+++ /dev/null
-use crate::util::patch::MirPatch;
-use rustc_hir as hir;
-use rustc_hir::lang_items::LangItem;
-use rustc_index::vec::Idx;
-use rustc_middle::mir::*;
-use rustc_middle::traits::Reveal;
-use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::util::IntTypeExt;
-use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_target::abi::VariantIdx;
-use std::fmt;
-
-/// The value of an inserted drop flag.
-#[derive(Debug, PartialEq, Eq, Copy, Clone)]
-pub enum DropFlagState {
- /// The tracked value is initialized and needs to be dropped when leaving its scope.
- Present,
-
- /// The tracked value is uninitialized or was moved out of and does not need to be dropped when
- /// leaving its scope.
- Absent,
-}
-
-impl DropFlagState {
- pub fn value(self) -> bool {
- match self {
- DropFlagState::Present => true,
- DropFlagState::Absent => false,
- }
- }
-}
-
-/// Describes how/if a value should be dropped.
-#[derive(Debug)]
-pub enum DropStyle {
- /// The value is already dead at the drop location, no drop will be executed.
- Dead,
-
- /// The value is known to always be initialized at the drop location, drop will always be
- /// executed.
- Static,
-
- /// Whether the value needs to be dropped depends on its drop flag.
- Conditional,
-
- /// An "open" drop is one where only the fields of a value are dropped.
- ///
- /// For example, this happens when moving out of a struct field: The rest of the struct will be
- /// dropped in such an "open" drop. It is also used to generate drop glue for the individual
- /// components of a value, for example for dropping array elements.
- Open,
-}
-
-/// Which drop flags to affect/check with an operation.
-#[derive(Debug)]
-pub enum DropFlagMode {
- /// Only affect the top-level drop flag, not that of any contained fields.
- Shallow,
- /// Affect all nested drop flags in addition to the top-level one.
- Deep,
-}
-
-/// Describes if unwinding is necessary and where to unwind to if a panic occurs.
-#[derive(Copy, Clone, Debug)]
-pub enum Unwind {
- /// Unwind to this block.
- To(BasicBlock),
- /// Already in an unwind path, any panic will cause an abort.
- 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 {
- /// The type representing paths that can be moved out of.
- ///
- /// Users can move out of individual fields of a struct, such as `a.b.c`. This type is used to
- /// represent such move paths. Sometimes tracking individual move paths is not necessary, in
- /// which case this may be set to (for example) `()`.
- type Path: Copy + fmt::Debug;
-
- // Accessors
-
- 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>;
-
- // Drop logic
-
- /// Returns how `path` should be dropped, given `mode`.
- fn drop_style(&self, path: Self::Path, mode: DropFlagMode) -> DropStyle;
-
- /// Returns the drop flag of `path` as a MIR `Operand` (or `None` if `path` has no drop flag).
- fn get_drop_flag(&mut self, path: Self::Path) -> Option<Operand<'tcx>>;
-
- /// Modifies the MIR patch so that the drop flag of `path` (if any) is cleared at `location`.
- ///
- /// If `mode` is deep, drop flags of all child paths should also be cleared by inserting
- /// additional statements.
- fn clear_drop_flag(&mut self, location: Location, path: Self::Path, mode: DropFlagMode);
-
- // Subpaths
-
- /// Returns the subpath of a field of `path` (or `None` if there is no dedicated subpath).
- ///
- /// If this returns `None`, `field` will not get a dedicated drop flag.
- fn field_subpath(&self, path: Self::Path, field: Field) -> Option<Self::Path>;
-
- /// Returns the subpath of a dereference of `path` (or `None` if there is no dedicated subpath).
- ///
- /// If this returns `None`, `*path` will not get a dedicated drop flag.
- ///
- /// This is only relevant for `Box<T>`, where the contained `T` can be moved out of the box.
- fn deref_subpath(&self, path: Self::Path) -> Option<Self::Path>;
-
- /// Returns the subpath of downcasting `path` to one of its variants.
- ///
- /// If this returns `None`, the downcast of `path` will not get a dedicated drop flag.
- fn downcast_subpath(&self, path: Self::Path, variant: VariantIdx) -> Option<Self::Path>;
-
- /// Returns the subpath of indexing a fixed-size array `path`.
- ///
- /// If this returns `None`, elements of `path` will not get a dedicated drop flag.
- ///
- /// This is only relevant for array patterns, which can move out of individual array elements.
- fn array_subpath(&self, path: Self::Path, index: u64, size: u64) -> Option<Self::Path>;
-}
-
-#[derive(Debug)]
-struct DropCtxt<'l, 'b, 'tcx, D>
-where
- D: DropElaborator<'b, 'tcx>,
-{
- elaborator: &'l mut D,
-
- source_info: SourceInfo,
-
- place: Place<'tcx>,
- path: D::Path,
- succ: BasicBlock,
- unwind: Unwind,
-}
-
-/// "Elaborates" a drop of `place`/`path` and patches `bb`'s terminator to execute it.
-///
-/// The passed `elaborator` is used to determine what should happen at the drop terminator. It
-/// decides whether the drop can be statically determined or whether it needs a dynamic drop flag,
-/// and whether the drop is "open", ie. should be expanded to drop all subfields of the dropped
-/// value.
-///
-/// When this returns, the MIR patch in the `elaborator` contains the necessary changes.
-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({:?}, {:?})", bb, self);
- let style = self.elaborator.drop_style(self.path, DropFlagMode::Deep);
- debug!("elaborate_drop({:?}, {:?}): live - {:?}", bb, self, style);
- match style {
- DropStyle::Dead => {
- self.elaborator
- .patch()
- .patch_terminator(bb, TerminatorKind::Goto { target: self.succ });
- }
- DropStyle::Static => {
- self.elaborator.patch().patch_terminator(
- bb,
- TerminatorKind::Drop {
- place: self.place,
- target: self.succ,
- unwind: self.unwind.into_option(),
- },
- );
- }
- DropStyle::Conditional => {
- let drop_bb = self.complete_drop(self.succ, self.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);
- let tcx = self.tcx();
-
- assert_eq!(self.elaborator.param_env().reveal(), Reveal::All);
- let field_ty =
- tcx.normalize_erasing_regions(self.elaborator.param_env(), f.ty(tcx, substs));
- (tcx.mk_place_field(base_place, 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(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(|(&(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.
- (self.drop_flag_reset_block(DropFlagMode::Shallow, self.succ, self.unwind), self.unwind)
- }
-
- /// 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(|&(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.tcx().mk_place_field(self.place, 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.tcx().mk_place_deref(self.place);
- let interior_path = self.elaborator.deref_subpath(self.path);
-
- let succ = self.box_free_block(adt, substs, self.succ, self.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.is_empty() {
- 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_with_drop_glue = false;
- let mut have_otherwise = false;
- let tcx = self.tcx();
-
- for (variant_index, discr) in adt.discriminants(tcx) {
- let variant = &adt.variants[variant_index];
- let subpath = self.elaborator.downcast_subpath(self.path, variant_index);
-
- if let Some(variant_path) = subpath {
- let base_place = tcx.mk_place_elem(
- self.place,
- ProjectionElem::Downcast(Some(variant.ident.name), variant_index),
- );
- let fields = self.move_paths_for_fields(base_place, variant_path, &variant, 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;
-
- let param_env = self.elaborator.param_env();
- let have_field_with_drop_glue = variant
- .fields
- .iter()
- .any(|field| field.ty(tcx, substs).needs_drop(tcx, param_env));
- if have_field_with_drop_glue {
- have_otherwise_with_drop_glue = true;
- }
- }
- }
-
- if !have_otherwise {
- values.pop();
- } else if !have_otherwise_with_drop_glue {
- normal_blocks.push(self.goto_block(succ, unwind));
- if let Unwind::To(unwind) = unwind {
- unwind_blocks.as_mut().unwrap().push(self.goto_block(unwind, Unwind::InCleanup));
- }
- } else {
- 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));
- }
- }
-
- (
- 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);
- 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,
- targets: SwitchTargets::new(
- values.iter().copied().zip(blocks.iter().copied()),
- *blocks.last().unwrap(),
- ),
- },
- }),
- 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.require_lang_item(LangItem::Drop, None);
- let drop_fn = tcx.associated_items(drop_trait).in_definition_order().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::Mut });
- 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,
- ),
- )],
- 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,
- fn_span: self.source_info.span,
- },
- 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 = cur
- /// cur = cur.offset(1)
- /// } else {
- /// ptr = &raw 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);
- let move_ = |place: Place<'tcx>| Operand::Move(place);
- let tcx = self.tcx();
-
- let ptr_ty = tcx.mk_ptr(ty::TypeAndMut { ty: ety, mutbl: hir::Mutability::Mut });
- let ptr = Place::from(self.new_temp(ptr_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::Use(copy(cur.into())),
- Rvalue::BinaryOp(BinOp::Offset, Box::new((move_(cur.into()), one))),
- )
- } else {
- (
- Rvalue::AddressOf(Mutability::Mut, tcx.mk_place_index(self.place, cur)),
- Rvalue::BinaryOp(BinOp::Add, Box::new((move_(cur.into()), 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,
- Box::new((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 {
- place: tcx.mk_place_deref(ptr),
- 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
- // }
-
- let tcx = self.tcx();
-
- if let Some(size) = opt_size {
- let fields: Vec<(Place<'tcx>, Option<D::Path>)> = (0..size)
- .map(|i| {
- (
- tcx.mk_place_elem(
- self.place,
- 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);
- let elem_size = Place::from(self.new_temp(tcx.types.usize));
- let len = Place::from(self.new_temp(tcx.types.usize));
-
- let base_block = BasicBlockData {
- statements: vec![
- self.assign(elem_size, Rvalue::NullaryOp(NullOp::SizeOf, ety)),
- self.assign(len, Rvalue::Len(self.place)),
- ],
- 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,
- targets: SwitchTargets::static_if(
- 0,
- self.drop_loop_pair(ety, false, len),
- self.drop_loop_pair(ety, true, len),
- ),
- },
- }),
- };
- self.elaborator.patch().new_block(base_block)
- }
-
- /// Creates 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 { Place::from(self.new_temp(iter_ty)) } else { length };
-
- 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 = &raw mut P;
- // cur = tmp as *mut T;
- // end = Offset(cur, len);
- vec![
- self.assign(tmp, Rvalue::AddressOf(Mutability::Mut, self.place)),
- self.assign(cur, Rvalue::Cast(CastKind::Misc, Operand::Move(tmp), iter_ty)),
- self.assign(
- length_or_end,
- Rvalue::BinaryOp(
- BinOp::Offset,
- Box::new((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.kind() {
- ty::Closure(_, substs) => {
- let tys: Vec<_> = substs.as_closure().upvar_tys().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(_, substs, _) => {
- let tys: Vec<_> = substs.as_generator().upvar_tys().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(..) => self.complete_drop(self.succ, self.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),
- }
- }
-
- fn complete_drop(&mut self, succ: BasicBlock, unwind: Unwind) -> BasicBlock {
- debug!("complete_drop(succ={:?}, unwind={:?})", succ, unwind);
-
- let drop_block = self.drop_block(succ, unwind);
-
- self.drop_flag_test_block(drop_block, succ, unwind)
- }
-
- /// Creates a block that resets the drop flag. If `mode` is deep, all children drop flags will
- /// also be cleared.
- fn drop_flag_reset_block(
- &mut self,
- mode: DropFlagMode,
- succ: BasicBlock,
- unwind: Unwind,
- ) -> BasicBlock {
- debug!("drop_flag_reset_block({:?},{:?})", self, mode);
-
- if unwind.is_cleanup() {
- // The drop flag isn't read again on the unwind path, so don't
- // bother setting it.
- return succ;
- }
- let block = self.new_block(unwind, TerminatorKind::Goto { target: succ });
- let block_start = Location { 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 blk = self.drop_block(self.succ, self.unwind);
- self.elaborate_drop(blk);
- blk
- }
-
- /// Creates a block that frees the backing memory of a `Box` if its drop is required (either
- /// statically or by checking its drop flag).
- ///
- /// The contained value will not be dropped.
- 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)
- }
-
- /// Creates a block that frees the backing memory of a `Box` (without dropping the contained
- /// value).
- 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(LangItem::BoxFree, 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(tcx, substs);
- Operand::Move(tcx.mk_place_field(self.place, field, field_ty))
- })
- .collect();
-
- let call = TerminatorKind::Call {
- func: Operand::function_handle(tcx, free_func, substs, self.source_info.span),
- args,
- destination: Some((unit_temp, target)),
- cleanup: None,
- from_hir_call: false,
- fn_span: self.source_info.span,
- }; // 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 { place: self.place, target, unwind: unwind.into_option() };
- self.new_block(unwind, block)
- }
-
- fn goto_block(&mut self, target: BasicBlock, unwind: Unwind) -> BasicBlock {
- let block = TerminatorKind::Goto { target };
- self.new_block(unwind, block)
- }
-
- /// Returns the block to jump to in order to test the drop flag and execute the drop.
- ///
- /// Depending on the required `DropStyle`, this might be a generated block with an `if`
- /// terminator (for dynamic/open drops), or it might be `on_set` or `on_unset` itself, in case
- /// the drop can be statically determined.
- 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 constant_usize(&self, val: u16) -> Operand<'tcx> {
- Operand::Constant(Box::new(Constant {
- span: self.source_info.span,
- user_ty: None,
- literal: ty::Const::from_usize(self.tcx(), val.into()).into(),
- }))
- }
-
- fn assign(&self, lhs: Place<'tcx>, rhs: Rvalue<'tcx>) -> Statement<'tcx> {
- Statement {
- source_info: self.source_info,
- kind: StatementKind::Assign(Box::new((lhs, rhs))),
- }
- }
-}
projects / rustc.git / blobdiff