67 lines
1.8 KiB
Rust
67 lines
1.8 KiB
Rust
use rustc_middle::mir::*;
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_target::abi::Align;
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/// Returns `true` if this place is allowed to be less aligned
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/// than its containing struct (because it is within a packed
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/// struct).
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pub fn is_disaligned<'tcx, L>(
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tcx: TyCtxt<'tcx>,
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local_decls: &L,
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param_env: ty::ParamEnv<'tcx>,
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place: Place<'tcx>,
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) -> bool
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where
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L: HasLocalDecls<'tcx>,
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{
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debug!("is_disaligned({:?})", place);
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let Some(pack) = is_within_packed(tcx, local_decls, place) else {
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debug!("is_disaligned({:?}) - not within packed", place);
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return false;
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};
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let ty = place.ty(local_decls, tcx).ty;
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match tcx.layout_of(param_env.and(ty)) {
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Ok(layout) if layout.align.abi <= pack => {
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// If the packed alignment is greater or equal to the field alignment, the type won't be
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// further disaligned.
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debug!(
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"is_disaligned({:?}) - align = {}, packed = {}; not disaligned",
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place,
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layout.align.abi.bytes(),
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pack.bytes()
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);
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false
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}
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_ => {
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debug!("is_disaligned({:?}) - true", place);
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true
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}
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}
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}
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fn is_within_packed<'tcx, L>(
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tcx: TyCtxt<'tcx>,
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local_decls: &L,
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place: Place<'tcx>,
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) -> Option<Align>
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where
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L: HasLocalDecls<'tcx>,
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{
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for (place_base, elem) in place.iter_projections().rev() {
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match elem {
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// encountered a Deref, which is ABI-aligned
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ProjectionElem::Deref => break,
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ProjectionElem::Field(..) => {
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let ty = place_base.ty(local_decls, tcx).ty;
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match ty.kind() {
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ty::Adt(def, _) => return def.repr.pack,
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_ => {}
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}
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}
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_ => {}
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}
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}
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None
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}
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