intentionally use the fallback for the _dyn functions

this fails locally for me

Author: folkertdev

Diff for: compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -552,7 +552,7 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 return Ok(());
             }
 
-            _ if name.as_str().starts_with("simd_") => {
+            _ if name.as_str().starts_with("simd_") && !name.as_str().ends_with("_dyn") => {
                 // Unpack non-power-of-2 #[repr(packed, simd)] arguments.
                 // This gives them the expected layout of a regular #[repr(simd)] vector.
                 let mut loaded_args = Vec::new();