fix and test attribute on extern declarations and functions

Author: RalfJung

src/librustc_codegen_llvm/attributes.rs

@@ -271,11 +271,7 @@ pub fn from_fn_attrs(
         false
     } else if let Some(id) = id {
         let sig = cx.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &sig);
-        if cx.tcx.is_foreign_item(id) {
-            // Foreign items like `extern "C" { fn foo(); }` and `extern "Rust" { fn bar(); }`
-            // are assumed not to unwind.
-            false
-        } else if cx.tcx.abort_on_panic_shim(id, sig.abi) {
+        if cx.tcx.abort_on_panic_shim(id, sig.abi) {
             // Since we are adding a shim to abort on panic, this cannot unwind.
             false
         } else {

src/test/codegen/extern-functions.rs

@@ -4,17 +4,17 @@
 #![feature(unwind_attributes)]
 
 extern {
-// CHECK: Function Attrs: nounwind
-// CHECK-NEXT: declare void @extern_fn
-    fn extern_fn(); // assumed not to unwind
+// CHECK-NOT: nounwind
+// CHECK: declare void @extern_fn
+    fn extern_fn();
 // CHECK-NOT: nounwind
 // CHECK: declare void @unwinding_extern_fn
     #[unwind(allowed)]
     fn unwinding_extern_fn();
-// CHECK-NOT: nounwind
-// CHECK: declare void @aborting_extern_fn
+// CHECK: Function Attrs: nounwind
+// CHECK-NEXT: declare void @aborting_extern_fn
     #[unwind(aborts)]
-    fn aborting_extern_fn(); // FIXME: we don't have the attribute here
+    fn aborting_extern_fn();
 }
 
 extern "Rust" {
@@ -25,10 +25,10 @@ extern "Rust" {
 // CHECK: declare void @rust_unwinding_extern_fn
     #[unwind(allowed)]
     fn rust_unwinding_extern_fn();
-// CHECK-NOT: nounwind
-// CHECK: declare void @rust_aborting_extern_fn
+// CHECK: Function Attrs: nounwind
+// CHECK-NEXT: declare void @rust_aborting_extern_fn
     #[unwind(aborts)]
-    fn rust_aborting_extern_fn(); // FIXME: we don't have the attribute here
+    fn rust_aborting_extern_fn();
 }
 
 pub unsafe fn force_declare() {