| use std::ops::ControlFlow; |
| |
| use super::{Byte, Def, Ref}; |
| |
| #[cfg(test)] |
| mod tests; |
| |
| /// A tree-based representation of a type layout. |
| /// |
| /// Invariants: |
| /// 1. All paths through the layout have the same length (in bytes). |
| /// |
| /// Nice-to-haves: |
| /// 1. An `Alt` is never directly nested beneath another `Alt`. |
| /// 2. A `Seq` is never directly nested beneath another `Seq`. |
| /// 3. `Seq`s and `Alt`s with a single member do not exist. |
| #[derive(Clone, Debug, Hash, PartialEq, Eq)] |
| pub(crate) enum Tree<D, R> |
| where |
| D: Def, |
| R: Ref, |
| { |
| /// A sequence of successive layouts. |
| Seq(Vec<Self>), |
| /// A choice between alternative layouts. |
| Alt(Vec<Self>), |
| /// A definition node. |
| Def(D), |
| /// A reference node. |
| Ref(R), |
| /// A byte node. |
| Byte(Byte), |
| } |
| |
| impl<D, R> Tree<D, R> |
| where |
| D: Def, |
| R: Ref, |
| { |
| /// A `Tree` consisting only of a definition node. |
| pub(crate) fn def(def: D) -> Self { |
| Self::Def(def) |
| } |
| |
| /// A `Tree` representing an uninhabited type. |
| pub(crate) fn uninhabited() -> Self { |
| Self::Alt(vec![]) |
| } |
| |
| /// A `Tree` representing a zero-sized type. |
| pub(crate) fn unit() -> Self { |
| Self::Seq(Vec::new()) |
| } |
| |
| /// A `Tree` containing a single, uninitialized byte. |
| pub(crate) fn uninit() -> Self { |
| Self::Byte(Byte::uninit()) |
| } |
| |
| /// A `Tree` representing the layout of `bool`. |
| pub(crate) fn bool() -> Self { |
| Self::Byte(Byte::new(0x00..=0x01)) |
| } |
| |
| /// A `Tree` whose layout matches that of a `u8`. |
| pub(crate) fn u8() -> Self { |
| Self::Byte(Byte::new(0x00..=0xFF)) |
| } |
| |
| /// A `Tree` whose layout accepts exactly the given bit pattern. |
| pub(crate) fn from_bits(bits: u8) -> Self { |
| Self::Byte(Byte::from_val(bits)) |
| } |
| |
| /// A `Tree` whose layout is a number of the given width. |
| pub(crate) fn number(width_in_bytes: usize) -> Self { |
| Self::Seq(vec![Self::u8(); width_in_bytes]) |
| } |
| |
| /// A `Tree` whose layout is entirely padding of the given width. |
| pub(crate) fn padding(width_in_bytes: usize) -> Self { |
| Self::Seq(vec![Self::uninit(); width_in_bytes]) |
| } |
| |
| /// Remove all `Def` nodes, and all branches of the layout for which `f` |
| /// produces `true`. |
| pub(crate) fn prune<F>(self, f: &F) -> Tree<!, R> |
| where |
| F: Fn(D) -> bool, |
| { |
| match self { |
| Self::Seq(elts) => match elts.into_iter().map(|elt| elt.prune(f)).try_fold( |
| Tree::unit(), |
| |elts, elt| { |
| if elt == Tree::uninhabited() { |
| ControlFlow::Break(Tree::uninhabited()) |
| } else { |
| ControlFlow::Continue(elts.then(elt)) |
| } |
| }, |
| ) { |
| ControlFlow::Break(node) | ControlFlow::Continue(node) => node, |
| }, |
| Self::Alt(alts) => alts |
| .into_iter() |
| .map(|alt| alt.prune(f)) |
| .fold(Tree::uninhabited(), |alts, alt| alts.or(alt)), |
| Self::Byte(b) => Tree::Byte(b), |
| Self::Ref(r) => Tree::Ref(r), |
| Self::Def(d) => { |
| if f(d) { |
| Tree::uninhabited() |
| } else { |
| Tree::unit() |
| } |
| } |
| } |
| } |
| |
| /// Produces `true` if `Tree` is an inhabited type; otherwise false. |
| pub(crate) fn is_inhabited(&self) -> bool { |
| match self { |
| Self::Seq(elts) => elts.into_iter().all(|elt| elt.is_inhabited()), |
| Self::Alt(alts) => alts.into_iter().any(|alt| alt.is_inhabited()), |
| Self::Byte(..) | Self::Ref(..) | Self::Def(..) => true, |
| } |
| } |
| } |
| |
| impl<D, R> Tree<D, R> |
| where |
| D: Def, |
| R: Ref, |
| { |
| /// Produces a new `Tree` where `other` is sequenced after `self`. |
| pub(crate) fn then(self, other: Self) -> Self { |
| match (self, other) { |
| (Self::Seq(elts), other) | (other, Self::Seq(elts)) if elts.len() == 0 => other, |
| (Self::Seq(mut lhs), Self::Seq(mut rhs)) => { |
| lhs.append(&mut rhs); |
| Self::Seq(lhs) |
| } |
| (Self::Seq(mut lhs), rhs) => { |
| lhs.push(rhs); |
| Self::Seq(lhs) |
| } |
| (lhs, Self::Seq(mut rhs)) => { |
| rhs.insert(0, lhs); |
| Self::Seq(rhs) |
| } |
| (lhs, rhs) => Self::Seq(vec![lhs, rhs]), |
| } |
| } |
| |
| /// Produces a new `Tree` accepting either `self` or `other` as alternative layouts. |
| pub(crate) fn or(self, other: Self) -> Self { |
| match (self, other) { |
| (Self::Alt(alts), other) | (other, Self::Alt(alts)) if alts.len() == 0 => other, |
| (Self::Alt(mut lhs), Self::Alt(rhs)) => { |
| lhs.extend(rhs); |
| Self::Alt(lhs) |
| } |
| (Self::Alt(mut alts), alt) | (alt, Self::Alt(mut alts)) => { |
| alts.push(alt); |
| Self::Alt(alts) |
| } |
| (lhs, rhs) => Self::Alt(vec![lhs, rhs]), |
| } |
| } |
| } |
| |
| #[cfg(feature = "rustc")] |
| pub(crate) mod rustc { |
| use rustc_abi::{ |
| FieldIdx, FieldsShape, Layout, Size, TagEncoding, TyAndLayout, VariantIdx, Variants, |
| }; |
| use rustc_middle::ty::layout::{HasTyCtxt, LayoutCx, LayoutError}; |
| use rustc_middle::ty::{self, AdtDef, AdtKind, List, ScalarInt, Ty, TyCtxt, TypeVisitableExt}; |
| use rustc_span::ErrorGuaranteed; |
| |
| use super::Tree; |
| use crate::layout::rustc::{Def, Ref, layout_of}; |
| |
| #[derive(Debug, Copy, Clone)] |
| pub(crate) enum Err { |
| /// The layout of the type is not yet supported. |
| NotYetSupported, |
| /// This error will be surfaced elsewhere by rustc, so don't surface it. |
| UnknownLayout, |
| /// Overflow size |
| SizeOverflow, |
| TypeError(ErrorGuaranteed), |
| } |
| |
| impl<'tcx> From<&LayoutError<'tcx>> for Err { |
| fn from(err: &LayoutError<'tcx>) -> Self { |
| match err { |
| LayoutError::Unknown(..) |
| | LayoutError::ReferencesError(..) |
| | LayoutError::TooGeneric(..) |
| | LayoutError::NormalizationFailure(..) => Self::UnknownLayout, |
| LayoutError::SizeOverflow(..) => Self::SizeOverflow, |
| LayoutError::Cycle(err) => Self::TypeError(*err), |
| } |
| } |
| } |
| |
| impl<'tcx> Tree<Def<'tcx>, Ref<'tcx>> { |
| pub(crate) fn from_ty(ty: Ty<'tcx>, cx: LayoutCx<'tcx>) -> Result<Self, Err> { |
| use rustc_abi::HasDataLayout; |
| let layout = layout_of(cx, ty)?; |
| |
| if let Err(e) = ty.error_reported() { |
| return Err(Err::TypeError(e)); |
| } |
| |
| let target = cx.data_layout(); |
| let pointer_size = target.pointer_size; |
| |
| match ty.kind() { |
| ty::Bool => Ok(Self::bool()), |
| |
| ty::Float(nty) => { |
| let width = nty.bit_width() / 8; |
| Ok(Self::number(width as _)) |
| } |
| |
| ty::Int(nty) => { |
| let width = nty.normalize(pointer_size.bits() as _).bit_width().unwrap() / 8; |
| Ok(Self::number(width as _)) |
| } |
| |
| ty::Uint(nty) => { |
| let width = nty.normalize(pointer_size.bits() as _).bit_width().unwrap() / 8; |
| Ok(Self::number(width as _)) |
| } |
| |
| ty::Tuple(members) => Self::from_tuple((ty, layout), members, cx), |
| |
| ty::Array(inner_ty, _len) => { |
| let FieldsShape::Array { stride, count } = &layout.fields else { |
| return Err(Err::NotYetSupported); |
| }; |
| let inner_layout = layout_of(cx, *inner_ty)?; |
| assert_eq!(*stride, inner_layout.size); |
| let elt = Tree::from_ty(*inner_ty, cx)?; |
| Ok(std::iter::repeat(elt) |
| .take(*count as usize) |
| .fold(Tree::unit(), |tree, elt| tree.then(elt))) |
| } |
| |
| ty::Adt(adt_def, _args_ref) if !ty.is_box() => match adt_def.adt_kind() { |
| AdtKind::Struct => Self::from_struct((ty, layout), *adt_def, cx), |
| AdtKind::Enum => Self::from_enum((ty, layout), *adt_def, cx), |
| AdtKind::Union => Self::from_union((ty, layout), *adt_def, cx), |
| }, |
| |
| ty::Ref(lifetime, ty, mutability) => { |
| let layout = layout_of(cx, *ty)?; |
| let align = layout.align.abi.bytes_usize(); |
| let size = layout.size.bytes_usize(); |
| Ok(Tree::Ref(Ref { |
| lifetime: *lifetime, |
| ty: *ty, |
| mutability: *mutability, |
| align, |
| size, |
| })) |
| } |
| |
| _ => Err(Err::NotYetSupported), |
| } |
| } |
| |
| /// Constructs a `Tree` from a tuple. |
| fn from_tuple( |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| members: &'tcx List<Ty<'tcx>>, |
| cx: LayoutCx<'tcx>, |
| ) -> Result<Self, Err> { |
| match &layout.fields { |
| FieldsShape::Primitive => { |
| assert_eq!(members.len(), 1); |
| let inner_ty = members[0]; |
| Self::from_ty(inner_ty, cx) |
| } |
| FieldsShape::Arbitrary { offsets, .. } => { |
| assert_eq!(offsets.len(), members.len()); |
| Self::from_variant(Def::Primitive, None, (ty, layout), layout.size, cx) |
| } |
| FieldsShape::Array { .. } | FieldsShape::Union(_) => Err(Err::NotYetSupported), |
| } |
| } |
| |
| /// Constructs a `Tree` from a struct. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `def` is not a struct definition. |
| fn from_struct( |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| def: AdtDef<'tcx>, |
| cx: LayoutCx<'tcx>, |
| ) -> Result<Self, Err> { |
| assert!(def.is_struct()); |
| let def = Def::Adt(def); |
| Self::from_variant(def, None, (ty, layout), layout.size, cx) |
| } |
| |
| /// Constructs a `Tree` from an enum. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `def` is not an enum definition. |
| fn from_enum( |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| def: AdtDef<'tcx>, |
| cx: LayoutCx<'tcx>, |
| ) -> Result<Self, Err> { |
| assert!(def.is_enum()); |
| |
| // Computes the layout of a variant. |
| let layout_of_variant = |
| |index, encoding: Option<TagEncoding<VariantIdx>>| -> Result<Self, Err> { |
| let variant_layout = ty_variant(cx, (ty, layout), index); |
| if variant_layout.is_uninhabited() { |
| return Ok(Self::uninhabited()); |
| } |
| let tag = cx.tcx().tag_for_variant((cx.tcx().erase_regions(ty), index)); |
| let variant_def = Def::Variant(def.variant(index)); |
| Self::from_variant( |
| variant_def, |
| tag.map(|tag| (tag, index, encoding.unwrap())), |
| (ty, variant_layout), |
| layout.size, |
| cx, |
| ) |
| }; |
| |
| match layout.variants() { |
| Variants::Empty => Ok(Self::uninhabited()), |
| Variants::Single { index } => { |
| // `Variants::Single` on enums with variants denotes that |
| // the enum delegates its layout to the variant at `index`. |
| layout_of_variant(*index, None) |
| } |
| Variants::Multiple { tag: _, tag_encoding, tag_field, .. } => { |
| // `Variants::Multiple` denotes an enum with multiple |
| // variants. The layout of such an enum is the disjunction |
| // of the layouts of its tagged variants. |
| |
| // For enums (but not coroutines), the tag field is |
| // currently always the first field of the layout. |
| assert_eq!(*tag_field, 0); |
| |
| let variants = def.discriminants(cx.tcx()).try_fold( |
| Self::uninhabited(), |
| |variants, (idx, _discriminant)| { |
| let variant = layout_of_variant(idx, Some(tag_encoding.clone()))?; |
| Result::<Self, Err>::Ok(variants.or(variant)) |
| }, |
| )?; |
| |
| Ok(Self::def(Def::Adt(def)).then(variants)) |
| } |
| } |
| } |
| |
| /// Constructs a `Tree` from a 'variant-like' layout. |
| /// |
| /// A 'variant-like' layout includes those of structs and, of course, |
| /// enum variants. Pragmatically speaking, this method supports anything |
| /// with `FieldsShape::Arbitrary`. |
| /// |
| /// Note: This routine assumes that the optional `tag` is the first |
| /// field, and enum callers should check that `tag_field` is, in fact, |
| /// `0`. |
| fn from_variant( |
| def: Def<'tcx>, |
| tag: Option<(ScalarInt, VariantIdx, TagEncoding<VariantIdx>)>, |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| total_size: Size, |
| cx: LayoutCx<'tcx>, |
| ) -> Result<Self, Err> { |
| // This constructor does not support non-`FieldsShape::Arbitrary` |
| // layouts. |
| let FieldsShape::Arbitrary { offsets, memory_index } = layout.fields() else { |
| return Err(Err::NotYetSupported); |
| }; |
| |
| // When this function is invoked with enum variants, |
| // `ty_and_layout.size` does not encompass the entire size of the |
| // enum. We rely on `total_size` for this. |
| assert!(layout.size <= total_size); |
| |
| let mut size = Size::ZERO; |
| let mut struct_tree = Self::def(def); |
| |
| // If a `tag` is provided, place it at the start of the layout. |
| if let Some((tag, index, encoding)) = &tag { |
| match encoding { |
| TagEncoding::Direct => { |
| size += tag.size(); |
| } |
| TagEncoding::Niche { niche_variants, .. } => { |
| if !niche_variants.contains(index) { |
| size += tag.size(); |
| } |
| } |
| } |
| struct_tree = struct_tree.then(Self::from_tag(*tag, cx.tcx())); |
| } |
| |
| // Append the fields, in memory order, to the layout. |
| let inverse_memory_index = memory_index.invert_bijective_mapping(); |
| for &field_idx in inverse_memory_index.iter() { |
| // Add interfield padding. |
| let padding_needed = offsets[field_idx] - size; |
| let padding = Self::padding(padding_needed.bytes_usize()); |
| |
| let field_ty = ty_field(cx, (ty, layout), field_idx); |
| let field_layout = layout_of(cx, field_ty)?; |
| let field_tree = Self::from_ty(field_ty, cx)?; |
| |
| struct_tree = struct_tree.then(padding).then(field_tree); |
| |
| size += padding_needed + field_layout.size; |
| } |
| |
| // Add trailing padding. |
| let padding_needed = total_size - size; |
| let trailing_padding = Self::padding(padding_needed.bytes_usize()); |
| |
| Ok(struct_tree.then(trailing_padding)) |
| } |
| |
| /// Constructs a `Tree` representing the value of a enum tag. |
| fn from_tag(tag: ScalarInt, tcx: TyCtxt<'tcx>) -> Self { |
| use rustc_abi::Endian; |
| let size = tag.size(); |
| let bits = tag.to_bits(size); |
| let bytes: [u8; 16]; |
| let bytes = match tcx.data_layout.endian { |
| Endian::Little => { |
| bytes = bits.to_le_bytes(); |
| &bytes[..size.bytes_usize()] |
| } |
| Endian::Big => { |
| bytes = bits.to_be_bytes(); |
| &bytes[bytes.len() - size.bytes_usize()..] |
| } |
| }; |
| Self::Seq(bytes.iter().map(|&b| Self::from_bits(b)).collect()) |
| } |
| |
| /// Constructs a `Tree` from a union. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `def` is not a union definition. |
| fn from_union( |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| def: AdtDef<'tcx>, |
| cx: LayoutCx<'tcx>, |
| ) -> Result<Self, Err> { |
| assert!(def.is_union()); |
| |
| // This constructor does not support non-`FieldsShape::Union` |
| // layouts. Fields of this shape are all placed at offset 0. |
| let FieldsShape::Union(_fields) = layout.fields() else { |
| return Err(Err::NotYetSupported); |
| }; |
| |
| let fields = &def.non_enum_variant().fields; |
| let fields = fields.iter_enumerated().try_fold( |
| Self::uninhabited(), |
| |fields, (idx, _field_def)| { |
| let field_ty = ty_field(cx, (ty, layout), idx); |
| let field_layout = layout_of(cx, field_ty)?; |
| let field = Self::from_ty(field_ty, cx)?; |
| let trailing_padding_needed = layout.size - field_layout.size; |
| let trailing_padding = Self::padding(trailing_padding_needed.bytes_usize()); |
| let field_and_padding = field.then(trailing_padding); |
| Result::<Self, Err>::Ok(fields.or(field_and_padding)) |
| }, |
| )?; |
| |
| Ok(Self::def(Def::Adt(def)).then(fields)) |
| } |
| } |
| |
| fn ty_field<'tcx>( |
| cx: LayoutCx<'tcx>, |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| i: FieldIdx, |
| ) -> Ty<'tcx> { |
| // We cannot use `ty_and_layout_field` to retrieve the field type, since |
| // `ty_and_layout_field` erases regions in the returned type. We must |
| // not erase regions here, since we may need to ultimately emit outlives |
| // obligations as a consequence of the transmutability analysis. |
| match ty.kind() { |
| ty::Adt(def, args) => { |
| match layout.variants { |
| Variants::Single { index } => { |
| let field = &def.variant(index).fields[i]; |
| field.ty(cx.tcx(), args) |
| } |
| Variants::Empty => panic!("there is no field in Variants::Empty types"), |
| // Discriminant field for enums (where applicable). |
| Variants::Multiple { tag, .. } => { |
| assert_eq!(i.as_usize(), 0); |
| ty::layout::PrimitiveExt::to_ty(&tag.primitive(), cx.tcx()) |
| } |
| } |
| } |
| ty::Tuple(fields) => fields[i.as_usize()], |
| kind => unimplemented!( |
| "only a subset of `Ty::ty_and_layout_field`'s functionality is implemented. implementation needed for {:?}", |
| kind |
| ), |
| } |
| } |
| |
| fn ty_variant<'tcx>( |
| cx: LayoutCx<'tcx>, |
| (ty, layout): (Ty<'tcx>, Layout<'tcx>), |
| i: VariantIdx, |
| ) -> Layout<'tcx> { |
| let ty = cx.tcx().erase_regions(ty); |
| TyAndLayout { ty, layout }.for_variant(&cx, i).layout |
| } |
| } |
