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use rustc::ty::{self, TyCtxt};
use rustc::mir::*;
/// Returns `true` if this place is allowed to be less aligned
/// than its containing struct (because it is within a packed
/// struct).
pub fn is_disaligned<'a, 'tcx, L>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
local_decls: &L,
param_env: ty::ParamEnv<'tcx>,
place: &Place<'tcx>)
-> bool
where L: HasLocalDecls<'tcx>
{
debug!("is_disaligned({:?})", place);
if !is_within_packed(tcx, local_decls, place) {
debug!("is_disaligned({:?}) - not within packed", place);
return false
}
let ty = place.ty(local_decls, tcx).ty;
match tcx.layout_raw(param_env.and(ty)) {
Ok(layout) if layout.align.abi.bytes() == 1 => {
// if the alignment is 1, the type can't be further
// disaligned.
debug!("is_disaligned({:?}) - align = 1", place);
false
}
_ => {
debug!("is_disaligned({:?}) - true", place);
true
}
}
}
fn is_within_packed<'a, 'tcx, L>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
local_decls: &L,
place: &Place<'tcx>)
-> bool
where L: HasLocalDecls<'tcx>
{
let mut place = place;
while let &Place::Projection(box Projection {
ref base, ref elem
}) = place {
match *elem {
// encountered a Deref, which is ABI-aligned
ProjectionElem::Deref => break,
ProjectionElem::Field(..) => {
let ty = base.ty(local_decls, tcx).ty;
match ty.sty {
ty::Adt(def, _) if def.repr.packed() => {
return true
}
_ => {}
}
}
_ => {}
}
place = base;
}
false
}
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