Struct AddMovesForPackedDrops 

pub(crate) 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_glue::<Vec<u8>> with a reference to data, which must be aligned. 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 policy(&self, _sess: &Session) -> PassPolicy

Describes how this pass is enabled and which mechanisms may disable it.

fn name(&self) -> &'static str

fn profiler_name(&self) -> &'static str

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