Add test for -Z panic-in-drop=abort

Author: Amanieu

src/test/codegen/panic-in-drop-abort.rs

@@ -0,0 +1,54 @@
+// compile-flags: -Z panic-in-drop=abort -O
+
+// Ensure that unwinding code paths are eliminated from the output after
+// optimization.
+
+#![crate_type = "lib"]
+use std::any::Any;
+use std::mem::forget;
+
+pub struct ExternDrop;
+impl Drop for ExternDrop {
+    #[inline(always)]
+    fn drop(&mut self) {
+        // This call may potentially unwind.
+        extern "Rust" {
+            fn extern_drop();
+        }
+        unsafe {
+            extern_drop();
+        }
+    }
+}
+
+struct AssertNeverDrop;
+impl Drop for AssertNeverDrop {
+    #[inline(always)]
+    fn drop(&mut self) {
+        // This call should be optimized away as unreachable.
+        extern "C" {
+            fn should_not_appear_in_output();
+        }
+        unsafe {
+            should_not_appear_in_output();
+        }
+    }
+}
+
+// CHECK-LABEL: normal_drop
+// CHECK-NOT: should_not_appear_in_output
+#[no_mangle]
+pub fn normal_drop(x: ExternDrop) {
+    let guard = AssertNeverDrop;
+    drop(x);
+    forget(guard);
+}
+
+// CHECK-LABEL: indirect_drop
+// CHECK-NOT: should_not_appear_in_output
+#[no_mangle]
+pub fn indirect_drop(x: Box<dyn Any>) {
+    let guard = AssertNeverDrop;
+    drop(x);
+    forget(guard);
+}