Have arrays' drop_glue just unsize and call the slice version

compiler/rustc_codegen_cranelift/example/mini_core.rs

@@ -550,14 +550,10 @@ unsafe extern "C" {
     fn _Unwind_Resume(exc: *mut ()) -> !;
 }
 
-#[lang = "drop_in_place"]
-#[allow(unconditional_recursion)]
-pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
+#[lang = "drop_glue"]
+pub unsafe fn drop_glue<T: ?Sized>(_to_drop: &mut T) {
     // Code here does not matter - this is replaced by the
     // real drop glue by the compiler.
-    unsafe {
-        drop_in_place(to_drop);
-    }
 }
 
 #[lang = "unpin"]

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -701,7 +701,7 @@ pub(crate) fn codegen_drop<'tcx>(
     unwind: UnwindAction,
 ) {
     let ty = drop_place.layout().ty;
-    let drop_instance = Instance::resolve_drop_in_place(fx.tcx, ty);
+    let drop_instance = Instance::resolve_drop_glue(fx.tcx, ty);
     let ret_block = fx.get_block(target);
 
     // AsyncDropGlueCtorShim can't be here
@@ -734,7 +734,7 @@ pub(crate) fn codegen_drop<'tcx>(
                 fx.bcx.switch_to_block(continued);
 
                 // FIXME(eddyb) perhaps move some of this logic into
-                // `Instance::resolve_drop_in_place`?
+                // `Instance::resolve_drop_glue`?
                 let virtual_drop = Instance {
                     def: ty::InstanceKind::Virtual(drop_instance.def_id(), 0),
                     args: drop_instance.args,

compiler/rustc_codegen_gcc/example/mini_core.rs

@@ -552,12 +552,10 @@ fn eh_personality() -> ! {
     loop {}
 }
 
-#[lang = "drop_in_place"]
-#[allow(unconditional_recursion)]
-pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
+#[lang = "drop_glue"]
+pub unsafe fn drop_glue<T: ?Sized>(_to_drop: &mut T) {
     // Code here does not matter - this is replaced by the
     // real drop glue by the compiler.
-    drop_in_place(to_drop);
 }
 
 #[lang = "unpin"]

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -403,19 +403,18 @@ fn upstream_monomorphizations_provider(
 
     let mut instances: DefIdMap<UnordMap<_, _>> = Default::default();
 
-    let drop_in_place_fn_def_id = tcx.lang_items().drop_in_place_fn();
+    let drop_glue_fn_def_id = tcx.lang_items().drop_glue_fn();
     let async_drop_in_place_fn_def_id = tcx.lang_items().async_drop_in_place_fn();
 
     for &cnum in cnums.iter() {
         for (exported_symbol, _) in tcx.exported_generic_symbols(cnum).iter() {
             let (def_id, args) = match *exported_symbol {
                 ExportedSymbol::Generic(def_id, args) => (def_id, args),
                 ExportedSymbol::DropGlue(ty) => {
-                    if let Some(drop_in_place_fn_def_id) = drop_in_place_fn_def_id {
+                    if let Some(drop_in_place_fn_def_id) = drop_glue_fn_def_id {
                         (drop_in_place_fn_def_id, tcx.mk_args(&[ty.into()]))
                     } else {
-                        // `drop_in_place` in place does not exist, don't try
-                        // to use it.
+                        // `drop_glue` does not exist, don't try to use it.
                         continue;
                     }
                 }
@@ -465,7 +464,7 @@ fn upstream_drop_glue_for_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
     args: GenericArgsRef<'tcx>,
 ) -> Option<CrateNum> {
-    let def_id = tcx.lang_items().drop_in_place_fn()?;
+    let def_id = tcx.lang_items().drop_glue_fn()?;
     tcx.upstream_monomorphizations_for(def_id)?.get(&args).cloned()
 }
 
@@ -587,7 +586,7 @@ pub(crate) fn symbol_name_for_instance_in_crate<'tcx>(
         }
         ExportedSymbol::DropGlue(ty) => rustc_symbol_mangling::symbol_name_for_instance_in_crate(
             tcx,
-            Instance::resolve_drop_in_place(tcx, ty),
+            Instance::resolve_drop_glue(tcx, ty),
             instantiating_crate,
         ),
         ExportedSymbol::AsyncDropGlueCtorShim(ty) => {

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -604,7 +604,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> MergingSucc {
         let ty = location.ty(self.mir, bx.tcx()).ty;
         let ty = self.monomorphize(ty);
-        let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
+        let drop_fn = Instance::resolve_drop_glue(bx.tcx(), ty);
 
         if let ty::InstanceKind::DropGlue(_, None) = drop_fn.def {
             // we don't actually need to drop anything.
@@ -622,7 +622,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         };
         let (maybe_null, drop_fn, fn_abi, drop_instance) = match ty.kind() {
             // FIXME(eddyb) perhaps move some of this logic into
-            // `Instance::resolve_drop_in_place`?
+            // `Instance::resolve_drop_glue`?
             ty::Dynamic(_, _) => {
                 // IN THIS ARM, WE HAVE:
                 // ty = *mut (dyn Trait)

compiler/rustc_const_eval/src/interpret/call.rs

@@ -886,19 +886,21 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             _ => {
                 debug_assert_eq!(
                     instance,
-                    ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty)
+                    ty::Instance::resolve_drop_glue(*self.tcx, place.layout.ty)
                 );
                 place
             }
         };
+
         let instance = {
-            let _trace =
-                enter_trace_span!(M, resolve::resolve_drop_in_place, ty = ?place.layout.ty);
-            ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty)
+            let _trace = enter_trace_span!(M, resolve::resolve_drop_glue, ty = ?place.layout.ty);
+            ty::Instance::resolve_drop_glue(*self.tcx, place.layout.ty)
         };
         let fn_abi = self.fn_abi_of_instance_no_deduced_attrs(instance, ty::List::empty())?;
 
-        let arg = self.mplace_to_imm_ptr(&place, None)?;
+        let ref_ty = Ty::new_mut_ref(self.tcx.tcx, self.tcx.lifetimes.re_erased, place.layout.ty);
+        let arg = self.mplace_to_imm_ptr(&place, Some(ref_ty))?;
+
         let ret = MPlaceTy::fake_alloc_zst(self.layout_of(self.tcx.types.unit)?);
 
         self.init_fn_call(

compiler/rustc_const_eval/src/interpret/step.rs

@@ -583,8 +583,8 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let place = self.eval_place(place)?;
                 let instance = {
                     let _trace =
-                        enter_trace_span!(M, resolve::resolve_drop_in_place, ty = ?place.layout.ty);
-                    Instance::resolve_drop_in_place(*self.tcx, place.layout.ty)
+                        enter_trace_span!(M, resolve::resolve_drop_glue, ty = ?place.layout.ty);
+                    Instance::resolve_drop_glue(*self.tcx, place.layout.ty)
                 };
                 if let ty::InstanceKind::DropGlue(_, None) = instance.def {
                     // This is the branch we enter if and only if the dropped type has no drop glue

compiler/rustc_hir/src/lang_items.rs

@@ -320,7 +320,8 @@ language_item_table! {
     FormatArgument,          sym::format_argument,     format_argument,            Target::Struct,         GenericRequirement::None;
     FormatArguments,         sym::format_arguments,    format_arguments,           Target::Struct,         GenericRequirement::None;
 
-    DropInPlace,             sym::drop_in_place,       drop_in_place_fn,           Target::Fn,             GenericRequirement::Minimum(1);
+    // Compiler-generated drop glue function, aka `core::ptr::drop_glue`
+    DropGlue,                sym::drop_glue,           drop_glue_fn,               Target::Fn,             GenericRequirement::Exact(1);
     AllocLayout,             sym::alloc_layout,        alloc_layout,               Target::Struct,         GenericRequirement::None;
 
     /// For all binary crates without `#![no_main]`, Rust will generate a "main" function.

compiler/rustc_middle/src/hir/mod.rs

@@ -315,8 +315,8 @@ impl<'tcx> TyCtxt<'tcx> {
             Node::Expr(parent_expr) => {
                 match parent_expr.kind {
                     // Addr-of, field projections, and LHS of assignment don't constitute reads.
-                    // Assignment does call `drop_in_place`, though, but its safety
-                    // requirements are not the same.
+                    // Assignment does call `drop_glue`, though, but its safety requirements are
+                    // not the same.
                     ExprKind::AddrOf(..) | ExprKind::Field(..) => false,
 
                     // Place-preserving expressions only constitute reads if their

compiler/rustc_middle/src/middle/exported_symbols.rs

@@ -66,7 +66,7 @@ impl<'tcx> ExportedSymbol<'tcx> {
                 tcx.symbol_name(ty::Instance::new_raw(def_id, args))
             }
             ExportedSymbol::DropGlue(ty) => {
-                tcx.symbol_name(ty::Instance::resolve_drop_in_place(tcx, ty))
+                tcx.symbol_name(ty::Instance::resolve_drop_glue(tcx, ty))
             }
             ExportedSymbol::AsyncDropGlueCtorShim(ty) => {
                 tcx.symbol_name(ty::Instance::resolve_async_drop_in_place(tcx, ty))

compiler/rustc_middle/src/mir/syntax.rs

@@ -753,7 +753,7 @@ pub enum TerminatorKind<'tcx> {
     ///
     /// After drop elaboration: `Drop` terminators are a complete nop for types that have no drop
     /// glue. For other types, `Drop` terminators behave exactly like a call to
-    /// `core::mem::drop_in_place` with a pointer to the given place.
+    /// `core::mem::drop_glue` with a reference to the given place.
     ///
     /// `Drop` before drop elaboration is a *conditional* execution of the drop glue. Specifically,
     /// the `Drop` will be executed if...

compiler/rustc_middle/src/mono.rs

@@ -69,7 +69,7 @@ fn opt_incr_drop_glue_mode<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Instantiati
     let Some(dtor) = adt_def.destructor(tcx) else {
         // We use LocalCopy for drops of enums only; this code is inherited from
         // https://github.com/rust-lang/rust/pull/67332 and the theory is that we get to optimize
-        // out code like drop_in_place(Option::None) before crate-local ThinLTO, which improves
+        // out code like `drop_glue(&mut Option::None)` before crate-local ThinLTO, which improves
         // compile time. At the time of writing, simply removing this entire check does seem to
         // regress incr-opt compile times. But it sure seems like a more sophisticated check could
         // do better here.
@@ -80,8 +80,8 @@ fn opt_incr_drop_glue_mode<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Instantiati
         }
     };
 
-    // We've gotten to a drop_in_place for a type that directly implements Drop.
-    // The drop glue is a wrapper for the Drop::drop impl, and we are an optimized build, so in an
+    // We've gotten to a `drop_glue` for a type that directly implements Drop.
+    // The drop glue is a wrapper for the `Drop::drop` impl, and we are an optimized build, so in an
     // effort to coordinate with the mode that the actual impl will get, we make the glue also
     // LocalCopy.
     if tcx.cross_crate_inlinable(dtor.did) {

compiler/rustc_middle/src/ty/instance.rs

@@ -147,11 +147,10 @@ pub enum InstanceKind<'tcx> {
     /// Proxy shim for async drop of future (def_id, proxy_cor_ty, impl_cor_ty)
     FutureDropPollShim(DefId, Ty<'tcx>, Ty<'tcx>),
 
-    /// `core::ptr::drop_in_place::<T>`.
+    /// `core::ptr::drop_glue::<T>`.
     ///
-    /// The `DefId` is for `core::ptr::drop_in_place`.
-    /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop
-    /// glue.
+    /// The `DefId` is for `core::ptr::drop_glue`.
+    /// The `Option<Ty<'tcx>>` is either `Some(T)`, or `None` for empty drop glue.
     DropGlue(DefId, Option<Ty<'tcx>>),
 
     /// Compiler-generated `<T as Clone>::clone` implementation.
@@ -293,7 +292,7 @@ impl<'tcx> InstanceKind<'tcx> {
         use rustc_hir::definitions::DefPathData;
         let def_id = match *self {
             ty::InstanceKind::Item(def) => def,
-            ty::InstanceKind::DropGlue(_, Some(_)) => return false,
+            ty::InstanceKind::DropGlue(_, Some(ty)) => return ty.is_array(),
             ty::InstanceKind::AsyncDropGlueCtorShim(_, ty) => return ty.is_coroutine(),
             ty::InstanceKind::FutureDropPollShim(_, _, _) => return false,
             ty::InstanceKind::AsyncDropGlue(_, _) => return false,
@@ -717,8 +716,8 @@ impl<'tcx> Instance<'tcx> {
         }
     }
 
-    pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
-        let def_id = tcx.require_lang_item(LangItem::DropInPlace, DUMMY_SP);
+    pub fn resolve_drop_glue(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
+        let def_id = tcx.require_lang_item(LangItem::DropGlue, DUMMY_SP);
         let args = tcx.mk_args(&[ty.into()]);
         Instance::expect_resolve(
             tcx,

compiler/rustc_middle/src/ty/layout.rs

@@ -1228,12 +1228,12 @@ pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: ExternAbi)
             return false;
         }
 
-        // With -Z panic-in-drop=abort, drop_in_place never unwinds.
+        // With -Z panic-in-drop=abort, `drop_glue` never unwinds.
         //
         // This is not part of `codegen_fn_attrs` as it can differ between crates
         // and therefore cannot be computed in core.
         if !tcx.sess.opts.unstable_opts.panic_in_drop.unwinds()
-            && tcx.is_lang_item(did, LangItem::DropInPlace)
+            && tcx.is_lang_item(did, LangItem::DropGlue)
         {
             return false;
         }

compiler/rustc_middle/src/ty/vtable.rs

@@ -122,7 +122,7 @@ pub(super) fn vtable_allocation_provider<'tcx>(
         let scalar = match *entry {
             VtblEntry::MetadataDropInPlace => {
                 if ty.needs_drop(tcx, ty::TypingEnv::fully_monomorphized()) {
-                    let instance = ty::Instance::resolve_drop_in_place(tcx, ty);
+                    let instance = ty::Instance::resolve_drop_glue(tcx, ty);
                     let fn_alloc_id = tcx.reserve_and_set_fn_alloc(instance, CTFE_ALLOC_SALT);
                     let fn_ptr = Pointer::from(fn_alloc_id);
                     Scalar::from_pointer(fn_ptr, &tcx)

compiler/rustc_mir_transform/src/add_moves_for_packed_drops.rs

@@ -10,6 +10,7 @@ use crate::util;
 /// they are dropped from an aligned address.
 ///
 /// For example, if we have something like
+///
 /// ```ignore (illustrative)
 /// #[repr(packed)]
 /// struct Foo {
@@ -20,9 +21,8 @@ use crate::util;
 /// let foo = ...;
 /// ```
 ///
-/// We want to call `drop_in_place::<Vec<u8>>` on `data` from an aligned
-/// address. This means we can't simply drop `foo.data` directly, because
-/// its address is not aligned.
+/// We want to call `drop_glue::<Vec<u8>>` with a reference to `data`, which must be aligned.
+/// This means we can't simply drop `foo.data` directly, because its address is not aligned.
 ///
 /// Instead, we move `foo.data` to a local and drop that:
 /// ```ignore (illustrative)

compiler/rustc_mir_transform/src/coroutine/drop.rs

@@ -569,7 +569,7 @@ pub(super) fn create_coroutine_drop_shim<'tcx>(
     // not a coroutine body itself; it just has its drop built out of it.
     let _ = body.coroutine.take();
     // Make sure the resume argument is not included here, since we're
-    // building a body for `drop_in_place`.
+    // building a body for `drop_glue`.
     body.arg_count = 1;
 
     let source_info = SourceInfo::outermost(body.span);
@@ -596,18 +596,14 @@ pub(super) fn create_coroutine_drop_shim<'tcx>(
 
     make_coroutine_state_argument_indirect(tcx, &mut body);
 
-    // Change the coroutine argument from &mut to *mut
-    body.local_decls[SELF_ARG] =
-        LocalDecl::with_source_info(Ty::new_mut_ptr(tcx, coroutine_ty), source_info);
-
     // Make sure we remove dead blocks to remove
     // unrelated code from the resume part of the function
     simplify::remove_dead_blocks(&mut body);
 
     // Update the body's def to become the drop glue.
     let coroutine_instance = body.source.instance;
-    let drop_in_place = tcx.require_lang_item(LangItem::DropInPlace, body.span);
-    let drop_instance = InstanceKind::DropGlue(drop_in_place, Some(coroutine_ty));
+    let drop_glue = tcx.require_lang_item(LangItem::DropGlue, body.span);
+    let drop_instance = InstanceKind::DropGlue(drop_glue, Some(coroutine_ty));
 
     // Temporary change MirSource to coroutine's instance so that dump_mir produces more sensible
     // filename.

compiler/rustc_mir_transform/src/elaborate_drop.rs

@@ -354,7 +354,6 @@ where
             let ty::Adt(adt_def, adt_args) = pin_obj_ty.kind() else {
                 bug!();
             };
-            let obj_ptr_ty = Ty::new_mut_ptr(tcx, drop_ty);
             let unwrap_ty = adt_def.non_enum_variant().fields[FieldIdx::ZERO].ty(tcx, adt_args);
             let obj_ref_place = Place::from(self.new_temp(unwrap_ty));
             call_statements.push(self.assign(
@@ -366,11 +365,7 @@ where
                 ))),
             ));
 
-            let obj_ptr_place = Place::from(self.new_temp(obj_ptr_ty));
-
-            let addr = Rvalue::RawPtr(RawPtrKind::Mut, tcx.mk_place_deref(obj_ref_place));
-            call_statements.push(self.assign(obj_ptr_place, addr));
-            obj_ptr_place
+            obj_ref_place
         };
         call_statements
             .push(Statement::new(self.source_info, StatementKind::StorageLive(fut.local)));