1 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
2 use crate::mir::{GeneratorLayout, GeneratorSavedLocal};
3 use crate::ty::normalize_erasing_regions::NormalizationError;
4 use crate::ty::subst::Subst;
5 use crate::ty::{self, subst::SubstsRef, ReprOptions, Ty, TyCtxt, TypeFoldable};
7 use rustc_attr as attr;
9 use rustc_hir::lang_items::LangItem;
10 use rustc_index::bit_set::BitSet;
11 use rustc_index::vec::{Idx, IndexVec};
12 use rustc_session::{config::OptLevel, DataTypeKind, FieldInfo, SizeKind, VariantInfo};
13 use rustc_span::symbol::Symbol;
14 use rustc_span::{Span, DUMMY_SP};
15 use rustc_target::abi::call::{
16 ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, Conv, FnAbi, PassMode, Reg, RegKind,
18 use rustc_target::abi::*;
19 use rustc_target::spec::{abi::Abi as SpecAbi, HasTargetSpec, PanicStrategy, Target};
24 use std::num::NonZeroUsize;
27 use rand::{seq::SliceRandom, SeedableRng};
28 use rand_xoshiro::Xoshiro128StarStar;
30 pub fn provide(providers: &mut ty::query::Providers) {
32 ty::query::Providers { layout_of, fn_abi_of_fn_ptr, fn_abi_of_instance, ..*providers };
35 pub trait IntegerExt {
36 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>, signed: bool) -> Ty<'tcx>;
37 fn from_attr<C: HasDataLayout>(cx: &C, ity: attr::IntType) -> Integer;
38 fn from_int_ty<C: HasDataLayout>(cx: &C, ity: ty::IntTy) -> Integer;
39 fn from_uint_ty<C: HasDataLayout>(cx: &C, uty: ty::UintTy) -> Integer;
49 impl IntegerExt for Integer {
51 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>, signed: bool) -> Ty<'tcx> {
52 match (*self, signed) {
53 (I8, false) => tcx.types.u8,
54 (I16, false) => tcx.types.u16,
55 (I32, false) => tcx.types.u32,
56 (I64, false) => tcx.types.u64,
57 (I128, false) => tcx.types.u128,
58 (I8, true) => tcx.types.i8,
59 (I16, true) => tcx.types.i16,
60 (I32, true) => tcx.types.i32,
61 (I64, true) => tcx.types.i64,
62 (I128, true) => tcx.types.i128,
66 /// Gets the Integer type from an attr::IntType.
67 fn from_attr<C: HasDataLayout>(cx: &C, ity: attr::IntType) -> Integer {
68 let dl = cx.data_layout();
71 attr::SignedInt(ast::IntTy::I8) | attr::UnsignedInt(ast::UintTy::U8) => I8,
72 attr::SignedInt(ast::IntTy::I16) | attr::UnsignedInt(ast::UintTy::U16) => I16,
73 attr::SignedInt(ast::IntTy::I32) | attr::UnsignedInt(ast::UintTy::U32) => I32,
74 attr::SignedInt(ast::IntTy::I64) | attr::UnsignedInt(ast::UintTy::U64) => I64,
75 attr::SignedInt(ast::IntTy::I128) | attr::UnsignedInt(ast::UintTy::U128) => I128,
76 attr::SignedInt(ast::IntTy::Isize) | attr::UnsignedInt(ast::UintTy::Usize) => {
77 dl.ptr_sized_integer()
82 fn from_int_ty<C: HasDataLayout>(cx: &C, ity: ty::IntTy) -> Integer {
85 ty::IntTy::I16 => I16,
86 ty::IntTy::I32 => I32,
87 ty::IntTy::I64 => I64,
88 ty::IntTy::I128 => I128,
89 ty::IntTy::Isize => cx.data_layout().ptr_sized_integer(),
92 fn from_uint_ty<C: HasDataLayout>(cx: &C, ity: ty::UintTy) -> Integer {
95 ty::UintTy::U16 => I16,
96 ty::UintTy::U32 => I32,
97 ty::UintTy::U64 => I64,
98 ty::UintTy::U128 => I128,
99 ty::UintTy::Usize => cx.data_layout().ptr_sized_integer(),
103 /// Finds the appropriate Integer type and signedness for the given
104 /// signed discriminant range and `#[repr]` attribute.
105 /// N.B.: `u128` values above `i128::MAX` will be treated as signed, but
106 /// that shouldn't affect anything, other than maybe debuginfo.
113 ) -> (Integer, bool) {
114 // Theoretically, negative values could be larger in unsigned representation
115 // than the unsigned representation of the signed minimum. However, if there
116 // are any negative values, the only valid unsigned representation is u128
117 // which can fit all i128 values, so the result remains unaffected.
118 let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u128, max as u128));
119 let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
121 if let Some(ity) = repr.int {
122 let discr = Integer::from_attr(&tcx, ity);
123 let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
126 "Integer::repr_discr: `#[repr]` hint too small for \
127 discriminant range of enum `{}",
131 return (discr, ity.is_signed());
134 let at_least = if repr.c() {
135 // This is usually I32, however it can be different on some platforms,
136 // notably hexagon and arm-none/thumb-none
137 tcx.data_layout().c_enum_min_size
139 // repr(Rust) enums try to be as small as possible
143 // If there are no negative values, we can use the unsigned fit.
145 (cmp::max(unsigned_fit, at_least), false)
147 (cmp::max(signed_fit, at_least), true)
152 pub trait PrimitiveExt {
153 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
154 fn to_int_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
157 impl PrimitiveExt for Primitive {
159 fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
161 Int(i, signed) => i.to_ty(tcx, signed),
162 F32 => tcx.types.f32,
163 F64 => tcx.types.f64,
164 Pointer => tcx.mk_mut_ptr(tcx.mk_unit()),
168 /// Return an *integer* type matching this primitive.
169 /// Useful in particular when dealing with enum discriminants.
171 fn to_int_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
173 Int(i, signed) => i.to_ty(tcx, signed),
174 Pointer => tcx.types.usize,
175 F32 | F64 => bug!("floats do not have an int type"),
180 /// The first half of a fat pointer.
182 /// - For a trait object, this is the address of the box.
183 /// - For a slice, this is the base address.
184 pub const FAT_PTR_ADDR: usize = 0;
186 /// The second half of a fat pointer.
188 /// - For a trait object, this is the address of the vtable.
189 /// - For a slice, this is the length.
190 pub const FAT_PTR_EXTRA: usize = 1;
192 /// The maximum supported number of lanes in a SIMD vector.
194 /// This value is selected based on backend support:
195 /// * LLVM does not appear to have a vector width limit.
196 /// * Cranelift stores the base-2 log of the lane count in a 4 bit integer.
197 pub const MAX_SIMD_LANES: u64 = 1 << 0xF;
199 #[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
200 pub enum LayoutError<'tcx> {
202 SizeOverflow(Ty<'tcx>),
203 NormalizationFailure(Ty<'tcx>, NormalizationError<'tcx>),
206 impl<'tcx> fmt::Display for LayoutError<'tcx> {
207 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
209 LayoutError::Unknown(ty) => write!(f, "the type `{}` has an unknown layout", ty),
210 LayoutError::SizeOverflow(ty) => {
211 write!(f, "values of the type `{}` are too big for the current architecture", ty)
213 LayoutError::NormalizationFailure(t, e) => write!(
215 "unable to determine layout for `{}` because `{}` cannot be normalized",
217 e.get_type_for_failure()
223 #[instrument(skip(tcx, query), level = "debug")]
226 query: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
227 ) -> Result<TyAndLayout<'tcx>, LayoutError<'tcx>> {
228 ty::tls::with_related_context(tcx, move |icx| {
229 let (param_env, ty) = query.into_parts();
232 if !tcx.recursion_limit().value_within_limit(icx.layout_depth) {
233 tcx.sess.fatal(&format!("overflow representing the type `{}`", ty));
236 // Update the ImplicitCtxt to increase the layout_depth
237 let icx = ty::tls::ImplicitCtxt { layout_depth: icx.layout_depth + 1, ..icx.clone() };
239 ty::tls::enter_context(&icx, |_| {
240 let param_env = param_env.with_reveal_all_normalized(tcx);
241 let unnormalized_ty = ty;
243 // FIXME: We might want to have two different versions of `layout_of`:
244 // One that can be called after typecheck has completed and can use
245 // `normalize_erasing_regions` here and another one that can be called
246 // before typecheck has completed and uses `try_normalize_erasing_regions`.
247 let ty = match tcx.try_normalize_erasing_regions(param_env, ty) {
249 Err(normalization_error) => {
250 return Err(LayoutError::NormalizationFailure(ty, normalization_error));
254 if ty != unnormalized_ty {
255 // Ensure this layout is also cached for the normalized type.
256 return tcx.layout_of(param_env.and(ty));
259 let cx = LayoutCx { tcx, param_env };
261 let layout = cx.layout_of_uncached(ty)?;
262 let layout = TyAndLayout { ty, layout };
264 cx.record_layout_for_printing(layout);
266 // Type-level uninhabitedness should always imply ABI uninhabitedness.
267 if tcx.conservative_is_privately_uninhabited(param_env.and(ty)) {
268 assert!(layout.abi.is_uninhabited());
276 pub struct LayoutCx<'tcx, C> {
278 pub param_env: ty::ParamEnv<'tcx>,
281 #[derive(Copy, Clone, Debug)]
283 /// A tuple, closure, or univariant which cannot be coerced to unsized.
285 /// A univariant, the last field of which may be coerced to unsized.
287 /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
288 Prefixed(Size, Align),
291 // Invert a bijective mapping, i.e. `invert(map)[y] = x` if `map[x] = y`.
292 // This is used to go between `memory_index` (source field order to memory order)
293 // and `inverse_memory_index` (memory order to source field order).
294 // See also `FieldsShape::Arbitrary::memory_index` for more details.
295 // FIXME(eddyb) build a better abstraction for permutations, if possible.
296 fn invert_mapping(map: &[u32]) -> Vec<u32> {
297 let mut inverse = vec![0; map.len()];
298 for i in 0..map.len() {
299 inverse[map[i] as usize] = i as u32;
304 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
305 fn scalar_pair(&self, a: Scalar, b: Scalar) -> LayoutS<'tcx> {
306 let dl = self.data_layout();
307 let b_align = b.align(dl);
308 let align = a.align(dl).max(b_align).max(dl.aggregate_align);
309 let b_offset = a.size(dl).align_to(b_align.abi);
310 let size = (b_offset + b.size(dl)).align_to(align.abi);
312 // HACK(nox): We iter on `b` and then `a` because `max_by_key`
313 // returns the last maximum.
314 let largest_niche = Niche::from_scalar(dl, b_offset, b)
316 .chain(Niche::from_scalar(dl, Size::ZERO, a))
317 .max_by_key(|niche| niche.available(dl));
320 variants: Variants::Single { index: VariantIdx::new(0) },
321 fields: FieldsShape::Arbitrary {
322 offsets: vec![Size::ZERO, b_offset],
323 memory_index: vec![0, 1],
325 abi: Abi::ScalarPair(a, b),
332 fn univariant_uninterned(
335 fields: &[TyAndLayout<'_>],
338 ) -> Result<LayoutS<'tcx>, LayoutError<'tcx>> {
339 let dl = self.data_layout();
340 let pack = repr.pack;
341 if pack.is_some() && repr.align.is_some() {
342 self.tcx.sess.delay_span_bug(DUMMY_SP, "struct cannot be packed and aligned");
343 return Err(LayoutError::Unknown(ty));
346 let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align };
348 let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
350 let optimize = !repr.inhibit_struct_field_reordering_opt();
353 if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() };
354 let optimizing = &mut inverse_memory_index[..end];
355 let field_align = |f: &TyAndLayout<'_>| {
356 if let Some(pack) = pack { f.align.abi.min(pack) } else { f.align.abi }
359 // If `-Z randomize-layout` was enabled for the type definition we can shuffle
360 // the field ordering to try and catch some code making assumptions about layouts
361 // we don't guarantee
362 if repr.can_randomize_type_layout() {
363 // `ReprOptions.layout_seed` is a deterministic seed that we can use to
364 // randomize field ordering with
365 let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed);
367 // Shuffle the ordering of the fields
368 optimizing.shuffle(&mut rng);
370 // Otherwise we just leave things alone and actually optimize the type's fields
373 StructKind::AlwaysSized | StructKind::MaybeUnsized => {
374 optimizing.sort_by_key(|&x| {
375 // Place ZSTs first to avoid "interesting offsets",
376 // especially with only one or two non-ZST fields.
377 let f = &fields[x as usize];
378 (!f.is_zst(), cmp::Reverse(field_align(f)))
382 StructKind::Prefixed(..) => {
383 // Sort in ascending alignment so that the layout stays optimal
384 // regardless of the prefix
385 optimizing.sort_by_key(|&x| field_align(&fields[x as usize]));
389 // FIXME(Kixiron): We can always shuffle fields within a given alignment class
390 // regardless of the status of `-Z randomize-layout`
394 // inverse_memory_index holds field indices by increasing memory offset.
395 // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
396 // We now write field offsets to the corresponding offset slot;
397 // field 5 with offset 0 puts 0 in offsets[5].
398 // At the bottom of this function, we invert `inverse_memory_index` to
399 // produce `memory_index` (see `invert_mapping`).
401 let mut sized = true;
402 let mut offsets = vec![Size::ZERO; fields.len()];
403 let mut offset = Size::ZERO;
404 let mut largest_niche = None;
405 let mut largest_niche_available = 0;
407 if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
409 if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align };
410 align = align.max(AbiAndPrefAlign::new(prefix_align));
411 offset = prefix_size.align_to(prefix_align);
414 for &i in &inverse_memory_index {
415 let field = fields[i as usize];
417 self.tcx.sess.delay_span_bug(
420 "univariant: field #{} of `{}` comes after unsized field",
427 if field.is_unsized() {
431 // Invariant: offset < dl.obj_size_bound() <= 1<<61
432 let field_align = if let Some(pack) = pack {
433 field.align.min(AbiAndPrefAlign::new(pack))
437 offset = offset.align_to(field_align.abi);
438 align = align.max(field_align);
440 debug!("univariant offset: {:?} field: {:#?}", offset, field);
441 offsets[i as usize] = offset;
443 if !repr.hide_niche() {
444 if let Some(mut niche) = field.largest_niche {
445 let available = niche.available(dl);
446 if available > largest_niche_available {
447 largest_niche_available = available;
448 niche.offset += offset;
449 largest_niche = Some(niche);
454 offset = offset.checked_add(field.size, dl).ok_or(LayoutError::SizeOverflow(ty))?;
457 if let Some(repr_align) = repr.align {
458 align = align.max(AbiAndPrefAlign::new(repr_align));
461 debug!("univariant min_size: {:?}", offset);
462 let min_size = offset;
464 // As stated above, inverse_memory_index holds field indices by increasing offset.
465 // This makes it an already-sorted view of the offsets vec.
466 // To invert it, consider:
467 // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
468 // Field 5 would be the first element, so memory_index is i:
469 // Note: if we didn't optimize, it's already right.
472 if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index };
474 let size = min_size.align_to(align.abi);
475 let mut abi = Abi::Aggregate { sized };
477 // Unpack newtype ABIs and find scalar pairs.
478 if sized && size.bytes() > 0 {
479 // All other fields must be ZSTs.
480 let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst());
482 match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) {
483 // We have exactly one non-ZST field.
484 (Some((i, field)), None, None) => {
485 // Field fills the struct and it has a scalar or scalar pair ABI.
486 if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
489 // For plain scalars, or vectors of them, we can't unpack
490 // newtypes for `#[repr(C)]`, as that affects C ABIs.
491 Abi::Scalar(_) | Abi::Vector { .. } if optimize => {
494 // But scalar pairs are Rust-specific and get
495 // treated as aggregates by C ABIs anyway.
496 Abi::ScalarPair(..) => {
504 // Two non-ZST fields, and they're both scalars.
505 (Some((i, a)), Some((j, b)), None) => {
506 match (a.abi, b.abi) {
507 (Abi::Scalar(a), Abi::Scalar(b)) => {
508 // Order by the memory placement, not source order.
509 let ((i, a), (j, b)) = if offsets[i] < offsets[j] {
514 let pair = self.scalar_pair(a, b);
515 let pair_offsets = match pair.fields {
516 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
517 assert_eq!(memory_index, &[0, 1]);
522 if offsets[i] == pair_offsets[0]
523 && offsets[j] == pair_offsets[1]
524 && align == pair.align
527 // We can use `ScalarPair` only when it matches our
528 // already computed layout (including `#[repr(C)]`).
540 if fields.iter().any(|f| f.abi.is_uninhabited()) {
541 abi = Abi::Uninhabited;
545 variants: Variants::Single { index: VariantIdx::new(0) },
546 fields: FieldsShape::Arbitrary { offsets, memory_index },
554 fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<Layout<'tcx>, LayoutError<'tcx>> {
556 let param_env = self.param_env;
557 let dl = self.data_layout();
558 let scalar_unit = |value: Primitive| {
559 let size = value.size(dl);
560 assert!(size.bits() <= 128);
561 Scalar::Initialized { value, valid_range: WrappingRange::full(size) }
564 |value: Primitive| tcx.intern_layout(LayoutS::scalar(self, scalar_unit(value)));
566 let univariant = |fields: &[TyAndLayout<'_>], repr: &ReprOptions, kind| {
567 Ok(tcx.intern_layout(self.univariant_uninterned(ty, fields, repr, kind)?))
569 debug_assert!(!ty.has_infer_types_or_consts());
571 Ok(match *ty.kind() {
573 ty::Bool => tcx.intern_layout(LayoutS::scalar(
575 Scalar::Initialized {
576 value: Int(I8, false),
577 valid_range: WrappingRange { start: 0, end: 1 },
580 ty::Char => tcx.intern_layout(LayoutS::scalar(
582 Scalar::Initialized {
583 value: Int(I32, false),
584 valid_range: WrappingRange { start: 0, end: 0x10FFFF },
587 ty::Int(ity) => scalar(Int(Integer::from_int_ty(dl, ity), true)),
588 ty::Uint(ity) => scalar(Int(Integer::from_uint_ty(dl, ity), false)),
589 ty::Float(fty) => scalar(match fty {
590 ty::FloatTy::F32 => F32,
591 ty::FloatTy::F64 => F64,
594 let mut ptr = scalar_unit(Pointer);
595 ptr.valid_range_mut().start = 1;
596 tcx.intern_layout(LayoutS::scalar(self, ptr))
600 ty::Never => tcx.intern_layout(LayoutS {
601 variants: Variants::Single { index: VariantIdx::new(0) },
602 fields: FieldsShape::Primitive,
603 abi: Abi::Uninhabited,
609 // Potentially-wide pointers.
610 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
611 let mut data_ptr = scalar_unit(Pointer);
612 if !ty.is_unsafe_ptr() {
613 data_ptr.valid_range_mut().start = 1;
616 let pointee = tcx.normalize_erasing_regions(param_env, pointee);
617 if pointee.is_sized(tcx.at(DUMMY_SP), param_env) {
618 return Ok(tcx.intern_layout(LayoutS::scalar(self, data_ptr)));
621 let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
622 let metadata = match unsized_part.kind() {
624 return Ok(tcx.intern_layout(LayoutS::scalar(self, data_ptr)));
626 ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)),
628 let mut vtable = scalar_unit(Pointer);
629 vtable.valid_range_mut().start = 1;
632 _ => return Err(LayoutError::Unknown(unsized_part)),
635 // Effectively a (ptr, meta) tuple.
636 tcx.intern_layout(self.scalar_pair(data_ptr, metadata))
639 // Arrays and slices.
640 ty::Array(element, mut count) => {
641 if count.has_projections() {
642 count = tcx.normalize_erasing_regions(param_env, count);
643 if count.has_projections() {
644 return Err(LayoutError::Unknown(ty));
648 let count = count.try_eval_usize(tcx, param_env).ok_or(LayoutError::Unknown(ty))?;
649 let element = self.layout_of(element)?;
651 element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow(ty))?;
654 if count != 0 && tcx.conservative_is_privately_uninhabited(param_env.and(ty)) {
657 Abi::Aggregate { sized: true }
660 let largest_niche = if count != 0 { element.largest_niche } else { None };
662 tcx.intern_layout(LayoutS {
663 variants: Variants::Single { index: VariantIdx::new(0) },
664 fields: FieldsShape::Array { stride: element.size, count },
667 align: element.align,
671 ty::Slice(element) => {
672 let element = self.layout_of(element)?;
673 tcx.intern_layout(LayoutS {
674 variants: Variants::Single { index: VariantIdx::new(0) },
675 fields: FieldsShape::Array { stride: element.size, count: 0 },
676 abi: Abi::Aggregate { sized: false },
678 align: element.align,
682 ty::Str => tcx.intern_layout(LayoutS {
683 variants: Variants::Single { index: VariantIdx::new(0) },
684 fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 },
685 abi: Abi::Aggregate { sized: false },
692 ty::FnDef(..) => univariant(&[], &ReprOptions::default(), StructKind::AlwaysSized)?,
693 ty::Dynamic(..) | ty::Foreign(..) => {
694 let mut unit = self.univariant_uninterned(
697 &ReprOptions::default(),
698 StructKind::AlwaysSized,
701 Abi::Aggregate { ref mut sized } => *sized = false,
704 tcx.intern_layout(unit)
707 ty::Generator(def_id, substs, _) => self.generator_layout(ty, def_id, substs)?,
709 ty::Closure(_, ref substs) => {
710 let tys = substs.as_closure().upvar_tys();
712 &tys.map(|ty| self.layout_of(ty)).collect::<Result<Vec<_>, _>>()?,
713 &ReprOptions::default(),
714 StructKind::AlwaysSized,
720 if tys.len() == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized };
723 &tys.iter().map(|k| self.layout_of(k)).collect::<Result<Vec<_>, _>>()?,
724 &ReprOptions::default(),
729 // SIMD vector types.
730 ty::Adt(def, substs) if def.repr().simd() => {
731 if !def.is_struct() {
732 // Should have yielded E0517 by now.
733 tcx.sess.delay_span_bug(
735 "#[repr(simd)] was applied to an ADT that is not a struct",
737 return Err(LayoutError::Unknown(ty));
740 // Supported SIMD vectors are homogeneous ADTs with at least one field:
742 // * #[repr(simd)] struct S(T, T, T, T);
743 // * #[repr(simd)] struct S { x: T, y: T, z: T, w: T }
744 // * #[repr(simd)] struct S([T; 4])
746 // where T is a primitive scalar (integer/float/pointer).
748 // SIMD vectors with zero fields are not supported.
749 // (should be caught by typeck)
750 if def.non_enum_variant().fields.is_empty() {
751 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` of zero length", ty));
754 // Type of the first ADT field:
755 let f0_ty = def.non_enum_variant().fields[0].ty(tcx, substs);
757 // Heterogeneous SIMD vectors are not supported:
758 // (should be caught by typeck)
759 for fi in &def.non_enum_variant().fields {
760 if fi.ty(tcx, substs) != f0_ty {
761 tcx.sess.fatal(&format!("monomorphising heterogeneous SIMD type `{}`", ty));
765 // The element type and number of elements of the SIMD vector
766 // are obtained from:
768 // * the element type and length of the single array field, if
769 // the first field is of array type, or
771 // * the homogenous field type and the number of fields.
772 let (e_ty, e_len, is_array) = if let ty::Array(e_ty, _) = f0_ty.kind() {
773 // First ADT field is an array:
775 // SIMD vectors with multiple array fields are not supported:
776 // (should be caught by typeck)
777 if def.non_enum_variant().fields.len() != 1 {
778 tcx.sess.fatal(&format!(
779 "monomorphising SIMD type `{}` with more than one array field",
784 // Extract the number of elements from the layout of the array field:
785 let FieldsShape::Array { count, .. } = self.layout_of(f0_ty)?.layout.fields() else {
786 return Err(LayoutError::Unknown(ty));
789 (*e_ty, *count, true)
791 // First ADT field is not an array:
792 (f0_ty, def.non_enum_variant().fields.len() as _, false)
795 // SIMD vectors of zero length are not supported.
796 // Additionally, lengths are capped at 2^16 as a fixed maximum backends must
799 // Can't be caught in typeck if the array length is generic.
801 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` of zero length", ty));
802 } else if e_len > MAX_SIMD_LANES {
803 tcx.sess.fatal(&format!(
804 "monomorphising SIMD type `{}` of length greater than {}",
809 // Compute the ABI of the element type:
810 let e_ly = self.layout_of(e_ty)?;
811 let Abi::Scalar(e_abi) = e_ly.abi else {
812 // This error isn't caught in typeck, e.g., if
813 // the element type of the vector is generic.
814 tcx.sess.fatal(&format!(
815 "monomorphising SIMD type `{}` with a non-primitive-scalar \
816 (integer/float/pointer) element type `{}`",
821 // Compute the size and alignment of the vector:
822 let size = e_ly.size.checked_mul(e_len, dl).ok_or(LayoutError::SizeOverflow(ty))?;
823 let align = dl.vector_align(size);
824 let size = size.align_to(align.abi);
826 // Compute the placement of the vector fields:
827 let fields = if is_array {
828 FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] }
830 FieldsShape::Array { stride: e_ly.size, count: e_len }
833 tcx.intern_layout(LayoutS {
834 variants: Variants::Single { index: VariantIdx::new(0) },
836 abi: Abi::Vector { element: e_abi, count: e_len },
837 largest_niche: e_ly.largest_niche,
844 ty::Adt(def, substs) => {
845 // Cache the field layouts.
852 .map(|field| self.layout_of(field.ty(tcx, substs)))
853 .collect::<Result<Vec<_>, _>>()
855 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
858 if def.repr().pack.is_some() && def.repr().align.is_some() {
859 self.tcx.sess.delay_span_bug(
860 tcx.def_span(def.did()),
861 "union cannot be packed and aligned",
863 return Err(LayoutError::Unknown(ty));
867 if def.repr().pack.is_some() { dl.i8_align } else { dl.aggregate_align };
869 if let Some(repr_align) = def.repr().align {
870 align = align.max(AbiAndPrefAlign::new(repr_align));
873 let optimize = !def.repr().inhibit_union_abi_opt();
874 let mut size = Size::ZERO;
875 let mut abi = Abi::Aggregate { sized: true };
876 let index = VariantIdx::new(0);
877 for field in &variants[index] {
878 assert!(!field.is_unsized());
879 align = align.max(field.align);
881 // If all non-ZST fields have the same ABI, forward this ABI
882 if optimize && !field.is_zst() {
883 // Discard valid range information and allow undef
884 let field_abi = match field.abi {
885 Abi::Scalar(x) => Abi::Scalar(x.to_union()),
886 Abi::ScalarPair(x, y) => {
887 Abi::ScalarPair(x.to_union(), y.to_union())
889 Abi::Vector { element: x, count } => {
890 Abi::Vector { element: x.to_union(), count }
892 Abi::Uninhabited | Abi::Aggregate { .. } => {
893 Abi::Aggregate { sized: true }
897 if size == Size::ZERO {
898 // first non ZST: initialize 'abi'
900 } else if abi != field_abi {
901 // different fields have different ABI: reset to Aggregate
902 abi = Abi::Aggregate { sized: true };
906 size = cmp::max(size, field.size);
909 if let Some(pack) = def.repr().pack {
910 align = align.min(AbiAndPrefAlign::new(pack));
913 return Ok(tcx.intern_layout(LayoutS {
914 variants: Variants::Single { index },
915 fields: FieldsShape::Union(
916 NonZeroUsize::new(variants[index].len())
917 .ok_or(LayoutError::Unknown(ty))?,
922 size: size.align_to(align.abi),
926 // A variant is absent if it's uninhabited and only has ZST fields.
927 // Present uninhabited variants only require space for their fields,
928 // but *not* an encoding of the discriminant (e.g., a tag value).
929 // See issue #49298 for more details on the need to leave space
930 // for non-ZST uninhabited data (mostly partial initialization).
931 let absent = |fields: &[TyAndLayout<'_>]| {
932 let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
933 let is_zst = fields.iter().all(|f| f.is_zst());
934 uninhabited && is_zst
936 let (present_first, present_second) = {
937 let mut present_variants = variants
939 .filter_map(|(i, v)| if absent(v) { None } else { Some(i) });
940 (present_variants.next(), present_variants.next())
942 let present_first = match present_first {
943 Some(present_first) => present_first,
944 // Uninhabited because it has no variants, or only absent ones.
945 None if def.is_enum() => {
946 return Ok(tcx.layout_of(param_env.and(tcx.types.never))?.layout);
948 // If it's a struct, still compute a layout so that we can still compute the
950 None => VariantIdx::new(0),
953 let is_struct = !def.is_enum() ||
954 // Only one variant is present.
955 (present_second.is_none() &&
956 // Representation optimizations are allowed.
957 !def.repr().inhibit_enum_layout_opt());
959 // Struct, or univariant enum equivalent to a struct.
960 // (Typechecking will reject discriminant-sizing attrs.)
962 let v = present_first;
963 let kind = if def.is_enum() || variants[v].is_empty() {
964 StructKind::AlwaysSized
966 let param_env = tcx.param_env(def.did());
967 let last_field = def.variant(v).fields.last().unwrap();
969 tcx.type_of(last_field.did).is_sized(tcx.at(DUMMY_SP), param_env);
971 StructKind::MaybeUnsized
973 StructKind::AlwaysSized
977 let mut st = self.univariant_uninterned(ty, &variants[v], &def.repr(), kind)?;
978 st.variants = Variants::Single { index: v };
979 let (start, end) = self.tcx.layout_scalar_valid_range(def.did());
981 Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
982 // the asserts ensure that we are not using the
983 // `#[rustc_layout_scalar_valid_range(n)]`
984 // attribute to widen the range of anything as that would probably
985 // result in UB somewhere
986 // FIXME(eddyb) the asserts are probably not needed,
987 // as larger validity ranges would result in missed
988 // optimizations, *not* wrongly assuming the inner
989 // value is valid. e.g. unions enlarge validity ranges,
990 // because the values may be uninitialized.
991 if let Bound::Included(start) = start {
992 // FIXME(eddyb) this might be incorrect - it doesn't
993 // account for wrap-around (end < start) ranges.
994 let valid_range = scalar.valid_range_mut();
995 assert!(valid_range.start <= start);
996 valid_range.start = start;
998 if let Bound::Included(end) = end {
999 // FIXME(eddyb) this might be incorrect - it doesn't
1000 // account for wrap-around (end < start) ranges.
1001 let valid_range = scalar.valid_range_mut();
1002 assert!(valid_range.end >= end);
1003 valid_range.end = end;
1006 // Update `largest_niche` if we have introduced a larger niche.
1007 let niche = if def.repr().hide_niche() {
1010 Niche::from_scalar(dl, Size::ZERO, *scalar)
1012 if let Some(niche) = niche {
1013 match st.largest_niche {
1014 Some(largest_niche) => {
1015 // Replace the existing niche even if they're equal,
1016 // because this one is at a lower offset.
1017 if largest_niche.available(dl) <= niche.available(dl) {
1018 st.largest_niche = Some(niche);
1021 None => st.largest_niche = Some(niche),
1026 start == Bound::Unbounded && end == Bound::Unbounded,
1027 "nonscalar layout for layout_scalar_valid_range type {:?}: {:#?}",
1033 return Ok(tcx.intern_layout(st));
1036 // At this point, we have handled all unions and
1037 // structs. (We have also handled univariant enums
1038 // that allow representation optimization.)
1039 assert!(def.is_enum());
1041 // The current code for niche-filling relies on variant indices
1042 // instead of actual discriminants, so dataful enums with
1043 // explicit discriminants (RFC #2363) would misbehave.
1044 let no_explicit_discriminants = def
1047 .all(|(i, v)| v.discr == ty::VariantDiscr::Relative(i.as_u32()));
1049 let mut niche_filling_layout = None;
1051 // Niche-filling enum optimization.
1052 if !def.repr().inhibit_enum_layout_opt() && no_explicit_discriminants {
1053 let mut dataful_variant = None;
1054 let mut niche_variants = VariantIdx::MAX..=VariantIdx::new(0);
1056 // Find one non-ZST variant.
1057 'variants: for (v, fields) in variants.iter_enumerated() {
1063 if dataful_variant.is_none() {
1064 dataful_variant = Some(v);
1067 dataful_variant = None;
1072 niche_variants = *niche_variants.start().min(&v)..=v;
1075 if niche_variants.start() > niche_variants.end() {
1076 dataful_variant = None;
1079 if let Some(i) = dataful_variant {
1080 let count = (niche_variants.end().as_u32()
1081 - niche_variants.start().as_u32()
1084 // Find the field with the largest niche
1085 let niche_candidate = variants[i]
1088 .filter_map(|(j, field)| Some((j, field.largest_niche?)))
1089 .max_by_key(|(_, niche)| niche.available(dl));
1091 if let Some((field_index, niche, (niche_start, niche_scalar))) =
1092 niche_candidate.and_then(|(field_index, niche)| {
1093 Some((field_index, niche, niche.reserve(self, count)?))
1096 let mut align = dl.aggregate_align;
1100 let mut st = self.univariant_uninterned(
1104 StructKind::AlwaysSized,
1106 st.variants = Variants::Single { index: j };
1108 align = align.max(st.align);
1110 Ok(tcx.intern_layout(st))
1112 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1114 let offset = st[i].fields().offset(field_index) + niche.offset;
1115 let size = st[i].size();
1117 let abi = if st.iter().all(|v| v.abi().is_uninhabited()) {
1121 Abi::Scalar(_) => Abi::Scalar(niche_scalar),
1122 Abi::ScalarPair(first, second) => {
1123 // We need to use scalar_unit to reset the
1124 // valid range to the maximal one for that
1125 // primitive, because only the niche is
1126 // guaranteed to be initialised, not the
1128 if offset.bytes() == 0 {
1131 scalar_unit(second.primitive()),
1135 scalar_unit(first.primitive()),
1140 _ => Abi::Aggregate { sized: true },
1144 let largest_niche = Niche::from_scalar(dl, offset, niche_scalar);
1146 niche_filling_layout = Some(LayoutS {
1147 variants: Variants::Multiple {
1149 tag_encoding: TagEncoding::Niche {
1157 fields: FieldsShape::Arbitrary {
1158 offsets: vec![offset],
1159 memory_index: vec![0],
1170 let (mut min, mut max) = (i128::MAX, i128::MIN);
1171 let discr_type = def.repr().discr_type();
1172 let bits = Integer::from_attr(self, discr_type).size().bits();
1173 for (i, discr) in def.discriminants(tcx) {
1174 if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
1177 let mut x = discr.val as i128;
1178 if discr_type.is_signed() {
1179 // sign extend the raw representation to be an i128
1180 x = (x << (128 - bits)) >> (128 - bits);
1189 // We might have no inhabited variants, so pretend there's at least one.
1190 if (min, max) == (i128::MAX, i128::MIN) {
1194 assert!(min <= max, "discriminant range is {}...{}", min, max);
1195 let (min_ity, signed) = Integer::repr_discr(tcx, ty, &def.repr(), min, max);
1197 let mut align = dl.aggregate_align;
1198 let mut size = Size::ZERO;
1200 // We're interested in the smallest alignment, so start large.
1201 let mut start_align = Align::from_bytes(256).unwrap();
1202 assert_eq!(Integer::for_align(dl, start_align), None);
1204 // repr(C) on an enum tells us to make a (tag, union) layout,
1205 // so we need to grow the prefix alignment to be at least
1206 // the alignment of the union. (This value is used both for
1207 // determining the alignment of the overall enum, and the
1208 // determining the alignment of the payload after the tag.)
1209 let mut prefix_align = min_ity.align(dl).abi;
1211 for fields in &variants {
1212 for field in fields {
1213 prefix_align = prefix_align.max(field.align.abi);
1218 // Create the set of structs that represent each variant.
1219 let mut layout_variants = variants
1221 .map(|(i, field_layouts)| {
1222 let mut st = self.univariant_uninterned(
1226 StructKind::Prefixed(min_ity.size(), prefix_align),
1228 st.variants = Variants::Single { index: i };
1229 // Find the first field we can't move later
1230 // to make room for a larger discriminant.
1232 st.fields.index_by_increasing_offset().map(|j| field_layouts[j])
1234 if !field.is_zst() || field.align.abi.bytes() != 1 {
1235 start_align = start_align.min(field.align.abi);
1239 size = cmp::max(size, st.size);
1240 align = align.max(st.align);
1243 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1245 // Align the maximum variant size to the largest alignment.
1246 size = size.align_to(align.abi);
1248 if size.bytes() >= dl.obj_size_bound() {
1249 return Err(LayoutError::SizeOverflow(ty));
1252 let typeck_ity = Integer::from_attr(dl, def.repr().discr_type());
1253 if typeck_ity < min_ity {
1254 // It is a bug if Layout decided on a greater discriminant size than typeck for
1255 // some reason at this point (based on values discriminant can take on). Mostly
1256 // because this discriminant will be loaded, and then stored into variable of
1257 // type calculated by typeck. Consider such case (a bug): typeck decided on
1258 // byte-sized discriminant, but layout thinks we need a 16-bit to store all
1259 // discriminant values. That would be a bug, because then, in codegen, in order
1260 // to store this 16-bit discriminant into 8-bit sized temporary some of the
1261 // space necessary to represent would have to be discarded (or layout is wrong
1262 // on thinking it needs 16 bits)
1264 "layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
1268 // However, it is fine to make discr type however large (as an optimisation)
1269 // after this point – we’ll just truncate the value we load in codegen.
1272 // Check to see if we should use a different type for the
1273 // discriminant. We can safely use a type with the same size
1274 // as the alignment of the first field of each variant.
1275 // We increase the size of the discriminant to avoid LLVM copying
1276 // padding when it doesn't need to. This normally causes unaligned
1277 // load/stores and excessive memcpy/memset operations. By using a
1278 // bigger integer size, LLVM can be sure about its contents and
1279 // won't be so conservative.
1281 // Use the initial field alignment
1282 let mut ity = if def.repr().c() || def.repr().int.is_some() {
1285 Integer::for_align(dl, start_align).unwrap_or(min_ity)
1288 // If the alignment is not larger than the chosen discriminant size,
1289 // don't use the alignment as the final size.
1293 // Patch up the variants' first few fields.
1294 let old_ity_size = min_ity.size();
1295 let new_ity_size = ity.size();
1296 for variant in &mut layout_variants {
1297 match variant.fields {
1298 FieldsShape::Arbitrary { ref mut offsets, .. } => {
1300 if *i <= old_ity_size {
1301 assert_eq!(*i, old_ity_size);
1305 // We might be making the struct larger.
1306 if variant.size <= old_ity_size {
1307 variant.size = new_ity_size;
1315 let tag_mask = ity.size().unsigned_int_max();
1316 let tag = Scalar::Initialized {
1317 value: Int(ity, signed),
1318 valid_range: WrappingRange {
1319 start: (min as u128 & tag_mask),
1320 end: (max as u128 & tag_mask),
1323 let mut abi = Abi::Aggregate { sized: true };
1325 // Without latter check aligned enums with custom discriminant values
1326 // Would result in ICE see the issue #92464 for more info
1327 if tag.size(dl) == size || variants.iter().all(|layout| layout.is_empty()) {
1328 abi = Abi::Scalar(tag);
1330 // Try to use a ScalarPair for all tagged enums.
1331 let mut common_prim = None;
1332 for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
1333 let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else {
1337 iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
1338 let (field, offset) = match (fields.next(), fields.next()) {
1339 (None, None) => continue,
1340 (Some(pair), None) => pair,
1346 let prim = match field.abi {
1347 Abi::Scalar(scalar) => scalar.primitive(),
1353 if let Some(pair) = common_prim {
1354 // This is pretty conservative. We could go fancier
1355 // by conflating things like i32 and u32, or even
1356 // realising that (u8, u8) could just cohabit with
1358 if pair != (prim, offset) {
1363 common_prim = Some((prim, offset));
1366 if let Some((prim, offset)) = common_prim {
1367 let pair = self.scalar_pair(tag, scalar_unit(prim));
1368 let pair_offsets = match pair.fields {
1369 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
1370 assert_eq!(memory_index, &[0, 1]);
1375 if pair_offsets[0] == Size::ZERO
1376 && pair_offsets[1] == *offset
1377 && align == pair.align
1378 && size == pair.size
1380 // We can use `ScalarPair` only when it matches our
1381 // already computed layout (including `#[repr(C)]`).
1387 if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
1388 abi = Abi::Uninhabited;
1391 let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
1393 let layout_variants =
1394 layout_variants.into_iter().map(|v| tcx.intern_layout(v)).collect();
1396 let tagged_layout = LayoutS {
1397 variants: Variants::Multiple {
1399 tag_encoding: TagEncoding::Direct,
1401 variants: layout_variants,
1403 fields: FieldsShape::Arbitrary {
1404 offsets: vec![Size::ZERO],
1405 memory_index: vec![0],
1413 let best_layout = match (tagged_layout, niche_filling_layout) {
1414 (tagged_layout, Some(niche_filling_layout)) => {
1415 // Pick the smaller layout; otherwise,
1416 // pick the layout with the larger niche; otherwise,
1417 // pick tagged as it has simpler codegen.
1418 cmp::min_by_key(tagged_layout, niche_filling_layout, |layout| {
1419 let niche_size = layout.largest_niche.map_or(0, |n| n.available(dl));
1420 (layout.size, cmp::Reverse(niche_size))
1423 (tagged_layout, None) => tagged_layout,
1426 tcx.intern_layout(best_layout)
1429 // Types with no meaningful known layout.
1430 ty::Projection(_) | ty::Opaque(..) => {
1431 // NOTE(eddyb) `layout_of` query should've normalized these away,
1432 // if that was possible, so there's no reason to try again here.
1433 return Err(LayoutError::Unknown(ty));
1436 ty::Placeholder(..) | ty::GeneratorWitness(..) | ty::Infer(_) => {
1437 bug!("Layout::compute: unexpected type `{}`", ty)
1440 ty::Bound(..) | ty::Param(_) | ty::Error(_) => {
1441 return Err(LayoutError::Unknown(ty));
1447 /// Overlap eligibility and variant assignment for each GeneratorSavedLocal.
1448 #[derive(Clone, Debug, PartialEq)]
1449 enum SavedLocalEligibility {
1451 Assigned(VariantIdx),
1452 // FIXME: Use newtype_index so we aren't wasting bytes
1453 Ineligible(Option<u32>),
1456 // When laying out generators, we divide our saved local fields into two
1457 // categories: overlap-eligible and overlap-ineligible.
1459 // Those fields which are ineligible for overlap go in a "prefix" at the
1460 // beginning of the layout, and always have space reserved for them.
1462 // Overlap-eligible fields are only assigned to one variant, so we lay
1463 // those fields out for each variant and put them right after the
1466 // Finally, in the layout details, we point to the fields from the
1467 // variants they are assigned to. It is possible for some fields to be
1468 // included in multiple variants. No field ever "moves around" in the
1469 // layout; its offset is always the same.
1471 // Also included in the layout are the upvars and the discriminant.
1472 // These are included as fields on the "outer" layout; they are not part
1474 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
1475 /// Compute the eligibility and assignment of each local.
1476 fn generator_saved_local_eligibility(
1478 info: &GeneratorLayout<'tcx>,
1479 ) -> (BitSet<GeneratorSavedLocal>, IndexVec<GeneratorSavedLocal, SavedLocalEligibility>) {
1480 use SavedLocalEligibility::*;
1482 let mut assignments: IndexVec<GeneratorSavedLocal, SavedLocalEligibility> =
1483 IndexVec::from_elem_n(Unassigned, info.field_tys.len());
1485 // The saved locals not eligible for overlap. These will get
1486 // "promoted" to the prefix of our generator.
1487 let mut ineligible_locals = BitSet::new_empty(info.field_tys.len());
1489 // Figure out which of our saved locals are fields in only
1490 // one variant. The rest are deemed ineligible for overlap.
1491 for (variant_index, fields) in info.variant_fields.iter_enumerated() {
1492 for local in fields {
1493 match assignments[*local] {
1495 assignments[*local] = Assigned(variant_index);
1498 // We've already seen this local at another suspension
1499 // point, so it is no longer a candidate.
1501 "removing local {:?} in >1 variant ({:?}, {:?})",
1506 ineligible_locals.insert(*local);
1507 assignments[*local] = Ineligible(None);
1514 // Next, check every pair of eligible locals to see if they
1516 for local_a in info.storage_conflicts.rows() {
1517 let conflicts_a = info.storage_conflicts.count(local_a);
1518 if ineligible_locals.contains(local_a) {
1522 for local_b in info.storage_conflicts.iter(local_a) {
1523 // local_a and local_b are storage live at the same time, therefore they
1524 // cannot overlap in the generator layout. The only way to guarantee
1525 // this is if they are in the same variant, or one is ineligible
1526 // (which means it is stored in every variant).
1527 if ineligible_locals.contains(local_b)
1528 || assignments[local_a] == assignments[local_b]
1533 // If they conflict, we will choose one to make ineligible.
1534 // This is not always optimal; it's just a greedy heuristic that
1535 // seems to produce good results most of the time.
1536 let conflicts_b = info.storage_conflicts.count(local_b);
1537 let (remove, other) =
1538 if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) };
1539 ineligible_locals.insert(remove);
1540 assignments[remove] = Ineligible(None);
1541 trace!("removing local {:?} due to conflict with {:?}", remove, other);
1545 // Count the number of variants in use. If only one of them, then it is
1546 // impossible to overlap any locals in our layout. In this case it's
1547 // always better to make the remaining locals ineligible, so we can
1548 // lay them out with the other locals in the prefix and eliminate
1549 // unnecessary padding bytes.
1551 let mut used_variants = BitSet::new_empty(info.variant_fields.len());
1552 for assignment in &assignments {
1553 if let Assigned(idx) = assignment {
1554 used_variants.insert(*idx);
1557 if used_variants.count() < 2 {
1558 for assignment in assignments.iter_mut() {
1559 *assignment = Ineligible(None);
1561 ineligible_locals.insert_all();
1565 // Write down the order of our locals that will be promoted to the prefix.
1567 for (idx, local) in ineligible_locals.iter().enumerate() {
1568 assignments[local] = Ineligible(Some(idx as u32));
1571 debug!("generator saved local assignments: {:?}", assignments);
1573 (ineligible_locals, assignments)
1576 /// Compute the full generator layout.
1577 fn generator_layout(
1580 def_id: hir::def_id::DefId,
1581 substs: SubstsRef<'tcx>,
1582 ) -> Result<Layout<'tcx>, LayoutError<'tcx>> {
1583 use SavedLocalEligibility::*;
1585 let subst_field = |ty: Ty<'tcx>| ty.subst(tcx, substs);
1587 let Some(info) = tcx.generator_layout(def_id) else {
1588 return Err(LayoutError::Unknown(ty));
1590 let (ineligible_locals, assignments) = self.generator_saved_local_eligibility(&info);
1592 // Build a prefix layout, including "promoting" all ineligible
1593 // locals as part of the prefix. We compute the layout of all of
1594 // these fields at once to get optimal packing.
1595 let tag_index = substs.as_generator().prefix_tys().count();
1597 // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
1598 let max_discr = (info.variant_fields.len() - 1) as u128;
1599 let discr_int = Integer::fit_unsigned(max_discr);
1600 let discr_int_ty = discr_int.to_ty(tcx, false);
1601 let tag = Scalar::Initialized {
1602 value: Primitive::Int(discr_int, false),
1603 valid_range: WrappingRange { start: 0, end: max_discr },
1605 let tag_layout = self.tcx.intern_layout(LayoutS::scalar(self, tag));
1606 let tag_layout = TyAndLayout { ty: discr_int_ty, layout: tag_layout };
1608 let promoted_layouts = ineligible_locals
1610 .map(|local| subst_field(info.field_tys[local]))
1611 .map(|ty| tcx.mk_maybe_uninit(ty))
1612 .map(|ty| self.layout_of(ty));
1613 let prefix_layouts = substs
1616 .map(|ty| self.layout_of(ty))
1617 .chain(iter::once(Ok(tag_layout)))
1618 .chain(promoted_layouts)
1619 .collect::<Result<Vec<_>, _>>()?;
1620 let prefix = self.univariant_uninterned(
1623 &ReprOptions::default(),
1624 StructKind::AlwaysSized,
1627 let (prefix_size, prefix_align) = (prefix.size, prefix.align);
1629 // Split the prefix layout into the "outer" fields (upvars and
1630 // discriminant) and the "promoted" fields. Promoted fields will
1631 // get included in each variant that requested them in
1633 debug!("prefix = {:#?}", prefix);
1634 let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
1635 FieldsShape::Arbitrary { mut offsets, memory_index } => {
1636 let mut inverse_memory_index = invert_mapping(&memory_index);
1638 // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
1639 // "outer" and "promoted" fields respectively.
1640 let b_start = (tag_index + 1) as u32;
1641 let offsets_b = offsets.split_off(b_start as usize);
1642 let offsets_a = offsets;
1644 // Disentangle the "a" and "b" components of `inverse_memory_index`
1645 // by preserving the order but keeping only one disjoint "half" each.
1646 // FIXME(eddyb) build a better abstraction for permutations, if possible.
1647 let inverse_memory_index_b: Vec<_> =
1648 inverse_memory_index.iter().filter_map(|&i| i.checked_sub(b_start)).collect();
1649 inverse_memory_index.retain(|&i| i < b_start);
1650 let inverse_memory_index_a = inverse_memory_index;
1652 // Since `inverse_memory_index_{a,b}` each only refer to their
1653 // respective fields, they can be safely inverted
1654 let memory_index_a = invert_mapping(&inverse_memory_index_a);
1655 let memory_index_b = invert_mapping(&inverse_memory_index_b);
1658 FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a };
1659 (outer_fields, offsets_b, memory_index_b)
1664 let mut size = prefix.size;
1665 let mut align = prefix.align;
1669 .map(|(index, variant_fields)| {
1670 // Only include overlap-eligible fields when we compute our variant layout.
1671 let variant_only_tys = variant_fields
1673 .filter(|local| match assignments[**local] {
1674 Unassigned => bug!(),
1675 Assigned(v) if v == index => true,
1676 Assigned(_) => bug!("assignment does not match variant"),
1677 Ineligible(_) => false,
1679 .map(|local| subst_field(info.field_tys[*local]));
1681 let mut variant = self.univariant_uninterned(
1684 .map(|ty| self.layout_of(ty))
1685 .collect::<Result<Vec<_>, _>>()?,
1686 &ReprOptions::default(),
1687 StructKind::Prefixed(prefix_size, prefix_align.abi),
1689 variant.variants = Variants::Single { index };
1691 let FieldsShape::Arbitrary { offsets, memory_index } = variant.fields else {
1695 // Now, stitch the promoted and variant-only fields back together in
1696 // the order they are mentioned by our GeneratorLayout.
1697 // Because we only use some subset (that can differ between variants)
1698 // of the promoted fields, we can't just pick those elements of the
1699 // `promoted_memory_index` (as we'd end up with gaps).
1700 // So instead, we build an "inverse memory_index", as if all of the
1701 // promoted fields were being used, but leave the elements not in the
1702 // subset as `INVALID_FIELD_IDX`, which we can filter out later to
1703 // obtain a valid (bijective) mapping.
1704 const INVALID_FIELD_IDX: u32 = !0;
1705 let mut combined_inverse_memory_index =
1706 vec![INVALID_FIELD_IDX; promoted_memory_index.len() + memory_index.len()];
1707 let mut offsets_and_memory_index = iter::zip(offsets, memory_index);
1708 let combined_offsets = variant_fields
1712 let (offset, memory_index) = match assignments[*local] {
1713 Unassigned => bug!(),
1715 let (offset, memory_index) =
1716 offsets_and_memory_index.next().unwrap();
1717 (offset, promoted_memory_index.len() as u32 + memory_index)
1719 Ineligible(field_idx) => {
1720 let field_idx = field_idx.unwrap() as usize;
1721 (promoted_offsets[field_idx], promoted_memory_index[field_idx])
1724 combined_inverse_memory_index[memory_index as usize] = i as u32;
1729 // Remove the unused slots and invert the mapping to obtain the
1730 // combined `memory_index` (also see previous comment).
1731 combined_inverse_memory_index.retain(|&i| i != INVALID_FIELD_IDX);
1732 let combined_memory_index = invert_mapping(&combined_inverse_memory_index);
1734 variant.fields = FieldsShape::Arbitrary {
1735 offsets: combined_offsets,
1736 memory_index: combined_memory_index,
1739 size = size.max(variant.size);
1740 align = align.max(variant.align);
1741 Ok(tcx.intern_layout(variant))
1743 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1745 size = size.align_to(align.abi);
1748 if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi().is_uninhabited()) {
1751 Abi::Aggregate { sized: true }
1754 let layout = tcx.intern_layout(LayoutS {
1755 variants: Variants::Multiple {
1757 tag_encoding: TagEncoding::Direct,
1758 tag_field: tag_index,
1761 fields: outer_fields,
1763 largest_niche: prefix.largest_niche,
1767 debug!("generator layout ({:?}): {:#?}", ty, layout);
1771 /// This is invoked by the `layout_of` query to record the final
1772 /// layout of each type.
1774 fn record_layout_for_printing(&self, layout: TyAndLayout<'tcx>) {
1775 // If we are running with `-Zprint-type-sizes`, maybe record layouts
1776 // for dumping later.
1777 if self.tcx.sess.opts.debugging_opts.print_type_sizes {
1778 self.record_layout_for_printing_outlined(layout)
1782 fn record_layout_for_printing_outlined(&self, layout: TyAndLayout<'tcx>) {
1783 // Ignore layouts that are done with non-empty environments or
1784 // non-monomorphic layouts, as the user only wants to see the stuff
1785 // resulting from the final codegen session.
1786 if layout.ty.has_param_types_or_consts() || !self.param_env.caller_bounds().is_empty() {
1790 // (delay format until we actually need it)
1791 let record = |kind, packed, opt_discr_size, variants| {
1792 let type_desc = format!("{:?}", layout.ty);
1793 self.tcx.sess.code_stats.record_type_size(
1804 let adt_def = match *layout.ty.kind() {
1805 ty::Adt(ref adt_def, _) => {
1806 debug!("print-type-size t: `{:?}` process adt", layout.ty);
1810 ty::Closure(..) => {
1811 debug!("print-type-size t: `{:?}` record closure", layout.ty);
1812 record(DataTypeKind::Closure, false, None, vec![]);
1817 debug!("print-type-size t: `{:?}` skip non-nominal", layout.ty);
1822 let adt_kind = adt_def.adt_kind();
1823 let adt_packed = adt_def.repr().pack.is_some();
1825 let build_variant_info = |n: Option<Symbol>, flds: &[Symbol], layout: TyAndLayout<'tcx>| {
1826 let mut min_size = Size::ZERO;
1827 let field_info: Vec<_> = flds
1831 let field_layout = layout.field(self, i);
1832 let offset = layout.fields.offset(i);
1833 let field_end = offset + field_layout.size;
1834 if min_size < field_end {
1835 min_size = field_end;
1838 name: name.to_string(),
1839 offset: offset.bytes(),
1840 size: field_layout.size.bytes(),
1841 align: field_layout.align.abi.bytes(),
1847 name: n.map(|n| n.to_string()),
1848 kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact },
1849 align: layout.align.abi.bytes(),
1850 size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() },
1855 match layout.variants {
1856 Variants::Single { index } => {
1857 if !adt_def.variants().is_empty() && layout.fields != FieldsShape::Primitive {
1859 "print-type-size `{:#?}` variant {}",
1861 adt_def.variant(index).name
1863 let variant_def = &adt_def.variant(index);
1864 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1869 vec![build_variant_info(Some(variant_def.name), &fields, layout)],
1872 // (This case arises for *empty* enums; so give it
1874 record(adt_kind.into(), adt_packed, None, vec![]);
1878 Variants::Multiple { tag, ref tag_encoding, .. } => {
1880 "print-type-size `{:#?}` adt general variants def {}",
1882 adt_def.variants().len()
1884 let variant_infos: Vec<_> = adt_def
1887 .map(|(i, variant_def)| {
1888 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1890 Some(variant_def.name),
1892 layout.for_variant(self, i),
1899 match tag_encoding {
1900 TagEncoding::Direct => Some(tag.size(self)),
1910 /// Type size "skeleton", i.e., the only information determining a type's size.
1911 /// While this is conservative, (aside from constant sizes, only pointers,
1912 /// newtypes thereof and null pointer optimized enums are allowed), it is
1913 /// enough to statically check common use cases of transmute.
1914 #[derive(Copy, Clone, Debug)]
1915 pub enum SizeSkeleton<'tcx> {
1916 /// Any statically computable Layout.
1919 /// A potentially-fat pointer.
1921 /// If true, this pointer is never null.
1923 /// The type which determines the unsized metadata, if any,
1924 /// of this pointer. Either a type parameter or a projection
1925 /// depending on one, with regions erased.
1930 impl<'tcx> SizeSkeleton<'tcx> {
1934 param_env: ty::ParamEnv<'tcx>,
1935 ) -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
1936 debug_assert!(!ty.has_infer_types_or_consts());
1938 // First try computing a static layout.
1939 let err = match tcx.layout_of(param_env.and(ty)) {
1941 return Ok(SizeSkeleton::Known(layout.size));
1947 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1948 let non_zero = !ty.is_unsafe_ptr();
1949 let tail = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
1951 ty::Param(_) | ty::Projection(_) => {
1952 debug_assert!(tail.has_param_types_or_consts());
1953 Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
1956 "SizeSkeleton::compute({}): layout errored ({}), yet \
1957 tail `{}` is not a type parameter or a projection",
1965 ty::Adt(def, substs) => {
1966 // Only newtypes and enums w/ nullable pointer optimization.
1967 if def.is_union() || def.variants().is_empty() || def.variants().len() > 2 {
1971 // Get a zero-sized variant or a pointer newtype.
1972 let zero_or_ptr_variant = |i| {
1973 let i = VariantIdx::new(i);
1975 def.variant(i).fields.iter().map(|field| {
1976 SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env)
1979 for field in fields {
1982 SizeSkeleton::Known(size) => {
1983 if size.bytes() > 0 {
1987 SizeSkeleton::Pointer { .. } => {
1998 let v0 = zero_or_ptr_variant(0)?;
2000 if def.variants().len() == 1 {
2001 if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
2002 return Ok(SizeSkeleton::Pointer {
2004 || match tcx.layout_scalar_valid_range(def.did()) {
2005 (Bound::Included(start), Bound::Unbounded) => start > 0,
2006 (Bound::Included(start), Bound::Included(end)) => {
2007 0 < start && start < end
2018 let v1 = zero_or_ptr_variant(1)?;
2019 // Nullable pointer enum optimization.
2021 (Some(SizeSkeleton::Pointer { non_zero: true, tail }), None)
2022 | (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
2023 Ok(SizeSkeleton::Pointer { non_zero: false, tail })
2029 ty::Projection(_) | ty::Opaque(..) => {
2030 let normalized = tcx.normalize_erasing_regions(param_env, ty);
2031 if ty == normalized {
2034 SizeSkeleton::compute(normalized, tcx, param_env)
2042 pub fn same_size(self, other: SizeSkeleton<'_>) -> bool {
2043 match (self, other) {
2044 (SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
2045 (SizeSkeleton::Pointer { tail: a, .. }, SizeSkeleton::Pointer { tail: b, .. }) => {
2053 pub trait HasTyCtxt<'tcx>: HasDataLayout {
2054 fn tcx(&self) -> TyCtxt<'tcx>;
2057 pub trait HasParamEnv<'tcx> {
2058 fn param_env(&self) -> ty::ParamEnv<'tcx>;
2061 impl<'tcx> HasDataLayout for TyCtxt<'tcx> {
2063 fn data_layout(&self) -> &TargetDataLayout {
2068 impl<'tcx> HasTargetSpec for TyCtxt<'tcx> {
2069 fn target_spec(&self) -> &Target {
2074 impl<'tcx> HasTyCtxt<'tcx> for TyCtxt<'tcx> {
2076 fn tcx(&self) -> TyCtxt<'tcx> {
2081 impl<'tcx> HasDataLayout for ty::query::TyCtxtAt<'tcx> {
2083 fn data_layout(&self) -> &TargetDataLayout {
2088 impl<'tcx> HasTargetSpec for ty::query::TyCtxtAt<'tcx> {
2089 fn target_spec(&self) -> &Target {
2094 impl<'tcx> HasTyCtxt<'tcx> for ty::query::TyCtxtAt<'tcx> {
2096 fn tcx(&self) -> TyCtxt<'tcx> {
2101 impl<'tcx, C> HasParamEnv<'tcx> for LayoutCx<'tcx, C> {
2102 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2107 impl<'tcx, T: HasDataLayout> HasDataLayout for LayoutCx<'tcx, T> {
2108 fn data_layout(&self) -> &TargetDataLayout {
2109 self.tcx.data_layout()
2113 impl<'tcx, T: HasTargetSpec> HasTargetSpec for LayoutCx<'tcx, T> {
2114 fn target_spec(&self) -> &Target {
2115 self.tcx.target_spec()
2119 impl<'tcx, T: HasTyCtxt<'tcx>> HasTyCtxt<'tcx> for LayoutCx<'tcx, T> {
2120 fn tcx(&self) -> TyCtxt<'tcx> {
2125 pub trait MaybeResult<T> {
2128 fn from(x: Result<T, Self::Error>) -> Self;
2129 fn to_result(self) -> Result<T, Self::Error>;
2132 impl<T> MaybeResult<T> for T {
2135 fn from(Ok(x): Result<T, Self::Error>) -> Self {
2138 fn to_result(self) -> Result<T, Self::Error> {
2143 impl<T, E> MaybeResult<T> for Result<T, E> {
2146 fn from(x: Result<T, Self::Error>) -> Self {
2149 fn to_result(self) -> Result<T, Self::Error> {
2154 pub type TyAndLayout<'tcx> = rustc_target::abi::TyAndLayout<'tcx, Ty<'tcx>>;
2156 /// Trait for contexts that want to be able to compute layouts of types.
2157 /// This automatically gives access to `LayoutOf`, through a blanket `impl`.
2158 pub trait LayoutOfHelpers<'tcx>: HasDataLayout + HasTyCtxt<'tcx> + HasParamEnv<'tcx> {
2159 /// The `TyAndLayout`-wrapping type (or `TyAndLayout` itself), which will be
2160 /// returned from `layout_of` (see also `handle_layout_err`).
2161 type LayoutOfResult: MaybeResult<TyAndLayout<'tcx>>;
2163 /// `Span` to use for `tcx.at(span)`, from `layout_of`.
2164 // FIXME(eddyb) perhaps make this mandatory to get contexts to track it better?
2166 fn layout_tcx_at_span(&self) -> Span {
2170 /// Helper used for `layout_of`, to adapt `tcx.layout_of(...)` into a
2171 /// `Self::LayoutOfResult` (which does not need to be a `Result<...>`).
2173 /// Most `impl`s, which propagate `LayoutError`s, should simply return `err`,
2174 /// but this hook allows e.g. codegen to return only `TyAndLayout` from its
2175 /// `cx.layout_of(...)`, without any `Result<...>` around it to deal with
2176 /// (and any `LayoutError`s are turned into fatal errors or ICEs).
2177 fn handle_layout_err(
2179 err: LayoutError<'tcx>,
2182 ) -> <Self::LayoutOfResult as MaybeResult<TyAndLayout<'tcx>>>::Error;
2185 /// Blanket extension trait for contexts that can compute layouts of types.
2186 pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
2187 /// Computes the layout of a type. Note that this implicitly
2188 /// executes in "reveal all" mode, and will normalize the input type.
2190 fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
2191 self.spanned_layout_of(ty, DUMMY_SP)
2194 /// Computes the layout of a type, at `span`. Note that this implicitly
2195 /// executes in "reveal all" mode, and will normalize the input type.
2196 // FIXME(eddyb) avoid passing information like this, and instead add more
2197 // `TyCtxt::at`-like APIs to be able to do e.g. `cx.at(span).layout_of(ty)`.
2199 fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::LayoutOfResult {
2200 let span = if !span.is_dummy() { span } else { self.layout_tcx_at_span() };
2201 let tcx = self.tcx().at(span);
2204 tcx.layout_of(self.param_env().and(ty))
2205 .map_err(|err| self.handle_layout_err(err, span, ty)),
2210 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
2212 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
2213 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2216 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2221 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, ty::query::TyCtxtAt<'tcx>> {
2222 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2225 fn layout_tcx_at_span(&self) -> Span {
2230 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2235 impl<'tcx, C> TyAbiInterface<'tcx, C> for Ty<'tcx>
2237 C: HasTyCtxt<'tcx> + HasParamEnv<'tcx>,
2239 fn ty_and_layout_for_variant(
2240 this: TyAndLayout<'tcx>,
2242 variant_index: VariantIdx,
2243 ) -> TyAndLayout<'tcx> {
2244 let layout = match this.variants {
2245 Variants::Single { index }
2246 // If all variants but one are uninhabited, the variant layout is the enum layout.
2247 if index == variant_index &&
2248 // Don't confuse variants of uninhabited enums with the enum itself.
2249 // For more details see https://github.com/rust-lang/rust/issues/69763.
2250 this.fields != FieldsShape::Primitive =>
2255 Variants::Single { index } => {
2257 let param_env = cx.param_env();
2259 // Deny calling for_variant more than once for non-Single enums.
2260 if let Ok(original_layout) = tcx.layout_of(param_env.and(this.ty)) {
2261 assert_eq!(original_layout.variants, Variants::Single { index });
2264 let fields = match this.ty.kind() {
2265 ty::Adt(def, _) if def.variants().is_empty() =>
2266 bug!("for_variant called on zero-variant enum"),
2267 ty::Adt(def, _) => def.variant(variant_index).fields.len(),
2270 tcx.intern_layout(LayoutS {
2271 variants: Variants::Single { index: variant_index },
2272 fields: match NonZeroUsize::new(fields) {
2273 Some(fields) => FieldsShape::Union(fields),
2274 None => FieldsShape::Arbitrary { offsets: vec![], memory_index: vec![] },
2276 abi: Abi::Uninhabited,
2277 largest_niche: None,
2278 align: tcx.data_layout.i8_align,
2283 Variants::Multiple { ref variants, .. } => variants[variant_index],
2286 assert_eq!(*layout.variants(), Variants::Single { index: variant_index });
2288 TyAndLayout { ty: this.ty, layout }
2291 fn ty_and_layout_field(this: TyAndLayout<'tcx>, cx: &C, i: usize) -> TyAndLayout<'tcx> {
2292 enum TyMaybeWithLayout<'tcx> {
2294 TyAndLayout(TyAndLayout<'tcx>),
2297 fn field_ty_or_layout<'tcx>(
2298 this: TyAndLayout<'tcx>,
2299 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
2301 ) -> TyMaybeWithLayout<'tcx> {
2303 let tag_layout = |tag: Scalar| -> TyAndLayout<'tcx> {
2305 layout: tcx.intern_layout(LayoutS::scalar(cx, tag)),
2306 ty: tag.primitive().to_ty(tcx),
2310 match *this.ty.kind() {
2319 | ty::GeneratorWitness(..)
2321 | ty::Dynamic(..) => bug!("TyAndLayout::field({:?}): not applicable", this),
2323 // Potentially-fat pointers.
2324 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
2325 assert!(i < this.fields.count());
2327 // Reuse the fat `*T` type as its own thin pointer data field.
2328 // This provides information about, e.g., DST struct pointees
2329 // (which may have no non-DST form), and will work as long
2330 // as the `Abi` or `FieldsShape` is checked by users.
2332 let nil = tcx.mk_unit();
2333 let unit_ptr_ty = if this.ty.is_unsafe_ptr() {
2336 tcx.mk_mut_ref(tcx.lifetimes.re_static, nil)
2339 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing
2340 // the `Result` should always work because the type is
2341 // always either `*mut ()` or `&'static mut ()`.
2342 return TyMaybeWithLayout::TyAndLayout(TyAndLayout {
2344 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()
2348 match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() {
2349 ty::Slice(_) | ty::Str => TyMaybeWithLayout::Ty(tcx.types.usize),
2350 ty::Dynamic(_, _) => {
2351 TyMaybeWithLayout::Ty(tcx.mk_imm_ref(
2352 tcx.lifetimes.re_static,
2353 tcx.mk_array(tcx.types.usize, 3),
2355 /* FIXME: use actual fn pointers
2356 Warning: naively computing the number of entries in the
2357 vtable by counting the methods on the trait + methods on
2358 all parent traits does not work, because some methods can
2359 be not object safe and thus excluded from the vtable.
2360 Increase this counter if you tried to implement this but
2361 failed to do it without duplicating a lot of code from
2362 other places in the compiler: 2
2364 tcx.mk_array(tcx.types.usize, 3),
2365 tcx.mk_array(Option<fn()>),
2369 _ => bug!("TyAndLayout::field({:?}): not applicable", this),
2373 // Arrays and slices.
2374 ty::Array(element, _) | ty::Slice(element) => TyMaybeWithLayout::Ty(element),
2375 ty::Str => TyMaybeWithLayout::Ty(tcx.types.u8),
2377 // Tuples, generators and closures.
2378 ty::Closure(_, ref substs) => field_ty_or_layout(
2379 TyAndLayout { ty: substs.as_closure().tupled_upvars_ty(), ..this },
2384 ty::Generator(def_id, ref substs, _) => match this.variants {
2385 Variants::Single { index } => TyMaybeWithLayout::Ty(
2388 .state_tys(def_id, tcx)
2389 .nth(index.as_usize())
2394 Variants::Multiple { tag, tag_field, .. } => {
2396 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2398 TyMaybeWithLayout::Ty(substs.as_generator().prefix_tys().nth(i).unwrap())
2402 ty::Tuple(tys) => TyMaybeWithLayout::Ty(tys[i]),
2405 ty::Adt(def, substs) => {
2406 match this.variants {
2407 Variants::Single { index } => {
2408 TyMaybeWithLayout::Ty(def.variant(index).fields[i].ty(tcx, substs))
2411 // Discriminant field for enums (where applicable).
2412 Variants::Multiple { tag, .. } => {
2414 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2421 | ty::Placeholder(..)
2425 | ty::Error(_) => bug!("TyAndLayout::field: unexpected type `{}`", this.ty),
2429 match field_ty_or_layout(this, cx, i) {
2430 TyMaybeWithLayout::Ty(field_ty) => {
2431 cx.tcx().layout_of(cx.param_env().and(field_ty)).unwrap_or_else(|e| {
2433 "failed to get layout for `{}`: {},\n\
2434 despite it being a field (#{}) of an existing layout: {:#?}",
2442 TyMaybeWithLayout::TyAndLayout(field_layout) => field_layout,
2446 fn ty_and_layout_pointee_info_at(
2447 this: TyAndLayout<'tcx>,
2450 ) -> Option<PointeeInfo> {
2452 let param_env = cx.param_env();
2454 let addr_space_of_ty = |ty: Ty<'tcx>| {
2455 if ty.is_fn() { cx.data_layout().instruction_address_space } else { AddressSpace::DATA }
2458 let pointee_info = match *this.ty.kind() {
2459 ty::RawPtr(mt) if offset.bytes() == 0 => {
2460 tcx.layout_of(param_env.and(mt.ty)).ok().map(|layout| PointeeInfo {
2462 align: layout.align.abi,
2464 address_space: addr_space_of_ty(mt.ty),
2467 ty::FnPtr(fn_sig) if offset.bytes() == 0 => {
2468 tcx.layout_of(param_env.and(tcx.mk_fn_ptr(fn_sig))).ok().map(|layout| PointeeInfo {
2470 align: layout.align.abi,
2472 address_space: cx.data_layout().instruction_address_space,
2475 ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
2476 let address_space = addr_space_of_ty(ty);
2477 let kind = if tcx.sess.opts.optimize == OptLevel::No {
2478 // Use conservative pointer kind if not optimizing. This saves us the
2479 // Freeze/Unpin queries, and can save time in the codegen backend (noalias
2480 // attributes in LLVM have compile-time cost even in unoptimized builds).
2484 hir::Mutability::Not => {
2485 if ty.is_freeze(tcx.at(DUMMY_SP), cx.param_env()) {
2491 hir::Mutability::Mut => {
2492 // References to self-referential structures should not be considered
2493 // noalias, as another pointer to the structure can be obtained, that
2494 // is not based-on the original reference. We consider all !Unpin
2495 // types to be potentially self-referential here.
2496 if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) {
2497 PointerKind::UniqueBorrowed
2505 tcx.layout_of(param_env.and(ty)).ok().map(|layout| PointeeInfo {
2507 align: layout.align.abi,
2514 let mut data_variant = match this.variants {
2515 // Within the discriminant field, only the niche itself is
2516 // always initialized, so we only check for a pointer at its
2519 // If the niche is a pointer, it's either valid (according
2520 // to its type), or null (which the niche field's scalar
2521 // validity range encodes). This allows using
2522 // `dereferenceable_or_null` for e.g., `Option<&T>`, and
2523 // this will continue to work as long as we don't start
2524 // using more niches than just null (e.g., the first page of
2525 // the address space, or unaligned pointers).
2526 Variants::Multiple {
2527 tag_encoding: TagEncoding::Niche { dataful_variant, .. },
2530 } if this.fields.offset(tag_field) == offset => {
2531 Some(this.for_variant(cx, dataful_variant))
2536 if let Some(variant) = data_variant {
2537 // We're not interested in any unions.
2538 if let FieldsShape::Union(_) = variant.fields {
2539 data_variant = None;
2543 let mut result = None;
2545 if let Some(variant) = data_variant {
2546 let ptr_end = offset + Pointer.size(cx);
2547 for i in 0..variant.fields.count() {
2548 let field_start = variant.fields.offset(i);
2549 if field_start <= offset {
2550 let field = variant.field(cx, i);
2551 result = field.to_result().ok().and_then(|field| {
2552 if ptr_end <= field_start + field.size {
2553 // We found the right field, look inside it.
2555 field.pointee_info_at(cx, offset - field_start);
2561 if result.is_some() {
2568 // FIXME(eddyb) This should be for `ptr::Unique<T>`, not `Box<T>`.
2569 if let Some(ref mut pointee) = result {
2570 if let ty::Adt(def, _) = this.ty.kind() {
2571 if def.is_box() && offset.bytes() == 0 {
2572 pointee.safe = Some(PointerKind::UniqueOwned);
2582 "pointee_info_at (offset={:?}, type kind: {:?}) => {:?}",
2592 impl<'tcx> ty::Instance<'tcx> {
2593 // NOTE(eddyb) this is private to avoid using it from outside of
2594 // `fn_abi_of_instance` - any other uses are either too high-level
2595 // for `Instance` (e.g. typeck would use `Ty::fn_sig` instead),
2596 // or should go through `FnAbi` instead, to avoid losing any
2597 // adjustments `fn_abi_of_instance` might be performing.
2598 fn fn_sig_for_fn_abi(
2601 param_env: ty::ParamEnv<'tcx>,
2602 ) -> ty::PolyFnSig<'tcx> {
2603 let ty = self.ty(tcx, param_env);
2606 // HACK(davidtwco,eddyb): This is a workaround for polymorphization considering
2607 // parameters unused if they show up in the signature, but not in the `mir::Body`
2608 // (i.e. due to being inside a projection that got normalized, see
2609 // `src/test/ui/polymorphization/normalized_sig_types.rs`), and codegen not keeping
2610 // track of a polymorphization `ParamEnv` to allow normalizing later.
2611 let mut sig = match *ty.kind() {
2612 ty::FnDef(def_id, substs) => tcx
2613 .normalize_erasing_regions(tcx.param_env(def_id), tcx.fn_sig(def_id))
2614 .subst(tcx, substs),
2615 _ => unreachable!(),
2618 if let ty::InstanceDef::VtableShim(..) = self.def {
2619 // Modify `fn(self, ...)` to `fn(self: *mut Self, ...)`.
2620 sig = sig.map_bound(|mut sig| {
2621 let mut inputs_and_output = sig.inputs_and_output.to_vec();
2622 inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
2623 sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
2629 ty::Closure(def_id, substs) => {
2630 let sig = substs.as_closure().sig();
2632 let bound_vars = tcx.mk_bound_variable_kinds(
2635 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2637 let br = ty::BoundRegion {
2638 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2639 kind: ty::BoundRegionKind::BrEnv,
2641 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2642 let env_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
2644 let sig = sig.skip_binder();
2645 ty::Binder::bind_with_vars(
2647 iter::once(env_ty).chain(sig.inputs().iter().cloned()),
2656 ty::Generator(_, substs, _) => {
2657 let sig = substs.as_generator().poly_sig();
2659 let bound_vars = tcx.mk_bound_variable_kinds(
2662 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2664 let br = ty::BoundRegion {
2665 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2666 kind: ty::BoundRegionKind::BrEnv,
2668 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2669 let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
2671 let pin_did = tcx.require_lang_item(LangItem::Pin, None);
2672 let pin_adt_ref = tcx.adt_def(pin_did);
2673 let pin_substs = tcx.intern_substs(&[env_ty.into()]);
2674 let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
2676 let sig = sig.skip_binder();
2677 let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
2678 let state_adt_ref = tcx.adt_def(state_did);
2679 let state_substs = tcx.intern_substs(&[sig.yield_ty.into(), sig.return_ty.into()]);
2680 let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
2681 ty::Binder::bind_with_vars(
2683 [env_ty, sig.resume_ty].iter(),
2686 hir::Unsafety::Normal,
2687 rustc_target::spec::abi::Abi::Rust,
2692 _ => bug!("unexpected type {:?} in Instance::fn_sig", ty),
2697 /// Calculates whether a function's ABI can unwind or not.
2699 /// This takes two primary parameters:
2701 /// * `codegen_fn_attr_flags` - these are flags calculated as part of the
2702 /// codegen attrs for a defined function. For function pointers this set of
2703 /// flags is the empty set. This is only applicable for Rust-defined
2704 /// functions, and generally isn't needed except for small optimizations where
2705 /// we try to say a function which otherwise might look like it could unwind
2706 /// doesn't actually unwind (such as for intrinsics and such).
2708 /// * `abi` - this is the ABI that the function is defined with. This is the
2709 /// primary factor for determining whether a function can unwind or not.
2711 /// Note that in this case unwinding is not necessarily panicking in Rust. Rust
2712 /// panics are implemented with unwinds on most platform (when
2713 /// `-Cpanic=unwind`), but this also accounts for `-Cpanic=abort` build modes.
2714 /// Notably unwinding is disallowed for more non-Rust ABIs unless it's
2715 /// specifically in the name (e.g. `"C-unwind"`). Unwinding within each ABI is
2716 /// defined for each ABI individually, but it always corresponds to some form of
2717 /// stack-based unwinding (the exact mechanism of which varies
2718 /// platform-by-platform).
2720 /// Rust functions are classified whether or not they can unwind based on the
2721 /// active "panic strategy". In other words Rust functions are considered to
2722 /// unwind in `-Cpanic=unwind` mode and cannot unwind in `-Cpanic=abort` mode.
2723 /// Note that Rust supports intermingling panic=abort and panic=unwind code, but
2724 /// only if the final panic mode is panic=abort. In this scenario any code
2725 /// previously compiled assuming that a function can unwind is still correct, it
2726 /// just never happens to actually unwind at runtime.
2728 /// This function's answer to whether or not a function can unwind is quite
2729 /// impactful throughout the compiler. This affects things like:
2731 /// * Calling a function which can't unwind means codegen simply ignores any
2732 /// associated unwinding cleanup.
2733 /// * Calling a function which can unwind from a function which can't unwind
2734 /// causes the `abort_unwinding_calls` MIR pass to insert a landing pad that
2735 /// aborts the process.
2736 /// * This affects whether functions have the LLVM `nounwind` attribute, which
2737 /// affects various optimizations and codegen.
2739 /// FIXME: this is actually buggy with respect to Rust functions. Rust functions
2740 /// compiled with `-Cpanic=unwind` and referenced from another crate compiled
2741 /// with `-Cpanic=abort` will look like they can't unwind when in fact they
2742 /// might (from a foreign exception or similar).
2744 pub fn fn_can_unwind<'tcx>(
2746 codegen_fn_attr_flags: CodegenFnAttrFlags,
2749 // Special attribute for functions which can't unwind.
2750 if codegen_fn_attr_flags.contains(CodegenFnAttrFlags::NEVER_UNWIND) {
2754 // Otherwise if this isn't special then unwinding is generally determined by
2755 // the ABI of the itself. ABIs like `C` have variants which also
2756 // specifically allow unwinding (`C-unwind`), but not all platform-specific
2757 // ABIs have such an option. Otherwise the only other thing here is Rust
2758 // itself, and those ABIs are determined by the panic strategy configured
2759 // for this compilation.
2761 // Unfortunately at this time there's also another caveat. Rust [RFC
2762 // 2945][rfc] has been accepted and is in the process of being implemented
2763 // and stabilized. In this interim state we need to deal with historical
2764 // rustc behavior as well as plan for future rustc behavior.
2766 // Historically functions declared with `extern "C"` were marked at the
2767 // codegen layer as `nounwind`. This happened regardless of `panic=unwind`
2768 // or not. This is UB for functions in `panic=unwind` mode that then
2769 // actually panic and unwind. Note that this behavior is true for both
2770 // externally declared functions as well as Rust-defined function.
2772 // To fix this UB rustc would like to change in the future to catch unwinds
2773 // from function calls that may unwind within a Rust-defined `extern "C"`
2774 // function and forcibly abort the process, thereby respecting the
2775 // `nounwind` attribute emitted for `extern "C"`. This behavior change isn't
2776 // ready to roll out, so determining whether or not the `C` family of ABIs
2777 // unwinds is conditional not only on their definition but also whether the
2778 // `#![feature(c_unwind)]` feature gate is active.
2780 // Note that this means that unlike historical compilers rustc now, by
2781 // default, unconditionally thinks that the `C` ABI may unwind. This will
2782 // prevent some optimization opportunities, however, so we try to scope this
2783 // change and only assume that `C` unwinds with `panic=unwind` (as opposed
2784 // to `panic=abort`).
2786 // Eventually the check against `c_unwind` here will ideally get removed and
2787 // this'll be a little cleaner as it'll be a straightforward check of the
2790 // [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
2796 | Stdcall { unwind }
2797 | Fastcall { unwind }
2798 | Vectorcall { unwind }
2799 | Thiscall { unwind }
2802 | SysV64 { unwind } => {
2804 || (!tcx.features().c_unwind && tcx.sess.panic_strategy() == PanicStrategy::Unwind)
2812 | AvrNonBlockingInterrupt
2813 | CCmseNonSecureCall
2817 | Unadjusted => false,
2818 Rust | RustCall => tcx.sess.panic_strategy() == PanicStrategy::Unwind,
2823 pub fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv {
2824 use rustc_target::spec::abi::Abi::*;
2825 match tcx.sess.target.adjust_abi(abi) {
2826 RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
2828 // It's the ABI's job to select this, not ours.
2829 System { .. } => bug!("system abi should be selected elsewhere"),
2830 EfiApi => bug!("eficall abi should be selected elsewhere"),
2832 Stdcall { .. } => Conv::X86Stdcall,
2833 Fastcall { .. } => Conv::X86Fastcall,
2834 Vectorcall { .. } => Conv::X86VectorCall,
2835 Thiscall { .. } => Conv::X86ThisCall,
2836 C { .. } => Conv::C,
2837 Unadjusted => Conv::C,
2838 Win64 { .. } => Conv::X86_64Win64,
2839 SysV64 { .. } => Conv::X86_64SysV,
2840 Aapcs { .. } => Conv::ArmAapcs,
2841 CCmseNonSecureCall => Conv::CCmseNonSecureCall,
2842 PtxKernel => Conv::PtxKernel,
2843 Msp430Interrupt => Conv::Msp430Intr,
2844 X86Interrupt => Conv::X86Intr,
2845 AmdGpuKernel => Conv::AmdGpuKernel,
2846 AvrInterrupt => Conv::AvrInterrupt,
2847 AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt,
2850 // These API constants ought to be more specific...
2851 Cdecl { .. } => Conv::C,
2855 /// Error produced by attempting to compute or adjust a `FnAbi`.
2856 #[derive(Copy, Clone, Debug, HashStable)]
2857 pub enum FnAbiError<'tcx> {
2858 /// Error produced by a `layout_of` call, while computing `FnAbi` initially.
2859 Layout(LayoutError<'tcx>),
2861 /// Error produced by attempting to adjust a `FnAbi`, for a "foreign" ABI.
2862 AdjustForForeignAbi(call::AdjustForForeignAbiError),
2865 impl<'tcx> From<LayoutError<'tcx>> for FnAbiError<'tcx> {
2866 fn from(err: LayoutError<'tcx>) -> Self {
2871 impl From<call::AdjustForForeignAbiError> for FnAbiError<'_> {
2872 fn from(err: call::AdjustForForeignAbiError) -> Self {
2873 Self::AdjustForForeignAbi(err)
2877 impl<'tcx> fmt::Display for FnAbiError<'tcx> {
2878 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2880 Self::Layout(err) => err.fmt(f),
2881 Self::AdjustForForeignAbi(err) => err.fmt(f),
2886 // FIXME(eddyb) maybe use something like this for an unified `fn_abi_of`, not
2887 // just for error handling.
2889 pub enum FnAbiRequest<'tcx> {
2890 OfFnPtr { sig: ty::PolyFnSig<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2891 OfInstance { instance: ty::Instance<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2894 /// Trait for contexts that want to be able to compute `FnAbi`s.
2895 /// This automatically gives access to `FnAbiOf`, through a blanket `impl`.
2896 pub trait FnAbiOfHelpers<'tcx>: LayoutOfHelpers<'tcx> {
2897 /// The `&FnAbi`-wrapping type (or `&FnAbi` itself), which will be
2898 /// returned from `fn_abi_of_*` (see also `handle_fn_abi_err`).
2899 type FnAbiOfResult: MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>;
2901 /// Helper used for `fn_abi_of_*`, to adapt `tcx.fn_abi_of_*(...)` into a
2902 /// `Self::FnAbiOfResult` (which does not need to be a `Result<...>`).
2904 /// Most `impl`s, which propagate `FnAbiError`s, should simply return `err`,
2905 /// but this hook allows e.g. codegen to return only `&FnAbi` from its
2906 /// `cx.fn_abi_of_*(...)`, without any `Result<...>` around it to deal with
2907 /// (and any `FnAbiError`s are turned into fatal errors or ICEs).
2908 fn handle_fn_abi_err(
2910 err: FnAbiError<'tcx>,
2912 fn_abi_request: FnAbiRequest<'tcx>,
2913 ) -> <Self::FnAbiOfResult as MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>>::Error;
2916 /// Blanket extension trait for contexts that can compute `FnAbi`s.
2917 pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
2918 /// Compute a `FnAbi` suitable for indirect calls, i.e. to `fn` pointers.
2920 /// NB: this doesn't handle virtual calls - those should use `fn_abi_of_instance`
2921 /// instead, where the instance is an `InstanceDef::Virtual`.
2923 fn fn_abi_of_fn_ptr(
2925 sig: ty::PolyFnSig<'tcx>,
2926 extra_args: &'tcx ty::List<Ty<'tcx>>,
2927 ) -> Self::FnAbiOfResult {
2928 // FIXME(eddyb) get a better `span` here.
2929 let span = self.layout_tcx_at_span();
2930 let tcx = self.tcx().at(span);
2932 MaybeResult::from(tcx.fn_abi_of_fn_ptr(self.param_env().and((sig, extra_args))).map_err(
2933 |err| self.handle_fn_abi_err(err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
2937 /// Compute a `FnAbi` suitable for declaring/defining an `fn` instance, and for
2938 /// direct calls to an `fn`.
2940 /// NB: that includes virtual calls, which are represented by "direct calls"
2941 /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
2943 fn fn_abi_of_instance(
2945 instance: ty::Instance<'tcx>,
2946 extra_args: &'tcx ty::List<Ty<'tcx>>,
2947 ) -> Self::FnAbiOfResult {
2948 // FIXME(eddyb) get a better `span` here.
2949 let span = self.layout_tcx_at_span();
2950 let tcx = self.tcx().at(span);
2953 tcx.fn_abi_of_instance(self.param_env().and((instance, extra_args))).map_err(|err| {
2954 // HACK(eddyb) at least for definitions of/calls to `Instance`s,
2955 // we can get some kind of span even if one wasn't provided.
2956 // However, we don't do this early in order to avoid calling
2957 // `def_span` unconditionally (which may have a perf penalty).
2958 let span = if !span.is_dummy() { span } else { tcx.def_span(instance.def_id()) };
2959 self.handle_fn_abi_err(err, span, FnAbiRequest::OfInstance { instance, extra_args })
2965 impl<'tcx, C: FnAbiOfHelpers<'tcx>> FnAbiOf<'tcx> for C {}
2967 fn fn_abi_of_fn_ptr<'tcx>(
2969 query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2970 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2971 let (param_env, (sig, extra_args)) = query.into_parts();
2973 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
2977 CodegenFnAttrFlags::empty(),
2982 fn fn_abi_of_instance<'tcx>(
2984 query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2985 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2986 let (param_env, (instance, extra_args)) = query.into_parts();
2988 let sig = instance.fn_sig_for_fn_abi(tcx, param_env);
2990 let caller_location = if instance.def.requires_caller_location(tcx) {
2991 Some(tcx.caller_location_ty())
2996 let attrs = tcx.codegen_fn_attrs(instance.def_id()).flags;
2998 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
3003 matches!(instance.def, ty::InstanceDef::Virtual(..)),
3007 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
3008 // FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
3009 // arguments of this method, into a separate `struct`.
3010 fn fn_abi_new_uncached(
3012 sig: ty::PolyFnSig<'tcx>,
3013 extra_args: &[Ty<'tcx>],
3014 caller_location: Option<Ty<'tcx>>,
3015 codegen_fn_attr_flags: CodegenFnAttrFlags,
3016 // FIXME(eddyb) replace this with something typed, like an `enum`.
3017 force_thin_self_ptr: bool,
3018 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
3019 debug!("fn_abi_new_uncached({:?}, {:?})", sig, extra_args);
3021 let sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, sig);
3023 let conv = conv_from_spec_abi(self.tcx(), sig.abi);
3025 let mut inputs = sig.inputs();
3026 let extra_args = if sig.abi == RustCall {
3027 assert!(!sig.c_variadic && extra_args.is_empty());
3029 if let Some(input) = sig.inputs().last() {
3030 if let ty::Tuple(tupled_arguments) = input.kind() {
3031 inputs = &sig.inputs()[0..sig.inputs().len() - 1];
3035 "argument to function with \"rust-call\" ABI \
3041 "argument to function with \"rust-call\" ABI \
3046 assert!(sig.c_variadic || extra_args.is_empty());
3050 let target = &self.tcx.sess.target;
3051 let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
3052 let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
3053 let linux_s390x_gnu_like =
3054 target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
3055 let linux_sparc64_gnu_like =
3056 target.os == "linux" && target.arch == "sparc64" && target_env_gnu_like;
3057 let linux_powerpc_gnu_like =
3058 target.os == "linux" && target.arch == "powerpc" && target_env_gnu_like;
3060 let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall);
3062 // Handle safe Rust thin and fat pointers.
3063 let adjust_for_rust_scalar = |attrs: &mut ArgAttributes,
3065 layout: TyAndLayout<'tcx>,
3068 // Booleans are always a noundef i1 that needs to be zero-extended.
3069 if scalar.is_bool() {
3070 attrs.ext(ArgExtension::Zext);
3071 attrs.set(ArgAttribute::NoUndef);
3075 // Scalars which have invalid values cannot be undef.
3076 if !scalar.is_always_valid(self) {
3077 attrs.set(ArgAttribute::NoUndef);
3080 // Only pointer types handled below.
3081 let Scalar::Initialized { value: Pointer, valid_range} = scalar else { return };
3083 if !valid_range.contains(0) {
3084 attrs.set(ArgAttribute::NonNull);
3087 if let Some(pointee) = layout.pointee_info_at(self, offset) {
3088 if let Some(kind) = pointee.safe {
3089 attrs.pointee_align = Some(pointee.align);
3091 // `Box` (`UniqueBorrowed`) are not necessarily dereferenceable
3092 // for the entire duration of the function as they can be deallocated
3093 // at any time. Set their valid size to 0.
3094 attrs.pointee_size = match kind {
3095 PointerKind::UniqueOwned => Size::ZERO,
3099 // `Box`, `&T`, and `&mut T` cannot be undef.
3100 // Note that this only applies to the value of the pointer itself;
3101 // this attribute doesn't make it UB for the pointed-to data to be undef.
3102 attrs.set(ArgAttribute::NoUndef);
3104 // `Box` pointer parameters never alias because ownership is transferred
3105 // `&mut` pointer parameters never alias other parameters,
3106 // or mutable global data
3108 // `&T` where `T` contains no `UnsafeCell<U>` is immutable,
3109 // and can be marked as both `readonly` and `noalias`, as
3110 // LLVM's definition of `noalias` is based solely on memory
3111 // dependencies rather than pointer equality
3113 // Due to past miscompiles in LLVM, we apply a separate NoAliasMutRef attribute
3114 // for UniqueBorrowed arguments, so that the codegen backend can decide whether
3115 // or not to actually emit the attribute. It can also be controlled with the
3116 // `-Zmutable-noalias` debugging option.
3117 let no_alias = match kind {
3118 PointerKind::Shared | PointerKind::UniqueBorrowed => false,
3119 PointerKind::UniqueOwned => true,
3120 PointerKind::Frozen => !is_return,
3123 attrs.set(ArgAttribute::NoAlias);
3126 if kind == PointerKind::Frozen && !is_return {
3127 attrs.set(ArgAttribute::ReadOnly);
3130 if kind == PointerKind::UniqueBorrowed && !is_return {
3131 attrs.set(ArgAttribute::NoAliasMutRef);
3137 let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
3138 let is_return = arg_idx.is_none();
3140 let layout = self.layout_of(ty)?;
3141 let layout = if force_thin_self_ptr && arg_idx == Some(0) {
3142 // Don't pass the vtable, it's not an argument of the virtual fn.
3143 // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
3144 // or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen
3145 make_thin_self_ptr(self, layout)
3150 let mut arg = ArgAbi::new(self, layout, |layout, scalar, offset| {
3151 let mut attrs = ArgAttributes::new();
3152 adjust_for_rust_scalar(&mut attrs, scalar, *layout, offset, is_return);
3156 if arg.layout.is_zst() {
3157 // For some forsaken reason, x86_64-pc-windows-gnu
3158 // doesn't ignore zero-sized struct arguments.
3159 // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
3163 && !linux_s390x_gnu_like
3164 && !linux_sparc64_gnu_like
3165 && !linux_powerpc_gnu_like)
3167 arg.mode = PassMode::Ignore;
3174 let mut fn_abi = FnAbi {
3175 ret: arg_of(sig.output(), None)?,
3179 .chain(extra_args.iter().copied())
3180 .chain(caller_location)
3182 .map(|(i, ty)| arg_of(ty, Some(i)))
3183 .collect::<Result<_, _>>()?,
3184 c_variadic: sig.c_variadic,
3185 fixed_count: inputs.len(),
3187 can_unwind: fn_can_unwind(self.tcx(), codegen_fn_attr_flags, sig.abi),
3189 self.fn_abi_adjust_for_abi(&mut fn_abi, sig.abi)?;
3190 debug!("fn_abi_new_uncached = {:?}", fn_abi);
3191 Ok(self.tcx.arena.alloc(fn_abi))
3194 fn fn_abi_adjust_for_abi(
3196 fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
3198 ) -> Result<(), FnAbiError<'tcx>> {
3199 if abi == SpecAbi::Unadjusted {
3203 if abi == SpecAbi::Rust
3204 || abi == SpecAbi::RustCall
3205 || abi == SpecAbi::RustIntrinsic
3206 || abi == SpecAbi::PlatformIntrinsic
3208 let fixup = |arg: &mut ArgAbi<'tcx, Ty<'tcx>>| {
3209 if arg.is_ignore() {
3213 match arg.layout.abi {
3214 Abi::Aggregate { .. } => {}
3216 // This is a fun case! The gist of what this is doing is
3217 // that we want callers and callees to always agree on the
3218 // ABI of how they pass SIMD arguments. If we were to *not*
3219 // make these arguments indirect then they'd be immediates
3220 // in LLVM, which means that they'd used whatever the
3221 // appropriate ABI is for the callee and the caller. That
3222 // means, for example, if the caller doesn't have AVX
3223 // enabled but the callee does, then passing an AVX argument
3224 // across this boundary would cause corrupt data to show up.
3226 // This problem is fixed by unconditionally passing SIMD
3227 // arguments through memory between callers and callees
3228 // which should get them all to agree on ABI regardless of
3229 // target feature sets. Some more information about this
3230 // issue can be found in #44367.
3232 // Note that the platform intrinsic ABI is exempt here as
3233 // that's how we connect up to LLVM and it's unstable
3234 // anyway, we control all calls to it in libstd.
3236 if abi != SpecAbi::PlatformIntrinsic
3237 && self.tcx.sess.target.simd_types_indirect =>
3239 arg.make_indirect();
3246 let size = arg.layout.size;
3247 if arg.layout.is_unsized() || size > Pointer.size(self) {
3248 arg.make_indirect();
3250 // We want to pass small aggregates as immediates, but using
3251 // a LLVM aggregate type for this leads to bad optimizations,
3252 // so we pick an appropriately sized integer type instead.
3253 arg.cast_to(Reg { kind: RegKind::Integer, size });
3256 fixup(&mut fn_abi.ret);
3257 for arg in &mut fn_abi.args {
3261 fn_abi.adjust_for_foreign_abi(self, abi)?;
3268 fn make_thin_self_ptr<'tcx>(
3269 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
3270 layout: TyAndLayout<'tcx>,
3271 ) -> TyAndLayout<'tcx> {
3273 let fat_pointer_ty = if layout.is_unsized() {
3274 // unsized `self` is passed as a pointer to `self`
3275 // FIXME (mikeyhew) change this to use &own if it is ever added to the language
3276 tcx.mk_mut_ptr(layout.ty)
3279 Abi::ScalarPair(..) => (),
3280 _ => bug!("receiver type has unsupported layout: {:?}", layout),
3283 // In the case of Rc<Self>, we need to explicitly pass a *mut RcBox<Self>
3284 // with a Scalar (not ScalarPair) ABI. This is a hack that is understood
3285 // elsewhere in the compiler as a method on a `dyn Trait`.
3286 // To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we
3287 // get a built-in pointer type
3288 let mut fat_pointer_layout = layout;
3289 'descend_newtypes: while !fat_pointer_layout.ty.is_unsafe_ptr()
3290 && !fat_pointer_layout.ty.is_region_ptr()
3292 for i in 0..fat_pointer_layout.fields.count() {
3293 let field_layout = fat_pointer_layout.field(cx, i);
3295 if !field_layout.is_zst() {
3296 fat_pointer_layout = field_layout;
3297 continue 'descend_newtypes;
3301 bug!("receiver has no non-zero-sized fields {:?}", fat_pointer_layout);
3304 fat_pointer_layout.ty
3307 // we now have a type like `*mut RcBox<dyn Trait>`
3308 // change its layout to that of `*mut ()`, a thin pointer, but keep the same type
3309 // this is understood as a special case elsewhere in the compiler
3310 let unit_ptr_ty = tcx.mk_mut_ptr(tcx.mk_unit());
3315 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result`
3316 // should always work because the type is always `*mut ()`.
3317 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()