const-eval: do not call immediate_const_vector on vector of pointers

Author: folkertdev

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -1074,8 +1074,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 if constant_ty.is_simd() {
                     // However, some SIMD types do not actually use the vector ABI
                     // (in particular, packed SIMD types do not). Ensure we exclude those.
+                    //
+                    // We also have to exclude vectors of pointers because `immediate_const_vector`
+                    // does not work for those.
                     let layout = bx.layout_of(constant_ty);
-                    if let BackendRepr::SimdVector { .. } = layout.backend_repr {
+                    let (_, element_ty) = constant_ty.simd_size_and_type(bx.tcx());
+                    if let BackendRepr::SimdVector { .. } = layout.backend_repr
+                        && element_ty.is_numeric()
+                    {
                         let (llval, ty) = self.immediate_const_vector(bx, constant);
                         return OperandRef {
                             val: OperandValue::Immediate(llval),

tests/ui/simd/intrinsic/splat.rs

@@ -41,12 +41,8 @@ fn main() {
 
         static ZERO: u8 = 0u8;
         let x: Simd<*const u8, 2> = simd_splat(&raw const ZERO);
+        let y: Simd<*const u8, 2> = const { simd_splat(&raw const ZERO) };
         assert_eq!(x.into_array(), [&raw const ZERO; 2]);
-
-        // FIXME: this hits "could not evaluate shuffle_indices at compile time",
-        // emitted in `immediate_const_vector`. const-eval should be able to handle
-        // this though I think? `const { [&raw const ZERO; 2] }` appears to work.
-        // let y: Simd<*const u8, 2> = const { simd_splat(&raw const ZERO) };
-        // assert_eq!(x.into_array(), y.into_array());
+        assert_eq!(x.into_array(), y.into_array());
     }
 }