simd_shuffle: require index argument to be a vector

Author: RalfJung

src/intrinsics/simd.rs

@@ -180,34 +180,20 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
                 return;
             }
 
-            // Make sure this is actually an array, since typeck only checks the length-suffixed
-            // version of this intrinsic.
+            // Make sure this is actually a SIMD vector.
             let idx_ty = fx.monomorphize(idx.node.ty(fx.mir, fx.tcx));
-            let n: u16 = match idx_ty.kind() {
-                ty::Array(ty, len) if matches!(ty.kind(), ty::Uint(ty::UintTy::U32)) => len
-                    .try_eval_target_usize(fx.tcx, ty::ParamEnv::reveal_all())
-                    .unwrap_or_else(|| {
-                        span_bug!(span, "could not evaluate shuffle index array length")
-                    })
-                    .try_into()
-                    .unwrap(),
-                _ if idx_ty.is_simd()
-                    && matches!(
-                        idx_ty.simd_size_and_type(fx.tcx).1.kind(),
-                        ty::Uint(ty::UintTy::U32)
-                    ) =>
-                {
-                    idx_ty.simd_size_and_type(fx.tcx).0.try_into().unwrap()
-                }
-                _ => {
-                    fx.tcx.dcx().span_err(
-                        span,
-                        format!("simd_shuffle index must be an array of `u32`, got `{}`", idx_ty),
-                    );
-                    // Prevent verifier error
-                    fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
-                    return;
-                }
+            let n: u16 = if idx_ty.is_simd()
+                && matches!(idx_ty.simd_size_and_type(fx.tcx).1.kind(), ty::Uint(ty::UintTy::U32))
+            {
+                idx_ty.simd_size_and_type(fx.tcx).0.try_into().unwrap()
+            } else {
+                fx.tcx.dcx().span_err(
+                    span,
+                    format!("simd_shuffle index must be a SIMD vector of `u32`, got `{}`", idx_ty),
+                );
+                // Prevent verifier error
+                fx.bcx.ins().trap(TrapCode::UnreachableCodeReached);
+                return;
             };
 
             assert_eq!(x.layout(), y.layout());