Rollup merge of #130268 - RalfJung:simd-shuffle-idx-vector, r=compiler-errors

simd_shuffle: require index argument to be a vector

Remove some codegen hacks by forcing the SIMD shuffle `index` argument to be a vector, which means (thanks to rust-lang/rust#128537) that it will automatically be passed as an immediate in LLVM. The only special-casing we still have is for the extra sanity-checks we add that ensure that the indices are all in-bounds. (And the GCC backend needs to do a bunch of work since the Rust intrinsic is modeled after what LLVM expects, which seems to be quite different from what GCC expects.)

Fixes rust-lang/rust#128738, see that issue for more context.

Author: fmease

src/intrinsics/simd.rs

@@ -664,15 +664,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let [left, right, index] = check_arg_count(args)?;
                 let (left, left_len) = this.project_to_simd(left)?;
                 let (right, right_len) = this.project_to_simd(right)?;
+                let (index, index_len) = this.project_to_simd(index)?;
                 let (dest, dest_len) = this.project_to_simd(dest)?;
 
-                // `index` is an array or a SIMD type
-                let (index, index_len) = match index.layout.ty.kind() {
-                    // FIXME: remove this once `index` must always be a SIMD vector.
-                    ty::Array(..) => (index.clone(), index.len(this)?),
-                    _ => this.project_to_simd(index)?,
-                };
-
                 assert_eq!(left_len, right_len);
                 assert_eq!(index_len, dest_len);
 

tests/pass/intrinsics/portable-simd.rs

@@ -619,7 +619,6 @@ fn simd_intrinsics() {
             i32x4::from_array([10, 2, 10, 10])
         );
         assert_eq!(simd_shuffle_generic::<_, i32x4, { &[3, 1, 0, 2] }>(a, b), a,);
-        assert_eq!(simd_shuffle::<_, _, i32x4>(a, b, const { [3u32, 1, 0, 2] }), a,);
         assert_eq!(
             simd_shuffle::<_, _, i32x4>(a, b, const { u32x4::from_array([3u32, 1, 0, 2]) }),
             a,
@@ -628,10 +627,6 @@ fn simd_intrinsics() {
             simd_shuffle_generic::<_, i32x4, { &[7, 5, 4, 6] }>(a, b),
             i32x4::from_array([4, 2, 1, 10]),
         );
-        assert_eq!(
-            simd_shuffle::<_, _, i32x4>(a, b, const { [7u32, 5, 4, 6] }),
-            i32x4::from_array([4, 2, 1, 10]),
-        );
         assert_eq!(
             simd_shuffle::<_, _, i32x4>(a, b, const { u32x4::from_array([7u32, 5, 4, 6]) }),
             i32x4::from_array([4, 2, 1, 10]),