rustc_trans: use the drop glue of T instead of Box<T> in Trait's vtable, be it &Trait or Box<Trait>.

Author: eddyb

src/librustc_trans/trans/_match.rs

@@ -660,7 +660,7 @@ fn bind_subslice_pat(bcx: Block,
                      offset_right: uint) -> ValueRef {
     let _icx = push_ctxt("match::bind_subslice_pat");
     let vec_ty = node_id_type(bcx, pat_id);
-    let vt = tvec::vec_types(bcx, ty::sequence_element_type(bcx.tcx(), ty::type_content(vec_ty)));
+    let unit_ty = ty::sequence_element_type(bcx.tcx(), ty::type_content(vec_ty));
     let vec_datum = match_datum(val, vec_ty);
     let (base, len) = vec_datum.get_vec_base_and_len(bcx);
 
@@ -669,7 +669,7 @@ fn bind_subslice_pat(bcx: Block,
     let slice_len = Sub(bcx, len, slice_len_offset, DebugLoc::None);
     let slice_ty = ty::mk_slice(bcx.tcx(),
                                 bcx.tcx().mk_region(ty::ReStatic),
-                                ty::mt {ty: vt.unit_ty, mutbl: ast::MutImmutable});
+                                ty::mt {ty: unit_ty, mutbl: ast::MutImmutable});
     let scratch = rvalue_scratch_datum(bcx, slice_ty, "");
     Store(bcx, slice_begin,
           GEPi(bcx, scratch.val, &[0, abi::FAT_PTR_ADDR]));

src/librustc_trans/trans/base.rs

@@ -702,6 +702,10 @@ pub fn iter_structural_ty<'blk, 'tcx, F>(cx: Block<'blk, 'tcx>,
         let unit_ty = ty::sequence_element_type(cx.tcx(), t);
         cx = tvec::iter_vec_raw(cx, base, unit_ty, len, f);
       }
+      ty::ty_vec(_, None) | ty::ty_str => {
+        let unit_ty = ty::sequence_element_type(cx.tcx(), t);
+        cx = tvec::iter_vec_raw(cx, data_ptr, unit_ty, info.unwrap(), f);
+      }
       ty::ty_tup(ref args) => {
           let repr = adt::represent_type(cx.ccx(), t);
           for (i, arg) in args.iter().enumerate() {

src/librustc_trans/trans/consts.rs

@@ -314,7 +314,6 @@ pub fn const_expr<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
                     let info =
                         expr::unsized_info(
                             cx, k, e.id, ty, param_substs,
-                            |t| ty::mk_imm_rptr(cx.tcx(), cx.tcx().mk_region(ty::ReStatic), t),
                             || const_get_elt(cx, llconst, &[abi::FAT_PTR_EXTRA as u32]));
 
                     let unsized_ty = ty::unsize_ty(cx.tcx(), ty, k, e.span);

src/librustc_trans/trans/context.rs

@@ -102,7 +102,7 @@ pub struct LocalCrateContext<'tcx> {
     monomorphized: RefCell<FnvHashMap<MonoId<'tcx>, ValueRef>>,
     monomorphizing: RefCell<DefIdMap<uint>>,
     /// Cache generated vtables
-    vtables: RefCell<FnvHashMap<(Ty<'tcx>, ty::PolyTraitRef<'tcx>), ValueRef>>,
+    vtables: RefCell<FnvHashMap<ty::PolyTraitRef<'tcx>, ValueRef>>,
     /// Cache of constant strings,
     const_cstr_cache: RefCell<FnvHashMap<InternedString, ValueRef>>,
 
@@ -614,8 +614,7 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
         &self.local.monomorphizing
     }
 
-    pub fn vtables<'a>(&'a self) -> &'a RefCell<FnvHashMap<(Ty<'tcx>, ty::PolyTraitRef<'tcx>),
-                                                            ValueRef>> {
+    pub fn vtables<'a>(&'a self) -> &'a RefCell<FnvHashMap<ty::PolyTraitRef<'tcx>, ValueRef>> {
         &self.local.vtables
     }
 

src/librustc_trans/trans/expr.rs

@@ -288,64 +288,47 @@ pub fn get_dataptr(bcx: Block, fat_ptr: ValueRef) -> ValueRef {
 // Retrieve the information we are losing (making dynamic) in an unsizing
 // adjustment.
 //
-// When making a dtor, we need to do different things depending on the
-// ownership of the object.. mk_ty is a function for turning `unadjusted_ty`
-// into a type to be destructed. If we want to end up with a Box pointer,
-// then mk_ty should make a Box pointer (T -> Box<T>), if we want a
-// borrowed reference then it should be T -> &T.
-//
 // The `unadjusted_val` argument is a bit funny. It is intended
 // for use in an upcast, where the new vtable for an object will
 // be drived from the old one. Hence it is a pointer to the fat
 // pointer.
-pub fn unsized_info_bcx<'blk, 'tcx, F>(bcx: Block<'blk, 'tcx>,
-                                       kind: &ty::UnsizeKind<'tcx>,
-                                       id: ast::NodeId,
-                                       unadjusted_ty: Ty<'tcx>,
-                                       unadjusted_val: ValueRef, // see above (*)
-                                       param_substs: &'tcx subst::Substs<'tcx>,
-                                       mk_ty: F)
-                                       -> ValueRef
-    where F: FnOnce(Ty<'tcx>) -> Ty<'tcx>
-{
+pub fn unsized_info_bcx<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
+                                    kind: &ty::UnsizeKind<'tcx>,
+                                    id: ast::NodeId,
+                                    unadjusted_ty: Ty<'tcx>,
+                                    unadjusted_val: ValueRef, // see above (*)
+                                    param_substs: &'tcx subst::Substs<'tcx>)
+                                    -> ValueRef {
     unsized_info(
         bcx.ccx(),
         kind,
         id,
         unadjusted_ty,
         param_substs,
-        mk_ty,
         || Load(bcx, GEPi(bcx, unadjusted_val, &[0, abi::FAT_PTR_EXTRA])))
 }
 
 // Same as `unsize_info_bcx`, but does not require a bcx -- instead it
 // takes an extra closure to compute the upcast vtable.
-pub fn unsized_info<'ccx, 'tcx, MK_TY, MK_UPCAST_VTABLE>(
+pub fn unsized_info<'ccx, 'tcx, MK_UPCAST_VTABLE>(
     ccx: &CrateContext<'ccx, 'tcx>,
     kind: &ty::UnsizeKind<'tcx>,
     id: ast::NodeId,
     unadjusted_ty: Ty<'tcx>,
     param_substs: &'tcx subst::Substs<'tcx>,
-    mk_ty: MK_TY,
     mk_upcast_vtable: MK_UPCAST_VTABLE) // see notes above
     -> ValueRef
-    where MK_TY: FnOnce(Ty<'tcx>) -> Ty<'tcx>,
-          MK_UPCAST_VTABLE: FnOnce() -> ValueRef,
+    where MK_UPCAST_VTABLE: FnOnce() -> ValueRef
 {
-    // FIXME(#19596) workaround: `|t| t` causes monomorphization recursion
-    fn identity<T>(t: T) -> T { t }
-
     debug!("unsized_info(kind={:?}, id={}, unadjusted_ty={})",
            kind, id, unadjusted_ty.repr(ccx.tcx()));
     match kind {
         &ty::UnsizeLength(len) => C_uint(ccx, len),
         &ty::UnsizeStruct(box ref k, tp_index) => match unadjusted_ty.sty {
             ty::ty_struct(_, ref substs) => {
                 let ty_substs = substs.types.get_slice(subst::TypeSpace);
-                // The dtor for a field treats it like a value, so mk_ty
-                // should just be the identity function.
                 unsized_info(ccx, k, id, ty_substs[tp_index], param_substs,
-                             identity, mk_upcast_vtable)
+                             mk_upcast_vtable)
             }
             _ => ccx.sess().bug(&format!("UnsizeStruct with bad sty: {}",
                                          unadjusted_ty.repr(ccx.tcx())))
@@ -359,8 +342,7 @@ pub fn unsized_info<'ccx, 'tcx, MK_TY, MK_UPCAST_VTABLE>(
             let trait_ref = monomorphize::apply_param_substs(ccx.tcx(),
                                                              param_substs,
                                                              &trait_ref);
-            let box_ty = mk_ty(unadjusted_ty);
-            consts::ptrcast(meth::get_vtable(ccx, box_ty, trait_ref, param_substs),
+            consts::ptrcast(meth::get_vtable(ccx, trait_ref, param_substs),
                             Type::vtable_ptr(ccx))
         }
         &ty::UnsizeUpcast(_) => {
@@ -498,8 +480,7 @@ fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         let unsized_ty = ty::unsize_ty(tcx, datum_ty, k, expr.span);
         debug!("unsized_ty={}", unsized_ty.repr(bcx.tcx()));
 
-        let info = unsized_info_bcx(bcx, k, expr.id, datum_ty, datum.val, bcx.fcx.param_substs,
-                                    |t| ty::mk_imm_rptr(tcx, tcx.mk_region(ty::ReStatic), t));
+        let info = unsized_info_bcx(bcx, k, expr.id, datum_ty, datum.val, bcx.fcx.param_substs);
 
         // Arrange cleanup
         let lval = unpack_datum!(bcx, datum.to_lvalue_datum(bcx, "into_fat_ptr", expr.id));
@@ -590,8 +571,7 @@ fn apply_adjustments<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         let base = PointerCast(bcx, get_dataptr(bcx, scratch.val), llbox_ty.ptr_to());
         bcx = datum.store_to(bcx, base);
 
-        let info = unsized_info_bcx(bcx, k, expr.id, unboxed_ty, base, bcx.fcx.param_substs,
-                                    |t| ty::mk_uniq(tcx, t));
+        let info = unsized_info_bcx(bcx, k, expr.id, unboxed_ty, base, bcx.fcx.param_substs);
         Store(bcx, info, get_len(bcx, scratch.val));
 
         DatumBlock::new(bcx, scratch.to_expr_datum())
@@ -888,10 +868,7 @@ fn trans_index<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                 }
             };
 
-            let vt =
-                tvec::vec_types(bcx,
-                                ty::sequence_element_type(bcx.tcx(),
-                                                          base_datum.ty));
+            let unit_ty = ty::sequence_element_type(bcx.tcx(), base_datum.ty);
 
             let (base, len) = base_datum.get_vec_base_and_len(bcx);
 
@@ -916,8 +893,8 @@ fn trans_index<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
                                                      len)
             });
             let elt = InBoundsGEP(bcx, base, &[ix_val]);
-            let elt = PointerCast(bcx, elt, vt.llunit_ty.ptr_to());
-            Datum::new(elt, vt.unit_ty, LvalueExpr)
+            let elt = PointerCast(bcx, elt, type_of::type_of(ccx, unit_ty).ptr_to());
+            Datum::new(elt, unit_ty, LvalueExpr)
         }
     };
 

src/librustc_trans/trans/glue.rs

@@ -32,7 +32,6 @@ use trans::datum;
 use trans::debuginfo::DebugLoc;
 use trans::expr;
 use trans::machine::*;
-use trans::tvec;
 use trans::type_::Type;
 use trans::type_of::{self, type_of, sizing_type_of, align_of};
 use middle::ty::{self, Ty};
@@ -386,51 +385,34 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
     let _icx = push_ctxt("make_drop_glue");
     match t.sty {
         ty::ty_uniq(content_ty) => {
-            match content_ty.sty {
-                ty::ty_vec(ty, None) => {
-                    tvec::make_drop_glue_unboxed(bcx, v0, ty, true)
-                }
-                ty::ty_str => {
-                    let unit_ty = ty::sequence_element_type(bcx.tcx(), content_ty);
-                    tvec::make_drop_glue_unboxed(bcx, v0, unit_ty, true)
-                }
-                ty::ty_trait(..) => {
-                    let lluniquevalue = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
-                    // Only drop the value when it is non-null
-                    let concrete_ptr = Load(bcx, lluniquevalue);
-                    with_cond(bcx, IsNotNull(bcx, concrete_ptr), |bcx| {
-                        let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
-                        let dtor = Load(bcx, dtor_ptr);
-                        Call(bcx,
-                             dtor,
-                             &[PointerCast(bcx, lluniquevalue, Type::i8p(bcx.ccx()))],
-                             None,
-                             DebugLoc::None);
-                        bcx
-                    })
-                }
-                ty::ty_struct(..) if !type_is_sized(bcx.tcx(), content_ty) => {
-                    let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
-                    let llbox = Load(bcx, llval);
-                    let not_null = IsNotNull(bcx, llbox);
-                    with_cond(bcx, not_null, |bcx| {
-                        let bcx = drop_ty(bcx, v0, content_ty, DebugLoc::None);
-                        let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
-                        let info = Load(bcx, info);
-                        let (llsize, llalign) = size_and_align_of_dst(bcx, content_ty, info);
+            if !type_is_sized(bcx.tcx(), content_ty) {
+                let llval = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
+                let llbox = Load(bcx, llval);
+                let not_null = IsNotNull(bcx, llbox);
+                with_cond(bcx, not_null, |bcx| {
+                    let bcx = drop_ty(bcx, v0, content_ty, DebugLoc::None);
+                    let info = GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]);
+                    let info = Load(bcx, info);
+                    let (llsize, llalign) = size_and_align_of_dst(bcx, content_ty, info);
+
+                    // `Box<ZeroSizeType>` does not allocate.
+                    let needs_free = ICmp(bcx,
+                                          llvm::IntNE,
+                                          llsize,
+                                          C_uint(bcx.ccx(), 0u64),
+                                          DebugLoc::None);
+                    with_cond(bcx, needs_free, |bcx| {
                         trans_exchange_free_dyn(bcx, llbox, llsize, llalign, DebugLoc::None)
                     })
-                }
-                _ => {
-                    assert!(type_is_sized(bcx.tcx(), content_ty));
-                    let llval = v0;
-                    let llbox = Load(bcx, llval);
-                    let not_null = IsNotNull(bcx, llbox);
-                    with_cond(bcx, not_null, |bcx| {
-                        let bcx = drop_ty(bcx, llbox, content_ty, DebugLoc::None);
-                        trans_exchange_free_ty(bcx, llbox, content_ty, DebugLoc::None)
-                    })
-                }
+                })
+            } else {
+                let llval = v0;
+                let llbox = Load(bcx, llval);
+                let not_null = IsNotNull(bcx, llbox);
+                with_cond(bcx, not_null, |bcx| {
+                    let bcx = drop_ty(bcx, llbox, content_ty, DebugLoc::None);
+                    trans_exchange_free_ty(bcx, llbox, content_ty, DebugLoc::None)
+                })
             }
         }
         ty::ty_struct(did, substs) | ty::ty_enum(did, substs) => {
@@ -462,34 +444,19 @@ fn make_drop_glue<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, v0: ValueRef, t: Ty<'tcx>)
                 }
             }
         }
-        ty::ty_closure(..) => {
-            iter_structural_ty(bcx,
-                               v0,
-                               t,
-                               |bb, vv, tt| drop_ty(bb, vv, tt, DebugLoc::None))
-        }
         ty::ty_trait(..) => {
-            // No need to do a null check here (as opposed to the Box<trait case
-            // above), because this happens for a trait field in an unsized
-            // struct. If anything is null, it is the whole struct and we won't
-            // get here.
-            let lluniquevalue = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
-            let dtor_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
-            let dtor = Load(bcx, dtor_ptr);
+            let data_ptr = GEPi(bcx, v0, &[0, abi::FAT_PTR_ADDR]);
+            let vtable_ptr = Load(bcx, GEPi(bcx, v0, &[0, abi::FAT_PTR_EXTRA]));
+            let dtor = Load(bcx, vtable_ptr);
             Call(bcx,
                  dtor,
-                 &[PointerCast(bcx, Load(bcx, lluniquevalue), Type::i8p(bcx.ccx()))],
+                 &[PointerCast(bcx, Load(bcx, data_ptr), Type::i8p(bcx.ccx()))],
                  None,
                  DebugLoc::None);
             bcx
-        },
-        ty::ty_vec(_, None) | ty::ty_str => {
-            let unit_ty = ty::sequence_element_type(bcx.tcx(), t);
-            tvec::make_drop_glue_unboxed(bcx, v0, unit_ty, false)
-        },
+        }
         _ => {
-            assert!(type_is_sized(bcx.tcx(), t));
-            if bcx.fcx.type_needs_drop(t) && ty::type_is_structural(t) {
+            if bcx.fcx.type_needs_drop(t) {
                 iter_structural_ty(bcx,
                                    v0,
                                    t,

src/librustc_trans/trans/meth.rs

@@ -680,25 +680,19 @@ pub fn trans_object_shim<'a, 'tcx>(
 ///
 /// The `trait_ref` encodes the erased self type. Hence if we are
 /// making an object `Foo<Trait>` from a value of type `Foo<T>`, then
-/// `trait_ref` would map `T:Trait`, but `box_ty` would be
-/// `Foo<T>`. This `box_ty` is primarily used to encode the destructor.
-/// This will hopefully change now that DST is underway.
+/// `trait_ref` would map `T:Trait`.
 pub fn get_vtable<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
-                            box_ty: Ty<'tcx>,
                             trait_ref: ty::PolyTraitRef<'tcx>,
                             param_substs: &'tcx subst::Substs<'tcx>)
                             -> ValueRef
 {
     let tcx = ccx.tcx();
     let _icx = push_ctxt("meth::get_vtable");
 
-    debug!("get_vtable(box_ty={}, trait_ref={})",
-           box_ty.repr(tcx),
-           trait_ref.repr(tcx));
+    debug!("get_vtable(trait_ref={})", trait_ref.repr(tcx));
 
     // Check the cache.
-    let cache_key = (box_ty, trait_ref.clone());
-    match ccx.vtables().borrow().get(&cache_key) {
+    match ccx.vtables().borrow().get(&trait_ref) {
         Some(&val) => { return val }
         None => { }
     }
@@ -755,15 +749,15 @@ pub fn get_vtable<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
     let components: Vec<_> = vec![
         // Generate a destructor for the vtable.
-        glue::get_drop_glue(ccx, box_ty),
+        glue::get_drop_glue(ccx, trait_ref.self_ty()),
         C_uint(ccx, size),
         C_uint(ccx, align)
     ].into_iter().chain(methods).collect();
 
     let vtable = consts::addr_of(ccx, C_struct(ccx, &components, false),
                                  "vtable", trait_ref.def_id().node);
 
-    ccx.vtables().borrow_mut().insert(cache_key, vtable);
+    ccx.vtables().borrow_mut().insert(trait_ref, vtable);
     vtable
 }
 
@@ -842,16 +836,15 @@ pub fn trans_trait_cast<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
     debug!("trans_trait_cast: trait_ref={}",
            trait_ref.repr(bcx.tcx()));
 
-    let datum_ty = datum.ty;
-    let llbox_ty = type_of(bcx.ccx(), datum_ty);
+    let llty = type_of(bcx.ccx(), datum.ty);
 
     // Store the pointer into the first half of pair.
     let llboxdest = GEPi(bcx, lldest, &[0, abi::FAT_PTR_ADDR]);
-    let llboxdest = PointerCast(bcx, llboxdest, llbox_ty.ptr_to());
+    let llboxdest = PointerCast(bcx, llboxdest, llty.ptr_to());
     bcx = datum.store_to(bcx, llboxdest);
 
     // Store the vtable into the second half of pair.
-    let vtable = get_vtable(bcx.ccx(), datum_ty, trait_ref, bcx.fcx.param_substs);
+    let vtable = get_vtable(bcx.ccx(), trait_ref, bcx.fcx.param_substs);
     let llvtabledest = GEPi(bcx, lldest, &[0, abi::FAT_PTR_EXTRA]);
     let llvtabledest = PointerCast(bcx, llvtabledest, val_ty(vtable).ptr_to());
     Store(bcx, vtable, llvtabledest);