add a fallback implementation

Author: folkertdev

library/core/src/intrinsics/simd.rs

@@ -26,11 +26,12 @@ pub unsafe fn simd_insert<T, U>(_x: T, _idx: u32, _val: U) -> T {
 ///
 /// `idx` must be in-bounds of the vector.
 #[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
 #[rustc_nounwind]
 #[cfg(not(bootstrap))]
-pub unsafe fn simd_insert_dyn<T, U>(_x: T, _idx: u32, _val: U) -> T {
-    unreachable!()
+pub unsafe fn simd_insert_dyn<T, U>(mut x: T, idx: u32, val: U) -> T {
+    // SAFETY: `idx` must be in-bounds
+    unsafe { (&mut x as *mut T as *mut U).add(idx as usize).write(val) }
+    x
 }
 
 /// Extracts an element from a vector.
@@ -57,11 +58,11 @@ pub unsafe fn simd_extract<T, U>(_x: T, _idx: u32) -> U {
 ///
 /// `idx` must be in-bounds of the vector.
 #[rustc_intrinsic]
-#[rustc_intrinsic_must_be_overridden]
 #[rustc_nounwind]
 #[cfg(not(bootstrap))]
-pub unsafe fn simd_extract_dyn<T, U>(_x: T, _idx: u32) -> U {
-    unreachable!()
+pub unsafe fn simd_extract_dyn<T, U>(x: T, idx: u32) -> U {
+    // SAFETY: `idx` must be in-bounds
+    unsafe { (&x as *const T as *const U).add(idx as usize).read() }
 }
 
 /// Adds two simd vectors elementwise.

tests/ui/simd/intrinsic/generic-elements-pass.rs

@@ -19,9 +19,14 @@ struct i32x8([i32; 8]);
 #[rustc_intrinsic]
 unsafe fn simd_insert<T, E>(x: T, idx: u32, y: E) -> T;
 
+#[rustc_intrinsic]
+unsafe fn simd_insert_dyn<T, E>(x: T, idx: u32, y: E) -> T;
+
 #[rustc_intrinsic]
 unsafe fn simd_extract<T, E>(x: T, idx: u32) -> E;
 
+#[rustc_intrinsic]
+unsafe fn simd_extract_dyn<T, E>(x: T, idx: u32) -> E;
 
 #[rustc_intrinsic]
 unsafe fn simd_shuffle<T, I, U>(x: T, y: T, idx: I) -> U;
@@ -79,6 +84,41 @@ fn main() {
         all_eq!(simd_extract(x8, 6), 86);
         all_eq!(simd_extract(x8, 7), 87);
     }
+    unsafe {
+        all_eq!(simd_insert_dyn(x2, 0, 100), i32x2([100, 21]));
+        all_eq!(simd_insert_dyn(x2, 1, 100), i32x2([20, 100]));
+
+        all_eq!(simd_insert_dyn(x4, 0, 100), i32x4([100, 41, 42, 43]));
+        all_eq!(simd_insert_dyn(x4, 1, 100), i32x4([40, 100, 42, 43]));
+        all_eq!(simd_insert_dyn(x4, 2, 100), i32x4([40, 41, 100, 43]));
+        all_eq!(simd_insert_dyn(x4, 3, 100), i32x4([40, 41, 42, 100]));
+
+        all_eq!(simd_insert_dyn(x8, 0, 100), i32x8([100, 81, 82, 83, 84, 85, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 1, 100), i32x8([80, 100, 82, 83, 84, 85, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 2, 100), i32x8([80, 81, 100, 83, 84, 85, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 3, 100), i32x8([80, 81, 82, 100, 84, 85, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 4, 100), i32x8([80, 81, 82, 83, 100, 85, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 5, 100), i32x8([80, 81, 82, 83, 84, 100, 86, 87]));
+        all_eq!(simd_insert_dyn(x8, 6, 100), i32x8([80, 81, 82, 83, 84, 85, 100, 87]));
+        all_eq!(simd_insert_dyn(x8, 7, 100), i32x8([80, 81, 82, 83, 84, 85, 86, 100]));
+
+        all_eq!(simd_extract_dyn(x2, 0), 20);
+        all_eq!(simd_extract_dyn(x2, 1), 21);
+
+        all_eq!(simd_extract_dyn(x4, 0), 40);
+        all_eq!(simd_extract_dyn(x4, 1), 41);
+        all_eq!(simd_extract_dyn(x4, 2), 42);
+        all_eq!(simd_extract_dyn(x4, 3), 43);
+
+        all_eq!(simd_extract_dyn(x8, 0), 80);
+        all_eq!(simd_extract_dyn(x8, 1), 81);
+        all_eq!(simd_extract_dyn(x8, 2), 82);
+        all_eq!(simd_extract_dyn(x8, 3), 83);
+        all_eq!(simd_extract_dyn(x8, 4), 84);
+        all_eq!(simd_extract_dyn(x8, 5), 85);
+        all_eq!(simd_extract_dyn(x8, 6), 86);
+        all_eq!(simd_extract_dyn(x8, 7), 87);
+    }
 
     let y2 = i32x2([120, 121]);
     let y4 = i32x4([140, 141, 142, 143]);