Shl<$vector::<LANES>>>::shl,
+                    &shl,
+                    &|_, _| true,
+                );
+                test_helpers::test_binary_scalar_rhs_elementwise(
+                    &<$vector::<LANES> as Shl<$scalar>>::shl,
+                    &shl,
+                    &|_, _| true,
+                );
+            }
+
             fn reduce_sum<const LANES: usize>() {
                 test_helpers::test_1(&|x| {
                     test_helpers::prop_assert_biteq! (