Struct rustc_mir_transform::add_moves_for_packed_drops::AddMovesForPackedDrops

pub struct AddMovesForPackedDrops;

This pass moves values being dropped that are within a packed struct to a separate local before dropping them, to ensure that they are dropped from an aligned address.

For example, if we have something like

#[repr(packed)]
struct Foo {
    dealign: u8,
    data: Vec<u8>
}

let foo = ...;

We want to call drop_in_place::<Vec<u8>> on data from an aligned address. This means we can’t simply drop foo.data directly, because its address is not aligned.

Instead, we move foo.data to a local and drop that:

    storage.live(drop_temp)
    drop_temp = foo.data;
    drop(drop_temp) -> next
next:
    storage.dead(drop_temp)

The storage instructions are required to avoid stack space blowup.

Trait Implementations

impl<'tcx> MirPass<'tcx> for AddMovesForPackedDrops

fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>)

fn name(&self) -> &str

fn is_enabled(&self, _sess: &Session) -> bool

Returns true if this pass is enabled with the current combination of compiler flags.

fn is_mir_dump_enabled(&self) -> bool

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

Size: 0 bytes