From c5441acf67f0a9766fe361dd8a9e8182648e433d Mon Sep 17 00:00:00 2001
From: Eric Holk <ericholk@microsoft.com>
Date: Wed, 27 Jul 2022 14:50:11 -0700
Subject: Call destructors when dyn* object goes out of scope

---
 compiler/rustc_codegen_ssa/src/meth.rs       |  3 +--
 compiler/rustc_codegen_ssa/src/mir/block.rs  | 24 ++++++++++++++++++++++--
 compiler/rustc_codegen_ssa/src/mir/rvalue.rs | 13 ++++++++++---
 3 files changed, 33 insertions(+), 7 deletions(-)

(limited to 'compiler/rustc_codegen_ssa/src')

diff --git a/compiler/rustc_codegen_ssa/src/meth.rs b/compiler/rustc_codegen_ssa/src/meth.rs
index f6b9ddf2eea..cae46ebd2e9 100644
--- a/compiler/rustc_codegen_ssa/src/meth.rs
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -86,6 +86,7 @@ fn expect_dyn_trait_in_self<'tcx>(ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'
 /// The `trait_ref` encodes the erased self type. Hence if we are
 /// making an object `Foo<dyn Trait>` from a value of type `Foo<T>`, then
 /// `trait_ref` would map `T: Trait`.
+#[instrument(level = "debug", skip(cx))]
 pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
     cx: &Cx,
     ty: Ty<'tcx>,
@@ -93,8 +94,6 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
 ) -> Cx::Value {
     let tcx = cx.tcx();
 
-    debug!("get_vtable(ty={:?}, trait_ref={:?})", ty, trait_ref);
-
     // Check the cache.
     if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
         return val;
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index fb75ecc1735..438bb133fd1 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -16,7 +16,7 @@ use rustc_index::vec::Idx;
 use rustc_middle::mir::{self, AssertKind, SwitchTargets};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
-use rustc_middle::ty::{self, Instance, Ty, TypeVisitable, TraitObjectRepresentation};
+use rustc_middle::ty::{self, Instance, TraitObjectRepresentation, Ty, TypeVisitable};
 use rustc_span::source_map::Span;
 use rustc_span::{sym, Symbol};
 use rustc_symbol_mangling::typeid::typeid_for_fnabi;
@@ -451,7 +451,27 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
                 //
                 // SO THEN WE CAN USE THE ABOVE CODE.
-                todo!()
+                let virtual_drop = Instance {
+                    def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
+                    substs: drop_fn.substs,
+                };
+                debug!("ty = {:?}", ty);
+                debug!("drop_fn = {:?}", drop_fn);
+                debug!("args = {:?}", args);
+                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
+                let data = args[0];
+                let data_ty = bx.cx().backend_type(place.layout);
+                let vtable_ptr =
+                    bx.gep(data_ty, data, &[bx.cx().const_i32(0), bx.cx().const_i32(1)]);
+                let vtable = bx.load(bx.type_i8p(), vtable_ptr, abi::Align::ONE);
+                // Truncate vtable off of args list
+                args = &args[..1];
+                debug!("args' = {:?}", args);
+                (
+                    meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
+                        .get_fn(&mut bx, vtable, ty, &fn_abi),
+                    fn_abi,
+                )
             }
             _ => (bx.get_fn_addr(drop_fn), bx.fn_abi_of_instance(drop_fn, ty::List::empty())),
         };
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index d3c6b731de3..d68a89fe793 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -4,6 +4,7 @@ use super::{FunctionCx, LocalRef};
 
 use crate::base;
 use crate::common::{self, IntPredicate};
+use crate::meth::get_vtable;
 use crate::traits::*;
 use crate::MemFlags;
 
@@ -11,6 +12,7 @@ use rustc_middle::mir;
 use rustc_middle::mir::Operand;
 use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
+use rustc_middle::ty::TraitObjectRepresentation;
 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
 use rustc_span::source_map::{Span, DUMMY_SP};
 
@@ -271,14 +273,19 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    #[allow(unreachable_code, unused)] // FIXME: remove this
                     mir::CastKind::DynStar => {
                         let data = match operand.val {
                             OperandValue::Ref(_, _, _) => todo!(),
-                            OperandValue::Immediate(_) => todo!(),
+                            OperandValue::Immediate(v) => v,
                             OperandValue::Pair(_, _) => todo!(),
                         };
-                        let vtable = todo!();
+                        // FIXME: find the real vtable!
+                        let trait_ref = if let ty::Dynamic(data, _, TraitObjectRepresentation::Sized) = cast.ty.kind() {
+                            data.principal()
+                        } else {
+                            bug!("Only valid to do a DynStar cast into a DynStar type")
+                        };
+                        let vtable = get_vtable(bx.cx(), source.ty(self.mir, bx.tcx()), trait_ref);
                         OperandValue::Pair(data, vtable)
                     }
                     mir::CastKind::Pointer(
-- 
cgit 1.4.1-3-g733a5