diff options
Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_ty_utils/src/layout.rs | 991 |
1 files changed, 50 insertions, 941 deletions
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs index 52ba0eee9..fbc055b5d 100644 --- a/compiler/rustc_ty_utils/src/layout.rs +++ b/compiler/rustc_ty_utils/src/layout.rs @@ -13,13 +13,8 @@ use rustc_span::symbol::Symbol; 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; @@ -66,16 +61,6 @@ fn layout_of<'tcx>( 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). @@ -89,40 +74,13 @@ fn invert_mapping(map: &[u32]) -> Vec<u32> { 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() { @@ -130,208 +88,7 @@ fn univariant_uninterned<'tcx>( 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 field_align = |f: &TyAndLayout<'_>| { - if let Some(pack) = pack { f.align.abi.min(pack) } else { f.align.abi } - }; - - // 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. - let f = &fields[x as usize]; - (!f.is_zst(), cmp::Reverse(field_align(f))) - }); - } - - StructKind::Prefixed(..) => { - // Sort in ascending alignment so that the layout stays optimal - // regardless of the prefix - optimizing.sort_by_key(|&x| field_align(&fields[x as usize])); - } - } - - // 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>( @@ -382,14 +139,7 @@ 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, .. }) => { @@ -418,7 +168,7 @@ fn layout_of_uncached<'tcx>( }; // 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) => { @@ -426,7 +176,7 @@ fn layout_of_uncached<'tcx>( 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. @@ -442,8 +192,7 @@ fn layout_of_uncached<'tcx>( let element = cx.layout_of(element)?; let size = element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow(ty))?; - let abi = if count != 0 && tcx.conservative_is_privately_uninhabited(param_env.and(ty)) - { + let abi = if count != 0 && ty.is_privately_uninhabited(tcx, param_env) { Abi::Uninhabited } else { Abi::Aggregate { sized: true } @@ -576,8 +325,8 @@ fn layout_of_uncached<'tcx>( // 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 { @@ -602,14 +351,14 @@ fn layout_of_uncached<'tcx>( // 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))?; @@ -656,681 +405,41 @@ fn layout_of_uncached<'tcx>( 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_unsized()); - 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) - { - 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)?))) + .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())), { - 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. @@ -1488,8 +597,8 @@ fn generator_layout<'tcx>( 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 @@ -1592,8 +701,8 @@ fn generator_layout<'tcx>( 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. @@ -1640,13 +749,13 @@ fn generator_layout<'tcx>( 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 } |