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use rustc_middle::mir::*;
use rustc_middle::ty::{self, TyCtxt};
/// 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<'tcx, L>(
tcx: TyCtxt<'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<'tcx, L>(tcx: TyCtxt<'tcx>, local_decls: &L, place: Place<'tcx>) -> bool
where
L: HasLocalDecls<'tcx>,
{
for (place_base, elem) in place.iter_projections().rev() {
match elem {
// encountered a Deref, which is ABI-aligned
ProjectionElem::Deref => break,
ProjectionElem::Field(..) => {
let ty = place_base.ty(local_decls, tcx).ty;
match ty.kind() {
ty::Adt(def, _) if def.repr.packed() => return true,
_ => {}
}
}
_ => {}
}
}
false
}
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