Struct rustc_mir_dataflow::elaborate_drops::DropCtxt

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,
}

Fields

elaborator: &'l mut D

source_info: SourceInfo

place: Place<'tcx>

path: D::Path

succ: BasicBlock

unwind: Unwind

Implementations

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>

fn tcx(&self) -> TyCtxt<'tcx>

pub fn elaborate_drop(&mut self, bb: BasicBlock)

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).

fn move_paths_for_fields(
    &self,
    base_place: Place<'tcx>,
    variant_path: D::Path,
    variant: &'tcx VariantDef,
    substs: SubstsRef<'tcx>
) -> Vec<(Place<'tcx>, Option<D::Path>)>

Returns the place and move path for each field of variant, (the move path is None if the field is a rest field).

fn drop_subpath(
    &mut self,
    place: Place<'tcx>,
    path: Option<D::Path>,
    succ: BasicBlock,
    unwind: Unwind
) -> BasicBlock

fn drop_halfladder(
    &mut self,
    unwind_ladder: &[Unwind],
    succ: BasicBlock,
    fields: &[(Place<'tcx>, Option<D::Path>)]
) -> Vec<BasicBlock>

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_ladder_bottom(&mut self) -> (BasicBlock, Unwind)

fn drop_ladder(
    &mut self,
    fields: Vec<(Place<'tcx>, Option<D::Path>)>,
    succ: BasicBlock,
    unwind: Unwind
) -> (BasicBlock, 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 open_drop_for_tuple(&mut self, tys: &[Ty<'tcx>]) -> BasicBlock

fn open_drop_for_box(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>
) -> BasicBlock

fn open_drop_for_adt(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>
) -> BasicBlock

fn open_drop_for_adt_contents(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>
) -> (BasicBlock, Unwind)

fn open_drop_for_multivariant(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>,
    succ: BasicBlock,
    unwind: Unwind
) -> (BasicBlock, Unwind)

fn adt_switch_block(
    &mut self,
    adt: AdtDef<'tcx>,
    blocks: Vec<BasicBlock>,
    values: &[u128],
    succ: BasicBlock,
    unwind: Unwind
) -> BasicBlock

fn destructor_call_block(
    &mut self,
    (succ, unwind): (BasicBlock, Unwind)
) -> BasicBlock

fn drop_loop(
    &mut self,
    succ: BasicBlock,
    cur: Local,
    length_or_end: Place<'tcx>,
    ety: Ty<'tcx>,
    unwind: Unwind,
    ptr_based: bool
) -> BasicBlock

Create a loop that drops an array:

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 open_drop_for_array(
    &mut self,
    ety: Ty<'tcx>,
    opt_size: Option<u64>
) -> BasicBlock

fn drop_loop_pair(
    &mut self,
    ety: Ty<'tcx>,
    ptr_based: bool,
    length: Place<'tcx>
) -> BasicBlock

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 open_drop(&mut self) -> BasicBlock

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 complete_drop(&mut self, succ: BasicBlock, unwind: Unwind) -> BasicBlock

fn drop_flag_reset_block(
    &mut self,
    mode: DropFlagMode,
    succ: BasicBlock,
    unwind: Unwind
) -> BasicBlock

Creates a block that resets the drop flag. If mode is deep, all children drop flags will also be cleared.

fn elaborated_drop_block(&mut self) -> BasicBlock

fn box_free_block(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>,
    target: BasicBlock,
    unwind: Unwind
) -> BasicBlock

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 unelaborated_free_block(
    &mut self,
    adt: AdtDef<'tcx>,
    substs: SubstsRef<'tcx>,
    target: BasicBlock,
    unwind: Unwind
) -> BasicBlock

Creates a block that frees the backing memory of a Box (without dropping the contained value).

fn drop_block(&mut self, target: BasicBlock, unwind: Unwind) -> BasicBlock

fn goto_block(&mut self, target: BasicBlock, unwind: Unwind) -> BasicBlock

fn drop_flag_test_block(
    &mut self,
    on_set: BasicBlock,
    on_unset: BasicBlock,
    unwind: Unwind
) -> BasicBlock

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 new_block(&mut self, unwind: Unwind, k: TerminatorKind<'tcx>) -> BasicBlock

fn new_temp(&mut self, ty: Ty<'tcx>) -> Local

fn constant_usize(&self, val: u16) -> Operand<'tcx>

fn assign(&self, lhs: Place<'tcx>, rhs: Rvalue<'tcx>) -> Statement<'tcx>

Trait Implementations

impl<'l, 'b, 'tcx, D> Debug for DropCtxt<'l, 'b, 'tcx, D>where
    D: DropElaborator<'b, 'tcx> + Debug,
    D::Path: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.