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) -> Layout {
306 let dl = self.data_layout();
307 let b_align = b.value.align(dl);
308 let align = a.value.align(dl).max(b_align).max(dl.aggregate_align);
309 let b_offset = a.value.size(dl).align_to(b_align.abi);
310 let size = (b_offset + b.value.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<Layout, 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.
506 Some((i, &TyAndLayout { layout: &Layout { abi: Abi::Scalar(a), .. }, .. })),
507 Some((j, &TyAndLayout { layout: &Layout { abi: Abi::Scalar(b), .. }, .. })),
510 // Order by the memory placement, not source order.
511 let ((i, a), (j, b)) =
512 if offsets[i] < offsets[j] { ((i, a), (j, b)) } else { ((j, b), (i, a)) };
513 let pair = self.scalar_pair(a, b);
514 let pair_offsets = match pair.fields {
515 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
516 assert_eq!(memory_index, &[0, 1]);
521 if offsets[i] == pair_offsets[0]
522 && offsets[j] == pair_offsets[1]
523 && align == pair.align
526 // We can use `ScalarPair` only when it matches our
527 // already computed layout (including `#[repr(C)]`).
536 if fields.iter().any(|f| f.abi.is_uninhabited()) {
537 abi = Abi::Uninhabited;
541 variants: Variants::Single { index: VariantIdx::new(0) },
542 fields: FieldsShape::Arbitrary { offsets, memory_index },
550 fn layout_of_uncached(&self, ty: Ty<'tcx>) -> Result<&'tcx Layout, LayoutError<'tcx>> {
552 let param_env = self.param_env;
553 let dl = self.data_layout();
554 let scalar_unit = |value: Primitive| {
555 let size = value.size(dl);
556 assert!(size.bits() <= 128);
557 Scalar { value, valid_range: WrappingRange { start: 0, end: size.unsigned_int_max() } }
559 let scalar = |value: Primitive| tcx.intern_layout(Layout::scalar(self, scalar_unit(value)));
561 let univariant = |fields: &[TyAndLayout<'_>], repr: &ReprOptions, kind| {
562 Ok(tcx.intern_layout(self.univariant_uninterned(ty, fields, repr, kind)?))
564 debug_assert!(!ty.has_infer_types_or_consts());
566 Ok(match *ty.kind() {
568 ty::Bool => tcx.intern_layout(Layout::scalar(
570 Scalar { value: Int(I8, false), valid_range: WrappingRange { start: 0, end: 1 } },
572 ty::Char => tcx.intern_layout(Layout::scalar(
575 value: Int(I32, false),
576 valid_range: WrappingRange { start: 0, end: 0x10FFFF },
579 ty::Int(ity) => scalar(Int(Integer::from_int_ty(dl, ity), true)),
580 ty::Uint(ity) => scalar(Int(Integer::from_uint_ty(dl, ity), false)),
581 ty::Float(fty) => scalar(match fty {
582 ty::FloatTy::F32 => F32,
583 ty::FloatTy::F64 => F64,
586 let mut ptr = scalar_unit(Pointer);
587 ptr.valid_range = ptr.valid_range.with_start(1);
588 tcx.intern_layout(Layout::scalar(self, ptr))
592 ty::Never => tcx.intern_layout(Layout {
593 variants: Variants::Single { index: VariantIdx::new(0) },
594 fields: FieldsShape::Primitive,
595 abi: Abi::Uninhabited,
601 // Potentially-wide pointers.
602 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
603 let mut data_ptr = scalar_unit(Pointer);
604 if !ty.is_unsafe_ptr() {
605 data_ptr.valid_range = data_ptr.valid_range.with_start(1);
608 let pointee = tcx.normalize_erasing_regions(param_env, pointee);
609 if pointee.is_sized(tcx.at(DUMMY_SP), param_env) {
610 return Ok(tcx.intern_layout(Layout::scalar(self, data_ptr)));
613 let unsized_part = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
614 let metadata = match unsized_part.kind() {
616 return Ok(tcx.intern_layout(Layout::scalar(self, data_ptr)));
618 ty::Slice(_) | ty::Str => scalar_unit(Int(dl.ptr_sized_integer(), false)),
620 let mut vtable = scalar_unit(Pointer);
621 vtable.valid_range = vtable.valid_range.with_start(1);
624 _ => return Err(LayoutError::Unknown(unsized_part)),
627 // Effectively a (ptr, meta) tuple.
628 tcx.intern_layout(self.scalar_pair(data_ptr, metadata))
631 // Arrays and slices.
632 ty::Array(element, mut count) => {
633 if count.has_projections() {
634 count = tcx.normalize_erasing_regions(param_env, count);
635 if count.has_projections() {
636 return Err(LayoutError::Unknown(ty));
640 let count = count.try_eval_usize(tcx, param_env).ok_or(LayoutError::Unknown(ty))?;
641 let element = self.layout_of(element)?;
643 element.size.checked_mul(count, dl).ok_or(LayoutError::SizeOverflow(ty))?;
646 if count != 0 && tcx.conservative_is_privately_uninhabited(param_env.and(ty)) {
649 Abi::Aggregate { sized: true }
652 let largest_niche = if count != 0 { element.largest_niche } else { None };
654 tcx.intern_layout(Layout {
655 variants: Variants::Single { index: VariantIdx::new(0) },
656 fields: FieldsShape::Array { stride: element.size, count },
659 align: element.align,
663 ty::Slice(element) => {
664 let element = self.layout_of(element)?;
665 tcx.intern_layout(Layout {
666 variants: Variants::Single { index: VariantIdx::new(0) },
667 fields: FieldsShape::Array { stride: element.size, count: 0 },
668 abi: Abi::Aggregate { sized: false },
670 align: element.align,
674 ty::Str => tcx.intern_layout(Layout {
675 variants: Variants::Single { index: VariantIdx::new(0) },
676 fields: FieldsShape::Array { stride: Size::from_bytes(1), count: 0 },
677 abi: Abi::Aggregate { sized: false },
684 ty::FnDef(..) => univariant(&[], &ReprOptions::default(), StructKind::AlwaysSized)?,
685 ty::Dynamic(..) | ty::Foreign(..) => {
686 let mut unit = self.univariant_uninterned(
689 &ReprOptions::default(),
690 StructKind::AlwaysSized,
693 Abi::Aggregate { ref mut sized } => *sized = false,
696 tcx.intern_layout(unit)
699 ty::Generator(def_id, substs, _) => self.generator_layout(ty, def_id, substs)?,
701 ty::Closure(_, ref substs) => {
702 let tys = substs.as_closure().upvar_tys();
704 &tys.map(|ty| self.layout_of(ty)).collect::<Result<Vec<_>, _>>()?,
705 &ReprOptions::default(),
706 StructKind::AlwaysSized,
712 if tys.len() == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized };
716 .map(|k| self.layout_of(k.expect_ty()))
717 .collect::<Result<Vec<_>, _>>()?,
718 &ReprOptions::default(),
723 // SIMD vector types.
724 ty::Adt(def, substs) if def.repr.simd() => {
725 if !def.is_struct() {
726 // Should have yielded E0517 by now.
727 tcx.sess.delay_span_bug(
729 "#[repr(simd)] was applied to an ADT that is not a struct",
731 return Err(LayoutError::Unknown(ty));
734 // Supported SIMD vectors are homogeneous ADTs with at least one field:
736 // * #[repr(simd)] struct S(T, T, T, T);
737 // * #[repr(simd)] struct S { x: T, y: T, z: T, w: T }
738 // * #[repr(simd)] struct S([T; 4])
740 // where T is a primitive scalar (integer/float/pointer).
742 // SIMD vectors with zero fields are not supported.
743 // (should be caught by typeck)
744 if def.non_enum_variant().fields.is_empty() {
745 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` of zero length", ty));
748 // Type of the first ADT field:
749 let f0_ty = def.non_enum_variant().fields[0].ty(tcx, substs);
751 // Heterogeneous SIMD vectors are not supported:
752 // (should be caught by typeck)
753 for fi in &def.non_enum_variant().fields {
754 if fi.ty(tcx, substs) != f0_ty {
755 tcx.sess.fatal(&format!("monomorphising heterogeneous SIMD type `{}`", ty));
759 // The element type and number of elements of the SIMD vector
760 // are obtained from:
762 // * the element type and length of the single array field, if
763 // the first field is of array type, or
765 // * the homogenous field type and the number of fields.
766 let (e_ty, e_len, is_array) = if let ty::Array(e_ty, _) = f0_ty.kind() {
767 // First ADT field is an array:
769 // SIMD vectors with multiple array fields are not supported:
770 // (should be caught by typeck)
771 if def.non_enum_variant().fields.len() != 1 {
772 tcx.sess.fatal(&format!(
773 "monomorphising SIMD type `{}` with more than one array field",
778 // Extract the number of elements from the layout of the array field:
780 layout: Layout { fields: FieldsShape::Array { count, .. }, .. },
782 }) = self.layout_of(f0_ty) else {
783 return Err(LayoutError::Unknown(ty));
786 (*e_ty, *count, true)
788 // First ADT field is not an array:
789 (f0_ty, def.non_enum_variant().fields.len() as _, false)
792 // SIMD vectors of zero length are not supported.
793 // Additionally, lengths are capped at 2^16 as a fixed maximum backends must
796 // Can't be caught in typeck if the array length is generic.
798 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` of zero length", ty));
799 } else if e_len > MAX_SIMD_LANES {
800 tcx.sess.fatal(&format!(
801 "monomorphising SIMD type `{}` of length greater than {}",
806 // Compute the ABI of the element type:
807 let e_ly = self.layout_of(e_ty)?;
808 let Abi::Scalar(e_abi) = e_ly.abi else {
809 // This error isn't caught in typeck, e.g., if
810 // the element type of the vector is generic.
811 tcx.sess.fatal(&format!(
812 "monomorphising SIMD type `{}` with a non-primitive-scalar \
813 (integer/float/pointer) element type `{}`",
818 // Compute the size and alignment of the vector:
819 let size = e_ly.size.checked_mul(e_len, dl).ok_or(LayoutError::SizeOverflow(ty))?;
820 let align = dl.vector_align(size);
821 let size = size.align_to(align.abi);
823 // Compute the placement of the vector fields:
824 let fields = if is_array {
825 FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] }
827 FieldsShape::Array { stride: e_ly.size, count: e_len }
830 tcx.intern_layout(Layout {
831 variants: Variants::Single { index: VariantIdx::new(0) },
833 abi: Abi::Vector { element: e_abi, count: e_len },
834 largest_niche: e_ly.largest_niche,
841 ty::Adt(def, substs) => {
842 // Cache the field layouts.
849 .map(|field| self.layout_of(field.ty(tcx, substs)))
850 .collect::<Result<Vec<_>, _>>()
852 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
855 if def.repr.pack.is_some() && def.repr.align.is_some() {
856 self.tcx.sess.delay_span_bug(
857 tcx.def_span(def.did),
858 "union cannot be packed and aligned",
860 return Err(LayoutError::Unknown(ty));
864 if def.repr.pack.is_some() { dl.i8_align } else { dl.aggregate_align };
866 if let Some(repr_align) = def.repr.align {
867 align = align.max(AbiAndPrefAlign::new(repr_align));
870 let optimize = !def.repr.inhibit_union_abi_opt();
871 let mut size = Size::ZERO;
872 let mut abi = Abi::Aggregate { sized: true };
873 let index = VariantIdx::new(0);
874 for field in &variants[index] {
875 assert!(!field.is_unsized());
876 align = align.max(field.align);
878 // If all non-ZST fields have the same ABI, forward this ABI
879 if optimize && !field.is_zst() {
880 // Normalize scalar_unit to the maximal valid range
881 let field_abi = match field.abi {
882 Abi::Scalar(x) => Abi::Scalar(scalar_unit(x.value)),
883 Abi::ScalarPair(x, y) => {
884 Abi::ScalarPair(scalar_unit(x.value), scalar_unit(y.value))
886 Abi::Vector { element: x, count } => {
887 Abi::Vector { element: scalar_unit(x.value), count }
889 Abi::Uninhabited | Abi::Aggregate { .. } => {
890 Abi::Aggregate { sized: true }
894 if size == Size::ZERO {
895 // first non ZST: initialize 'abi'
897 } else if abi != field_abi {
898 // different fields have different ABI: reset to Aggregate
899 abi = Abi::Aggregate { sized: true };
903 size = cmp::max(size, field.size);
906 if let Some(pack) = def.repr.pack {
907 align = align.min(AbiAndPrefAlign::new(pack));
910 return Ok(tcx.intern_layout(Layout {
911 variants: Variants::Single { index },
912 fields: FieldsShape::Union(
913 NonZeroUsize::new(variants[index].len())
914 .ok_or(LayoutError::Unknown(ty))?,
919 size: size.align_to(align.abi),
923 // A variant is absent if it's uninhabited and only has ZST fields.
924 // Present uninhabited variants only require space for their fields,
925 // but *not* an encoding of the discriminant (e.g., a tag value).
926 // See issue #49298 for more details on the need to leave space
927 // for non-ZST uninhabited data (mostly partial initialization).
928 let absent = |fields: &[TyAndLayout<'_>]| {
929 let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited());
930 let is_zst = fields.iter().all(|f| f.is_zst());
931 uninhabited && is_zst
933 let (present_first, present_second) = {
934 let mut present_variants = variants
936 .filter_map(|(i, v)| if absent(v) { None } else { Some(i) });
937 (present_variants.next(), present_variants.next())
939 let present_first = match present_first {
940 Some(present_first) => present_first,
941 // Uninhabited because it has no variants, or only absent ones.
942 None if def.is_enum() => {
943 return Ok(tcx.layout_of(param_env.and(tcx.types.never))?.layout);
945 // If it's a struct, still compute a layout so that we can still compute the
947 None => VariantIdx::new(0),
950 let is_struct = !def.is_enum() ||
951 // Only one variant is present.
952 (present_second.is_none() &&
953 // Representation optimizations are allowed.
954 !def.repr.inhibit_enum_layout_opt());
956 // Struct, or univariant enum equivalent to a struct.
957 // (Typechecking will reject discriminant-sizing attrs.)
959 let v = present_first;
960 let kind = if def.is_enum() || variants[v].is_empty() {
961 StructKind::AlwaysSized
963 let param_env = tcx.param_env(def.did);
964 let last_field = def.variants[v].fields.last().unwrap();
966 tcx.type_of(last_field.did).is_sized(tcx.at(DUMMY_SP), param_env);
968 StructKind::MaybeUnsized
970 StructKind::AlwaysSized
974 let mut st = self.univariant_uninterned(ty, &variants[v], &def.repr, kind)?;
975 st.variants = Variants::Single { index: v };
976 let (start, end) = self.tcx.layout_scalar_valid_range(def.did);
978 Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => {
979 // the asserts ensure that we are not using the
980 // `#[rustc_layout_scalar_valid_range(n)]`
981 // attribute to widen the range of anything as that would probably
982 // result in UB somewhere
983 // FIXME(eddyb) the asserts are probably not needed,
984 // as larger validity ranges would result in missed
985 // optimizations, *not* wrongly assuming the inner
986 // value is valid. e.g. unions enlarge validity ranges,
987 // because the values may be uninitialized.
988 if let Bound::Included(start) = start {
989 // FIXME(eddyb) this might be incorrect - it doesn't
990 // account for wrap-around (end < start) ranges.
991 assert!(scalar.valid_range.start <= start);
992 scalar.valid_range.start = start;
994 if let Bound::Included(end) = end {
995 // FIXME(eddyb) this might be incorrect - it doesn't
996 // account for wrap-around (end < start) ranges.
997 assert!(scalar.valid_range.end >= end);
998 scalar.valid_range.end = end;
1001 // Update `largest_niche` if we have introduced a larger niche.
1002 let niche = if def.repr.hide_niche() {
1005 Niche::from_scalar(dl, Size::ZERO, *scalar)
1007 if let Some(niche) = niche {
1008 match st.largest_niche {
1009 Some(largest_niche) => {
1010 // Replace the existing niche even if they're equal,
1011 // because this one is at a lower offset.
1012 if largest_niche.available(dl) <= niche.available(dl) {
1013 st.largest_niche = Some(niche);
1016 None => st.largest_niche = Some(niche),
1021 start == Bound::Unbounded && end == Bound::Unbounded,
1022 "nonscalar layout for layout_scalar_valid_range type {:?}: {:#?}",
1028 return Ok(tcx.intern_layout(st));
1031 // At this point, we have handled all unions and
1032 // structs. (We have also handled univariant enums
1033 // that allow representation optimization.)
1034 assert!(def.is_enum());
1036 // The current code for niche-filling relies on variant indices
1037 // instead of actual discriminants, so dataful enums with
1038 // explicit discriminants (RFC #2363) would misbehave.
1039 let no_explicit_discriminants = def
1042 .all(|(i, v)| v.discr == ty::VariantDiscr::Relative(i.as_u32()));
1044 let mut niche_filling_layout = None;
1046 // Niche-filling enum optimization.
1047 if !def.repr.inhibit_enum_layout_opt() && no_explicit_discriminants {
1048 let mut dataful_variant = None;
1049 let mut niche_variants = VariantIdx::MAX..=VariantIdx::new(0);
1051 // Find one non-ZST variant.
1052 'variants: for (v, fields) in variants.iter_enumerated() {
1058 if dataful_variant.is_none() {
1059 dataful_variant = Some(v);
1062 dataful_variant = None;
1067 niche_variants = *niche_variants.start().min(&v)..=v;
1070 if niche_variants.start() > niche_variants.end() {
1071 dataful_variant = None;
1074 if let Some(i) = dataful_variant {
1075 let count = (niche_variants.end().as_u32()
1076 - niche_variants.start().as_u32()
1079 // Find the field with the largest niche
1080 let niche_candidate = variants[i]
1083 .filter_map(|(j, field)| Some((j, field.largest_niche?)))
1084 .max_by_key(|(_, niche)| niche.available(dl));
1086 if let Some((field_index, niche, (niche_start, niche_scalar))) =
1087 niche_candidate.and_then(|(field_index, niche)| {
1088 Some((field_index, niche, niche.reserve(self, count)?))
1091 let mut align = dl.aggregate_align;
1095 let mut st = self.univariant_uninterned(
1099 StructKind::AlwaysSized,
1101 st.variants = Variants::Single { index: j };
1103 align = align.max(st.align);
1107 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1109 let offset = st[i].fields.offset(field_index) + niche.offset;
1110 let size = st[i].size;
1112 let abi = if st.iter().all(|v| v.abi.is_uninhabited()) {
1116 Abi::Scalar(_) => Abi::Scalar(niche_scalar),
1117 Abi::ScalarPair(first, second) => {
1118 // We need to use scalar_unit to reset the
1119 // valid range to the maximal one for that
1120 // primitive, because only the niche is
1121 // guaranteed to be initialised, not the
1123 if offset.bytes() == 0 {
1124 Abi::ScalarPair(niche_scalar, scalar_unit(second.value))
1126 Abi::ScalarPair(scalar_unit(first.value), niche_scalar)
1129 _ => Abi::Aggregate { sized: true },
1133 let largest_niche = Niche::from_scalar(dl, offset, niche_scalar);
1135 niche_filling_layout = Some(Layout {
1136 variants: Variants::Multiple {
1138 tag_encoding: TagEncoding::Niche {
1146 fields: FieldsShape::Arbitrary {
1147 offsets: vec![offset],
1148 memory_index: vec![0],
1159 let (mut min, mut max) = (i128::MAX, i128::MIN);
1160 let discr_type = def.repr.discr_type();
1161 let bits = Integer::from_attr(self, discr_type).size().bits();
1162 for (i, discr) in def.discriminants(tcx) {
1163 if variants[i].iter().any(|f| f.abi.is_uninhabited()) {
1166 let mut x = discr.val as i128;
1167 if discr_type.is_signed() {
1168 // sign extend the raw representation to be an i128
1169 x = (x << (128 - bits)) >> (128 - bits);
1178 // We might have no inhabited variants, so pretend there's at least one.
1179 if (min, max) == (i128::MAX, i128::MIN) {
1183 assert!(min <= max, "discriminant range is {}...{}", min, max);
1184 let (min_ity, signed) = Integer::repr_discr(tcx, ty, &def.repr, min, max);
1186 let mut align = dl.aggregate_align;
1187 let mut size = Size::ZERO;
1189 // We're interested in the smallest alignment, so start large.
1190 let mut start_align = Align::from_bytes(256).unwrap();
1191 assert_eq!(Integer::for_align(dl, start_align), None);
1193 // repr(C) on an enum tells us to make a (tag, union) layout,
1194 // so we need to grow the prefix alignment to be at least
1195 // the alignment of the union. (This value is used both for
1196 // determining the alignment of the overall enum, and the
1197 // determining the alignment of the payload after the tag.)
1198 let mut prefix_align = min_ity.align(dl).abi;
1200 for fields in &variants {
1201 for field in fields {
1202 prefix_align = prefix_align.max(field.align.abi);
1207 // Create the set of structs that represent each variant.
1208 let mut layout_variants = variants
1210 .map(|(i, field_layouts)| {
1211 let mut st = self.univariant_uninterned(
1215 StructKind::Prefixed(min_ity.size(), prefix_align),
1217 st.variants = Variants::Single { index: i };
1218 // Find the first field we can't move later
1219 // to make room for a larger discriminant.
1221 st.fields.index_by_increasing_offset().map(|j| field_layouts[j])
1223 if !field.is_zst() || field.align.abi.bytes() != 1 {
1224 start_align = start_align.min(field.align.abi);
1228 size = cmp::max(size, st.size);
1229 align = align.max(st.align);
1232 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1234 // Align the maximum variant size to the largest alignment.
1235 size = size.align_to(align.abi);
1237 if size.bytes() >= dl.obj_size_bound() {
1238 return Err(LayoutError::SizeOverflow(ty));
1241 let typeck_ity = Integer::from_attr(dl, def.repr.discr_type());
1242 if typeck_ity < min_ity {
1243 // It is a bug if Layout decided on a greater discriminant size than typeck for
1244 // some reason at this point (based on values discriminant can take on). Mostly
1245 // because this discriminant will be loaded, and then stored into variable of
1246 // type calculated by typeck. Consider such case (a bug): typeck decided on
1247 // byte-sized discriminant, but layout thinks we need a 16-bit to store all
1248 // discriminant values. That would be a bug, because then, in codegen, in order
1249 // to store this 16-bit discriminant into 8-bit sized temporary some of the
1250 // space necessary to represent would have to be discarded (or layout is wrong
1251 // on thinking it needs 16 bits)
1253 "layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
1257 // However, it is fine to make discr type however large (as an optimisation)
1258 // after this point – we’ll just truncate the value we load in codegen.
1261 // Check to see if we should use a different type for the
1262 // discriminant. We can safely use a type with the same size
1263 // as the alignment of the first field of each variant.
1264 // We increase the size of the discriminant to avoid LLVM copying
1265 // padding when it doesn't need to. This normally causes unaligned
1266 // load/stores and excessive memcpy/memset operations. By using a
1267 // bigger integer size, LLVM can be sure about its contents and
1268 // won't be so conservative.
1270 // Use the initial field alignment
1271 let mut ity = if def.repr.c() || def.repr.int.is_some() {
1274 Integer::for_align(dl, start_align).unwrap_or(min_ity)
1277 // If the alignment is not larger than the chosen discriminant size,
1278 // don't use the alignment as the final size.
1282 // Patch up the variants' first few fields.
1283 let old_ity_size = min_ity.size();
1284 let new_ity_size = ity.size();
1285 for variant in &mut layout_variants {
1286 match variant.fields {
1287 FieldsShape::Arbitrary { ref mut offsets, .. } => {
1289 if *i <= old_ity_size {
1290 assert_eq!(*i, old_ity_size);
1294 // We might be making the struct larger.
1295 if variant.size <= old_ity_size {
1296 variant.size = new_ity_size;
1304 let tag_mask = ity.size().unsigned_int_max();
1306 value: Int(ity, signed),
1307 valid_range: WrappingRange {
1308 start: (min as u128 & tag_mask),
1309 end: (max as u128 & tag_mask),
1312 let mut abi = Abi::Aggregate { sized: true };
1314 // Without latter check aligned enums with custom discriminant values
1315 // Would result in ICE see the issue #92464 for more info
1316 if tag.value.size(dl) == size || variants.iter().all(|layout| layout.is_empty()) {
1317 abi = Abi::Scalar(tag);
1319 // Try to use a ScalarPair for all tagged enums.
1320 let mut common_prim = None;
1321 for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
1322 let offsets = match layout_variant.fields {
1323 FieldsShape::Arbitrary { ref offsets, .. } => offsets,
1327 iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
1328 let (field, offset) = match (fields.next(), fields.next()) {
1329 (None, None) => continue,
1330 (Some(pair), None) => pair,
1336 let prim = match field.abi {
1337 Abi::Scalar(scalar) => scalar.value,
1343 if let Some(pair) = common_prim {
1344 // This is pretty conservative. We could go fancier
1345 // by conflating things like i32 and u32, or even
1346 // realising that (u8, u8) could just cohabit with
1348 if pair != (prim, offset) {
1353 common_prim = Some((prim, offset));
1356 if let Some((prim, offset)) = common_prim {
1357 let pair = self.scalar_pair(tag, scalar_unit(prim));
1358 let pair_offsets = match pair.fields {
1359 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
1360 assert_eq!(memory_index, &[0, 1]);
1365 if pair_offsets[0] == Size::ZERO
1366 && pair_offsets[1] == *offset
1367 && align == pair.align
1368 && size == pair.size
1370 // We can use `ScalarPair` only when it matches our
1371 // already computed layout (including `#[repr(C)]`).
1377 if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
1378 abi = Abi::Uninhabited;
1381 let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
1383 let tagged_layout = Layout {
1384 variants: Variants::Multiple {
1386 tag_encoding: TagEncoding::Direct,
1388 variants: layout_variants,
1390 fields: FieldsShape::Arbitrary {
1391 offsets: vec![Size::ZERO],
1392 memory_index: vec![0],
1400 let best_layout = match (tagged_layout, niche_filling_layout) {
1401 (tagged_layout, Some(niche_filling_layout)) => {
1402 // Pick the smaller layout; otherwise,
1403 // pick the layout with the larger niche; otherwise,
1404 // pick tagged as it has simpler codegen.
1405 cmp::min_by_key(tagged_layout, niche_filling_layout, |layout| {
1406 let niche_size = layout.largest_niche.map_or(0, |n| n.available(dl));
1407 (layout.size, cmp::Reverse(niche_size))
1410 (tagged_layout, None) => tagged_layout,
1413 tcx.intern_layout(best_layout)
1416 // Types with no meaningful known layout.
1417 ty::Projection(_) | ty::Opaque(..) => {
1418 // NOTE(eddyb) `layout_of` query should've normalized these away,
1419 // if that was possible, so there's no reason to try again here.
1420 return Err(LayoutError::Unknown(ty));
1423 ty::Placeholder(..) | ty::GeneratorWitness(..) | ty::Infer(_) => {
1424 bug!("Layout::compute: unexpected type `{}`", ty)
1427 ty::Bound(..) | ty::Param(_) | ty::Error(_) => {
1428 return Err(LayoutError::Unknown(ty));
1434 /// Overlap eligibility and variant assignment for each GeneratorSavedLocal.
1435 #[derive(Clone, Debug, PartialEq)]
1436 enum SavedLocalEligibility {
1438 Assigned(VariantIdx),
1439 // FIXME: Use newtype_index so we aren't wasting bytes
1440 Ineligible(Option<u32>),
1443 // When laying out generators, we divide our saved local fields into two
1444 // categories: overlap-eligible and overlap-ineligible.
1446 // Those fields which are ineligible for overlap go in a "prefix" at the
1447 // beginning of the layout, and always have space reserved for them.
1449 // Overlap-eligible fields are only assigned to one variant, so we lay
1450 // those fields out for each variant and put them right after the
1453 // Finally, in the layout details, we point to the fields from the
1454 // variants they are assigned to. It is possible for some fields to be
1455 // included in multiple variants. No field ever "moves around" in the
1456 // layout; its offset is always the same.
1458 // Also included in the layout are the upvars and the discriminant.
1459 // These are included as fields on the "outer" layout; they are not part
1461 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
1462 /// Compute the eligibility and assignment of each local.
1463 fn generator_saved_local_eligibility(
1465 info: &GeneratorLayout<'tcx>,
1466 ) -> (BitSet<GeneratorSavedLocal>, IndexVec<GeneratorSavedLocal, SavedLocalEligibility>) {
1467 use SavedLocalEligibility::*;
1469 let mut assignments: IndexVec<GeneratorSavedLocal, SavedLocalEligibility> =
1470 IndexVec::from_elem_n(Unassigned, info.field_tys.len());
1472 // The saved locals not eligible for overlap. These will get
1473 // "promoted" to the prefix of our generator.
1474 let mut ineligible_locals = BitSet::new_empty(info.field_tys.len());
1476 // Figure out which of our saved locals are fields in only
1477 // one variant. The rest are deemed ineligible for overlap.
1478 for (variant_index, fields) in info.variant_fields.iter_enumerated() {
1479 for local in fields {
1480 match assignments[*local] {
1482 assignments[*local] = Assigned(variant_index);
1485 // We've already seen this local at another suspension
1486 // point, so it is no longer a candidate.
1488 "removing local {:?} in >1 variant ({:?}, {:?})",
1493 ineligible_locals.insert(*local);
1494 assignments[*local] = Ineligible(None);
1501 // Next, check every pair of eligible locals to see if they
1503 for local_a in info.storage_conflicts.rows() {
1504 let conflicts_a = info.storage_conflicts.count(local_a);
1505 if ineligible_locals.contains(local_a) {
1509 for local_b in info.storage_conflicts.iter(local_a) {
1510 // local_a and local_b are storage live at the same time, therefore they
1511 // cannot overlap in the generator layout. The only way to guarantee
1512 // this is if they are in the same variant, or one is ineligible
1513 // (which means it is stored in every variant).
1514 if ineligible_locals.contains(local_b)
1515 || assignments[local_a] == assignments[local_b]
1520 // If they conflict, we will choose one to make ineligible.
1521 // This is not always optimal; it's just a greedy heuristic that
1522 // seems to produce good results most of the time.
1523 let conflicts_b = info.storage_conflicts.count(local_b);
1524 let (remove, other) =
1525 if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) };
1526 ineligible_locals.insert(remove);
1527 assignments[remove] = Ineligible(None);
1528 trace!("removing local {:?} due to conflict with {:?}", remove, other);
1532 // Count the number of variants in use. If only one of them, then it is
1533 // impossible to overlap any locals in our layout. In this case it's
1534 // always better to make the remaining locals ineligible, so we can
1535 // lay them out with the other locals in the prefix and eliminate
1536 // unnecessary padding bytes.
1538 let mut used_variants = BitSet::new_empty(info.variant_fields.len());
1539 for assignment in &assignments {
1540 if let Assigned(idx) = assignment {
1541 used_variants.insert(*idx);
1544 if used_variants.count() < 2 {
1545 for assignment in assignments.iter_mut() {
1546 *assignment = Ineligible(None);
1548 ineligible_locals.insert_all();
1552 // Write down the order of our locals that will be promoted to the prefix.
1554 for (idx, local) in ineligible_locals.iter().enumerate() {
1555 assignments[local] = Ineligible(Some(idx as u32));
1558 debug!("generator saved local assignments: {:?}", assignments);
1560 (ineligible_locals, assignments)
1563 /// Compute the full generator layout.
1564 fn generator_layout(
1567 def_id: hir::def_id::DefId,
1568 substs: SubstsRef<'tcx>,
1569 ) -> Result<&'tcx Layout, LayoutError<'tcx>> {
1570 use SavedLocalEligibility::*;
1572 let subst_field = |ty: Ty<'tcx>| ty.subst(tcx, substs);
1574 let info = match tcx.generator_layout(def_id) {
1575 None => return Err(LayoutError::Unknown(ty)),
1578 let (ineligible_locals, assignments) = self.generator_saved_local_eligibility(&info);
1580 // Build a prefix layout, including "promoting" all ineligible
1581 // locals as part of the prefix. We compute the layout of all of
1582 // these fields at once to get optimal packing.
1583 let tag_index = substs.as_generator().prefix_tys().count();
1585 // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
1586 let max_discr = (info.variant_fields.len() - 1) as u128;
1587 let discr_int = Integer::fit_unsigned(max_discr);
1588 let discr_int_ty = discr_int.to_ty(tcx, false);
1590 value: Primitive::Int(discr_int, false),
1591 valid_range: WrappingRange { start: 0, end: max_discr },
1593 let tag_layout = self.tcx.intern_layout(Layout::scalar(self, tag));
1594 let tag_layout = TyAndLayout { ty: discr_int_ty, layout: tag_layout };
1596 let promoted_layouts = ineligible_locals
1598 .map(|local| subst_field(info.field_tys[local]))
1599 .map(|ty| tcx.mk_maybe_uninit(ty))
1600 .map(|ty| self.layout_of(ty));
1601 let prefix_layouts = substs
1604 .map(|ty| self.layout_of(ty))
1605 .chain(iter::once(Ok(tag_layout)))
1606 .chain(promoted_layouts)
1607 .collect::<Result<Vec<_>, _>>()?;
1608 let prefix = self.univariant_uninterned(
1611 &ReprOptions::default(),
1612 StructKind::AlwaysSized,
1615 let (prefix_size, prefix_align) = (prefix.size, prefix.align);
1617 // Split the prefix layout into the "outer" fields (upvars and
1618 // discriminant) and the "promoted" fields. Promoted fields will
1619 // get included in each variant that requested them in
1621 debug!("prefix = {:#?}", prefix);
1622 let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
1623 FieldsShape::Arbitrary { mut offsets, memory_index } => {
1624 let mut inverse_memory_index = invert_mapping(&memory_index);
1626 // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
1627 // "outer" and "promoted" fields respectively.
1628 let b_start = (tag_index + 1) as u32;
1629 let offsets_b = offsets.split_off(b_start as usize);
1630 let offsets_a = offsets;
1632 // Disentangle the "a" and "b" components of `inverse_memory_index`
1633 // by preserving the order but keeping only one disjoint "half" each.
1634 // FIXME(eddyb) build a better abstraction for permutations, if possible.
1635 let inverse_memory_index_b: Vec<_> =
1636 inverse_memory_index.iter().filter_map(|&i| i.checked_sub(b_start)).collect();
1637 inverse_memory_index.retain(|&i| i < b_start);
1638 let inverse_memory_index_a = inverse_memory_index;
1640 // Since `inverse_memory_index_{a,b}` each only refer to their
1641 // respective fields, they can be safely inverted
1642 let memory_index_a = invert_mapping(&inverse_memory_index_a);
1643 let memory_index_b = invert_mapping(&inverse_memory_index_b);
1646 FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a };
1647 (outer_fields, offsets_b, memory_index_b)
1652 let mut size = prefix.size;
1653 let mut align = prefix.align;
1657 .map(|(index, variant_fields)| {
1658 // Only include overlap-eligible fields when we compute our variant layout.
1659 let variant_only_tys = variant_fields
1661 .filter(|local| match assignments[**local] {
1662 Unassigned => bug!(),
1663 Assigned(v) if v == index => true,
1664 Assigned(_) => bug!("assignment does not match variant"),
1665 Ineligible(_) => false,
1667 .map(|local| subst_field(info.field_tys[*local]));
1669 let mut variant = self.univariant_uninterned(
1672 .map(|ty| self.layout_of(ty))
1673 .collect::<Result<Vec<_>, _>>()?,
1674 &ReprOptions::default(),
1675 StructKind::Prefixed(prefix_size, prefix_align.abi),
1677 variant.variants = Variants::Single { index };
1679 let (offsets, memory_index) = match variant.fields {
1680 FieldsShape::Arbitrary { offsets, memory_index } => (offsets, memory_index),
1684 // Now, stitch the promoted and variant-only fields back together in
1685 // the order they are mentioned by our GeneratorLayout.
1686 // Because we only use some subset (that can differ between variants)
1687 // of the promoted fields, we can't just pick those elements of the
1688 // `promoted_memory_index` (as we'd end up with gaps).
1689 // So instead, we build an "inverse memory_index", as if all of the
1690 // promoted fields were being used, but leave the elements not in the
1691 // subset as `INVALID_FIELD_IDX`, which we can filter out later to
1692 // obtain a valid (bijective) mapping.
1693 const INVALID_FIELD_IDX: u32 = !0;
1694 let mut combined_inverse_memory_index =
1695 vec![INVALID_FIELD_IDX; promoted_memory_index.len() + memory_index.len()];
1696 let mut offsets_and_memory_index = iter::zip(offsets, memory_index);
1697 let combined_offsets = variant_fields
1701 let (offset, memory_index) = match assignments[*local] {
1702 Unassigned => bug!(),
1704 let (offset, memory_index) =
1705 offsets_and_memory_index.next().unwrap();
1706 (offset, promoted_memory_index.len() as u32 + memory_index)
1708 Ineligible(field_idx) => {
1709 let field_idx = field_idx.unwrap() as usize;
1710 (promoted_offsets[field_idx], promoted_memory_index[field_idx])
1713 combined_inverse_memory_index[memory_index as usize] = i as u32;
1718 // Remove the unused slots and invert the mapping to obtain the
1719 // combined `memory_index` (also see previous comment).
1720 combined_inverse_memory_index.retain(|&i| i != INVALID_FIELD_IDX);
1721 let combined_memory_index = invert_mapping(&combined_inverse_memory_index);
1723 variant.fields = FieldsShape::Arbitrary {
1724 offsets: combined_offsets,
1725 memory_index: combined_memory_index,
1728 size = size.max(variant.size);
1729 align = align.max(variant.align);
1732 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1734 size = size.align_to(align.abi);
1736 let abi = if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi.is_uninhabited())
1740 Abi::Aggregate { sized: true }
1743 let layout = tcx.intern_layout(Layout {
1744 variants: Variants::Multiple {
1746 tag_encoding: TagEncoding::Direct,
1747 tag_field: tag_index,
1750 fields: outer_fields,
1752 largest_niche: prefix.largest_niche,
1756 debug!("generator layout ({:?}): {:#?}", ty, layout);
1760 /// This is invoked by the `layout_of` query to record the final
1761 /// layout of each type.
1763 fn record_layout_for_printing(&self, layout: TyAndLayout<'tcx>) {
1764 // If we are running with `-Zprint-type-sizes`, maybe record layouts
1765 // for dumping later.
1766 if self.tcx.sess.opts.debugging_opts.print_type_sizes {
1767 self.record_layout_for_printing_outlined(layout)
1771 fn record_layout_for_printing_outlined(&self, layout: TyAndLayout<'tcx>) {
1772 // Ignore layouts that are done with non-empty environments or
1773 // non-monomorphic layouts, as the user only wants to see the stuff
1774 // resulting from the final codegen session.
1775 if layout.ty.has_param_types_or_consts() || !self.param_env.caller_bounds().is_empty() {
1779 // (delay format until we actually need it)
1780 let record = |kind, packed, opt_discr_size, variants| {
1781 let type_desc = format!("{:?}", layout.ty);
1782 self.tcx.sess.code_stats.record_type_size(
1793 let adt_def = match *layout.ty.kind() {
1794 ty::Adt(ref adt_def, _) => {
1795 debug!("print-type-size t: `{:?}` process adt", layout.ty);
1799 ty::Closure(..) => {
1800 debug!("print-type-size t: `{:?}` record closure", layout.ty);
1801 record(DataTypeKind::Closure, false, None, vec![]);
1806 debug!("print-type-size t: `{:?}` skip non-nominal", layout.ty);
1811 let adt_kind = adt_def.adt_kind();
1812 let adt_packed = adt_def.repr.pack.is_some();
1814 let build_variant_info = |n: Option<Symbol>, flds: &[Symbol], layout: TyAndLayout<'tcx>| {
1815 let mut min_size = Size::ZERO;
1816 let field_info: Vec<_> = flds
1820 let field_layout = layout.field(self, i);
1821 let offset = layout.fields.offset(i);
1822 let field_end = offset + field_layout.size;
1823 if min_size < field_end {
1824 min_size = field_end;
1827 name: name.to_string(),
1828 offset: offset.bytes(),
1829 size: field_layout.size.bytes(),
1830 align: field_layout.align.abi.bytes(),
1836 name: n.map(|n| n.to_string()),
1837 kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact },
1838 align: layout.align.abi.bytes(),
1839 size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() },
1844 match layout.variants {
1845 Variants::Single { index } => {
1846 if !adt_def.variants.is_empty() && layout.fields != FieldsShape::Primitive {
1848 "print-type-size `{:#?}` variant {}",
1849 layout, adt_def.variants[index].name
1851 let variant_def = &adt_def.variants[index];
1852 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1857 vec![build_variant_info(Some(variant_def.name), &fields, layout)],
1860 // (This case arises for *empty* enums; so give it
1862 record(adt_kind.into(), adt_packed, None, vec![]);
1866 Variants::Multiple { tag, ref tag_encoding, .. } => {
1868 "print-type-size `{:#?}` adt general variants def {}",
1870 adt_def.variants.len()
1872 let variant_infos: Vec<_> = adt_def
1875 .map(|(i, variant_def)| {
1876 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1878 Some(variant_def.name),
1880 layout.for_variant(self, i),
1887 match tag_encoding {
1888 TagEncoding::Direct => Some(tag.value.size(self)),
1898 /// Type size "skeleton", i.e., the only information determining a type's size.
1899 /// While this is conservative, (aside from constant sizes, only pointers,
1900 /// newtypes thereof and null pointer optimized enums are allowed), it is
1901 /// enough to statically check common use cases of transmute.
1902 #[derive(Copy, Clone, Debug)]
1903 pub enum SizeSkeleton<'tcx> {
1904 /// Any statically computable Layout.
1907 /// A potentially-fat pointer.
1909 /// If true, this pointer is never null.
1911 /// The type which determines the unsized metadata, if any,
1912 /// of this pointer. Either a type parameter or a projection
1913 /// depending on one, with regions erased.
1918 impl<'tcx> SizeSkeleton<'tcx> {
1922 param_env: ty::ParamEnv<'tcx>,
1923 ) -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
1924 debug_assert!(!ty.has_infer_types_or_consts());
1926 // First try computing a static layout.
1927 let err = match tcx.layout_of(param_env.and(ty)) {
1929 return Ok(SizeSkeleton::Known(layout.size));
1935 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1936 let non_zero = !ty.is_unsafe_ptr();
1937 let tail = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
1939 ty::Param(_) | ty::Projection(_) => {
1940 debug_assert!(tail.has_param_types_or_consts());
1941 Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
1944 "SizeSkeleton::compute({}): layout errored ({}), yet \
1945 tail `{}` is not a type parameter or a projection",
1953 ty::Adt(def, substs) => {
1954 // Only newtypes and enums w/ nullable pointer optimization.
1955 if def.is_union() || def.variants.is_empty() || def.variants.len() > 2 {
1959 // Get a zero-sized variant or a pointer newtype.
1960 let zero_or_ptr_variant = |i| {
1961 let i = VariantIdx::new(i);
1962 let fields = def.variants[i]
1965 .map(|field| SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env));
1967 for field in fields {
1970 SizeSkeleton::Known(size) => {
1971 if size.bytes() > 0 {
1975 SizeSkeleton::Pointer { .. } => {
1986 let v0 = zero_or_ptr_variant(0)?;
1988 if def.variants.len() == 1 {
1989 if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
1990 return Ok(SizeSkeleton::Pointer {
1992 || match tcx.layout_scalar_valid_range(def.did) {
1993 (Bound::Included(start), Bound::Unbounded) => start > 0,
1994 (Bound::Included(start), Bound::Included(end)) => {
1995 0 < start && start < end
2006 let v1 = zero_or_ptr_variant(1)?;
2007 // Nullable pointer enum optimization.
2009 (Some(SizeSkeleton::Pointer { non_zero: true, tail }), None)
2010 | (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
2011 Ok(SizeSkeleton::Pointer { non_zero: false, tail })
2017 ty::Projection(_) | ty::Opaque(..) => {
2018 let normalized = tcx.normalize_erasing_regions(param_env, ty);
2019 if ty == normalized {
2022 SizeSkeleton::compute(normalized, tcx, param_env)
2030 pub fn same_size(self, other: SizeSkeleton<'_>) -> bool {
2031 match (self, other) {
2032 (SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
2033 (SizeSkeleton::Pointer { tail: a, .. }, SizeSkeleton::Pointer { tail: b, .. }) => {
2041 pub trait HasTyCtxt<'tcx>: HasDataLayout {
2042 fn tcx(&self) -> TyCtxt<'tcx>;
2045 pub trait HasParamEnv<'tcx> {
2046 fn param_env(&self) -> ty::ParamEnv<'tcx>;
2049 impl<'tcx> HasDataLayout for TyCtxt<'tcx> {
2051 fn data_layout(&self) -> &TargetDataLayout {
2056 impl<'tcx> HasTargetSpec for TyCtxt<'tcx> {
2057 fn target_spec(&self) -> &Target {
2062 impl<'tcx> HasTyCtxt<'tcx> for TyCtxt<'tcx> {
2064 fn tcx(&self) -> TyCtxt<'tcx> {
2069 impl<'tcx> HasDataLayout for ty::query::TyCtxtAt<'tcx> {
2071 fn data_layout(&self) -> &TargetDataLayout {
2076 impl<'tcx> HasTargetSpec for ty::query::TyCtxtAt<'tcx> {
2077 fn target_spec(&self) -> &Target {
2082 impl<'tcx> HasTyCtxt<'tcx> for ty::query::TyCtxtAt<'tcx> {
2084 fn tcx(&self) -> TyCtxt<'tcx> {
2089 impl<'tcx, C> HasParamEnv<'tcx> for LayoutCx<'tcx, C> {
2090 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2095 impl<'tcx, T: HasDataLayout> HasDataLayout for LayoutCx<'tcx, T> {
2096 fn data_layout(&self) -> &TargetDataLayout {
2097 self.tcx.data_layout()
2101 impl<'tcx, T: HasTargetSpec> HasTargetSpec for LayoutCx<'tcx, T> {
2102 fn target_spec(&self) -> &Target {
2103 self.tcx.target_spec()
2107 impl<'tcx, T: HasTyCtxt<'tcx>> HasTyCtxt<'tcx> for LayoutCx<'tcx, T> {
2108 fn tcx(&self) -> TyCtxt<'tcx> {
2113 pub trait MaybeResult<T> {
2116 fn from(x: Result<T, Self::Error>) -> Self;
2117 fn to_result(self) -> Result<T, Self::Error>;
2120 impl<T> MaybeResult<T> for T {
2123 fn from(Ok(x): Result<T, Self::Error>) -> Self {
2126 fn to_result(self) -> Result<T, Self::Error> {
2131 impl<T, E> MaybeResult<T> for Result<T, E> {
2134 fn from(x: Result<T, Self::Error>) -> Self {
2137 fn to_result(self) -> Result<T, Self::Error> {
2142 pub type TyAndLayout<'tcx> = rustc_target::abi::TyAndLayout<'tcx, Ty<'tcx>>;
2144 /// Trait for contexts that want to be able to compute layouts of types.
2145 /// This automatically gives access to `LayoutOf`, through a blanket `impl`.
2146 pub trait LayoutOfHelpers<'tcx>: HasDataLayout + HasTyCtxt<'tcx> + HasParamEnv<'tcx> {
2147 /// The `TyAndLayout`-wrapping type (or `TyAndLayout` itself), which will be
2148 /// returned from `layout_of` (see also `handle_layout_err`).
2149 type LayoutOfResult: MaybeResult<TyAndLayout<'tcx>>;
2151 /// `Span` to use for `tcx.at(span)`, from `layout_of`.
2152 // FIXME(eddyb) perhaps make this mandatory to get contexts to track it better?
2154 fn layout_tcx_at_span(&self) -> Span {
2158 /// Helper used for `layout_of`, to adapt `tcx.layout_of(...)` into a
2159 /// `Self::LayoutOfResult` (which does not need to be a `Result<...>`).
2161 /// Most `impl`s, which propagate `LayoutError`s, should simply return `err`,
2162 /// but this hook allows e.g. codegen to return only `TyAndLayout` from its
2163 /// `cx.layout_of(...)`, without any `Result<...>` around it to deal with
2164 /// (and any `LayoutError`s are turned into fatal errors or ICEs).
2165 fn handle_layout_err(
2167 err: LayoutError<'tcx>,
2170 ) -> <Self::LayoutOfResult as MaybeResult<TyAndLayout<'tcx>>>::Error;
2173 /// Blanket extension trait for contexts that can compute layouts of types.
2174 pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
2175 /// Computes the layout of a type. Note that this implicitly
2176 /// executes in "reveal all" mode, and will normalize the input type.
2178 fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
2179 self.spanned_layout_of(ty, DUMMY_SP)
2182 /// Computes the layout of a type, at `span`. Note that this implicitly
2183 /// executes in "reveal all" mode, and will normalize the input type.
2184 // FIXME(eddyb) avoid passing information like this, and instead add more
2185 // `TyCtxt::at`-like APIs to be able to do e.g. `cx.at(span).layout_of(ty)`.
2187 fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::LayoutOfResult {
2188 let span = if !span.is_dummy() { span } else { self.layout_tcx_at_span() };
2189 let tcx = self.tcx().at(span);
2192 tcx.layout_of(self.param_env().and(ty))
2193 .map_err(|err| self.handle_layout_err(err, span, ty)),
2198 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
2200 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
2201 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2204 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2209 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, ty::query::TyCtxtAt<'tcx>> {
2210 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2213 fn layout_tcx_at_span(&self) -> Span {
2218 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2223 impl<'tcx, C> TyAbiInterface<'tcx, C> for Ty<'tcx>
2225 C: HasTyCtxt<'tcx> + HasParamEnv<'tcx>,
2227 fn ty_and_layout_for_variant(
2228 this: TyAndLayout<'tcx>,
2230 variant_index: VariantIdx,
2231 ) -> TyAndLayout<'tcx> {
2232 let layout = match this.variants {
2233 Variants::Single { index }
2234 // If all variants but one are uninhabited, the variant layout is the enum layout.
2235 if index == variant_index &&
2236 // Don't confuse variants of uninhabited enums with the enum itself.
2237 // For more details see https://github.com/rust-lang/rust/issues/69763.
2238 this.fields != FieldsShape::Primitive =>
2243 Variants::Single { index } => {
2245 let param_env = cx.param_env();
2247 // Deny calling for_variant more than once for non-Single enums.
2248 if let Ok(original_layout) = tcx.layout_of(param_env.and(this.ty)) {
2249 assert_eq!(original_layout.variants, Variants::Single { index });
2252 let fields = match this.ty.kind() {
2253 ty::Adt(def, _) if def.variants.is_empty() =>
2254 bug!("for_variant called on zero-variant enum"),
2255 ty::Adt(def, _) => def.variants[variant_index].fields.len(),
2258 tcx.intern_layout(Layout {
2259 variants: Variants::Single { index: variant_index },
2260 fields: match NonZeroUsize::new(fields) {
2261 Some(fields) => FieldsShape::Union(fields),
2262 None => FieldsShape::Arbitrary { offsets: vec![], memory_index: vec![] },
2264 abi: Abi::Uninhabited,
2265 largest_niche: None,
2266 align: tcx.data_layout.i8_align,
2271 Variants::Multiple { ref variants, .. } => &variants[variant_index],
2274 assert_eq!(layout.variants, Variants::Single { index: variant_index });
2276 TyAndLayout { ty: this.ty, layout }
2279 fn ty_and_layout_field(this: TyAndLayout<'tcx>, cx: &C, i: usize) -> TyAndLayout<'tcx> {
2280 enum TyMaybeWithLayout<'tcx> {
2282 TyAndLayout(TyAndLayout<'tcx>),
2285 fn field_ty_or_layout<'tcx>(
2286 this: TyAndLayout<'tcx>,
2287 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
2289 ) -> TyMaybeWithLayout<'tcx> {
2291 let tag_layout = |tag: Scalar| -> TyAndLayout<'tcx> {
2292 let layout = Layout::scalar(cx, tag);
2293 TyAndLayout { layout: tcx.intern_layout(layout), ty: tag.value.to_ty(tcx) }
2296 match *this.ty.kind() {
2305 | ty::GeneratorWitness(..)
2307 | ty::Dynamic(..) => bug!("TyAndLayout::field({:?}): not applicable", this),
2309 // Potentially-fat pointers.
2310 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
2311 assert!(i < this.fields.count());
2313 // Reuse the fat `*T` type as its own thin pointer data field.
2314 // This provides information about, e.g., DST struct pointees
2315 // (which may have no non-DST form), and will work as long
2316 // as the `Abi` or `FieldsShape` is checked by users.
2318 let nil = tcx.mk_unit();
2319 let unit_ptr_ty = if this.ty.is_unsafe_ptr() {
2322 tcx.mk_mut_ref(tcx.lifetimes.re_static, nil)
2325 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing
2326 // the `Result` should always work because the type is
2327 // always either `*mut ()` or `&'static mut ()`.
2328 return TyMaybeWithLayout::TyAndLayout(TyAndLayout {
2330 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()
2334 match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() {
2335 ty::Slice(_) | ty::Str => TyMaybeWithLayout::Ty(tcx.types.usize),
2336 ty::Dynamic(_, _) => {
2337 TyMaybeWithLayout::Ty(tcx.mk_imm_ref(
2338 tcx.lifetimes.re_static,
2339 tcx.mk_array(tcx.types.usize, 3),
2341 /* FIXME: use actual fn pointers
2342 Warning: naively computing the number of entries in the
2343 vtable by counting the methods on the trait + methods on
2344 all parent traits does not work, because some methods can
2345 be not object safe and thus excluded from the vtable.
2346 Increase this counter if you tried to implement this but
2347 failed to do it without duplicating a lot of code from
2348 other places in the compiler: 2
2350 tcx.mk_array(tcx.types.usize, 3),
2351 tcx.mk_array(Option<fn()>),
2355 _ => bug!("TyAndLayout::field({:?}): not applicable", this),
2359 // Arrays and slices.
2360 ty::Array(element, _) | ty::Slice(element) => TyMaybeWithLayout::Ty(element),
2361 ty::Str => TyMaybeWithLayout::Ty(tcx.types.u8),
2363 // Tuples, generators and closures.
2364 ty::Closure(_, ref substs) => field_ty_or_layout(
2365 TyAndLayout { ty: substs.as_closure().tupled_upvars_ty(), ..this },
2370 ty::Generator(def_id, ref substs, _) => match this.variants {
2371 Variants::Single { index } => TyMaybeWithLayout::Ty(
2374 .state_tys(def_id, tcx)
2375 .nth(index.as_usize())
2380 Variants::Multiple { tag, tag_field, .. } => {
2382 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2384 TyMaybeWithLayout::Ty(substs.as_generator().prefix_tys().nth(i).unwrap())
2388 ty::Tuple(tys) => TyMaybeWithLayout::Ty(tys[i].expect_ty()),
2391 ty::Adt(def, substs) => {
2392 match this.variants {
2393 Variants::Single { index } => {
2394 TyMaybeWithLayout::Ty(def.variants[index].fields[i].ty(tcx, substs))
2397 // Discriminant field for enums (where applicable).
2398 Variants::Multiple { tag, .. } => {
2400 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2407 | ty::Placeholder(..)
2411 | ty::Error(_) => bug!("TyAndLayout::field: unexpected type `{}`", this.ty),
2415 match field_ty_or_layout(this, cx, i) {
2416 TyMaybeWithLayout::Ty(field_ty) => {
2417 cx.tcx().layout_of(cx.param_env().and(field_ty)).unwrap_or_else(|e| {
2419 "failed to get layout for `{}`: {},\n\
2420 despite it being a field (#{}) of an existing layout: {:#?}",
2428 TyMaybeWithLayout::TyAndLayout(field_layout) => field_layout,
2432 fn ty_and_layout_pointee_info_at(
2433 this: TyAndLayout<'tcx>,
2436 ) -> Option<PointeeInfo> {
2438 let param_env = cx.param_env();
2440 let addr_space_of_ty = |ty: Ty<'tcx>| {
2441 if ty.is_fn() { cx.data_layout().instruction_address_space } else { AddressSpace::DATA }
2444 let pointee_info = match *this.ty.kind() {
2445 ty::RawPtr(mt) if offset.bytes() == 0 => {
2446 tcx.layout_of(param_env.and(mt.ty)).ok().map(|layout| PointeeInfo {
2448 align: layout.align.abi,
2450 address_space: addr_space_of_ty(mt.ty),
2453 ty::FnPtr(fn_sig) if offset.bytes() == 0 => {
2454 tcx.layout_of(param_env.and(tcx.mk_fn_ptr(fn_sig))).ok().map(|layout| PointeeInfo {
2456 align: layout.align.abi,
2458 address_space: cx.data_layout().instruction_address_space,
2461 ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
2462 let address_space = addr_space_of_ty(ty);
2463 let kind = if tcx.sess.opts.optimize == OptLevel::No {
2464 // Use conservative pointer kind if not optimizing. This saves us the
2465 // Freeze/Unpin queries, and can save time in the codegen backend (noalias
2466 // attributes in LLVM have compile-time cost even in unoptimized builds).
2470 hir::Mutability::Not => {
2471 if ty.is_freeze(tcx.at(DUMMY_SP), cx.param_env()) {
2477 hir::Mutability::Mut => {
2478 // References to self-referential structures should not be considered
2479 // noalias, as another pointer to the structure can be obtained, that
2480 // is not based-on the original reference. We consider all !Unpin
2481 // types to be potentially self-referential here.
2482 if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) {
2483 PointerKind::UniqueBorrowed
2491 tcx.layout_of(param_env.and(ty)).ok().map(|layout| PointeeInfo {
2493 align: layout.align.abi,
2500 let mut data_variant = match this.variants {
2501 // Within the discriminant field, only the niche itself is
2502 // always initialized, so we only check for a pointer at its
2505 // If the niche is a pointer, it's either valid (according
2506 // to its type), or null (which the niche field's scalar
2507 // validity range encodes). This allows using
2508 // `dereferenceable_or_null` for e.g., `Option<&T>`, and
2509 // this will continue to work as long as we don't start
2510 // using more niches than just null (e.g., the first page of
2511 // the address space, or unaligned pointers).
2512 Variants::Multiple {
2513 tag_encoding: TagEncoding::Niche { dataful_variant, .. },
2516 } if this.fields.offset(tag_field) == offset => {
2517 Some(this.for_variant(cx, dataful_variant))
2522 if let Some(variant) = data_variant {
2523 // We're not interested in any unions.
2524 if let FieldsShape::Union(_) = variant.fields {
2525 data_variant = None;
2529 let mut result = None;
2531 if let Some(variant) = data_variant {
2532 let ptr_end = offset + Pointer.size(cx);
2533 for i in 0..variant.fields.count() {
2534 let field_start = variant.fields.offset(i);
2535 if field_start <= offset {
2536 let field = variant.field(cx, i);
2537 result = field.to_result().ok().and_then(|field| {
2538 if ptr_end <= field_start + field.size {
2539 // We found the right field, look inside it.
2541 field.pointee_info_at(cx, offset - field_start);
2547 if result.is_some() {
2554 // FIXME(eddyb) This should be for `ptr::Unique<T>`, not `Box<T>`.
2555 if let Some(ref mut pointee) = result {
2556 if let ty::Adt(def, _) = this.ty.kind() {
2557 if def.is_box() && offset.bytes() == 0 {
2558 pointee.safe = Some(PointerKind::UniqueOwned);
2568 "pointee_info_at (offset={:?}, type kind: {:?}) => {:?}",
2578 impl<'tcx> ty::Instance<'tcx> {
2579 // NOTE(eddyb) this is private to avoid using it from outside of
2580 // `fn_abi_of_instance` - any other uses are either too high-level
2581 // for `Instance` (e.g. typeck would use `Ty::fn_sig` instead),
2582 // or should go through `FnAbi` instead, to avoid losing any
2583 // adjustments `fn_abi_of_instance` might be performing.
2584 fn fn_sig_for_fn_abi(
2587 param_env: ty::ParamEnv<'tcx>,
2588 ) -> ty::PolyFnSig<'tcx> {
2589 let ty = self.ty(tcx, param_env);
2592 // HACK(davidtwco,eddyb): This is a workaround for polymorphization considering
2593 // parameters unused if they show up in the signature, but not in the `mir::Body`
2594 // (i.e. due to being inside a projection that got normalized, see
2595 // `src/test/ui/polymorphization/normalized_sig_types.rs`), and codegen not keeping
2596 // track of a polymorphization `ParamEnv` to allow normalizing later.
2597 let mut sig = match *ty.kind() {
2598 ty::FnDef(def_id, substs) => tcx
2599 .normalize_erasing_regions(tcx.param_env(def_id), tcx.fn_sig(def_id))
2600 .subst(tcx, substs),
2601 _ => unreachable!(),
2604 if let ty::InstanceDef::VtableShim(..) = self.def {
2605 // Modify `fn(self, ...)` to `fn(self: *mut Self, ...)`.
2606 sig = sig.map_bound(|mut sig| {
2607 let mut inputs_and_output = sig.inputs_and_output.to_vec();
2608 inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
2609 sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
2615 ty::Closure(def_id, substs) => {
2616 let sig = substs.as_closure().sig();
2618 let bound_vars = tcx.mk_bound_variable_kinds(
2621 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2623 let br = ty::BoundRegion {
2624 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2625 kind: ty::BoundRegionKind::BrEnv,
2627 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2628 let env_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
2630 let sig = sig.skip_binder();
2631 ty::Binder::bind_with_vars(
2633 iter::once(env_ty).chain(sig.inputs().iter().cloned()),
2642 ty::Generator(_, substs, _) => {
2643 let sig = substs.as_generator().poly_sig();
2645 let bound_vars = tcx.mk_bound_variable_kinds(
2648 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2650 let br = ty::BoundRegion {
2651 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2652 kind: ty::BoundRegionKind::BrEnv,
2654 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2655 let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
2657 let pin_did = tcx.require_lang_item(LangItem::Pin, None);
2658 let pin_adt_ref = tcx.adt_def(pin_did);
2659 let pin_substs = tcx.intern_substs(&[env_ty.into()]);
2660 let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
2662 let sig = sig.skip_binder();
2663 let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
2664 let state_adt_ref = tcx.adt_def(state_did);
2665 let state_substs = tcx.intern_substs(&[sig.yield_ty.into(), sig.return_ty.into()]);
2666 let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
2667 ty::Binder::bind_with_vars(
2669 [env_ty, sig.resume_ty].iter(),
2672 hir::Unsafety::Normal,
2673 rustc_target::spec::abi::Abi::Rust,
2678 _ => bug!("unexpected type {:?} in Instance::fn_sig", ty),
2683 /// Calculates whether a function's ABI can unwind or not.
2685 /// This takes two primary parameters:
2687 /// * `codegen_fn_attr_flags` - these are flags calculated as part of the
2688 /// codegen attrs for a defined function. For function pointers this set of
2689 /// flags is the empty set. This is only applicable for Rust-defined
2690 /// functions, and generally isn't needed except for small optimizations where
2691 /// we try to say a function which otherwise might look like it could unwind
2692 /// doesn't actually unwind (such as for intrinsics and such).
2694 /// * `abi` - this is the ABI that the function is defined with. This is the
2695 /// primary factor for determining whether a function can unwind or not.
2697 /// Note that in this case unwinding is not necessarily panicking in Rust. Rust
2698 /// panics are implemented with unwinds on most platform (when
2699 /// `-Cpanic=unwind`), but this also accounts for `-Cpanic=abort` build modes.
2700 /// Notably unwinding is disallowed for more non-Rust ABIs unless it's
2701 /// specifically in the name (e.g. `"C-unwind"`). Unwinding within each ABI is
2702 /// defined for each ABI individually, but it always corresponds to some form of
2703 /// stack-based unwinding (the exact mechanism of which varies
2704 /// platform-by-platform).
2706 /// Rust functions are classfied whether or not they can unwind based on the
2707 /// active "panic strategy". In other words Rust functions are considered to
2708 /// unwind in `-Cpanic=unwind` mode and cannot unwind in `-Cpanic=abort` mode.
2709 /// Note that Rust supports intermingling panic=abort and panic=unwind code, but
2710 /// only if the final panic mode is panic=abort. In this scenario any code
2711 /// previously compiled assuming that a function can unwind is still correct, it
2712 /// just never happens to actually unwind at runtime.
2714 /// This function's answer to whether or not a function can unwind is quite
2715 /// impactful throughout the compiler. This affects things like:
2717 /// * Calling a function which can't unwind means codegen simply ignores any
2718 /// associated unwinding cleanup.
2719 /// * Calling a function which can unwind from a function which can't unwind
2720 /// causes the `abort_unwinding_calls` MIR pass to insert a landing pad that
2721 /// aborts the process.
2722 /// * This affects whether functions have the LLVM `nounwind` attribute, which
2723 /// affects various optimizations and codegen.
2725 /// FIXME: this is actually buggy with respect to Rust functions. Rust functions
2726 /// compiled with `-Cpanic=unwind` and referenced from another crate compiled
2727 /// with `-Cpanic=abort` will look like they can't unwind when in fact they
2728 /// might (from a foreign exception or similar).
2730 pub fn fn_can_unwind<'tcx>(
2732 codegen_fn_attr_flags: CodegenFnAttrFlags,
2735 // Special attribute for functions which can't unwind.
2736 if codegen_fn_attr_flags.contains(CodegenFnAttrFlags::NEVER_UNWIND) {
2740 // Otherwise if this isn't special then unwinding is generally determined by
2741 // the ABI of the itself. ABIs like `C` have variants which also
2742 // specifically allow unwinding (`C-unwind`), but not all platform-specific
2743 // ABIs have such an option. Otherwise the only other thing here is Rust
2744 // itself, and those ABIs are determined by the panic strategy configured
2745 // for this compilation.
2747 // Unfortunately at this time there's also another caveat. Rust [RFC
2748 // 2945][rfc] has been accepted and is in the process of being implemented
2749 // and stabilized. In this interim state we need to deal with historical
2750 // rustc behavior as well as plan for future rustc behavior.
2752 // Historically functions declared with `extern "C"` were marked at the
2753 // codegen layer as `nounwind`. This happened regardless of `panic=unwind`
2754 // or not. This is UB for functions in `panic=unwind` mode that then
2755 // actually panic and unwind. Note that this behavior is true for both
2756 // externally declared functions as well as Rust-defined function.
2758 // To fix this UB rustc would like to change in the future to catch unwinds
2759 // from function calls that may unwind within a Rust-defined `extern "C"`
2760 // function and forcibly abort the process, thereby respecting the
2761 // `nounwind` attribut emitted for `extern "C"`. This behavior change isn't
2762 // ready to roll out, so determining whether or not the `C` family of ABIs
2763 // unwinds is conditional not only on their definition but also whether the
2764 // `#![feature(c_unwind)]` feature gate is active.
2766 // Note that this means that unlike historical compilers rustc now, by
2767 // default, unconditionally thinks that the `C` ABI may unwind. This will
2768 // prevent some optimization opportunities, however, so we try to scope this
2769 // change and only assume that `C` unwinds with `panic=unwind` (as opposed
2770 // to `panic=abort`).
2772 // Eventually the check against `c_unwind` here will ideally get removed and
2773 // this'll be a little cleaner as it'll be a straightforward check of the
2776 // [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
2782 | Stdcall { unwind }
2783 | Fastcall { unwind }
2784 | Vectorcall { unwind }
2785 | Thiscall { unwind }
2788 | SysV64 { unwind } => {
2790 || (!tcx.features().c_unwind && tcx.sess.panic_strategy() == PanicStrategy::Unwind)
2798 | AvrNonBlockingInterrupt
2799 | CCmseNonSecureCall
2803 | Unadjusted => false,
2804 Rust | RustCall => tcx.sess.panic_strategy() == PanicStrategy::Unwind,
2809 pub fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv {
2810 use rustc_target::spec::abi::Abi::*;
2811 match tcx.sess.target.adjust_abi(abi) {
2812 RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
2814 // It's the ABI's job to select this, not ours.
2815 System { .. } => bug!("system abi should be selected elsewhere"),
2816 EfiApi => bug!("eficall abi should be selected elsewhere"),
2818 Stdcall { .. } => Conv::X86Stdcall,
2819 Fastcall { .. } => Conv::X86Fastcall,
2820 Vectorcall { .. } => Conv::X86VectorCall,
2821 Thiscall { .. } => Conv::X86ThisCall,
2822 C { .. } => Conv::C,
2823 Unadjusted => Conv::C,
2824 Win64 { .. } => Conv::X86_64Win64,
2825 SysV64 { .. } => Conv::X86_64SysV,
2826 Aapcs { .. } => Conv::ArmAapcs,
2827 CCmseNonSecureCall => Conv::CCmseNonSecureCall,
2828 PtxKernel => Conv::PtxKernel,
2829 Msp430Interrupt => Conv::Msp430Intr,
2830 X86Interrupt => Conv::X86Intr,
2831 AmdGpuKernel => Conv::AmdGpuKernel,
2832 AvrInterrupt => Conv::AvrInterrupt,
2833 AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt,
2836 // These API constants ought to be more specific...
2837 Cdecl { .. } => Conv::C,
2841 /// Error produced by attempting to compute or adjust a `FnAbi`.
2842 #[derive(Copy, Clone, Debug, HashStable)]
2843 pub enum FnAbiError<'tcx> {
2844 /// Error produced by a `layout_of` call, while computing `FnAbi` initially.
2845 Layout(LayoutError<'tcx>),
2847 /// Error produced by attempting to adjust a `FnAbi`, for a "foreign" ABI.
2848 AdjustForForeignAbi(call::AdjustForForeignAbiError),
2851 impl<'tcx> From<LayoutError<'tcx>> for FnAbiError<'tcx> {
2852 fn from(err: LayoutError<'tcx>) -> Self {
2857 impl From<call::AdjustForForeignAbiError> for FnAbiError<'_> {
2858 fn from(err: call::AdjustForForeignAbiError) -> Self {
2859 Self::AdjustForForeignAbi(err)
2863 impl<'tcx> fmt::Display for FnAbiError<'tcx> {
2864 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2866 Self::Layout(err) => err.fmt(f),
2867 Self::AdjustForForeignAbi(err) => err.fmt(f),
2872 // FIXME(eddyb) maybe use something like this for an unified `fn_abi_of`, not
2873 // just for error handling.
2875 pub enum FnAbiRequest<'tcx> {
2876 OfFnPtr { sig: ty::PolyFnSig<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2877 OfInstance { instance: ty::Instance<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2880 /// Trait for contexts that want to be able to compute `FnAbi`s.
2881 /// This automatically gives access to `FnAbiOf`, through a blanket `impl`.
2882 pub trait FnAbiOfHelpers<'tcx>: LayoutOfHelpers<'tcx> {
2883 /// The `&FnAbi`-wrapping type (or `&FnAbi` itself), which will be
2884 /// returned from `fn_abi_of_*` (see also `handle_fn_abi_err`).
2885 type FnAbiOfResult: MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>;
2887 /// Helper used for `fn_abi_of_*`, to adapt `tcx.fn_abi_of_*(...)` into a
2888 /// `Self::FnAbiOfResult` (which does not need to be a `Result<...>`).
2890 /// Most `impl`s, which propagate `FnAbiError`s, should simply return `err`,
2891 /// but this hook allows e.g. codegen to return only `&FnAbi` from its
2892 /// `cx.fn_abi_of_*(...)`, without any `Result<...>` around it to deal with
2893 /// (and any `FnAbiError`s are turned into fatal errors or ICEs).
2894 fn handle_fn_abi_err(
2896 err: FnAbiError<'tcx>,
2898 fn_abi_request: FnAbiRequest<'tcx>,
2899 ) -> <Self::FnAbiOfResult as MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>>::Error;
2902 /// Blanket extension trait for contexts that can compute `FnAbi`s.
2903 pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
2904 /// Compute a `FnAbi` suitable for indirect calls, i.e. to `fn` pointers.
2906 /// NB: this doesn't handle virtual calls - those should use `fn_abi_of_instance`
2907 /// instead, where the instance is an `InstanceDef::Virtual`.
2909 fn fn_abi_of_fn_ptr(
2911 sig: ty::PolyFnSig<'tcx>,
2912 extra_args: &'tcx ty::List<Ty<'tcx>>,
2913 ) -> Self::FnAbiOfResult {
2914 // FIXME(eddyb) get a better `span` here.
2915 let span = self.layout_tcx_at_span();
2916 let tcx = self.tcx().at(span);
2918 MaybeResult::from(tcx.fn_abi_of_fn_ptr(self.param_env().and((sig, extra_args))).map_err(
2919 |err| self.handle_fn_abi_err(err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
2923 /// Compute a `FnAbi` suitable for declaring/defining an `fn` instance, and for
2924 /// direct calls to an `fn`.
2926 /// NB: that includes virtual calls, which are represented by "direct calls"
2927 /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
2929 fn fn_abi_of_instance(
2931 instance: ty::Instance<'tcx>,
2932 extra_args: &'tcx ty::List<Ty<'tcx>>,
2933 ) -> Self::FnAbiOfResult {
2934 // FIXME(eddyb) get a better `span` here.
2935 let span = self.layout_tcx_at_span();
2936 let tcx = self.tcx().at(span);
2939 tcx.fn_abi_of_instance(self.param_env().and((instance, extra_args))).map_err(|err| {
2940 // HACK(eddyb) at least for definitions of/calls to `Instance`s,
2941 // we can get some kind of span even if one wasn't provided.
2942 // However, we don't do this early in order to avoid calling
2943 // `def_span` unconditionally (which may have a perf penalty).
2944 let span = if !span.is_dummy() { span } else { tcx.def_span(instance.def_id()) };
2945 self.handle_fn_abi_err(err, span, FnAbiRequest::OfInstance { instance, extra_args })
2951 impl<'tcx, C: FnAbiOfHelpers<'tcx>> FnAbiOf<'tcx> for C {}
2953 fn fn_abi_of_fn_ptr<'tcx>(
2955 query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2956 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2957 let (param_env, (sig, extra_args)) = query.into_parts();
2959 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
2963 CodegenFnAttrFlags::empty(),
2968 fn fn_abi_of_instance<'tcx>(
2970 query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2971 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2972 let (param_env, (instance, extra_args)) = query.into_parts();
2974 let sig = instance.fn_sig_for_fn_abi(tcx, param_env);
2976 let caller_location = if instance.def.requires_caller_location(tcx) {
2977 Some(tcx.caller_location_ty())
2982 let attrs = tcx.codegen_fn_attrs(instance.def_id()).flags;
2984 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
2989 matches!(instance.def, ty::InstanceDef::Virtual(..)),
2993 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
2994 // FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
2995 // arguments of this method, into a separate `struct`.
2996 fn fn_abi_new_uncached(
2998 sig: ty::PolyFnSig<'tcx>,
2999 extra_args: &[Ty<'tcx>],
3000 caller_location: Option<Ty<'tcx>>,
3001 codegen_fn_attr_flags: CodegenFnAttrFlags,
3002 // FIXME(eddyb) replace this with something typed, like an `enum`.
3003 force_thin_self_ptr: bool,
3004 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
3005 debug!("fn_abi_new_uncached({:?}, {:?})", sig, extra_args);
3007 let sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, sig);
3009 let conv = conv_from_spec_abi(self.tcx(), sig.abi);
3011 let mut inputs = sig.inputs();
3012 let extra_args = if sig.abi == RustCall {
3013 assert!(!sig.c_variadic && extra_args.is_empty());
3015 if let Some(input) = sig.inputs().last() {
3016 if let ty::Tuple(tupled_arguments) = input.kind() {
3017 inputs = &sig.inputs()[0..sig.inputs().len() - 1];
3018 tupled_arguments.iter().map(|k| k.expect_ty()).collect()
3021 "argument to function with \"rust-call\" ABI \
3027 "argument to function with \"rust-call\" ABI \
3032 assert!(sig.c_variadic || extra_args.is_empty());
3036 let target = &self.tcx.sess.target;
3037 let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
3038 let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
3039 let linux_s390x_gnu_like =
3040 target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
3041 let linux_sparc64_gnu_like =
3042 target.os == "linux" && target.arch == "sparc64" && target_env_gnu_like;
3043 let linux_powerpc_gnu_like =
3044 target.os == "linux" && target.arch == "powerpc" && target_env_gnu_like;
3046 let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall);
3048 // Handle safe Rust thin and fat pointers.
3049 let adjust_for_rust_scalar = |attrs: &mut ArgAttributes,
3051 layout: TyAndLayout<'tcx>,
3054 // Booleans are always a noundef i1 that needs to be zero-extended.
3055 if scalar.is_bool() {
3056 attrs.ext(ArgExtension::Zext);
3057 attrs.set(ArgAttribute::NoUndef);
3061 // Only pointer types handled below.
3062 if scalar.value != Pointer {
3066 if !scalar.valid_range.contains(0) {
3067 attrs.set(ArgAttribute::NonNull);
3070 if let Some(pointee) = layout.pointee_info_at(self, offset) {
3071 if let Some(kind) = pointee.safe {
3072 attrs.pointee_align = Some(pointee.align);
3074 // `Box` (`UniqueBorrowed`) are not necessarily dereferenceable
3075 // for the entire duration of the function as they can be deallocated
3076 // at any time. Set their valid size to 0.
3077 attrs.pointee_size = match kind {
3078 PointerKind::UniqueOwned => Size::ZERO,
3082 // `Box`, `&T`, and `&mut T` cannot be undef.
3083 // Note that this only applies to the value of the pointer itself;
3084 // this attribute doesn't make it UB for the pointed-to data to be undef.
3085 attrs.set(ArgAttribute::NoUndef);
3087 // `Box` pointer parameters never alias because ownership is transferred
3088 // `&mut` pointer parameters never alias other parameters,
3089 // or mutable global data
3091 // `&T` where `T` contains no `UnsafeCell<U>` is immutable,
3092 // and can be marked as both `readonly` and `noalias`, as
3093 // LLVM's definition of `noalias` is based solely on memory
3094 // dependencies rather than pointer equality
3096 // Due to past miscompiles in LLVM, we apply a separate NoAliasMutRef attribute
3097 // for UniqueBorrowed arguments, so that the codegen backend can decide whether
3098 // or not to actually emit the attribute. It can also be controlled with the
3099 // `-Zmutable-noalias` debugging option.
3100 let no_alias = match kind {
3101 PointerKind::Shared | PointerKind::UniqueBorrowed => false,
3102 PointerKind::UniqueOwned => true,
3103 PointerKind::Frozen => !is_return,
3106 attrs.set(ArgAttribute::NoAlias);
3109 if kind == PointerKind::Frozen && !is_return {
3110 attrs.set(ArgAttribute::ReadOnly);
3113 if kind == PointerKind::UniqueBorrowed && !is_return {
3114 attrs.set(ArgAttribute::NoAliasMutRef);
3120 let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
3121 let is_return = arg_idx.is_none();
3123 let layout = self.layout_of(ty)?;
3124 let layout = if force_thin_self_ptr && arg_idx == Some(0) {
3125 // Don't pass the vtable, it's not an argument of the virtual fn.
3126 // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
3127 // or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen
3128 make_thin_self_ptr(self, layout)
3133 let mut arg = ArgAbi::new(self, layout, |layout, scalar, offset| {
3134 let mut attrs = ArgAttributes::new();
3135 adjust_for_rust_scalar(&mut attrs, scalar, *layout, offset, is_return);
3139 if arg.layout.is_zst() {
3140 // For some forsaken reason, x86_64-pc-windows-gnu
3141 // doesn't ignore zero-sized struct arguments.
3142 // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
3146 && !linux_s390x_gnu_like
3147 && !linux_sparc64_gnu_like
3148 && !linux_powerpc_gnu_like)
3150 arg.mode = PassMode::Ignore;
3157 let mut fn_abi = FnAbi {
3158 ret: arg_of(sig.output(), None)?,
3163 .chain(caller_location)
3165 .map(|(i, ty)| arg_of(ty, Some(i)))
3166 .collect::<Result<_, _>>()?,
3167 c_variadic: sig.c_variadic,
3168 fixed_count: inputs.len(),
3170 can_unwind: fn_can_unwind(self.tcx(), codegen_fn_attr_flags, sig.abi),
3172 self.fn_abi_adjust_for_abi(&mut fn_abi, sig.abi)?;
3173 debug!("fn_abi_new_uncached = {:?}", fn_abi);
3174 Ok(self.tcx.arena.alloc(fn_abi))
3177 fn fn_abi_adjust_for_abi(
3179 fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
3181 ) -> Result<(), FnAbiError<'tcx>> {
3182 if abi == SpecAbi::Unadjusted {
3186 if abi == SpecAbi::Rust
3187 || abi == SpecAbi::RustCall
3188 || abi == SpecAbi::RustIntrinsic
3189 || abi == SpecAbi::PlatformIntrinsic
3191 let fixup = |arg: &mut ArgAbi<'tcx, Ty<'tcx>>| {
3192 if arg.is_ignore() {
3196 match arg.layout.abi {
3197 Abi::Aggregate { .. } => {}
3199 // This is a fun case! The gist of what this is doing is
3200 // that we want callers and callees to always agree on the
3201 // ABI of how they pass SIMD arguments. If we were to *not*
3202 // make these arguments indirect then they'd be immediates
3203 // in LLVM, which means that they'd used whatever the
3204 // appropriate ABI is for the callee and the caller. That
3205 // means, for example, if the caller doesn't have AVX
3206 // enabled but the callee does, then passing an AVX argument
3207 // across this boundary would cause corrupt data to show up.
3209 // This problem is fixed by unconditionally passing SIMD
3210 // arguments through memory between callers and callees
3211 // which should get them all to agree on ABI regardless of
3212 // target feature sets. Some more information about this
3213 // issue can be found in #44367.
3215 // Note that the platform intrinsic ABI is exempt here as
3216 // that's how we connect up to LLVM and it's unstable
3217 // anyway, we control all calls to it in libstd.
3219 if abi != SpecAbi::PlatformIntrinsic
3220 && self.tcx.sess.target.simd_types_indirect =>
3222 arg.make_indirect();
3229 // Pass and return structures up to 2 pointers in size by value, matching `ScalarPair`.
3230 // LLVM will usually pass these in 2 registers, which is more efficient than by-ref.
3231 let max_by_val_size = Pointer.size(self) * 2;
3232 let size = arg.layout.size;
3234 if arg.layout.is_unsized() || size > max_by_val_size {
3235 arg.make_indirect();
3237 // We want to pass small aggregates as immediates, but using
3238 // a LLVM aggregate type for this leads to bad optimizations,
3239 // so we pick an appropriately sized integer type instead.
3240 arg.cast_to(Reg { kind: RegKind::Integer, size });
3243 fixup(&mut fn_abi.ret);
3244 for arg in &mut fn_abi.args {
3248 fn_abi.adjust_for_foreign_abi(self, abi)?;
3255 fn make_thin_self_ptr<'tcx>(
3256 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
3257 layout: TyAndLayout<'tcx>,
3258 ) -> TyAndLayout<'tcx> {
3260 let fat_pointer_ty = if layout.is_unsized() {
3261 // unsized `self` is passed as a pointer to `self`
3262 // FIXME (mikeyhew) change this to use &own if it is ever added to the language
3263 tcx.mk_mut_ptr(layout.ty)
3266 Abi::ScalarPair(..) => (),
3267 _ => bug!("receiver type has unsupported layout: {:?}", layout),
3270 // In the case of Rc<Self>, we need to explicitly pass a *mut RcBox<Self>
3271 // with a Scalar (not ScalarPair) ABI. This is a hack that is understood
3272 // elsewhere in the compiler as a method on a `dyn Trait`.
3273 // To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we
3274 // get a built-in pointer type
3275 let mut fat_pointer_layout = layout;
3276 'descend_newtypes: while !fat_pointer_layout.ty.is_unsafe_ptr()
3277 && !fat_pointer_layout.ty.is_region_ptr()
3279 for i in 0..fat_pointer_layout.fields.count() {
3280 let field_layout = fat_pointer_layout.field(cx, i);
3282 if !field_layout.is_zst() {
3283 fat_pointer_layout = field_layout;
3284 continue 'descend_newtypes;
3288 bug!("receiver has no non-zero-sized fields {:?}", fat_pointer_layout);
3291 fat_pointer_layout.ty
3294 // we now have a type like `*mut RcBox<dyn Trait>`
3295 // change its layout to that of `*mut ()`, a thin pointer, but keep the same type
3296 // this is understood as a special case elsewhere in the compiler
3297 let unit_ptr_ty = tcx.mk_mut_ptr(tcx.mk_unit());
3302 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result`
3303 // should always work because the type is always `*mut ()`.
3304 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()