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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: Some(Box::new(Projection {
base: None,
elem: 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);
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(lhs.clone(), box rhs)
}
}
}
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