1 files changed, 73 insertions, 0 deletions
diff --git a/third_party/rust/packed_simd/src/api/select.rs b/third_party/rust/packed_simd/src/api/select.rs
new file mode 100644
index 0000000000..daf6294721
--- /dev/null
+++ b/third_party/rust/packed_simd/src/api/select.rs
@@ -0,0 +1,73 @@
+//! Implements mask's `select`.
+
+/// Implements mask select method
+macro_rules! impl_select {
+    ([$elem_ty:ident; $elem_count:expr]: $id:ident | $test_tt:tt) => {
+        impl $id {
+            /// Selects elements of `a` and `b` using mask.
+            ///
+            /// The lanes of the result for which the mask is `true` contain
+            /// the values of `a`. The remaining lanes contain the values of
+            /// `b`.
+            #[inline]
+            pub fn select<T>(self, a: Simd<T>, b: Simd<T>) -> Simd<T>
+            where
+                T: sealed::SimdArray<NT = <[$elem_ty; $elem_count] as sealed::SimdArray>::NT>,
+            {
+                use crate::llvm::simd_select;
+                Simd(unsafe { simd_select(self.0, a.0, b.0) })
+            }
+        }
+
+        test_select!(bool, $id, $id, (false, true) | $test_tt);
+    };
+}
+
+macro_rules! test_select {
+    (
+        $elem_ty:ident,
+        $mask_ty:ident,
+        $vec_ty:ident,($small:expr, $large:expr) |
+        $test_tt:tt
+    ) => {
+        test_if! {
+            $test_tt:
+            paste::item! {
+                pub mod [<$vec_ty _select>] {
+                    use super::*;
+
+                    #[cfg_attr(not(target_arch = "wasm32"), test)] #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
+                    fn select() {
+                        let o = $small as $elem_ty;
+                        let t = $large as $elem_ty;
+
+                        let a = $vec_ty::splat(o);
+                        let b = $vec_ty::splat(t);
+                        let m = a.lt(b);
+                        assert_eq!(m.select(a, b), a);
+
+                        let m = b.lt(a);
+                        assert_eq!(m.select(b, a), a);
+
+                        let mut c = a;
+                        let mut d = b;
+                        let mut m_e = $mask_ty::splat(false);
+                        for i in 0..$vec_ty::lanes() {
+                            if i % 2 == 0 {
+                                let c_tmp = c.extract(i);
+                                c = c.replace(i, d.extract(i));
+                                d = d.replace(i, c_tmp);
+                            } else {
+                                m_e = m_e.replace(i, true);
+                            }
+                        }
+
+                        let m = c.lt(d);
+                        assert_eq!(m_e, m);
+                        assert_eq!(m.select(c, d), a);
+                    }
+                }
+            }
+        }
+    };
+}