rustc: compute FnAbi's for virtual calls through FnAbi::of_instance.

src/librustc_codegen_llvm/callee.rs

@@ -40,7 +40,7 @@ pub fn get_fn(
     let sym = tcx.symbol_name(instance).name.as_str();
     debug!("get_fn({:?}: {:?}) => {}", instance, instance.ty(cx.tcx()), sym);
 
-    let fn_abi = FnAbi::of_instance(cx, instance);
+    let fn_abi = FnAbi::of_instance(cx, instance, &[]);
 
     let llfn = if let Some(llfn) = cx.get_declared_value(&sym) {
         // Create a fn pointer with the new signature.

src/librustc_codegen_llvm/mono_item.rs

@@ -43,7 +43,7 @@ fn predefine_fn(&self,
         assert!(!instance.substs.needs_infer() &&
                 !instance.substs.has_param_types());
 
-        let fn_abi = FnAbi::of_instance(self, instance);
+        let fn_abi = FnAbi::of_instance(self, instance, &[]);
         let lldecl = self.declare_fn(symbol_name, &fn_abi);
         unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
         let attrs = self.tcx.codegen_fn_attrs(instance.def_id());