| use std::fmt; |
| use rustc::hir; |
| use rustc::mir::*; |
| use rustc::middle::lang_items; |
| use rustc::traits::Reveal; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc::ty::layout::VariantIdx; |
| use rustc::ty::subst::SubstsRef; |
| use rustc::ty::util::IntTypeExt; |
| use rustc_data_structures::indexed_vec::Idx; |
| use crate::util::patch::MirPatch; |
| |
| use std::convert::TryInto; |
| |
| #[derive(Debug, PartialEq, Eq, Copy, Clone)] |
| pub enum DropFlagState { |
| Present, // i.e., initialized |
| Absent, // i.e., deinitialized or "moved" |
| } |
| |
| impl DropFlagState { |
| pub fn value(self) -> bool { |
| match self { |
| DropFlagState::Present => true, |
| DropFlagState::Absent => false |
| } |
| } |
| } |
| |
| #[derive(Debug)] |
| pub enum DropStyle { |
| Dead, |
| Static, |
| Conditional, |
| Open, |
| } |
| |
| #[derive(Debug)] |
| pub enum DropFlagMode { |
| Shallow, |
| Deep |
| } |
| |
| #[derive(Copy, Clone, Debug)] |
| pub enum Unwind { |
| To(BasicBlock), |
| InCleanup |
| } |
| |
| impl Unwind { |
| fn is_cleanup(self) -> bool { |
| match self { |
| Unwind::To(..) => false, |
| Unwind::InCleanup => true |
| } |
| } |
| |
| fn into_option(self) -> Option<BasicBlock> { |
| match self { |
| Unwind::To(bb) => Some(bb), |
| Unwind::InCleanup => None, |
| } |
| } |
| |
| fn map<F>(self, f: F) -> Self where F: FnOnce(BasicBlock) -> BasicBlock { |
| match self { |
| Unwind::To(bb) => Unwind::To(f(bb)), |
| Unwind::InCleanup => Unwind::InCleanup |
| } |
| } |
| } |
| |
| pub trait DropElaborator<'a, 'tcx>: fmt::Debug { |
| type Path : Copy + fmt::Debug; |
| |
| fn patch(&mut self) -> &mut MirPatch<'tcx>; |
| fn body(&self) -> &'a Body<'tcx>; |
| fn tcx(&self) -> TyCtxt<'tcx>; |
| fn param_env(&self) -> ty::ParamEnv<'tcx>; |
| |
| fn drop_style(&self, path: Self::Path, mode: DropFlagMode) -> DropStyle; |
| fn get_drop_flag(&mut self, path: Self::Path) -> Option<Operand<'tcx>>; |
| fn clear_drop_flag(&mut self, location: Location, path: Self::Path, mode: DropFlagMode); |
| |
| |
| fn field_subpath(&self, path: Self::Path, field: Field) -> Option<Self::Path>; |
| fn deref_subpath(&self, path: Self::Path) -> Option<Self::Path>; |
| fn downcast_subpath(&self, path: Self::Path, variant: VariantIdx) -> Option<Self::Path>; |
| fn array_subpath(&self, path: Self::Path, index: u32, size: u32) -> Option<Self::Path>; |
| } |
| |
| #[derive(Debug)] |
| struct DropCtxt<'l, 'b, 'tcx, D> |
| where |
| D: DropElaborator<'b, 'tcx>, |
| { |
| elaborator: &'l mut D, |
| |
| source_info: SourceInfo, |
| |
| place: &'l Place<'tcx>, |
| path: D::Path, |
| succ: BasicBlock, |
| unwind: Unwind, |
| } |
| |
| pub fn elaborate_drop<'b, 'tcx, D>( |
| elaborator: &mut D, |
| source_info: SourceInfo, |
| place: &Place<'tcx>, |
| path: D::Path, |
| succ: BasicBlock, |
| unwind: Unwind, |
| bb: BasicBlock, |
| ) where |
| D: DropElaborator<'b, 'tcx>, |
| 'tcx: 'b, |
| { |
| DropCtxt { |
| elaborator, source_info, place, path, succ, unwind |
| }.elaborate_drop(bb) |
| } |
| |
| impl<'l, 'b, 'tcx, D> DropCtxt<'l, 'b, 'tcx, D> |
| where |
| D: DropElaborator<'b, 'tcx>, |
| 'tcx: 'b, |
| { |
| fn place_ty(&self, place: &Place<'tcx>) -> Ty<'tcx> { |
| place.ty(self.elaborator.body(), self.tcx()).ty |
| } |
| |
| fn tcx(&self) -> TyCtxt<'tcx> { |
| self.elaborator.tcx() |
| } |
| |
| /// This elaborates a single drop instruction, located at `bb`, and |
| /// patches over it. |
| /// |
| /// The elaborated drop checks the drop flags to only drop what |
| /// is initialized. |
| /// |
| /// In addition, the relevant drop flags also need to be cleared |
| /// to avoid double-drops. However, in the middle of a complex |
| /// drop, one must avoid clearing some of the flags before they |
| /// are read, as that would cause a memory leak. |
| /// |
| /// In particular, when dropping an ADT, multiple fields may be |
| /// joined together under the `rest` subpath. They are all controlled |
| /// by the primary drop flag, but only the last rest-field dropped |
| /// should clear it (and it must also not clear anything else). |
| // |
| // FIXME: I think we should just control the flags externally, |
| // and then we do not need this machinery. |
| pub fn elaborate_drop(&mut self, bb: BasicBlock) { |
| debug!("elaborate_drop({:?})", self); |
| let style = self.elaborator.drop_style(self.path, DropFlagMode::Deep); |
| debug!("elaborate_drop({:?}): live - {:?}", self, style); |
| match style { |
| DropStyle::Dead => { |
| self.elaborator.patch().patch_terminator(bb, TerminatorKind::Goto { |
| target: self.succ |
| }); |
| } |
| DropStyle::Static => { |
| let loc = self.terminator_loc(bb); |
| self.elaborator.clear_drop_flag(loc, self.path, DropFlagMode::Deep); |
| self.elaborator.patch().patch_terminator(bb, TerminatorKind::Drop { |
| location: self.place.clone(), |
| target: self.succ, |
| unwind: self.unwind.into_option(), |
| }); |
| } |
| DropStyle::Conditional => { |
| let unwind = self.unwind; // FIXME(#43234) |
| let succ = self.succ; |
| let drop_bb = self.complete_drop(Some(DropFlagMode::Deep), succ, unwind); |
| self.elaborator.patch().patch_terminator(bb, TerminatorKind::Goto { |
| target: drop_bb |
| }); |
| } |
| DropStyle::Open => { |
| let drop_bb = self.open_drop(); |
| self.elaborator.patch().patch_terminator(bb, TerminatorKind::Goto { |
| target: drop_bb |
| }); |
| } |
| } |
| } |
| |
| /// Returns the place and move path for each field of `variant`, |
| /// (the move path is `None` if the field is a rest field). |
| fn move_paths_for_fields(&self, |
| base_place: &Place<'tcx>, |
| variant_path: D::Path, |
| variant: &'tcx ty::VariantDef, |
| substs: SubstsRef<'tcx>) |
| -> Vec<(Place<'tcx>, Option<D::Path>)> |
| { |
| variant.fields.iter().enumerate().map(|(i, f)| { |
| let field = Field::new(i); |
| let subpath = self.elaborator.field_subpath(variant_path, field); |
| |
| assert_eq!(self.elaborator.param_env().reveal, Reveal::All); |
| let field_ty = self.tcx().normalize_erasing_regions( |
| self.elaborator.param_env(), |
| f.ty(self.tcx(), substs), |
| ); |
| (base_place.clone().field(field, field_ty), subpath) |
| }).collect() |
| } |
| |
| fn drop_subpath(&mut self, |
| place: &Place<'tcx>, |
| path: Option<D::Path>, |
| succ: BasicBlock, |
| unwind: Unwind) |
| -> BasicBlock |
| { |
| if let Some(path) = path { |
| debug!("drop_subpath: for std field {:?}", place); |
| |
| DropCtxt { |
| elaborator: self.elaborator, |
| source_info: self.source_info, |
| path, place, succ, unwind, |
| }.elaborated_drop_block() |
| } else { |
| debug!("drop_subpath: for rest field {:?}", place); |
| |
| DropCtxt { |
| elaborator: self.elaborator, |
| source_info: self.source_info, |
| place, succ, unwind, |
| // Using `self.path` here to condition the drop on |
| // our own drop flag. |
| path: self.path |
| }.complete_drop(None, succ, unwind) |
| } |
| } |
| |
| /// Creates one-half of the drop ladder for a list of fields, and return |
| /// the list of steps in it in reverse order, with the first step |
| /// dropping 0 fields and so on. |
| /// |
| /// `unwind_ladder` is such a list of steps in reverse order, |
| /// which is called if the matching step of the drop glue panics. |
| fn drop_halfladder(&mut self, |
| unwind_ladder: &[Unwind], |
| mut succ: BasicBlock, |
| fields: &[(Place<'tcx>, Option<D::Path>)]) |
| -> Vec<BasicBlock> |
| { |
| Some(succ).into_iter().chain( |
| fields.iter().rev().zip(unwind_ladder) |
| .map(|(&(ref place, path), &unwind_succ)| { |
| succ = self.drop_subpath(place, path, succ, unwind_succ); |
| succ |
| }) |
| ).collect() |
| } |
| |
| fn drop_ladder_bottom(&mut self) -> (BasicBlock, Unwind) { |
| // Clear the "master" drop flag at the end. This is needed |
| // because the "master" drop protects the ADT's discriminant, |
| // which is invalidated after the ADT is dropped. |
| let (succ, unwind) = (self.succ, self.unwind); // FIXME(#43234) |
| ( |
| self.drop_flag_reset_block(DropFlagMode::Shallow, succ, unwind), |
| unwind.map(|unwind| { |
| self.drop_flag_reset_block(DropFlagMode::Shallow, unwind, Unwind::InCleanup) |
| }) |
| ) |
| } |
| |
| /// Creates a full drop ladder, consisting of 2 connected half-drop-ladders |
| /// |
| /// For example, with 3 fields, the drop ladder is |
| /// |
| /// .d0: |
| /// ELAB(drop location.0 [target=.d1, unwind=.c1]) |
| /// .d1: |
| /// ELAB(drop location.1 [target=.d2, unwind=.c2]) |
| /// .d2: |
| /// ELAB(drop location.2 [target=`self.succ`, unwind=`self.unwind`]) |
| /// .c1: |
| /// ELAB(drop location.1 [target=.c2]) |
| /// .c2: |
| /// ELAB(drop location.2 [target=`self.unwind`]) |
| /// |
| /// NOTE: this does not clear the master drop flag, so you need |
| /// to point succ/unwind on a `drop_ladder_bottom`. |
| fn drop_ladder( |
| &mut self, |
| fields: Vec<(Place<'tcx>, Option<D::Path>)>, |
| succ: BasicBlock, |
| unwind: Unwind, |
| ) -> (BasicBlock, Unwind) { |
| debug!("drop_ladder({:?}, {:?})", self, fields); |
| |
| let mut fields = fields; |
| fields.retain(|&(ref place, _)| { |
| self.place_ty(place).needs_drop(self.tcx(), self.elaborator.param_env()) |
| }); |
| |
| debug!("drop_ladder - fields needing drop: {:?}", fields); |
| |
| let unwind_ladder = vec![Unwind::InCleanup; fields.len() + 1]; |
| let unwind_ladder: Vec<_> = if let Unwind::To(target) = unwind { |
| let halfladder = self.drop_halfladder(&unwind_ladder, target, &fields); |
| halfladder.into_iter().map(Unwind::To).collect() |
| } else { |
| unwind_ladder |
| }; |
| |
| let normal_ladder = |
| self.drop_halfladder(&unwind_ladder, succ, &fields); |
| |
| (*normal_ladder.last().unwrap(), *unwind_ladder.last().unwrap()) |
| } |
| |
| fn open_drop_for_tuple(&mut self, tys: &[Ty<'tcx>]) -> BasicBlock { |
| debug!("open_drop_for_tuple({:?}, {:?})", self, tys); |
| |
| let fields = tys.iter().enumerate().map(|(i, &ty)| { |
| (self.place.clone().field(Field::new(i), ty), |
| self.elaborator.field_subpath(self.path, Field::new(i))) |
| }).collect(); |
| |
| let (succ, unwind) = self.drop_ladder_bottom(); |
| self.drop_ladder(fields, succ, unwind).0 |
| } |
| |
| fn open_drop_for_box(&mut self, adt: &'tcx ty::AdtDef, substs: SubstsRef<'tcx>) -> BasicBlock { |
| debug!("open_drop_for_box({:?}, {:?}, {:?})", self, adt, substs); |
| |
| let interior = self.place.clone().deref(); |
| let interior_path = self.elaborator.deref_subpath(self.path); |
| |
| let succ = self.succ; // FIXME(#43234) |
| let unwind = self.unwind; |
| let succ = self.box_free_block(adt, substs, succ, unwind); |
| let unwind_succ = self.unwind.map(|unwind| { |
| self.box_free_block(adt, substs, unwind, Unwind::InCleanup) |
| }); |
| |
| self.drop_subpath(&interior, interior_path, succ, unwind_succ) |
| } |
| |
| fn open_drop_for_adt(&mut self, adt: &'tcx ty::AdtDef, substs: SubstsRef<'tcx>) -> BasicBlock { |
| debug!("open_drop_for_adt({:?}, {:?}, {:?})", self, adt, substs); |
| if adt.variants.len() == 0 { |
| return self.elaborator.patch().new_block(BasicBlockData { |
| statements: vec![], |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| kind: TerminatorKind::Unreachable |
| }), |
| is_cleanup: self.unwind.is_cleanup() |
| }); |
| } |
| |
| let skip_contents = |
| adt.is_union() || Some(adt.did) == self.tcx().lang_items().manually_drop(); |
| let contents_drop = if skip_contents { |
| (self.succ, self.unwind) |
| } else { |
| self.open_drop_for_adt_contents(adt, substs) |
| }; |
| |
| if adt.has_dtor(self.tcx()) { |
| self.destructor_call_block(contents_drop) |
| } else { |
| contents_drop.0 |
| } |
| } |
| |
| fn open_drop_for_adt_contents(&mut self, adt: &'tcx ty::AdtDef, |
| substs: SubstsRef<'tcx>) |
| -> (BasicBlock, Unwind) { |
| let (succ, unwind) = self.drop_ladder_bottom(); |
| if !adt.is_enum() { |
| let fields = self.move_paths_for_fields( |
| self.place, |
| self.path, |
| &adt.variants[VariantIdx::new(0)], |
| substs |
| ); |
| self.drop_ladder(fields, succ, unwind) |
| } else { |
| self.open_drop_for_multivariant(adt, substs, succ, unwind) |
| } |
| } |
| |
| fn open_drop_for_multivariant(&mut self, adt: &'tcx ty::AdtDef, |
| substs: SubstsRef<'tcx>, |
| succ: BasicBlock, |
| unwind: Unwind) |
| -> (BasicBlock, Unwind) { |
| let mut values = Vec::with_capacity(adt.variants.len()); |
| let mut normal_blocks = Vec::with_capacity(adt.variants.len()); |
| let mut unwind_blocks = if unwind.is_cleanup() { |
| None |
| } else { |
| Some(Vec::with_capacity(adt.variants.len())) |
| }; |
| |
| let mut have_otherwise = false; |
| |
| for (variant_index, discr) in adt.discriminants(self.tcx()) { |
| let subpath = self.elaborator.downcast_subpath( |
| self.path, variant_index); |
| if let Some(variant_path) = subpath { |
| let base_place = self.place.clone().elem( |
| ProjectionElem::Downcast(Some(adt.variants[variant_index].ident.name), |
| variant_index)); |
| let fields = self.move_paths_for_fields( |
| &base_place, |
| variant_path, |
| &adt.variants[variant_index], |
| substs); |
| values.push(discr.val); |
| if let Unwind::To(unwind) = unwind { |
| // We can't use the half-ladder from the original |
| // drop ladder, because this breaks the |
| // "funclet can't have 2 successor funclets" |
| // requirement from MSVC: |
| // |
| // switch unwind-switch |
| // / \ / \ |
| // v1.0 v2.0 v2.0-unwind v1.0-unwind |
| // | | / | |
| // v1.1-unwind v2.1-unwind | |
| // ^ | |
| // \-------------------------------/ |
| // |
| // Create a duplicate half-ladder to avoid that. We |
| // could technically only do this on MSVC, but I |
| // I want to minimize the divergence between MSVC |
| // and non-MSVC. |
| |
| let unwind_blocks = unwind_blocks.as_mut().unwrap(); |
| let unwind_ladder = vec![Unwind::InCleanup; fields.len() + 1]; |
| let halfladder = |
| self.drop_halfladder(&unwind_ladder, unwind, &fields); |
| unwind_blocks.push(halfladder.last().cloned().unwrap()); |
| } |
| let (normal, _) = self.drop_ladder(fields, succ, unwind); |
| normal_blocks.push(normal); |
| } else { |
| have_otherwise = true; |
| } |
| } |
| |
| if have_otherwise { |
| normal_blocks.push(self.drop_block(succ, unwind)); |
| if let Unwind::To(unwind) = unwind { |
| unwind_blocks.as_mut().unwrap().push( |
| self.drop_block(unwind, Unwind::InCleanup) |
| ); |
| } |
| } else { |
| values.pop(); |
| } |
| |
| (self.adt_switch_block(adt, normal_blocks, &values, succ, unwind), |
| unwind.map(|unwind| { |
| self.adt_switch_block( |
| adt, unwind_blocks.unwrap(), &values, unwind, Unwind::InCleanup |
| ) |
| })) |
| } |
| |
| fn adt_switch_block(&mut self, |
| adt: &'tcx ty::AdtDef, |
| blocks: Vec<BasicBlock>, |
| values: &[u128], |
| succ: BasicBlock, |
| unwind: Unwind) |
| -> BasicBlock { |
| // If there are multiple variants, then if something |
| // is present within the enum the discriminant, tracked |
| // by the rest path, must be initialized. |
| // |
| // Additionally, we do not want to switch on the |
| // discriminant after it is free-ed, because that |
| // way lies only trouble. |
| let discr_ty = adt.repr.discr_type().to_ty(self.tcx()); |
| let discr = Place::from(self.new_temp(discr_ty)); |
| let discr_rv = Rvalue::Discriminant(self.place.clone()); |
| let switch_block = BasicBlockData { |
| statements: vec![self.assign(&discr, discr_rv)], |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| kind: TerminatorKind::SwitchInt { |
| discr: Operand::Move(discr), |
| switch_ty: discr_ty, |
| values: From::from(values.to_owned()), |
| targets: blocks, |
| } |
| }), |
| is_cleanup: unwind.is_cleanup(), |
| }; |
| let switch_block = self.elaborator.patch().new_block(switch_block); |
| self.drop_flag_test_block(switch_block, succ, unwind) |
| } |
| |
| fn destructor_call_block(&mut self, (succ, unwind): (BasicBlock, Unwind)) -> BasicBlock { |
| debug!("destructor_call_block({:?}, {:?})", self, succ); |
| let tcx = self.tcx(); |
| let drop_trait = tcx.lang_items().drop_trait().unwrap(); |
| let drop_fn = tcx.associated_items(drop_trait).next().unwrap(); |
| let ty = self.place_ty(self.place); |
| let substs = tcx.mk_substs_trait(ty, &[]); |
| |
| let ref_ty = tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut { |
| ty, |
| mutbl: hir::Mutability::MutMutable |
| }); |
| let ref_place = self.new_temp(ref_ty); |
| let unit_temp = Place::from(self.new_temp(tcx.mk_unit())); |
| |
| let result = BasicBlockData { |
| statements: vec![self.assign( |
| &Place::from(ref_place), |
| Rvalue::Ref(tcx.lifetimes.re_erased, |
| BorrowKind::Mut { allow_two_phase_borrow: false }, |
| self.place.clone()) |
| )], |
| terminator: Some(Terminator { |
| kind: TerminatorKind::Call { |
| func: Operand::function_handle(tcx, drop_fn.def_id, substs, |
| self.source_info.span), |
| args: vec![Operand::Move(Place::from(ref_place))], |
| destination: Some((unit_temp, succ)), |
| cleanup: unwind.into_option(), |
| from_hir_call: true, |
| }, |
| source_info: self.source_info, |
| }), |
| is_cleanup: unwind.is_cleanup(), |
| }; |
| self.elaborator.patch().new_block(result) |
| } |
| |
| /// Create a loop that drops an array: |
| /// |
| /// ```text |
| /// loop-block: |
| /// can_go = cur == length_or_end |
| /// if can_go then succ else drop-block |
| /// drop-block: |
| /// if ptr_based { |
| /// ptr = &mut *cur |
| /// cur = cur.offset(1) |
| /// } else { |
| /// ptr = &mut P[cur] |
| /// cur = cur + 1 |
| /// } |
| /// drop(ptr) |
| /// ``` |
| fn drop_loop( |
| &mut self, |
| succ: BasicBlock, |
| cur: Local, |
| length_or_end: &Place<'tcx>, |
| ety: Ty<'tcx>, |
| unwind: Unwind, |
| ptr_based: bool, |
| ) -> BasicBlock { |
| let copy = |place: &Place<'tcx>| Operand::Copy(place.clone()); |
| let move_ = |place: &Place<'tcx>| Operand::Move(place.clone()); |
| let tcx = self.tcx(); |
| |
| let ref_ty = tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut { |
| ty: ety, |
| mutbl: hir::Mutability::MutMutable |
| }); |
| let ptr = &Place::from(self.new_temp(ref_ty)); |
| let can_go = &Place::from(self.new_temp(tcx.types.bool)); |
| |
| let one = self.constant_usize(1); |
| let (ptr_next, cur_next) = if ptr_based { |
| (Rvalue::Ref( |
| tcx.lifetimes.re_erased, |
| BorrowKind::Mut { allow_two_phase_borrow: false }, |
| Place { |
| base: PlaceBase::Local(cur), |
| projection: Box::new([ProjectionElem::Deref]), |
| } |
| ), |
| Rvalue::BinaryOp(BinOp::Offset, move_(&Place::from(cur)), one)) |
| } else { |
| (Rvalue::Ref( |
| tcx.lifetimes.re_erased, |
| BorrowKind::Mut { allow_two_phase_borrow: false }, |
| self.place.clone().index(cur)), |
| Rvalue::BinaryOp(BinOp::Add, move_(&Place::from(cur)), one)) |
| }; |
| |
| let drop_block = BasicBlockData { |
| statements: vec![ |
| self.assign(ptr, ptr_next), |
| self.assign(&Place::from(cur), cur_next) |
| ], |
| is_cleanup: unwind.is_cleanup(), |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| // this gets overwritten by drop elaboration. |
| kind: TerminatorKind::Unreachable, |
| }) |
| }; |
| let drop_block = self.elaborator.patch().new_block(drop_block); |
| |
| let loop_block = BasicBlockData { |
| statements: vec![ |
| self.assign(can_go, Rvalue::BinaryOp(BinOp::Eq, |
| copy(&Place::from(cur)), |
| copy(length_or_end))) |
| ], |
| is_cleanup: unwind.is_cleanup(), |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| kind: TerminatorKind::if_(tcx, move_(can_go), succ, drop_block) |
| }) |
| }; |
| let loop_block = self.elaborator.patch().new_block(loop_block); |
| |
| self.elaborator.patch().patch_terminator(drop_block, TerminatorKind::Drop { |
| location: ptr.clone().deref(), |
| target: loop_block, |
| unwind: unwind.into_option() |
| }); |
| |
| loop_block |
| } |
| |
| fn open_drop_for_array(&mut self, ety: Ty<'tcx>, opt_size: Option<u64>) -> BasicBlock { |
| debug!("open_drop_for_array({:?}, {:?})", ety, opt_size); |
| |
| // if size_of::<ety>() == 0 { |
| // index_based_loop |
| // } else { |
| // ptr_based_loop |
| // } |
| |
| if let Some(size) = opt_size { |
| let size: u32 = size.try_into().unwrap_or_else(|_| { |
| bug!("move out check isn't implemented for array sizes bigger than u32::MAX"); |
| }); |
| let fields: Vec<(Place<'tcx>, Option<D::Path>)> = (0..size).map(|i| { |
| (self.place.clone().elem(ProjectionElem::ConstantIndex{ |
| offset: i, |
| min_length: size, |
| from_end: false |
| }), |
| self.elaborator.array_subpath(self.path, i, size)) |
| }).collect(); |
| |
| if fields.iter().any(|(_,path)| path.is_some()) { |
| let (succ, unwind) = self.drop_ladder_bottom(); |
| return self.drop_ladder(fields, succ, unwind).0 |
| } |
| } |
| |
| let move_ = |place: &Place<'tcx>| Operand::Move(place.clone()); |
| let tcx = self.tcx(); |
| let elem_size = &Place::from(self.new_temp(tcx.types.usize)); |
| let len = &Place::from(self.new_temp(tcx.types.usize)); |
| |
| static USIZE_SWITCH_ZERO: &[u128] = &[0]; |
| |
| let base_block = BasicBlockData { |
| statements: vec![ |
| self.assign(elem_size, Rvalue::NullaryOp(NullOp::SizeOf, ety)), |
| self.assign(len, Rvalue::Len(self.place.clone())), |
| ], |
| is_cleanup: self.unwind.is_cleanup(), |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| kind: TerminatorKind::SwitchInt { |
| discr: move_(elem_size), |
| switch_ty: tcx.types.usize, |
| values: From::from(USIZE_SWITCH_ZERO), |
| targets: vec![ |
| self.drop_loop_pair(ety, false, len.clone()), |
| self.drop_loop_pair(ety, true, len.clone()), |
| ], |
| }, |
| }) |
| }; |
| self.elaborator.patch().new_block(base_block) |
| } |
| |
| /// Ceates a pair of drop-loops of `place`, which drops its contents, even |
| /// in the case of 1 panic. If `ptr_based`, creates a pointer loop, |
| /// otherwise create an index loop. |
| fn drop_loop_pair( |
| &mut self, |
| ety: Ty<'tcx>, |
| ptr_based: bool, |
| length: Place<'tcx>, |
| ) -> BasicBlock { |
| debug!("drop_loop_pair({:?}, {:?})", ety, ptr_based); |
| let tcx = self.tcx(); |
| let iter_ty = if ptr_based { |
| tcx.mk_mut_ptr(ety) |
| } else { |
| tcx.types.usize |
| }; |
| |
| let cur = self.new_temp(iter_ty); |
| let length_or_end = if ptr_based { |
| // FIXME check if we want to make it return a `Place` directly |
| // if all use sites want a `Place::Base` anyway. |
| Place::from(self.new_temp(iter_ty)) |
| } else { |
| length.clone() |
| }; |
| |
| let unwind = self.unwind.map(|unwind| { |
| self.drop_loop(unwind, |
| cur, |
| &length_or_end, |
| ety, |
| Unwind::InCleanup, |
| ptr_based) |
| }); |
| |
| let loop_block = self.drop_loop( |
| self.succ, |
| cur, |
| &length_or_end, |
| ety, |
| unwind, |
| ptr_based); |
| |
| let cur = Place::from(cur); |
| let drop_block_stmts = if ptr_based { |
| let tmp_ty = tcx.mk_mut_ptr(self.place_ty(self.place)); |
| let tmp = Place::from(self.new_temp(tmp_ty)); |
| // tmp = &mut P; |
| // cur = tmp as *mut T; |
| // end = Offset(cur, len); |
| vec![ |
| self.assign(&tmp, Rvalue::Ref( |
| tcx.lifetimes.re_erased, |
| BorrowKind::Mut { allow_two_phase_borrow: false }, |
| self.place.clone() |
| )), |
| self.assign( |
| &cur, |
| Rvalue::Cast(CastKind::Misc, Operand::Move(tmp), iter_ty), |
| ), |
| self.assign( |
| &length_or_end, |
| Rvalue::BinaryOp(BinOp::Offset, Operand::Copy(cur), Operand::Move(length) |
| )), |
| ] |
| } else { |
| // cur = 0 (length already pushed) |
| let zero = self.constant_usize(0); |
| vec![self.assign(&cur, Rvalue::Use(zero))] |
| }; |
| let drop_block = self.elaborator.patch().new_block(BasicBlockData { |
| statements: drop_block_stmts, |
| is_cleanup: unwind.is_cleanup(), |
| terminator: Some(Terminator { |
| source_info: self.source_info, |
| kind: TerminatorKind::Goto { target: loop_block } |
| }) |
| }); |
| |
| // FIXME(#34708): handle partially-dropped array/slice elements. |
| let reset_block = self.drop_flag_reset_block(DropFlagMode::Deep, drop_block, unwind); |
| self.drop_flag_test_block(reset_block, self.succ, unwind) |
| } |
| |
| /// The slow-path - create an "open", elaborated drop for a type |
| /// which is moved-out-of only partially, and patch `bb` to a jump |
| /// to it. This must not be called on ADTs with a destructor, |
| /// as these can't be moved-out-of, except for `Box<T>`, which is |
| /// special-cased. |
| /// |
| /// This creates a "drop ladder" that drops the needed fields of the |
| /// ADT, both in the success case or if one of the destructors fail. |
| fn open_drop(&mut self) -> BasicBlock { |
| let ty = self.place_ty(self.place); |
| match ty.sty { |
| ty::Closure(def_id, substs) => { |
| let tys : Vec<_> = substs.upvar_tys(def_id, self.tcx()).collect(); |
| self.open_drop_for_tuple(&tys) |
| } |
| // Note that `elaborate_drops` only drops the upvars of a generator, |
| // and this is ok because `open_drop` here can only be reached |
| // within that own generator's resume function. |
| // This should only happen for the self argument on the resume function. |
| // It effetively only contains upvars until the generator transformation runs. |
| // See librustc_body/transform/generator.rs for more details. |
| ty::Generator(def_id, substs, _) => { |
| let tys : Vec<_> = substs.upvar_tys(def_id, self.tcx()).collect(); |
| self.open_drop_for_tuple(&tys) |
| } |
| ty::Tuple(..) => { |
| let tys: Vec<_> = ty.tuple_fields().collect(); |
| self.open_drop_for_tuple(&tys) |
| } |
| ty::Adt(def, substs) => { |
| if def.is_box() { |
| self.open_drop_for_box(def, substs) |
| } else { |
| self.open_drop_for_adt(def, substs) |
| } |
| } |
| ty::Dynamic(..) => { |
| let unwind = self.unwind; // FIXME(#43234) |
| let succ = self.succ; |
| self.complete_drop(Some(DropFlagMode::Deep), succ, unwind) |
| } |
| ty::Array(ety, size) => { |
| let size = size.try_eval_usize(self.tcx(), self.elaborator.param_env()); |
| self.open_drop_for_array(ety, size) |
| }, |
| ty::Slice(ety) => self.open_drop_for_array(ety, None), |
| |
| _ => bug!("open drop from non-ADT `{:?}`", ty) |
| } |
| } |
| |
| /// Returns a basic block that drop a place using the context |
| /// and path in `c`. If `mode` is something, also clear `c` |
| /// according to it. |
| /// |
| /// if FLAG(self.path) |
| /// if let Some(mode) = mode: FLAG(self.path)[mode] = false |
| /// drop(self.place) |
| fn complete_drop( |
| &mut self, |
| drop_mode: Option<DropFlagMode>, |
| succ: BasicBlock, |
| unwind: Unwind, |
| ) -> BasicBlock { |
| debug!("complete_drop({:?},{:?})", self, drop_mode); |
| |
| let drop_block = self.drop_block(succ, unwind); |
| let drop_block = if let Some(mode) = drop_mode { |
| self.drop_flag_reset_block(mode, drop_block, unwind) |
| } else { |
| drop_block |
| }; |
| |
| self.drop_flag_test_block(drop_block, succ, unwind) |
| } |
| |
| fn drop_flag_reset_block(&mut self, |
| mode: DropFlagMode, |
| succ: BasicBlock, |
| unwind: Unwind) -> BasicBlock |
| { |
| debug!("drop_flag_reset_block({:?},{:?})", self, mode); |
| |
| let block = self.new_block(unwind, TerminatorKind::Goto { target: succ }); |
| let block_start = Location { block: block, statement_index: 0 }; |
| self.elaborator.clear_drop_flag(block_start, self.path, mode); |
| block |
| } |
| |
| fn elaborated_drop_block(&mut self) -> BasicBlock { |
| debug!("elaborated_drop_block({:?})", self); |
| let unwind = self.unwind; // FIXME(#43234) |
| let succ = self.succ; |
| let blk = self.drop_block(succ, unwind); |
| self.elaborate_drop(blk); |
| blk |
| } |
| |
| fn box_free_block( |
| &mut self, |
| adt: &'tcx ty::AdtDef, |
| substs: SubstsRef<'tcx>, |
| target: BasicBlock, |
| unwind: Unwind, |
| ) -> BasicBlock { |
| let block = self.unelaborated_free_block(adt, substs, target, unwind); |
| self.drop_flag_test_block(block, target, unwind) |
| } |
| |
| fn unelaborated_free_block( |
| &mut self, |
| adt: &'tcx ty::AdtDef, |
| substs: SubstsRef<'tcx>, |
| target: BasicBlock, |
| unwind: Unwind, |
| ) -> BasicBlock { |
| let tcx = self.tcx(); |
| let unit_temp = Place::from(self.new_temp(tcx.mk_unit())); |
| let free_func = tcx.require_lang_item( |
| lang_items::BoxFreeFnLangItem, |
| Some(self.source_info.span) |
| ); |
| let args = adt.variants[VariantIdx::new(0)].fields.iter().enumerate().map(|(i, f)| { |
| let field = Field::new(i); |
| let field_ty = f.ty(self.tcx(), substs); |
| Operand::Move(self.place.clone().field(field, field_ty)) |
| }).collect(); |
| |
| let call = TerminatorKind::Call { |
| func: Operand::function_handle(tcx, free_func, substs, self.source_info.span), |
| args: args, |
| destination: Some((unit_temp, target)), |
| cleanup: None, |
| from_hir_call: false, |
| }; // FIXME(#43234) |
| let free_block = self.new_block(unwind, call); |
| |
| let block_start = Location { block: free_block, statement_index: 0 }; |
| self.elaborator.clear_drop_flag(block_start, self.path, DropFlagMode::Shallow); |
| free_block |
| } |
| |
| fn drop_block(&mut self, target: BasicBlock, unwind: Unwind) -> BasicBlock { |
| let block = TerminatorKind::Drop { |
| location: self.place.clone(), |
| target, |
| unwind: unwind.into_option() |
| }; |
| self.new_block(unwind, block) |
| } |
| |
| fn drop_flag_test_block(&mut self, |
| on_set: BasicBlock, |
| on_unset: BasicBlock, |
| unwind: Unwind) |
| -> BasicBlock |
| { |
| let style = self.elaborator.drop_style(self.path, DropFlagMode::Shallow); |
| debug!("drop_flag_test_block({:?},{:?},{:?},{:?}) - {:?}", |
| self, on_set, on_unset, unwind, style); |
| |
| match style { |
| DropStyle::Dead => on_unset, |
| DropStyle::Static => on_set, |
| DropStyle::Conditional | DropStyle::Open => { |
| let flag = self.elaborator.get_drop_flag(self.path).unwrap(); |
| let term = TerminatorKind::if_(self.tcx(), flag, on_set, on_unset); |
| self.new_block(unwind, term) |
| } |
| } |
| } |
| |
| fn new_block(&mut self, unwind: Unwind, k: TerminatorKind<'tcx>) -> BasicBlock { |
| self.elaborator.patch().new_block(BasicBlockData { |
| statements: vec![], |
| terminator: Some(Terminator { |
| source_info: self.source_info, kind: k |
| }), |
| is_cleanup: unwind.is_cleanup() |
| }) |
| } |
| |
| fn new_temp(&mut self, ty: Ty<'tcx>) -> Local { |
| self.elaborator.patch().new_temp(ty, self.source_info.span) |
| } |
| |
| fn terminator_loc(&mut self, bb: BasicBlock) -> Location { |
| let body = self.elaborator.body(); |
| self.elaborator.patch().terminator_loc(body, bb) |
| } |
| |
| fn constant_usize(&self, val: u16) -> Operand<'tcx> { |
| Operand::Constant(box Constant { |
| span: self.source_info.span, |
| user_ty: None, |
| literal: ty::Const::from_usize(self.tcx(), val.into()), |
| }) |
| } |
| |
| fn assign(&self, lhs: &Place<'tcx>, rhs: Rvalue<'tcx>) -> Statement<'tcx> { |
| Statement { |
| source_info: self.source_info, |
| kind: StatementKind::Assign(box(lhs.clone(), rhs)) |
| } |
| } |
| } |
