Implement dyn* support

bjorn3 · Sep 15, 2022 · 879c86f · 879c86f
1 parent f68742a
commit 879c86f
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Showing 5 changed files with 95 additions and 11 deletions.
diff --git a/src/abi/mod.rs b/src/abi/mod.rs
@@ -465,7 +465,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
             let sig = clif_sig_from_fn_abi(fx.tcx, fx.target_config.default_call_conv, &fn_abi);
             let sig = fx.bcx.import_signature(sig);
 
-            (CallTarget::Indirect(sig, method), Some(ptr))
+            (CallTarget::Indirect(sig, method), Some(ptr.get_addr(fx)))
         }
 
         // Normal call
@@ -560,7 +560,19 @@ pub(crate) fn codegen_drop<'tcx>(
         // we don't actually need to drop anything
     } else {
         match ty.kind() {
-            ty::Dynamic(..) => {
+            ty::Dynamic(_, _, ty::Dyn) => {
+                // IN THIS ARM, WE HAVE:
+                // ty = *mut (dyn Trait)
+                // which is: exists<T> ( *mut T,    Vtable<T: Trait> )
+                //                       args[0]    args[1]
+                //
+                // args = ( Data, Vtable )
+                //                  |
+                //                  v
+                //                /-------\
+                //                | ...   |
+                //                \-------/
+                //
                 let (ptr, vtable) = drop_place.to_ptr_maybe_unsized();
                 let ptr = ptr.get_addr(fx);
                 let drop_fn = crate::vtable::drop_fn_of_obj(fx, vtable.unwrap());
@@ -578,6 +590,44 @@ pub(crate) fn codegen_drop<'tcx>(
                 let sig = fx.bcx.import_signature(sig);
                 fx.bcx.ins().call_indirect(sig, drop_fn, &[ptr]);
             }
+            ty::Dynamic(_, _, ty::DynStar) => {
+                // IN THIS ARM, WE HAVE:
+                // ty = *mut (dyn* Trait)
+                // which is: *mut exists<T: sizeof(T) == sizeof(usize)> (T, Vtable<T: Trait>)
+                //
+                // args = [ * ]
+                //          |
+                //          v
+                //      ( Data, Vtable )
+                //                |
+                //                v
+                //              /-------\
+                //              | ...   |
+                //              \-------/
+                //
+                //
+                // WE CAN CONVERT THIS INTO THE ABOVE LOGIC BY DOING
+                //
+                // data = &(*args[0]).0    // gives a pointer to Data above (really the same pointer)
+                // vtable = (*args[0]).1   // loads the vtable out
+                // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
+                //
+                // SO THEN WE CAN USE THE ABOVE CODE.
+                let dyn_star = drop_place.to_cvalue(fx);
+                let (data, vtable) = dyn_star.load_scalar_pair(fx);
+                let drop_fn = crate::vtable::drop_fn_of_obj(fx, vtable);
+
+                let virtual_drop = Instance {
+                    def: ty::InstanceDef::Virtual(drop_instance.def_id(), 0),
+                    substs: drop_instance.substs,
+                };
+                let fn_abi =
+                    RevealAllLayoutCx(fx.tcx).fn_abi_of_instance(virtual_drop, ty::List::empty());
+
+                let sig = clif_sig_from_fn_abi(fx.tcx, fx.target_config.default_call_conv, &fn_abi);
+                let sig = fx.bcx.import_signature(sig);
+                fx.bcx.ins().call_indirect(sig, drop_fn, &[data]);
+            }
             _ => {
                 assert!(!matches!(drop_instance.def, InstanceDef::Virtual(_, _)));
 

diff --git a/src/base.rs b/src/base.rs
@@ -701,9 +701,9 @@ fn codegen_stmt<'tcx>(
                     let operand = codegen_operand(fx, operand);
                     operand.unsize_value(fx, lval);
                 }
-                Rvalue::Cast(CastKind::DynStar, _, _) => {
-                    // FIXME(dyn-star)
-                    unimplemented!()
+                Rvalue::Cast(CastKind::DynStar, ref operand, _) => {
+                    let operand = codegen_operand(fx, operand);
+                    operand.coerce_dyn_star(fx, lval);
                 }
                 Rvalue::Discriminant(place) => {
                     let place = codegen_place(fx, place);

diff --git a/src/unsize.rs b/src/unsize.rs
@@ -147,6 +147,22 @@ pub(crate) fn coerce_unsized_into<'tcx>(
     }
 }
 
+pub(crate) fn coerce_dyn_star<'tcx>(
+    fx: &mut FunctionCx<'_, '_, 'tcx>,
+    src: CValue<'tcx>,
+    dst: CPlace<'tcx>,
+) {
+    let data = src.load_scalar(fx);
+
+    let vtable = if let ty::Dynamic(data, _, ty::DynStar) = dst.layout().ty.kind() {
+        crate::vtable::get_vtable(fx, src.layout().ty, data.principal())
+    } else {
+        bug!("Only valid to do a DynStar cast into a DynStar type")
+    };
+
+    dst.write_cvalue(fx, CValue::by_val_pair(data, vtable, dst.layout()));
+}
+
 // Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
 
 pub(crate) fn size_and_align_of_dst<'tcx>(

diff --git a/src/value_and_place.rs b/src/value_and_place.rs
@@ -236,6 +236,10 @@ impl<'tcx> CValue<'tcx> {
         crate::unsize::coerce_unsized_into(fx, self, dest);
     }
 
+    pub(crate) fn coerce_dyn_star(self, fx: &mut FunctionCx<'_, '_, 'tcx>, dest: CPlace<'tcx>) {
+        crate::unsize::coerce_dyn_star(fx, self, dest);
+    }
+
     /// If `ty` is signed, `const_val` must already be sign extended.
     pub(crate) fn const_val(
         fx: &mut FunctionCx<'_, '_, 'tcx>,

diff --git a/src/vtable.rs b/src/vtable.rs
@@ -45,12 +45,26 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     arg: CValue<'tcx>,
     idx: usize,
-) -> (Value, Value) {
-    let (ptr, vtable) = if let Abi::ScalarPair(_, _) = arg.layout().abi {
-        arg.load_scalar_pair(fx)
-    } else {
-        let (ptr, vtable) = arg.try_to_ptr().unwrap();
-        (ptr.get_addr(fx), vtable.unwrap())
+) -> (Pointer, Value) {
+    let (ptr, vtable) = 'block: {
+        if let ty::Ref(_, ty, _) = arg.layout().ty.kind() {
+            if ty.is_dyn_star() {
+                let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap().ty);
+                let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout);
+                let ptr = dyn_star.place_field(fx, mir::Field::new(0)).to_ptr();
+                let vtable =
+                    dyn_star.place_field(fx, mir::Field::new(1)).to_cvalue(fx).load_scalar(fx);
+                break 'block (ptr, vtable);
+            }
+        }
+
+        if let Abi::ScalarPair(_, _) = arg.layout().abi {
+            let (ptr, vtable) = arg.load_scalar_pair(fx);
+            (Pointer::new(ptr), vtable)
+        } else {
+            let (ptr, vtable) = arg.try_to_ptr().unwrap();
+            (ptr, vtable.unwrap())
+        }
     };
 
     let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes();