Make dyn* have the same scalar pair ABI as corresponding fat pointer

Author: compiler-errors

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -329,7 +329,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
     ) -> &'a Type {
         // HACK(eddyb) special-case fat pointers until LLVM removes
         // pointee types, to avoid bitcasting every `OperandRef::deref`.
-        match self.ty.kind() {
+        match *self.ty.kind() {
             ty::Ref(..) | ty::RawPtr(_) => {
                 return self.field(cx, index).llvm_type(cx);
             }
@@ -339,6 +339,11 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
                 let ptr_ty = cx.tcx.mk_mut_ptr(self.ty.boxed_ty());
                 return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
             }
+            // `dyn* Trait` has the same ABI as `*mut dyn Trait`
+            ty::Dynamic(bounds, region, ty::DynStar) => {
+                let ptr_ty = cx.tcx.mk_mut_ptr(cx.tcx.mk_dynamic(bounds, region, ty::Dyn));
+                return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
+            }
             _ => {}
         }
 

tests/codegen/function-arguments.rs

@@ -281,7 +281,9 @@ pub fn enum_id_2(x: Option<u8>) -> Option<u8> {
   x
 }
 
-// CHECK: { {{i8\*|ptr}}, {{i.*\*|ptr}} } @dyn_star({{i8\*|ptr}} noundef %x.0, {{i.*\*|ptr}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}) %x.1)
+// CHECK: { {{\{\}\*|ptr}}, {{.+}} } @dyn_star({{\{\}\*|ptr}} noundef %x.0, {{.+}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}) %x.1)
+// Expect an ABI something like `{ {}*, [3 x i64]* }`, but that's hard to match on generically,
+// so do like the `trait_box` test and just match on `{{.+}}` for the vtable.
 #[no_mangle]
 pub fn dyn_star(x: dyn* Drop) -> dyn* Drop {
   x