use hir::def_id::DefId; use rustc_hir as hir; use rustc_index::bit_set::BitSet; use rustc_index::{IndexSlice, IndexVec}; use rustc_middle::mir::{GeneratorLayout, GeneratorSavedLocal}; use rustc_middle::query::Providers; use rustc_middle::ty::layout::{ IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout, MAX_SIMD_LANES, }; use rustc_middle::ty::{ self, subst::SubstsRef, AdtDef, EarlyBinder, ReprOptions, Ty, TyCtxt, TypeVisitableExt, }; use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo}; use rustc_span::symbol::Symbol; use rustc_span::DUMMY_SP; use rustc_target::abi::*; use std::fmt::Debug; use std::iter; use crate::errors::{ MultipleArrayFieldsSimdType, NonPrimitiveSimdType, OversizedSimdType, ZeroLengthSimdType, }; use crate::layout_sanity_check::sanity_check_layout; pub fn provide(providers: &mut Providers) { *providers = Providers { layout_of, ..*providers }; } #[instrument(skip(tcx, query), level = "debug")] fn layout_of<'tcx>( tcx: TyCtxt<'tcx>, query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>, ) -> Result, LayoutError<'tcx>> { let (param_env, ty) = query.into_parts(); debug!(?ty); let param_env = param_env.with_reveal_all_normalized(tcx); let unnormalized_ty = ty; // FIXME: We might want to have two different versions of `layout_of`: // One that can be called after typecheck has completed and can use // `normalize_erasing_regions` here and another one that can be called // before typecheck has completed and uses `try_normalize_erasing_regions`. let ty = match tcx.try_normalize_erasing_regions(param_env, ty) { Ok(t) => t, Err(normalization_error) => { return Err(LayoutError::NormalizationFailure(ty, normalization_error)); } }; if ty != unnormalized_ty { // Ensure this layout is also cached for the normalized type. return tcx.layout_of(param_env.and(ty)); } let cx = LayoutCx { tcx, param_env }; let layout = layout_of_uncached(&cx, ty)?; let layout = TyAndLayout { ty, layout }; record_layout_for_printing(&cx, layout); sanity_check_layout(&cx, &layout); Ok(layout) } fn univariant_uninterned<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, ty: Ty<'tcx>, fields: &IndexSlice>, repr: &ReprOptions, kind: StructKind, ) -> Result> { let dl = cx.data_layout(); let pack = repr.pack; if pack.is_some() && repr.align.is_some() { cx.tcx.sess.delay_span_bug(DUMMY_SP, "struct cannot be packed and aligned"); return Err(LayoutError::Unknown(ty)); } cx.univariant(dl, fields, repr, kind).ok_or(LayoutError::SizeOverflow(ty)) } fn layout_of_uncached<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, ty: Ty<'tcx>, ) -> Result, LayoutError<'tcx>> { let tcx = cx.tcx; let param_env = cx.param_env; let dl = cx.data_layout(); let scalar_unit = |value: Primitive| { let size = value.size(dl); assert!(size.bits() <= 128); Scalar::Initialized { value, valid_range: WrappingRange::full(size) } }; let scalar = |value: Primitive| tcx.mk_layout(LayoutS::scalar(cx, scalar_unit(value))); let univariant = |fields: &IndexSlice>, repr: &ReprOptions, kind| { Ok(tcx.mk_layout(univariant_uninterned(cx, ty, fields, repr, kind)?)) }; debug_assert!(!ty.has_non_region_infer()); Ok(match *ty.kind() { // Basic scalars. ty::Bool => tcx.mk_layout(LayoutS::scalar( cx, Scalar::Initialized { value: Int(I8, false), valid_range: WrappingRange { start: 0, end: 1 }, }, )), ty::Char => tcx.mk_layout(LayoutS::scalar( cx, Scalar::Initialized { value: Int(I32, false), valid_range: WrappingRange { start: 0, end: 0x10FFFF }, }, )), ty::Int(ity) => scalar(Int(Integer::from_int_ty(dl, ity), true)), ty::Uint(ity) => scalar(Int(Integer::from_uint_ty(dl, ity), false)), ty::Float(fty) => scalar(match fty { ty::FloatTy::F32 => F32, ty::FloatTy::F64 => F64, }), ty::FnPtr(_) => { let mut ptr = scalar_unit(Pointer(dl.instruction_address_space)); ptr.valid_range_mut().start = 1; tcx.mk_layout(LayoutS::scalar(cx, ptr)) } // The never type. ty::Never => tcx.mk_layout(cx.layout_of_never_type()), // Potentially-wide pointers. ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => { let mut data_ptr = scalar_unit(Pointer(AddressSpace::DATA)); if !ty.is_unsafe_ptr() { data_ptr.valid_range_mut().start = 1; } let pointee = tcx.normalize_erasing_regions(param_env, pointee); if pointee.is_sized(tcx, param_env) { return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr))); } let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env); let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type() // Projection eagerly bails out when the pointee references errors, // fall back to structurally deducing metadata. && !pointee.references_error() { let metadata_ty = tcx.normalize_erasing_regions( param_env, tcx.mk_projection(metadata_def_id, [pointee]), ); let metadata_layout = cx.layout_of(metadata_ty)?; // If the metadata is a 1-zst, then the pointer is thin. if metadata_layout.is_zst() && metadata_layout.align.abi.bytes() == 1 { return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr))); } let Abi::Scalar(metadata) = metadata_layout.abi else { return Err(LayoutError::Unknown(unsized_part)); }; metadata } else { match unsized_part.kind() { ty::Foreign(..) => { return Ok(tcx.mk_layout(LayoutS::scalar(cx, data_ptr))); } ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)), ty::Dynamic(..) => { let mut vtable = scalar_unit(Pointer(AddressSpace::DATA)); vtable.valid_range_mut().start = 1; vtable } _ => { return Err(LayoutError::Unknown(unsized_part)); } } }; // Effectively a (ptr, meta) tuple. tcx.mk_layout(cx.scalar_pair(data_ptr, metadata)) } ty::Dynamic(_, _, ty::DynStar) => { let mut data = scalar_unit(Pointer(AddressSpace::DATA)); data.valid_range_mut().start = 0; let mut vtable = scalar_unit(Pointer(AddressSpace::DATA)); vtable.valid_range_mut().start = 1; tcx.mk_layout(cx.scalar_pair(data, vtable)) } // Arrays and slices. ty::Array(element, mut count) => { if count.has_projections() { count = tcx.normalize_erasing_regions(param_env, count); if count.has_projections() { return Err(LayoutError::Unknown(ty)); } } let count = count.try_eval_target_usize(tcx, param_env).ok_or(LayoutError::Unknown(ty))?; let element = cx.layout_of(element)?; let size = element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow(ty))?; let abi = if count != 0 && ty.is_privately_uninhabited(tcx, param_env) { Abi::Uninhabited } else { Abi::Aggregate { sized: true } }; let largest_niche = if count != 0 { element.largest_niche } else { None }; tcx.mk_layout(LayoutS { variants: Variants::Single { index: FIRST_VARIANT }, fields: FieldsShape::Array { stride: element.size, count }, abi, largest_niche, align: element.align, size, }) } ty::Slice(element) => { let element = cx.layout_of(element)?; tcx.mk_layout(LayoutS { variants: Variants::Single { index: FIRST_VARIANT }, fields: FieldsShape::Array { stride: element.size, count: 0 }, abi: Abi::Aggregate { sized: false }, largest_niche: None, align: element.align, size: Size::ZERO, }) } ty::Str => tcx.mk_layout(LayoutS { variants: Variants::Single { index: FIRST_VARIANT }, fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 }, abi: Abi::Aggregate { sized: false }, largest_niche: None, align: dl.i8_align, size: Size::ZERO, }), // Odd unit types. ty::FnDef(..) => { univariant(IndexSlice::empty(), &ReprOptions::default(), StructKind::AlwaysSized)? } ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => { let mut unit = univariant_uninterned( cx, ty, IndexSlice::empty(), &ReprOptions::default(), StructKind::AlwaysSized, )?; match unit.abi { Abi::Aggregate { ref mut sized } => *sized = false, _ => bug!(), } tcx.mk_layout(unit) } ty::Generator(def_id, substs, _) => generator_layout(cx, ty, def_id, substs)?, ty::Closure(_, ref substs) => { let tys = substs.as_closure().upvar_tys(); univariant( &tys.map(|ty| Ok(cx.layout_of(ty)?.layout)).try_collect::>()?, &ReprOptions::default(), StructKind::AlwaysSized, )? } ty::Tuple(tys) => { let kind = if tys.len() == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized }; univariant( &tys.iter().map(|k| Ok(cx.layout_of(k)?.layout)).try_collect::>()?, &ReprOptions::default(), kind, )? } // SIMD vector types. ty::Adt(def, substs) if def.repr().simd() => { if !def.is_struct() { // Should have yielded E0517 by now. tcx.sess.delay_span_bug( DUMMY_SP, "#[repr(simd)] was applied to an ADT that is not a struct", ); return Err(LayoutError::Unknown(ty)); } let fields = &def.non_enum_variant().fields; // Supported SIMD vectors are homogeneous ADTs with at least one field: // // * #[repr(simd)] struct S(T, T, T, T); // * #[repr(simd)] struct S { x: T, y: T, z: T, w: T } // * #[repr(simd)] struct S([T; 4]) // // where T is a primitive scalar (integer/float/pointer). // SIMD vectors with zero fields are not supported. // (should be caught by typeck) if fields.is_empty() { tcx.sess.emit_fatal(ZeroLengthSimdType { ty }) } // Type of the first ADT field: let f0_ty = fields[FieldIdx::from_u32(0)].ty(tcx, substs); // Heterogeneous SIMD vectors are not supported: // (should be caught by typeck) for fi in fields { if fi.ty(tcx, substs) != f0_ty { tcx.sess.delay_span_bug( DUMMY_SP, "#[repr(simd)] was applied to an ADT with heterogeneous field type", ); return Err(LayoutError::Unknown(ty)); } } // The element type and number of elements of the SIMD vector // are obtained from: // // * the element type and length of the single array field, if // the first field is of array type, or // // * the homogeneous field type and the number of fields. let (e_ty, e_len, is_array) = if let ty::Array(e_ty, _) = f0_ty.kind() { // First ADT field is an array: // SIMD vectors with multiple array fields are not supported: // Can't be caught by typeck with a generic simd type. if def.non_enum_variant().fields.len() != 1 { tcx.sess.emit_fatal(MultipleArrayFieldsSimdType { ty }); } // 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)); }; (*e_ty, *count, true) } else { // First ADT field is not an array: (f0_ty, def.non_enum_variant().fields.len() as _, false) }; // SIMD vectors of zero length are not supported. // Additionally, lengths are capped at 2^16 as a fixed maximum backends must // support. // // Can't be caught in typeck if the array length is generic. if e_len == 0 { tcx.sess.emit_fatal(ZeroLengthSimdType { ty }); } else if e_len > MAX_SIMD_LANES { tcx.sess.emit_fatal(OversizedSimdType { ty, max_lanes: MAX_SIMD_LANES }); } // 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.emit_fatal(NonPrimitiveSimdType { 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))?; let align = dl.vector_align(size); let size = size.align_to(align.abi); // Compute the placement of the vector fields: let fields = if is_array { FieldsShape::Arbitrary { offsets: [Size::ZERO].into(), memory_index: [0].into() } } else { FieldsShape::Array { stride: e_ly.size, count: e_len } }; tcx.mk_layout(LayoutS { variants: Variants::Single { index: FIRST_VARIANT }, fields, abi: Abi::Vector { element: e_abi, count: e_len }, largest_niche: e_ly.largest_niche, size, align, }) } // ADTs. ty::Adt(def, substs) => { // Cache the field layouts. let variants = def .variants() .iter() .map(|v| { v.fields .iter() .map(|field| Ok(cx.layout_of(field.ty(tcx, substs))?.layout)) .try_collect::>() }) .try_collect::>()?; if def.is_union() { if def.repr().pack.is_some() && def.repr().align.is_some() { cx.tcx.sess.delay_span_bug( tcx.def_span(def.did()), "union cannot be packed and aligned", ); return Err(LayoutError::Unknown(ty)); } return Ok(tcx.mk_layout( cx.layout_of_union(&def.repr(), &variants).ok_or(LayoutError::Unknown(ty))?, )); } tcx.mk_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())), { let param_env = tcx.param_env(def.did()); def.is_struct() && match def.variants().iter().next().and_then(|x| x.fields.raw.last()) { Some(last_field) => tcx .type_of(last_field.did) .subst_identity() .is_sized(tcx, param_env), None => false, } }, ) .ok_or(LayoutError::SizeOverflow(ty))?, ) } // Types with no meaningful known layout. ty::Alias(..) => { // NOTE(eddyb) `layout_of` query should've normalized these away, // if that was possible, so there's no reason to try again here. return Err(LayoutError::Unknown(ty)); } ty::Bound(..) | ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) | ty::Infer(_) => { bug!("Layout::compute: unexpected type `{}`", ty) } ty::Placeholder(..) | ty::Param(_) | ty::Error(_) => { return Err(LayoutError::Unknown(ty)); } }) } /// Overlap eligibility and variant assignment for each GeneratorSavedLocal. #[derive(Clone, Debug, PartialEq)] enum SavedLocalEligibility { Unassigned, Assigned(VariantIdx), Ineligible(Option), } // When laying out generators, we divide our saved local fields into two // categories: overlap-eligible and overlap-ineligible. // // Those fields which are ineligible for overlap go in a "prefix" at the // beginning of the layout, and always have space reserved for them. // // Overlap-eligible fields are only assigned to one variant, so we lay // those fields out for each variant and put them right after the // prefix. // // Finally, in the layout details, we point to the fields from the // variants they are assigned to. It is possible for some fields to be // included in multiple variants. No field ever "moves around" in the // layout; its offset is always the same. // // Also included in the layout are the upvars and the discriminant. // These are included as fields on the "outer" layout; they are not part // of any variant. /// Compute the eligibility and assignment of each local. fn generator_saved_local_eligibility( info: &GeneratorLayout<'_>, ) -> (BitSet, IndexVec) { use SavedLocalEligibility::*; let mut assignments: IndexVec = IndexVec::from_elem(Unassigned, &info.field_tys); // The saved locals not eligible for overlap. These will get // "promoted" to the prefix of our generator. let mut ineligible_locals = BitSet::new_empty(info.field_tys.len()); // Figure out which of our saved locals are fields in only // one variant. The rest are deemed ineligible for overlap. for (variant_index, fields) in info.variant_fields.iter_enumerated() { for local in fields { match assignments[*local] { Unassigned => { assignments[*local] = Assigned(variant_index); } Assigned(idx) => { // We've already seen this local at another suspension // point, so it is no longer a candidate. trace!( "removing local {:?} in >1 variant ({:?}, {:?})", local, variant_index, idx ); ineligible_locals.insert(*local); assignments[*local] = Ineligible(None); } Ineligible(_) => {} } } } // Next, check every pair of eligible locals to see if they // conflict. for local_a in info.storage_conflicts.rows() { let conflicts_a = info.storage_conflicts.count(local_a); if ineligible_locals.contains(local_a) { continue; } for local_b in info.storage_conflicts.iter(local_a) { // local_a and local_b are storage live at the same time, therefore they // cannot overlap in the generator layout. The only way to guarantee // this is if they are in the same variant, or one is ineligible // (which means it is stored in every variant). if ineligible_locals.contains(local_b) || assignments[local_a] == assignments[local_b] { continue; } // If they conflict, we will choose one to make ineligible. // This is not always optimal; it's just a greedy heuristic that // seems to produce good results most of the time. let conflicts_b = info.storage_conflicts.count(local_b); let (remove, other) = if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) }; ineligible_locals.insert(remove); assignments[remove] = Ineligible(None); trace!("removing local {:?} due to conflict with {:?}", remove, other); } } // Count the number of variants in use. If only one of them, then it is // impossible to overlap any locals in our layout. In this case it's // always better to make the remaining locals ineligible, so we can // lay them out with the other locals in the prefix and eliminate // unnecessary padding bytes. { let mut used_variants = BitSet::new_empty(info.variant_fields.len()); for assignment in &assignments { if let Assigned(idx) = assignment { used_variants.insert(*idx); } } if used_variants.count() < 2 { for assignment in assignments.iter_mut() { *assignment = Ineligible(None); } ineligible_locals.insert_all(); } } // Write down the order of our locals that will be promoted to the prefix. { for (idx, local) in ineligible_locals.iter().enumerate() { assignments[local] = Ineligible(Some(FieldIdx::from_usize(idx))); } } debug!("generator saved local assignments: {:?}", assignments); (ineligible_locals, assignments) } /// Compute the full generator layout. fn generator_layout<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, ty: Ty<'tcx>, def_id: hir::def_id::DefId, substs: SubstsRef<'tcx>, ) -> Result, LayoutError<'tcx>> { use SavedLocalEligibility::*; let tcx = cx.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)); }; let (ineligible_locals, assignments) = generator_saved_local_eligibility(&info); // Build a prefix layout, including "promoting" all ineligible // locals as part of the prefix. We compute the layout of all of // these fields at once to get optimal packing. let tag_index = substs.as_generator().prefix_tys().count(); // `info.variant_fields` already accounts for the reserved variants, so no need to add them. let max_discr = (info.variant_fields.len() - 1) as u128; let discr_int = Integer::fit_unsigned(max_discr); let tag = Scalar::Initialized { value: Primitive::Int(discr_int, false), valid_range: WrappingRange { start: 0, end: max_discr }, }; let tag_layout = cx.tcx.mk_layout(LayoutS::scalar(cx, tag)); let promoted_layouts = ineligible_locals .iter() .map(|local| subst_field(info.field_tys[local].ty)) .map(|ty| tcx.mk_maybe_uninit(ty)) .map(|ty| Ok(cx.layout_of(ty)?.layout)); let prefix_layouts = substs .as_generator() .prefix_tys() .map(|ty| Ok(cx.layout_of(ty)?.layout)) .chain(iter::once(Ok(tag_layout))) .chain(promoted_layouts) .try_collect::>()?; let prefix = univariant_uninterned( cx, ty, &prefix_layouts, &ReprOptions::default(), StructKind::AlwaysSized, )?; let (prefix_size, prefix_align) = (prefix.size, prefix.align); // Split the prefix layout into the "outer" fields (upvars and // discriminant) and the "promoted" fields. Promoted fields will // get included in each variant that requested them in // GeneratorLayout. debug!("prefix = {:#?}", prefix); let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields { FieldsShape::Arbitrary { mut offsets, memory_index } => { let mut inverse_memory_index = memory_index.invert_bijective_mapping(); // "a" (`0..b_start`) and "b" (`b_start..`) correspond to // "outer" and "promoted" fields respectively. let b_start = FieldIdx::from_usize(tag_index + 1); let offsets_b = IndexVec::from_raw(offsets.raw.split_off(b_start.as_usize())); let offsets_a = offsets; // Disentangle the "a" and "b" components of `inverse_memory_index` // by preserving the order but keeping only one disjoint "half" each. // FIXME(eddyb) build a better abstraction for permutations, if possible. let inverse_memory_index_b: IndexVec = inverse_memory_index .iter() .filter_map(|&i| i.as_u32().checked_sub(b_start.as_u32()).map(FieldIdx::from_u32)) .collect(); inverse_memory_index.raw.retain(|&i| i < b_start); let inverse_memory_index_a = inverse_memory_index; // Since `inverse_memory_index_{a,b}` each only refer to their // respective fields, they can be safely inverted let memory_index_a = inverse_memory_index_a.invert_bijective_mapping(); let memory_index_b = inverse_memory_index_b.invert_bijective_mapping(); let outer_fields = FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a }; (outer_fields, offsets_b, memory_index_b) } _ => bug!(), }; let mut size = prefix.size; let mut align = prefix.align; let variants = info .variant_fields .iter_enumerated() .map(|(index, variant_fields)| { // Only include overlap-eligible fields when we compute our variant layout. let variant_only_tys = variant_fields .iter() .filter(|local| match assignments[**local] { Unassigned => bug!(), Assigned(v) if v == index => true, Assigned(_) => bug!("assignment does not match variant"), Ineligible(_) => false, }) .map(|local| subst_field(info.field_tys[*local].ty)); let mut variant = univariant_uninterned( cx, ty, &variant_only_tys .map(|ty| Ok(cx.layout_of(ty)?.layout)) .try_collect::>()?, &ReprOptions::default(), StructKind::Prefixed(prefix_size, prefix_align.abi), )?; variant.variants = Variants::Single { index }; let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else { bug!(); }; // Now, stitch the promoted and variant-only fields back together in // the order they are mentioned by our GeneratorLayout. // Because we only use some subset (that can differ between variants) // of the promoted fields, we can't just pick those elements of the // `promoted_memory_index` (as we'd end up with gaps). // So instead, we build an "inverse memory_index", as if all of the // promoted fields were being used, but leave the elements not in the // subset as `INVALID_FIELD_IDX`, which we can filter out later to // obtain a valid (bijective) mapping. const INVALID_FIELD_IDX: FieldIdx = FieldIdx::MAX; debug_assert!(variant_fields.next_index() <= INVALID_FIELD_IDX); let mut combined_inverse_memory_index = IndexVec::from_elem_n( INVALID_FIELD_IDX, promoted_memory_index.len() + memory_index.len(), ); let mut offsets_and_memory_index = iter::zip(offsets, memory_index); let combined_offsets = variant_fields .iter_enumerated() .map(|(i, local)| { let (offset, memory_index) = match assignments[*local] { Unassigned => bug!(), Assigned(_) => { let (offset, memory_index) = offsets_and_memory_index.next().unwrap(); (offset, promoted_memory_index.len() as u32 + memory_index) } Ineligible(field_idx) => { let field_idx = field_idx.unwrap(); (promoted_offsets[field_idx], promoted_memory_index[field_idx]) } }; combined_inverse_memory_index[memory_index] = i; offset }) .collect(); // Remove the unused slots and invert the mapping to obtain the // combined `memory_index` (also see previous comment). combined_inverse_memory_index.raw.retain(|&i| i != INVALID_FIELD_IDX); let combined_memory_index = combined_inverse_memory_index.invert_bijective_mapping(); variant.fields = FieldsShape::Arbitrary { offsets: combined_offsets, memory_index: combined_memory_index, }; size = size.max(variant.size); align = align.max(variant.align); Ok(variant) }) .try_collect::>()?; size = size.align_to(align.abi); let abi = if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi.is_uninhabited()) { Abi::Uninhabited } else { Abi::Aggregate { sized: true } }; let layout = tcx.mk_layout(LayoutS { variants: Variants::Multiple { tag, tag_encoding: TagEncoding::Direct, tag_field: tag_index, variants, }, fields: outer_fields, abi, largest_niche: prefix.largest_niche, size, align, }); debug!("generator layout ({:?}): {:#?}", ty, layout); Ok(layout) } /// This is invoked by the `layout_of` query to record the final /// layout of each type. #[inline(always)] fn record_layout_for_printing<'tcx>(cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: TyAndLayout<'tcx>) { // If we are running with `-Zprint-type-sizes`, maybe record layouts // for dumping later. if cx.tcx.sess.opts.unstable_opts.print_type_sizes { record_layout_for_printing_outlined(cx, layout) } } fn record_layout_for_printing_outlined<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: TyAndLayout<'tcx>, ) { // Ignore layouts that are done with non-empty environments or // non-monomorphic layouts, as the user only wants to see the stuff // resulting from the final codegen session. if layout.ty.has_non_region_param() || !cx.param_env.caller_bounds().is_empty() { return; } // (delay format until we actually need it) let record = |kind, packed, opt_discr_size, variants| { let type_desc = format!("{:?}", layout.ty); cx.tcx.sess.code_stats.record_type_size( kind, type_desc, layout.align.abi, layout.size, packed, opt_discr_size, variants, ); }; match *layout.ty.kind() { ty::Adt(adt_def, _) => { debug!("print-type-size t: `{:?}` process adt", layout.ty); let adt_kind = adt_def.adt_kind(); let adt_packed = adt_def.repr().pack.is_some(); let (variant_infos, opt_discr_size) = variant_info_for_adt(cx, layout, adt_def); record(adt_kind.into(), adt_packed, opt_discr_size, variant_infos); } ty::Generator(def_id, substs, _) => { debug!("print-type-size t: `{:?}` record generator", layout.ty); // Generators always have a begin/poisoned/end state with additional suspend points let (variant_infos, opt_discr_size) = variant_info_for_generator(cx, layout, def_id, substs); record(DataTypeKind::Generator, false, opt_discr_size, variant_infos); } ty::Closure(..) => { debug!("print-type-size t: `{:?}` record closure", layout.ty); record(DataTypeKind::Closure, false, None, vec![]); } _ => { debug!("print-type-size t: `{:?}` skip non-nominal", layout.ty); } }; } fn variant_info_for_adt<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: TyAndLayout<'tcx>, adt_def: AdtDef<'tcx>, ) -> (Vec, Option) { let build_variant_info = |n: Option, flds: &[Symbol], layout: TyAndLayout<'tcx>| { let mut min_size = Size::ZERO; let field_info: Vec<_> = flds .iter() .enumerate() .map(|(i, &name)| { let field_layout = layout.field(cx, i); let offset = layout.fields.offset(i); min_size = min_size.max(offset + field_layout.size); FieldInfo { kind: FieldKind::AdtField, name, offset: offset.bytes(), size: field_layout.size.bytes(), align: field_layout.align.abi.bytes(), } }) .collect(); VariantInfo { name: n, kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact }, align: layout.align.abi.bytes(), size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() }, fields: field_info, } }; match layout.variants { Variants::Single { index } => { if !adt_def.variants().is_empty() && layout.fields != FieldsShape::Primitive { debug!("print-type-size `{:#?}` variant {}", layout, adt_def.variant(index).name); let variant_def = &adt_def.variant(index); let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect(); (vec![build_variant_info(Some(variant_def.name), &fields, layout)], None) } else { (vec![], None) } } Variants::Multiple { tag, ref tag_encoding, .. } => { debug!( "print-type-size `{:#?}` adt general variants def {}", layout.ty, adt_def.variants().len() ); let variant_infos: Vec<_> = adt_def .variants() .iter_enumerated() .map(|(i, variant_def)| { let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect(); build_variant_info(Some(variant_def.name), &fields, layout.for_variant(cx, i)) }) .collect(); ( variant_infos, match tag_encoding { TagEncoding::Direct => Some(tag.size(cx)), _ => None, }, ) } } } fn variant_info_for_generator<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, layout: TyAndLayout<'tcx>, def_id: DefId, substs: ty::SubstsRef<'tcx>, ) -> (Vec, Option) { let Variants::Multiple { tag, ref tag_encoding, tag_field, .. } = layout.variants else { return (vec![], None); }; let (generator, state_specific_names) = cx.tcx.generator_layout_and_saved_local_names(def_id); let upvar_names = cx.tcx.closure_saved_names_of_captured_variables(def_id); let mut upvars_size = Size::ZERO; let upvar_fields: Vec<_> = substs .as_generator() .upvar_tys() .zip(upvar_names) .enumerate() .map(|(field_idx, (_, name))| { let field_layout = layout.field(cx, field_idx); let offset = layout.fields.offset(field_idx); upvars_size = upvars_size.max(offset + field_layout.size); FieldInfo { kind: FieldKind::Upvar, name: Symbol::intern(&name), offset: offset.bytes(), size: field_layout.size.bytes(), align: field_layout.align.abi.bytes(), } }) .collect(); let mut variant_infos: Vec<_> = generator .variant_fields .iter_enumerated() .map(|(variant_idx, variant_def)| { let variant_layout = layout.for_variant(cx, variant_idx); let mut variant_size = Size::ZERO; let fields = variant_def .iter() .enumerate() .map(|(field_idx, local)| { let field_layout = variant_layout.field(cx, field_idx); let offset = variant_layout.fields.offset(field_idx); // The struct is as large as the last field's end variant_size = variant_size.max(offset + field_layout.size); FieldInfo { kind: FieldKind::GeneratorLocal, name: state_specific_names.get(*local).copied().flatten().unwrap_or( Symbol::intern(&format!(".generator_field{}", local.as_usize())), ), offset: offset.bytes(), size: field_layout.size.bytes(), align: field_layout.align.abi.bytes(), } }) .chain(upvar_fields.iter().copied()) .collect(); // If the variant has no state-specific fields, then it's the size of the upvars. if variant_size == Size::ZERO { variant_size = upvars_size; } // This `if` deserves some explanation. // // The layout code has a choice of where to place the discriminant of this generator. // If the discriminant of the generator is placed early in the layout (before the // variant's own fields), then it'll implicitly be counted towards the size of the // variant, since we use the maximum offset to calculate size. // (side-note: I know this is a bit problematic given upvars placement, etc). // // This is important, since the layout printing code always subtracts this discriminant // size from the variant size if the struct is "enum"-like, so failing to account for it // will either lead to numerical underflow, or an underreported variant size... // // However, if the discriminant is placed past the end of the variant, then we need // to factor in the size of the discriminant manually. This really should be refactored // better, but this "works" for now. if layout.fields.offset(tag_field) >= variant_size { variant_size += match tag_encoding { TagEncoding::Direct => tag.size(cx), _ => Size::ZERO, }; } VariantInfo { name: Some(Symbol::intern(&ty::GeneratorSubsts::variant_name(variant_idx))), kind: SizeKind::Exact, size: variant_size.bytes(), align: variant_layout.align.abi.bytes(), fields, } }) .collect(); // The first three variants are hardcoded to be `UNRESUMED`, `RETURNED` and `POISONED`. // We will move the `RETURNED` and `POISONED` elements to the end so we // are left with a sorting order according to the generators yield points: // First `Unresumed`, then the `SuspendN` followed by `Returned` and `Panicked` (POISONED). let end_states = variant_infos.drain(1..=2); let end_states: Vec<_> = end_states.collect(); variant_infos.extend(end_states); ( variant_infos, match tag_encoding { TagEncoding::Direct => Some(tag.size(cx)), _ => None, }, ) }