use rustc_span::DUMMY_SP;
use rustc_target::abi::*;
-use std::cmp::{self, Ordering};
+use std::fmt::Debug;
use std::iter;
-use std::num::NonZeroUsize;
-use std::ops::Bound;
-
-use rand::{seq::SliceRandom, SeedableRng};
-use rand_xoshiro::Xoshiro128StarStar;
use crate::layout_sanity_check::sanity_check_layout;
Ok(layout)
}
-#[derive(Copy, Clone, Debug)]
-enum StructKind {
- /// A tuple, closure, or univariant which cannot be coerced to unsized.
- AlwaysSized,
- /// A univariant, the last field of which may be coerced to unsized.
- MaybeUnsized,
- /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
- Prefixed(Size, Align),
-}
-
// Invert a bijective mapping, i.e. `invert(map)[y] = x` if `map[x] = y`.
// This is used to go between `memory_index` (source field order to memory order)
// and `inverse_memory_index` (memory order to source field order).
inverse
}
-fn scalar_pair<'tcx>(cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, a: Scalar, b: Scalar) -> LayoutS<'tcx> {
- let dl = cx.data_layout();
- let b_align = b.align(dl);
- let align = a.align(dl).max(b_align).max(dl.aggregate_align);
- let b_offset = a.size(dl).align_to(b_align.abi);
- let size = (b_offset + b.size(dl)).align_to(align.abi);
-
- // HACK(nox): We iter on `b` and then `a` because `max_by_key`
- // returns the last maximum.
- let largest_niche = Niche::from_scalar(dl, b_offset, b)
- .into_iter()
- .chain(Niche::from_scalar(dl, Size::ZERO, a))
- .max_by_key(|niche| niche.available(dl));
-
- LayoutS {
- variants: Variants::Single { index: VariantIdx::new(0) },
- fields: FieldsShape::Arbitrary {
- offsets: vec![Size::ZERO, b_offset],
- memory_index: vec![0, 1],
- },
- abi: Abi::ScalarPair(a, b),
- largest_niche,
- align,
- size,
- }
-}
-
fn univariant_uninterned<'tcx>(
cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
ty: Ty<'tcx>,
fields: &[TyAndLayout<'_>],
repr: &ReprOptions,
kind: StructKind,
-) -> Result<LayoutS<'tcx>, LayoutError<'tcx>> {
+) -> Result<LayoutS<VariantIdx>, LayoutError<'tcx>> {
let dl = cx.data_layout();
let pack = repr.pack;
if pack.is_some() && repr.align.is_some() {
return Err(LayoutError::Unknown(ty));
}
- let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align };
-
- let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
-
- let optimize = !repr.inhibit_struct_field_reordering_opt();
- if optimize {
- let end = if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
- let optimizing = &mut inverse_memory_index[..end];
- let effective_field_align = |f: &TyAndLayout<'_>| {
- if let Some(pack) = pack {
- // return the packed alignment in bytes
- f.align.abi.min(pack).bytes()
- } else {
- // returns log2(effective-align).
- // This is ok since `pack` applies to all fields equally.
- // The calculation assumes that size is an integer multiple of align, except for ZSTs.
- //
- // group [u8; 4] with align-4 or [u8; 6] with align-2 fields
- f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64
- }
- };
-
- // If `-Z randomize-layout` was enabled for the type definition we can shuffle
- // the field ordering to try and catch some code making assumptions about layouts
- // we don't guarantee
- if repr.can_randomize_type_layout() {
- // `ReprOptions.layout_seed` is a deterministic seed that we can use to
- // randomize field ordering with
- let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed);
-
- // Shuffle the ordering of the fields
- optimizing.shuffle(&mut rng);
-
- // Otherwise we just leave things alone and actually optimize the type's fields
- } else {
- match kind {
- StructKind::AlwaysSized | StructKind::MaybeUnsized => {
- optimizing.sort_by_key(|&x| {
- // Place ZSTs first to avoid "interesting offsets",
- // especially with only one or two non-ZST fields.
- // Then place largest alignments first, largest niches within an alignment group last
- let f = &fields[x as usize];
- let niche_size = f.largest_niche.map_or(0, |n| n.available(cx));
- (!f.is_zst(), cmp::Reverse(effective_field_align(f)), niche_size)
- });
- }
-
- StructKind::Prefixed(..) => {
- // Sort in ascending alignment so that the layout stays optimal
- // regardless of the prefix.
- // And put the largest niche in an alignment group at the end
- // so it can be used as discriminant in jagged enums
- optimizing.sort_by_key(|&x| {
- let f = &fields[x as usize];
- let niche_size = f.largest_niche.map_or(0, |n| n.available(cx));
- (effective_field_align(f), niche_size)
- });
- }
- }
-
- // FIXME(Kixiron): We can always shuffle fields within a given alignment class
- // regardless of the status of `-Z randomize-layout`
- }
- }
-
- // inverse_memory_index holds field indices by increasing memory offset.
- // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
- // We now write field offsets to the corresponding offset slot;
- // field 5 with offset 0 puts 0 in offsets[5].
- // At the bottom of this function, we invert `inverse_memory_index` to
- // produce `memory_index` (see `invert_mapping`).
-
- let mut sized = true;
- let mut offsets = vec![Size::ZERO; fields.len()];
- let mut offset = Size::ZERO;
- let mut largest_niche = None;
- let mut largest_niche_available = 0;
-
- if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
- let prefix_align =
- if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align };
- align = align.max(AbiAndPrefAlign::new(prefix_align));
- offset = prefix_size.align_to(prefix_align);
- }
-
- for &i in &inverse_memory_index {
- let field = fields[i as usize];
- if !sized {
- cx.tcx.sess.delay_span_bug(
- DUMMY_SP,
- &format!(
- "univariant: field #{} of `{}` comes after unsized field",
- offsets.len(),
- ty
- ),
- );
- }
-
- if field.is_unsized() {
- sized = false;
- }
-
- // Invariant: offset < dl.obj_size_bound() <= 1<<61
- let field_align = if let Some(pack) = pack {
- field.align.min(AbiAndPrefAlign::new(pack))
- } else {
- field.align
- };
- offset = offset.align_to(field_align.abi);
- align = align.max(field_align);
-
- debug!("univariant offset: {:?} field: {:#?}", offset, field);
- offsets[i as usize] = offset;
-
- if let Some(mut niche) = field.largest_niche {
- let available = niche.available(dl);
- if available > largest_niche_available {
- largest_niche_available = available;
- niche.offset += offset;
- largest_niche = Some(niche);
- }
- }
-
- offset = offset.checked_add(field.size, dl).ok_or(LayoutError::SizeOverflow(ty))?;
- }
-
- if let Some(repr_align) = repr.align {
- align = align.max(AbiAndPrefAlign::new(repr_align));
- }
-
- debug!("univariant min_size: {:?}", offset);
- let min_size = offset;
-
- // As stated above, inverse_memory_index holds field indices by increasing offset.
- // This makes it an already-sorted view of the offsets vec.
- // To invert it, consider:
- // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
- // Field 5 would be the first element, so memory_index is i:
- // Note: if we didn't optimize, it's already right.
-
- let memory_index =
- if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
-
- let size = min_size.align_to(align.abi);
- let mut abi = Abi::Aggregate { sized };
-
- // Unpack newtype ABIs and find scalar pairs.
- if sized && size.bytes() > 0 {
- // All other fields must be ZSTs.
- let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst());
-
- match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) {
- // We have exactly one non-ZST field.
- (Some((i, field)), None, None) => {
- // Field fills the struct and it has a scalar or scalar pair ABI.
- if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size {
- match field.abi {
- // For plain scalars, or vectors of them, we can't unpack
- // newtypes for `#[repr(C)]`, as that affects C ABIs.
- Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
- abi = field.abi;
- }
- // But scalar pairs are Rust-specific and get
- // treated as aggregates by C ABIs anyway.
- Abi::ScalarPair(..) => {
- abi = field.abi;
- }
- _ => {}
- }
- }
- }
-
- // Two non-ZST fields, and they're both scalars.
- (Some((i, a)), Some((j, b)), None) => {
- match (a.abi, b.abi) {
- (Abi::Scalar(a), Abi::Scalar(b)) => {
- // Order by the memory placement, not source order.
- let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
- ((i, a), (j, b))
- } else {
- ((j, b), (i, a))
- };
- let pair = scalar_pair(cx, a, b);
- let pair_offsets = match pair.fields {
- FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
- assert_eq!(memory_index, &[0, 1]);
- offsets
- }
- _ => bug!(),
- };
- if offsets[i] == pair_offsets[0]
- && offsets[j] == pair_offsets[1]
- && align == pair.align
- && size == pair.size
- {
- // We can use `ScalarPair` only when it matches our
- // already computed layout (including `#[repr(C)]`).
- abi = pair.abi;
- }
- }
- _ => {}
- }
- }
-
- _ => {}
- }
- }
-
- if fields.iter().any(|f| f.abi.is_uninhabited()) {
- abi = Abi::Uninhabited;
- }
-
- Ok(LayoutS {
- variants: Variants::Single { index: VariantIdx::new(0) },
- fields: FieldsShape::Arbitrary { offsets, memory_index },
- abi,
- largest_niche,
- align,
- size,
- })
+ cx.univariant(dl, fields, repr, kind).ok_or(LayoutError::SizeOverflow(ty))
}
fn layout_of_uncached<'tcx>(
}
// The never type.
- ty::Never => tcx.intern_layout(LayoutS {
- variants: Variants::Single { index: VariantIdx::new(0) },
- fields: FieldsShape::Primitive,
- abi: Abi::Uninhabited,
- largest_niche: None,
- align: dl.i8_align,
- size: Size::ZERO,
- }),
+ ty::Never => tcx.intern_layout(cx.layout_of_never_type()),
// Potentially-wide pointers.
ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
};
// Effectively a (ptr, meta) tuple.
- tcx.intern_layout(scalar_pair(cx, data_ptr, metadata))
+ tcx.intern_layout(cx.scalar_pair(data_ptr, metadata))
}
ty::Dynamic(_, _, ty::DynStar) => {
data.valid_range_mut().start = 0;
let mut vtable = scalar_unit(Pointer);
vtable.valid_range_mut().start = 1;
- tcx.intern_layout(scalar_pair(cx, data, vtable))
+ tcx.intern_layout(cx.scalar_pair(data, vtable))
}
// Arrays and slices.
// Extract the number of elements from the layout of the array field:
let FieldsShape::Array { count, .. } = cx.layout_of(f0_ty)?.layout.fields() else {
- return Err(LayoutError::Unknown(ty));
- };
+ return Err(LayoutError::Unknown(ty));
+ };
(*e_ty, *count, true)
} else {
// Compute the ABI of the element type:
let e_ly = cx.layout_of(e_ty)?;
let Abi::Scalar(e_abi) = e_ly.abi else {
- // This error isn't caught in typeck, e.g., if
- // the element type of the vector is generic.
- tcx.sess.fatal(&format!(
- "monomorphising SIMD type `{}` with a non-primitive-scalar \
- (integer/float/pointer) element type `{}`",
- ty, e_ty
- ))
- };
+ // This error isn't caught in typeck, e.g., if
+ // the element type of the vector is generic.
+ tcx.sess.fatal(&format!(
+ "monomorphising SIMD type `{}` with a non-primitive-scalar \
+ (integer/float/pointer) element type `{}`",
+ ty, e_ty
+ ))
+ };
// Compute the size and alignment of the vector:
let size = e_ly.size.checked_mul(e_len, dl).ok_or(LayoutError::SizeOverflow(ty))?;
return Err(LayoutError::Unknown(ty));
}
- let mut align =
- if def.repr().pack.is_some() { dl.i8_align } else { dl.aggregate_align };
-
- if let Some(repr_align) = def.repr().align {
- align = align.max(AbiAndPrefAlign::new(repr_align));
- }
-
- let optimize = !def.repr().inhibit_union_abi_opt();
- let mut size = Size::ZERO;
- let mut abi = Abi::Aggregate { sized: true };
- let index = VariantIdx::new(0);
- for field in &variants[index] {
- assert!(field.is_sized());
- align = align.max(field.align);
-
- // If all non-ZST fields have the same ABI, forward this ABI
- if optimize && !field.is_zst() {
- // Discard valid range information and allow undef
- let field_abi = match field.abi {
- Abi::Scalar(x) => Abi::Scalar(x.to_union()),
- Abi::ScalarPair(x, y) => Abi::ScalarPair(x.to_union(), y.to_union()),
- Abi::Vector { element: x, count } => {
- Abi::Vector { element: x.to_union(), count }
- }
- Abi::Uninhabited | Abi::Aggregate { .. } => {
- Abi::Aggregate { sized: true }
- }
- };
-
- if size == Size::ZERO {
- // first non ZST: initialize 'abi'
- abi = field_abi;
- } else if abi != field_abi {
- // different fields have different ABI: reset to Aggregate
- abi = Abi::Aggregate { sized: true };
- }
- }
-
- size = cmp::max(size, field.size);
- }
-
- if let Some(pack) = def.repr().pack {
- align = align.min(AbiAndPrefAlign::new(pack));
- }
-
- return Ok(tcx.intern_layout(LayoutS {
- variants: Variants::Single { index },
- fields: FieldsShape::Union(
- NonZeroUsize::new(variants[index].len()).ok_or(LayoutError::Unknown(ty))?,
- ),
- abi,
- largest_niche: None,
- align,
- size: size.align_to(align.abi),
- }));
- }
-
- // A variant is absent if it's uninhabited and only has ZST fields.
- // Present uninhabited variants only require space for their fields,
- // but *not* an encoding of the discriminant (e.g., a tag value).
- // See issue #49298 for more details on the need to leave space
- // for non-ZST uninhabited data (mostly partial initialization).
- let absent = |fields: &[TyAndLayout<'_>]| {
- let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
- let is_zst = fields.iter().all(|f| f.is_zst());
- uninhabited && is_zst
- };
- let (present_first, present_second) = {
- let mut present_variants = variants
- .iter_enumerated()
- .filter_map(|(i, v)| if absent(v) { None } else { Some(i) });
- (present_variants.next(), present_variants.next())
- };
- let present_first = match present_first {
- Some(present_first) => present_first,
- // Uninhabited because it has no variants, or only absent ones.
- None if def.is_enum() => {
- return Ok(tcx.layout_of(param_env.and(tcx.types.never))?.layout);
- }
- // If it's a struct, still compute a layout so that we can still compute the
- // field offsets.
- None => VariantIdx::new(0),
- };
-
- let is_struct = !def.is_enum() ||
- // Only one variant is present.
- (present_second.is_none() &&
- // Representation optimizations are allowed.
- !def.repr().inhibit_enum_layout_opt());
- if is_struct {
- // Struct, or univariant enum equivalent to a struct.
- // (Typechecking will reject discriminant-sizing attrs.)
-
- let v = present_first;
- let kind = if def.is_enum() || variants[v].is_empty() {
- StructKind::AlwaysSized
- } else {
- let param_env = tcx.param_env(def.did());
- let last_field = def.variant(v).fields.last().unwrap();
- let always_sized = tcx.type_of(last_field.did).is_sized(tcx, param_env);
- if !always_sized { StructKind::MaybeUnsized } else { StructKind::AlwaysSized }
- };
-
- let mut st = univariant_uninterned(cx, ty, &variants[v], &def.repr(), kind)?;
- st.variants = Variants::Single { index: v };
-
- if def.is_unsafe_cell() {
- let hide_niches = |scalar: &mut _| match scalar {
- Scalar::Initialized { value, valid_range } => {
- *valid_range = WrappingRange::full(value.size(dl))
- }
- // Already doesn't have any niches
- Scalar::Union { .. } => {}
- };
- match &mut st.abi {
- Abi::Uninhabited => {}
- Abi::Scalar(scalar) => hide_niches(scalar),
- Abi::ScalarPair(a, b) => {
- hide_niches(a);
- hide_niches(b);
- }
- Abi::Vector { element, count: _ } => hide_niches(element),
- Abi::Aggregate { sized: _ } => {}
- }
- st.largest_niche = None;
- return Ok(tcx.intern_layout(st));
- }
-
- let (start, end) = cx.tcx.layout_scalar_valid_range(def.did());
- match st.abi {
- Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
- // the asserts ensure that we are not using the
- // `#[rustc_layout_scalar_valid_range(n)]`
- // attribute to widen the range of anything as that would probably
- // result in UB somewhere
- // FIXME(eddyb) the asserts are probably not needed,
- // as larger validity ranges would result in missed
- // optimizations, *not* wrongly assuming the inner
- // value is valid. e.g. unions enlarge validity ranges,
- // because the values may be uninitialized.
- if let Bound::Included(start) = start {
- // FIXME(eddyb) this might be incorrect - it doesn't
- // account for wrap-around (end < start) ranges.
- let valid_range = scalar.valid_range_mut();
- assert!(valid_range.start <= start);
- valid_range.start = start;
- }
- if let Bound::Included(end) = end {
- // FIXME(eddyb) this might be incorrect - it doesn't
- // account for wrap-around (end < start) ranges.
- let valid_range = scalar.valid_range_mut();
- assert!(valid_range.end >= end);
- valid_range.end = end;
- }
-
- // Update `largest_niche` if we have introduced a larger niche.
- let niche = Niche::from_scalar(dl, Size::ZERO, *scalar);
- if let Some(niche) = niche {
- match st.largest_niche {
- Some(largest_niche) => {
- // Replace the existing niche even if they're equal,
- // because this one is at a lower offset.
- if largest_niche.available(dl) <= niche.available(dl) {
- st.largest_niche = Some(niche);
- }
- }
- None => st.largest_niche = Some(niche),
- }
- }
- }
- _ => assert!(
- start == Bound::Unbounded && end == Bound::Unbounded,
- "nonscalar layout for layout_scalar_valid_range type {:?}: {:#?}",
- def,
- st,
- ),
- }
-
- return Ok(tcx.intern_layout(st));
- }
-
- // At this point, we have handled all unions and
- // structs. (We have also handled univariant enums
- // that allow representation optimization.)
- assert!(def.is_enum());
-
- // Until we've decided whether to use the tagged or
- // niche filling LayoutS, we don't want to intern the
- // variant layouts, so we can't store them in the
- // overall LayoutS. Store the overall LayoutS
- // and the variant LayoutSs here until then.
- struct TmpLayout<'tcx> {
- layout: LayoutS<'tcx>,
- variants: IndexVec<VariantIdx, LayoutS<'tcx>>,
+ return Ok(tcx.intern_layout(
+ cx.layout_of_union(&def.repr(), &variants).ok_or(LayoutError::Unknown(ty))?,
+ ));
}
- let calculate_niche_filling_layout =
- || -> Result<Option<TmpLayout<'tcx>>, LayoutError<'tcx>> {
- // The current code for niche-filling relies on variant indices
- // instead of actual discriminants, so enums with
- // explicit discriminants (RFC #2363) would misbehave.
- if def.repr().inhibit_enum_layout_opt()
+ tcx.intern_layout(
+ cx.layout_of_struct_or_enum(
+ &def.repr(),
+ &variants,
+ def.is_enum(),
+ def.is_unsafe_cell(),
+ tcx.layout_scalar_valid_range(def.did()),
+ |min, max| Integer::repr_discr(tcx, ty, &def.repr(), min, max),
+ def.is_enum()
+ .then(|| def.discriminants(tcx).map(|(v, d)| (v, d.val as i128)))
+ .into_iter()
+ .flatten(),
+ def.repr().inhibit_enum_layout_opt()
|| def
.variants()
.iter_enumerated()
- .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32()))
- {
- return Ok(None);
- }
-
- if variants.len() < 2 {
- return Ok(None);
- }
-
- let mut align = dl.aggregate_align;
- let mut variant_layouts = variants
- .iter_enumerated()
- .map(|(j, v)| {
- let mut st = univariant_uninterned(
- cx,
- ty,
- v,
- &def.repr(),
- StructKind::AlwaysSized,
- )?;
- st.variants = Variants::Single { index: j };
-
- align = align.max(st.align);
-
- Ok(st)
- })
- .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
-
- let largest_variant_index = match variant_layouts
- .iter_enumerated()
- .max_by_key(|(_i, layout)| layout.size.bytes())
- .map(|(i, _layout)| i)
+ .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())),
{
- None => return Ok(None),
- Some(i) => i,
- };
-
- let all_indices = VariantIdx::new(0)..=VariantIdx::new(variants.len() - 1);
- let needs_disc = |index: VariantIdx| {
- index != largest_variant_index && !absent(&variants[index])
- };
- let niche_variants = all_indices.clone().find(|v| needs_disc(*v)).unwrap()
- ..=all_indices.rev().find(|v| needs_disc(*v)).unwrap();
-
- let count = niche_variants.size_hint().1.unwrap() as u128;
-
- // Find the field with the largest niche
- let (field_index, niche, (niche_start, niche_scalar)) = match variants
- [largest_variant_index]
- .iter()
- .enumerate()
- .filter_map(|(j, field)| Some((j, field.largest_niche?)))
- .max_by_key(|(_, niche)| niche.available(dl))
- .and_then(|(j, niche)| Some((j, niche, niche.reserve(cx, count)?)))
- {
- None => return Ok(None),
- Some(x) => x,
- };
-
- let niche_offset = niche.offset
- + variant_layouts[largest_variant_index].fields.offset(field_index);
- let niche_size = niche.value.size(dl);
- let size = variant_layouts[largest_variant_index].size.align_to(align.abi);
-
- let all_variants_fit =
- variant_layouts.iter_enumerated_mut().all(|(i, layout)| {
- if i == largest_variant_index {
- return true;
- }
-
- layout.largest_niche = None;
-
- if layout.size <= niche_offset {
- // This variant will fit before the niche.
- return true;
- }
-
- // Determine if it'll fit after the niche.
- let this_align = layout.align.abi;
- let this_offset = (niche_offset + niche_size).align_to(this_align);
-
- if this_offset + layout.size > size {
- return false;
- }
-
- // It'll fit, but we need to make some adjustments.
- match layout.fields {
- FieldsShape::Arbitrary { ref mut offsets, .. } => {
- for (j, offset) in offsets.iter_mut().enumerate() {
- if !variants[i][j].is_zst() {
- *offset += this_offset;
- }
- }
- }
- _ => {
- panic!("Layout of fields should be Arbitrary for variants")
- }
- }
-
- // It can't be a Scalar or ScalarPair because the offset isn't 0.
- if !layout.abi.is_uninhabited() {
- layout.abi = Abi::Aggregate { sized: true };
- }
- layout.size += this_offset;
-
- true
- });
-
- if !all_variants_fit {
- return Ok(None);
- }
-
- let largest_niche = Niche::from_scalar(dl, niche_offset, niche_scalar);
-
- let others_zst = variant_layouts
- .iter_enumerated()
- .all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO);
- let same_size = size == variant_layouts[largest_variant_index].size;
- let same_align = align == variant_layouts[largest_variant_index].align;
-
- let abi = if variant_layouts.iter().all(|v| v.abi.is_uninhabited()) {
- Abi::Uninhabited
- } else if same_size && same_align && others_zst {
- match variant_layouts[largest_variant_index].abi {
- // When the total alignment and size match, we can use the
- // same ABI as the scalar variant with the reserved niche.
- Abi::Scalar(_) => Abi::Scalar(niche_scalar),
- Abi::ScalarPair(first, second) => {
- // Only the niche is guaranteed to be initialised,
- // so use union layouts for the other primitive.
- if niche_offset == Size::ZERO {
- Abi::ScalarPair(niche_scalar, second.to_union())
- } else {
- Abi::ScalarPair(first.to_union(), niche_scalar)
- }
- }
- _ => Abi::Aggregate { sized: true },
- }
- } else {
- Abi::Aggregate { sized: true }
- };
-
- let layout = LayoutS {
- variants: Variants::Multiple {
- tag: niche_scalar,
- tag_encoding: TagEncoding::Niche {
- untagged_variant: largest_variant_index,
- niche_variants,
- niche_start,
- },
- tag_field: 0,
- variants: IndexVec::new(),
- },
- fields: FieldsShape::Arbitrary {
- offsets: vec![niche_offset],
- memory_index: vec![0],
- },
- abi,
- largest_niche,
- size,
- align,
- };
-
- Ok(Some(TmpLayout { layout, variants: variant_layouts }))
- };
-
- let niche_filling_layout = calculate_niche_filling_layout()?;
-
- let (mut min, mut max) = (i128::MAX, i128::MIN);
- let discr_type = def.repr().discr_type();
- let bits = Integer::from_attr(cx, discr_type).size().bits();
- for (i, discr) in def.discriminants(tcx) {
- if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
- continue;
- }
- let mut x = discr.val as i128;
- if discr_type.is_signed() {
- // sign extend the raw representation to be an i128
- x = (x << (128 - bits)) >> (128 - bits);
- }
- if x < min {
- min = x;
- }
- if x > max {
- max = x;
- }
- }
- // We might have no inhabited variants, so pretend there's at least one.
- if (min, max) == (i128::MAX, i128::MIN) {
- min = 0;
- max = 0;
- }
- assert!(min <= max, "discriminant range is {}...{}", min, max);
- let (min_ity, signed) = Integer::repr_discr(tcx, ty, &def.repr(), min, max);
-
- let mut align = dl.aggregate_align;
- let mut size = Size::ZERO;
-
- // We're interested in the smallest alignment, so start large.
- let mut start_align = Align::from_bytes(256).unwrap();
- assert_eq!(Integer::for_align(dl, start_align), None);
-
- // repr(C) on an enum tells us to make a (tag, union) layout,
- // so we need to grow the prefix alignment to be at least
- // the alignment of the union. (This value is used both for
- // determining the alignment of the overall enum, and the
- // determining the alignment of the payload after the tag.)
- let mut prefix_align = min_ity.align(dl).abi;
- if def.repr().c() {
- for fields in &variants {
- for field in fields {
- prefix_align = prefix_align.max(field.align.abi);
- }
- }
- }
-
- // Create the set of structs that represent each variant.
- let mut layout_variants = variants
- .iter_enumerated()
- .map(|(i, field_layouts)| {
- let mut st = univariant_uninterned(
- cx,
- ty,
- &field_layouts,
- &def.repr(),
- StructKind::Prefixed(min_ity.size(), prefix_align),
- )?;
- st.variants = Variants::Single { index: i };
- // Find the first field we can't move later
- // to make room for a larger discriminant.
- for field in st.fields.index_by_increasing_offset().map(|j| field_layouts[j]) {
- if !field.is_zst() || field.align.abi.bytes() != 1 {
- start_align = start_align.min(field.align.abi);
- break;
- }
- }
- size = cmp::max(size, st.size);
- align = align.max(st.align);
- Ok(st)
- })
- .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
-
- // Align the maximum variant size to the largest alignment.
- size = size.align_to(align.abi);
-
- if size.bytes() >= dl.obj_size_bound() {
- return Err(LayoutError::SizeOverflow(ty));
- }
-
- let typeck_ity = Integer::from_attr(dl, def.repr().discr_type());
- if typeck_ity < min_ity {
- // It is a bug if Layout decided on a greater discriminant size than typeck for
- // some reason at this point (based on values discriminant can take on). Mostly
- // because this discriminant will be loaded, and then stored into variable of
- // type calculated by typeck. Consider such case (a bug): typeck decided on
- // byte-sized discriminant, but layout thinks we need a 16-bit to store all
- // discriminant values. That would be a bug, because then, in codegen, in order
- // to store this 16-bit discriminant into 8-bit sized temporary some of the
- // space necessary to represent would have to be discarded (or layout is wrong
- // on thinking it needs 16 bits)
- bug!(
- "layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
- min_ity,
- typeck_ity
- );
- // However, it is fine to make discr type however large (as an optimisation)
- // after this point – we’ll just truncate the value we load in codegen.
- }
-
- // Check to see if we should use a different type for the
- // discriminant. We can safely use a type with the same size
- // as the alignment of the first field of each variant.
- // We increase the size of the discriminant to avoid LLVM copying
- // padding when it doesn't need to. This normally causes unaligned
- // load/stores and excessive memcpy/memset operations. By using a
- // bigger integer size, LLVM can be sure about its contents and
- // won't be so conservative.
-
- // Use the initial field alignment
- let mut ity = if def.repr().c() || def.repr().int.is_some() {
- min_ity
- } else {
- Integer::for_align(dl, start_align).unwrap_or(min_ity)
- };
-
- // If the alignment is not larger than the chosen discriminant size,
- // don't use the alignment as the final size.
- if ity <= min_ity {
- ity = min_ity;
- } else {
- // Patch up the variants' first few fields.
- let old_ity_size = min_ity.size();
- let new_ity_size = ity.size();
- for variant in &mut layout_variants {
- match variant.fields {
- FieldsShape::Arbitrary { ref mut offsets, .. } => {
- for i in offsets {
- if *i <= old_ity_size {
- assert_eq!(*i, old_ity_size);
- *i = new_ity_size;
+ let param_env = tcx.param_env(def.did());
+ def.is_struct()
+ && match def.variants().iter().next().and_then(|x| x.fields.last()) {
+ Some(last_field) => {
+ tcx.type_of(last_field.did).is_sized(tcx, param_env)
}
+ None => false,
}
- // We might be making the struct larger.
- if variant.size <= old_ity_size {
- variant.size = new_ity_size;
- }
- }
- _ => bug!(),
- }
- }
- }
-
- let tag_mask = ity.size().unsigned_int_max();
- let tag = Scalar::Initialized {
- value: Int(ity, signed),
- valid_range: WrappingRange {
- start: (min as u128 & tag_mask),
- end: (max as u128 & tag_mask),
- },
- };
- let mut abi = Abi::Aggregate { sized: true };
-
- if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
- abi = Abi::Uninhabited;
- } else if tag.size(dl) == size {
- // Make sure we only use scalar layout when the enum is entirely its
- // own tag (i.e. it has no padding nor any non-ZST variant fields).
- abi = Abi::Scalar(tag);
- } else {
- // Try to use a ScalarPair for all tagged enums.
- let mut common_prim = None;
- let mut common_prim_initialized_in_all_variants = true;
- for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
- let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
- bug!();
- };
- let mut fields = iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
- let (field, offset) = match (fields.next(), fields.next()) {
- (None, None) => {
- common_prim_initialized_in_all_variants = false;
- continue;
- }
- (Some(pair), None) => pair,
- _ => {
- common_prim = None;
- break;
- }
- };
- let prim = match field.abi {
- Abi::Scalar(scalar) => {
- common_prim_initialized_in_all_variants &=
- matches!(scalar, Scalar::Initialized { .. });
- scalar.primitive()
- }
- _ => {
- common_prim = None;
- break;
- }
- };
- if let Some(pair) = common_prim {
- // This is pretty conservative. We could go fancier
- // by conflating things like i32 and u32, or even
- // realising that (u8, u8) could just cohabit with
- // u16 or even u32.
- if pair != (prim, offset) {
- common_prim = None;
- break;
- }
- } else {
- common_prim = Some((prim, offset));
- }
- }
- if let Some((prim, offset)) = common_prim {
- let prim_scalar = if common_prim_initialized_in_all_variants {
- scalar_unit(prim)
- } else {
- // Common prim might be uninit.
- Scalar::Union { value: prim }
- };
- let pair = scalar_pair(cx, tag, prim_scalar);
- let pair_offsets = match pair.fields {
- FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
- assert_eq!(memory_index, &[0, 1]);
- offsets
- }
- _ => bug!(),
- };
- if pair_offsets[0] == Size::ZERO
- && pair_offsets[1] == *offset
- && align == pair.align
- && size == pair.size
- {
- // We can use `ScalarPair` only when it matches our
- // already computed layout (including `#[repr(C)]`).
- abi = pair.abi;
- }
- }
- }
-
- // If we pick a "clever" (by-value) ABI, we might have to adjust the ABI of the
- // variants to ensure they are consistent. This is because a downcast is
- // semantically a NOP, and thus should not affect layout.
- if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) {
- for variant in &mut layout_variants {
- // We only do this for variants with fields; the others are not accessed anyway.
- // Also do not overwrite any already existing "clever" ABIs.
- if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) {
- variant.abi = abi;
- // Also need to bump up the size and alignment, so that the entire value fits in here.
- variant.size = cmp::max(variant.size, size);
- variant.align.abi = cmp::max(variant.align.abi, align.abi);
- }
- }
- }
-
- let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
-
- let tagged_layout = LayoutS {
- variants: Variants::Multiple {
- tag,
- tag_encoding: TagEncoding::Direct,
- tag_field: 0,
- variants: IndexVec::new(),
- },
- fields: FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] },
- largest_niche,
- abi,
- align,
- size,
- };
-
- let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants };
-
- let mut best_layout = match (tagged_layout, niche_filling_layout) {
- (tl, Some(nl)) => {
- // Pick the smaller layout; otherwise,
- // pick the layout with the larger niche; otherwise,
- // pick tagged as it has simpler codegen.
- use Ordering::*;
- let niche_size = |tmp_l: &TmpLayout<'_>| {
- tmp_l.layout.largest_niche.map_or(0, |n| n.available(dl))
- };
- match (
- tl.layout.size.cmp(&nl.layout.size),
- niche_size(&tl).cmp(&niche_size(&nl)),
- ) {
- (Greater, _) => nl,
- (Equal, Less) => nl,
- _ => tl,
- }
- }
- (tl, None) => tl,
- };
-
- // Now we can intern the variant layouts and store them in the enum layout.
- best_layout.layout.variants = match best_layout.layout.variants {
- Variants::Multiple { tag, tag_encoding, tag_field, .. } => Variants::Multiple {
- tag,
- tag_encoding,
- tag_field,
- variants: best_layout
- .variants
- .into_iter()
- .map(|layout| tcx.intern_layout(layout))
- .collect(),
- },
- _ => bug!(),
- };
-
- tcx.intern_layout(best_layout.layout)
+ },
+ )
+ .ok_or(LayoutError::SizeOverflow(ty))?,
+ )
}
// Types with no meaningful known layout.
let subst_field = |ty: Ty<'tcx>| EarlyBinder(ty).subst(tcx, substs);
let Some(info) = tcx.generator_layout(def_id) else {
- return Err(LayoutError::Unknown(ty));
- };
+ return Err(LayoutError::Unknown(ty));
+ };
let (ineligible_locals, assignments) = generator_saved_local_eligibility(&info);
// Build a prefix layout, including "promoting" all ineligible
variant.variants = Variants::Single { index };
let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else {
- bug!();
- };
+ bug!();
+ };
// Now, stitch the promoted and variant-only fields back together in
// the order they are mentioned by our GeneratorLayout.
size = size.max(variant.size);
align = align.max(variant.align);
- Ok(tcx.intern_layout(variant))
+ Ok(variant)
})
.collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
size = size.align_to(align.abi);
- let abi = if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi().is_uninhabited()) {
+ let abi = if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi.is_uninhabited()) {
Abi::Uninhabited
} else {
Abi::Aggregate { sized: true }
projects / rust.git / blobdiff