use codegen_unimplemented() for the try intrinsic (rust-lang#275)

* use codegen_unimplemented() for the try intrinsic

* Additional unit test

Author: danielsn

compiler/rustc_codegen_llvm/src/gotoc/intrinsic.rs

@@ -42,6 +42,14 @@ impl<'tcx> GotocCtx<'tcx> {
         let intrinsic = self.symbol_name(instance);
         let intrinsic = intrinsic.as_str();
         let loc = self.codegen_span_option2(span);
+        debug!(
+            "codegen_intrinsic:\n\tinstance {:?}\n\tfargs {:?}\n\tp {:?}\n\tspan {:?}",
+            instance, fargs, p, span
+        );
+        let sig = instance.ty(self.tcx, ty::ParamEnv::reveal_all()).fn_sig(self.tcx);
+        let sig = self.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig);
+        let ret_ty = self.monomorphize(sig.output());
+        let cbmc_ret_ty = self.codegen_ty(ret_ty);
 
         /// https://doc.rust-lang.org/core/intrinsics/fn.copy.html
         /// https://doc.rust-lang.org/core/intrinsics/fn.copy_nonoverlapping.html
@@ -171,6 +179,13 @@ impl<'tcx> GotocCtx<'tcx> {
             }};
         }
 
+        macro_rules! codegen_unimplemented_intrinsic {
+            ($url: expr) => {{
+                let e = self.codegen_unimplemented(intrinsic, cbmc_ret_ty, loc, $url);
+                self.codegen_expr_to_place(p, e)
+            }};
+        }
+
         // Most atomic intrinsics do:
         //   1. Perform an operation on a primary argument (e.g., addition)
         //   2. Return the previous value of the primary argument
@@ -202,14 +217,6 @@ impl<'tcx> GotocCtx<'tcx> {
             }};
         }
 
-        debug!(
-            "codegen_intrinsic:\n\tinstance {:?}\n\tfargs {:?}\n\tp {:?}\n\tspan {:?}",
-            instance, fargs, p, span
-        );
-        let sig = instance.ty(self.tcx, ty::ParamEnv::reveal_all()).fn_sig(self.tcx);
-        let sig = self.tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig);
-        let ret_ty = self.monomorphize(sig.output());
-
         match intrinsic {
             "abort" => Stmt::assert_false("abort intrinsic", loc),
             "add_with_overflow" => codegen_op_with_overflow!(add_overflow),
@@ -394,6 +401,9 @@ impl<'tcx> GotocCtx<'tcx> {
             "transmute" => self.codegen_intrinsic_transmute(fargs, ret_ty, p),
             "truncf32" => codegen_simple_intrinsic!(Truncf),
             "truncf64" => codegen_simple_intrinsic!(Trunc),
+            "try" => {
+                codegen_unimplemented_intrinsic!("https://github.com/model-checking/rmc/issues/267")
+            }
             "type_id" => codegen_intrinsic_const!(),
             "type_name" => codegen_intrinsic_const!(),
             "unaligned_volatile_load" => {

compiler/rustc_codegen_llvm/src/gotoc/rvalue.rs

@@ -628,7 +628,15 @@ impl<'tcx> GotocCtx<'tcx> {
         match k {
             PointerCast::ReifyFnPointer => self.codegen_operand(o).address_of(),
             PointerCast::UnsafeFnPointer => self.codegen_operand(o),
-            PointerCast::ClosureFnPointer(_) => unimplemented!(),
+            PointerCast::ClosureFnPointer(_) => {
+                let dest_typ = self.codegen_ty(t);
+                self.codegen_unimplemented(
+                    "PointerCast::ClosureFnPointer",
+                    dest_typ,
+                    Location::none(),
+                    "https://github.com/model-checking/rmc/issues/274",
+                )
+            }
             PointerCast::MutToConstPointer => self.codegen_operand(o),
             PointerCast::ArrayToPointer => {
                 // TODO: I am not sure whether it is correct or not.

src/test/cbmc/Intrinsics/fixme_catch_unwind.rs

@@ -0,0 +1,18 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// https://doc.rust-lang.org/std/panic/fn.catch_unwind.html
+// Stable way of calling the `try` intrinsic.
+use std::panic;
+
+fn main() {
+    let result = panic::catch_unwind(|| {
+        println!("hello!");
+    });
+    assert!(result.is_ok());
+
+    let result = panic::catch_unwind(|| {
+        panic!("oh no!");
+    });
+    assert!(result.is_err());
+}

src/test/cbmc/Intrinsics/fixme_try.rs

@@ -0,0 +1,18 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// See discussion on https://github.com/model-checking/rmc/issues/267
+#![feature(core_intrinsics)]
+use std::intrinsics::r#try;
+
+fn main() {
+    unsafe {
+        // Rust will make a best-effort to swallow the panic, and then execute the cleanup function.
+        // However, my understanding is that failure is still possible, since its just a best-effort
+        r#try(
+            |_a: *mut u8| panic!("foo"),
+            std::ptr::null_mut(),
+            |_a: *mut u8, _b: *mut u8| println!("bar"),
+        );
+    }
+}