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 };
1313 if tag.value.size(dl) == size {
1314 abi = Abi::Scalar(tag);
1316 // Try to use a ScalarPair for all tagged enums.
1317 let mut common_prim = None;
1318 for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) {
1319 let offsets = match layout_variant.fields {
1320 FieldsShape::Arbitrary { ref offsets, .. } => offsets,
1324 iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst());
1325 let (field, offset) = match (fields.next(), fields.next()) {
1326 (None, None) => continue,
1327 (Some(pair), None) => pair,
1333 let prim = match field.abi {
1334 Abi::Scalar(scalar) => scalar.value,
1340 if let Some(pair) = common_prim {
1341 // This is pretty conservative. We could go fancier
1342 // by conflating things like i32 and u32, or even
1343 // realising that (u8, u8) could just cohabit with
1345 if pair != (prim, offset) {
1350 common_prim = Some((prim, offset));
1353 if let Some((prim, offset)) = common_prim {
1354 let pair = self.scalar_pair(tag, scalar_unit(prim));
1355 let pair_offsets = match pair.fields {
1356 FieldsShape::Arbitrary { ref offsets, ref memory_index } => {
1357 assert_eq!(memory_index, &[0, 1]);
1362 if pair_offsets[0] == Size::ZERO
1363 && pair_offsets[1] == *offset
1364 && align == pair.align
1365 && size == pair.size
1367 // We can use `ScalarPair` only when it matches our
1368 // already computed layout (including `#[repr(C)]`).
1374 if layout_variants.iter().all(|v| v.abi.is_uninhabited()) {
1375 abi = Abi::Uninhabited;
1378 let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag);
1380 let tagged_layout = Layout {
1381 variants: Variants::Multiple {
1383 tag_encoding: TagEncoding::Direct,
1385 variants: layout_variants,
1387 fields: FieldsShape::Arbitrary {
1388 offsets: vec![Size::ZERO],
1389 memory_index: vec![0],
1397 let best_layout = match (tagged_layout, niche_filling_layout) {
1398 (tagged_layout, Some(niche_filling_layout)) => {
1399 // Pick the smaller layout; otherwise,
1400 // pick the layout with the larger niche; otherwise,
1401 // pick tagged as it has simpler codegen.
1402 cmp::min_by_key(tagged_layout, niche_filling_layout, |layout| {
1403 let niche_size = layout.largest_niche.map_or(0, |n| n.available(dl));
1404 (layout.size, cmp::Reverse(niche_size))
1407 (tagged_layout, None) => tagged_layout,
1410 tcx.intern_layout(best_layout)
1413 // Types with no meaningful known layout.
1414 ty::Projection(_) | ty::Opaque(..) => {
1415 // NOTE(eddyb) `layout_of` query should've normalized these away,
1416 // if that was possible, so there's no reason to try again here.
1417 return Err(LayoutError::Unknown(ty));
1420 ty::Placeholder(..) | ty::GeneratorWitness(..) | ty::Infer(_) => {
1421 bug!("Layout::compute: unexpected type `{}`", ty)
1424 ty::Bound(..) | ty::Param(_) | ty::Error(_) => {
1425 return Err(LayoutError::Unknown(ty));
1431 /// Overlap eligibility and variant assignment for each GeneratorSavedLocal.
1432 #[derive(Clone, Debug, PartialEq)]
1433 enum SavedLocalEligibility {
1435 Assigned(VariantIdx),
1436 // FIXME: Use newtype_index so we aren't wasting bytes
1437 Ineligible(Option<u32>),
1440 // When laying out generators, we divide our saved local fields into two
1441 // categories: overlap-eligible and overlap-ineligible.
1443 // Those fields which are ineligible for overlap go in a "prefix" at the
1444 // beginning of the layout, and always have space reserved for them.
1446 // Overlap-eligible fields are only assigned to one variant, so we lay
1447 // those fields out for each variant and put them right after the
1450 // Finally, in the layout details, we point to the fields from the
1451 // variants they are assigned to. It is possible for some fields to be
1452 // included in multiple variants. No field ever "moves around" in the
1453 // layout; its offset is always the same.
1455 // Also included in the layout are the upvars and the discriminant.
1456 // These are included as fields on the "outer" layout; they are not part
1458 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
1459 /// Compute the eligibility and assignment of each local.
1460 fn generator_saved_local_eligibility(
1462 info: &GeneratorLayout<'tcx>,
1463 ) -> (BitSet<GeneratorSavedLocal>, IndexVec<GeneratorSavedLocal, SavedLocalEligibility>) {
1464 use SavedLocalEligibility::*;
1466 let mut assignments: IndexVec<GeneratorSavedLocal, SavedLocalEligibility> =
1467 IndexVec::from_elem_n(Unassigned, info.field_tys.len());
1469 // The saved locals not eligible for overlap. These will get
1470 // "promoted" to the prefix of our generator.
1471 let mut ineligible_locals = BitSet::new_empty(info.field_tys.len());
1473 // Figure out which of our saved locals are fields in only
1474 // one variant. The rest are deemed ineligible for overlap.
1475 for (variant_index, fields) in info.variant_fields.iter_enumerated() {
1476 for local in fields {
1477 match assignments[*local] {
1479 assignments[*local] = Assigned(variant_index);
1482 // We've already seen this local at another suspension
1483 // point, so it is no longer a candidate.
1485 "removing local {:?} in >1 variant ({:?}, {:?})",
1490 ineligible_locals.insert(*local);
1491 assignments[*local] = Ineligible(None);
1498 // Next, check every pair of eligible locals to see if they
1500 for local_a in info.storage_conflicts.rows() {
1501 let conflicts_a = info.storage_conflicts.count(local_a);
1502 if ineligible_locals.contains(local_a) {
1506 for local_b in info.storage_conflicts.iter(local_a) {
1507 // local_a and local_b are storage live at the same time, therefore they
1508 // cannot overlap in the generator layout. The only way to guarantee
1509 // this is if they are in the same variant, or one is ineligible
1510 // (which means it is stored in every variant).
1511 if ineligible_locals.contains(local_b)
1512 || assignments[local_a] == assignments[local_b]
1517 // If they conflict, we will choose one to make ineligible.
1518 // This is not always optimal; it's just a greedy heuristic that
1519 // seems to produce good results most of the time.
1520 let conflicts_b = info.storage_conflicts.count(local_b);
1521 let (remove, other) =
1522 if conflicts_a > conflicts_b { (local_a, local_b) } else { (local_b, local_a) };
1523 ineligible_locals.insert(remove);
1524 assignments[remove] = Ineligible(None);
1525 trace!("removing local {:?} due to conflict with {:?}", remove, other);
1529 // Count the number of variants in use. If only one of them, then it is
1530 // impossible to overlap any locals in our layout. In this case it's
1531 // always better to make the remaining locals ineligible, so we can
1532 // lay them out with the other locals in the prefix and eliminate
1533 // unnecessary padding bytes.
1535 let mut used_variants = BitSet::new_empty(info.variant_fields.len());
1536 for assignment in &assignments {
1537 if let Assigned(idx) = assignment {
1538 used_variants.insert(*idx);
1541 if used_variants.count() < 2 {
1542 for assignment in assignments.iter_mut() {
1543 *assignment = Ineligible(None);
1545 ineligible_locals.insert_all();
1549 // Write down the order of our locals that will be promoted to the prefix.
1551 for (idx, local) in ineligible_locals.iter().enumerate() {
1552 assignments[local] = Ineligible(Some(idx as u32));
1555 debug!("generator saved local assignments: {:?}", assignments);
1557 (ineligible_locals, assignments)
1560 /// Compute the full generator layout.
1561 fn generator_layout(
1564 def_id: hir::def_id::DefId,
1565 substs: SubstsRef<'tcx>,
1566 ) -> Result<&'tcx Layout, LayoutError<'tcx>> {
1567 use SavedLocalEligibility::*;
1569 let subst_field = |ty: Ty<'tcx>| ty.subst(tcx, substs);
1571 let info = match tcx.generator_layout(def_id) {
1572 None => return Err(LayoutError::Unknown(ty)),
1575 let (ineligible_locals, assignments) = self.generator_saved_local_eligibility(&info);
1577 // Build a prefix layout, including "promoting" all ineligible
1578 // locals as part of the prefix. We compute the layout of all of
1579 // these fields at once to get optimal packing.
1580 let tag_index = substs.as_generator().prefix_tys().count();
1582 // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
1583 let max_discr = (info.variant_fields.len() - 1) as u128;
1584 let discr_int = Integer::fit_unsigned(max_discr);
1585 let discr_int_ty = discr_int.to_ty(tcx, false);
1587 value: Primitive::Int(discr_int, false),
1588 valid_range: WrappingRange { start: 0, end: max_discr },
1590 let tag_layout = self.tcx.intern_layout(Layout::scalar(self, tag));
1591 let tag_layout = TyAndLayout { ty: discr_int_ty, layout: tag_layout };
1593 let promoted_layouts = ineligible_locals
1595 .map(|local| subst_field(info.field_tys[local]))
1596 .map(|ty| tcx.mk_maybe_uninit(ty))
1597 .map(|ty| self.layout_of(ty));
1598 let prefix_layouts = substs
1601 .map(|ty| self.layout_of(ty))
1602 .chain(iter::once(Ok(tag_layout)))
1603 .chain(promoted_layouts)
1604 .collect::<Result<Vec<_>, _>>()?;
1605 let prefix = self.univariant_uninterned(
1608 &ReprOptions::default(),
1609 StructKind::AlwaysSized,
1612 let (prefix_size, prefix_align) = (prefix.size, prefix.align);
1614 // Split the prefix layout into the "outer" fields (upvars and
1615 // discriminant) and the "promoted" fields. Promoted fields will
1616 // get included in each variant that requested them in
1618 debug!("prefix = {:#?}", prefix);
1619 let (outer_fields, promoted_offsets, promoted_memory_index) = match prefix.fields {
1620 FieldsShape::Arbitrary { mut offsets, memory_index } => {
1621 let mut inverse_memory_index = invert_mapping(&memory_index);
1623 // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
1624 // "outer" and "promoted" fields respectively.
1625 let b_start = (tag_index + 1) as u32;
1626 let offsets_b = offsets.split_off(b_start as usize);
1627 let offsets_a = offsets;
1629 // Disentangle the "a" and "b" components of `inverse_memory_index`
1630 // by preserving the order but keeping only one disjoint "half" each.
1631 // FIXME(eddyb) build a better abstraction for permutations, if possible.
1632 let inverse_memory_index_b: Vec<_> =
1633 inverse_memory_index.iter().filter_map(|&i| i.checked_sub(b_start)).collect();
1634 inverse_memory_index.retain(|&i| i < b_start);
1635 let inverse_memory_index_a = inverse_memory_index;
1637 // Since `inverse_memory_index_{a,b}` each only refer to their
1638 // respective fields, they can be safely inverted
1639 let memory_index_a = invert_mapping(&inverse_memory_index_a);
1640 let memory_index_b = invert_mapping(&inverse_memory_index_b);
1643 FieldsShape::Arbitrary { offsets: offsets_a, memory_index: memory_index_a };
1644 (outer_fields, offsets_b, memory_index_b)
1649 let mut size = prefix.size;
1650 let mut align = prefix.align;
1654 .map(|(index, variant_fields)| {
1655 // Only include overlap-eligible fields when we compute our variant layout.
1656 let variant_only_tys = variant_fields
1658 .filter(|local| match assignments[**local] {
1659 Unassigned => bug!(),
1660 Assigned(v) if v == index => true,
1661 Assigned(_) => bug!("assignment does not match variant"),
1662 Ineligible(_) => false,
1664 .map(|local| subst_field(info.field_tys[*local]));
1666 let mut variant = self.univariant_uninterned(
1669 .map(|ty| self.layout_of(ty))
1670 .collect::<Result<Vec<_>, _>>()?,
1671 &ReprOptions::default(),
1672 StructKind::Prefixed(prefix_size, prefix_align.abi),
1674 variant.variants = Variants::Single { index };
1676 let (offsets, memory_index) = match variant.fields {
1677 FieldsShape::Arbitrary { offsets, memory_index } => (offsets, memory_index),
1681 // Now, stitch the promoted and variant-only fields back together in
1682 // the order they are mentioned by our GeneratorLayout.
1683 // Because we only use some subset (that can differ between variants)
1684 // of the promoted fields, we can't just pick those elements of the
1685 // `promoted_memory_index` (as we'd end up with gaps).
1686 // So instead, we build an "inverse memory_index", as if all of the
1687 // promoted fields were being used, but leave the elements not in the
1688 // subset as `INVALID_FIELD_IDX`, which we can filter out later to
1689 // obtain a valid (bijective) mapping.
1690 const INVALID_FIELD_IDX: u32 = !0;
1691 let mut combined_inverse_memory_index =
1692 vec![INVALID_FIELD_IDX; promoted_memory_index.len() + memory_index.len()];
1693 let mut offsets_and_memory_index = iter::zip(offsets, memory_index);
1694 let combined_offsets = variant_fields
1698 let (offset, memory_index) = match assignments[*local] {
1699 Unassigned => bug!(),
1701 let (offset, memory_index) =
1702 offsets_and_memory_index.next().unwrap();
1703 (offset, promoted_memory_index.len() as u32 + memory_index)
1705 Ineligible(field_idx) => {
1706 let field_idx = field_idx.unwrap() as usize;
1707 (promoted_offsets[field_idx], promoted_memory_index[field_idx])
1710 combined_inverse_memory_index[memory_index as usize] = i as u32;
1715 // Remove the unused slots and invert the mapping to obtain the
1716 // combined `memory_index` (also see previous comment).
1717 combined_inverse_memory_index.retain(|&i| i != INVALID_FIELD_IDX);
1718 let combined_memory_index = invert_mapping(&combined_inverse_memory_index);
1720 variant.fields = FieldsShape::Arbitrary {
1721 offsets: combined_offsets,
1722 memory_index: combined_memory_index,
1725 size = size.max(variant.size);
1726 align = align.max(variant.align);
1729 .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
1731 size = size.align_to(align.abi);
1733 let abi = if prefix.abi.is_uninhabited() || variants.iter().all(|v| v.abi.is_uninhabited())
1737 Abi::Aggregate { sized: true }
1740 let layout = tcx.intern_layout(Layout {
1741 variants: Variants::Multiple {
1743 tag_encoding: TagEncoding::Direct,
1744 tag_field: tag_index,
1747 fields: outer_fields,
1749 largest_niche: prefix.largest_niche,
1753 debug!("generator layout ({:?}): {:#?}", ty, layout);
1757 /// This is invoked by the `layout_of` query to record the final
1758 /// layout of each type.
1760 fn record_layout_for_printing(&self, layout: TyAndLayout<'tcx>) {
1761 // If we are running with `-Zprint-type-sizes`, maybe record layouts
1762 // for dumping later.
1763 if self.tcx.sess.opts.debugging_opts.print_type_sizes {
1764 self.record_layout_for_printing_outlined(layout)
1768 fn record_layout_for_printing_outlined(&self, layout: TyAndLayout<'tcx>) {
1769 // Ignore layouts that are done with non-empty environments or
1770 // non-monomorphic layouts, as the user only wants to see the stuff
1771 // resulting from the final codegen session.
1772 if layout.ty.has_param_types_or_consts() || !self.param_env.caller_bounds().is_empty() {
1776 // (delay format until we actually need it)
1777 let record = |kind, packed, opt_discr_size, variants| {
1778 let type_desc = format!("{:?}", layout.ty);
1779 self.tcx.sess.code_stats.record_type_size(
1790 let adt_def = match *layout.ty.kind() {
1791 ty::Adt(ref adt_def, _) => {
1792 debug!("print-type-size t: `{:?}` process adt", layout.ty);
1796 ty::Closure(..) => {
1797 debug!("print-type-size t: `{:?}` record closure", layout.ty);
1798 record(DataTypeKind::Closure, false, None, vec![]);
1803 debug!("print-type-size t: `{:?}` skip non-nominal", layout.ty);
1808 let adt_kind = adt_def.adt_kind();
1809 let adt_packed = adt_def.repr.pack.is_some();
1811 let build_variant_info = |n: Option<Symbol>, flds: &[Symbol], layout: TyAndLayout<'tcx>| {
1812 let mut min_size = Size::ZERO;
1813 let field_info: Vec<_> = flds
1817 let field_layout = layout.field(self, i);
1818 let offset = layout.fields.offset(i);
1819 let field_end = offset + field_layout.size;
1820 if min_size < field_end {
1821 min_size = field_end;
1824 name: name.to_string(),
1825 offset: offset.bytes(),
1826 size: field_layout.size.bytes(),
1827 align: field_layout.align.abi.bytes(),
1833 name: n.map(|n| n.to_string()),
1834 kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact },
1835 align: layout.align.abi.bytes(),
1836 size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() },
1841 match layout.variants {
1842 Variants::Single { index } => {
1843 if !adt_def.variants.is_empty() && layout.fields != FieldsShape::Primitive {
1845 "print-type-size `{:#?}` variant {}",
1846 layout, adt_def.variants[index].name
1848 let variant_def = &adt_def.variants[index];
1849 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1854 vec![build_variant_info(Some(variant_def.name), &fields, layout)],
1857 // (This case arises for *empty* enums; so give it
1859 record(adt_kind.into(), adt_packed, None, vec![]);
1863 Variants::Multiple { tag, ref tag_encoding, .. } => {
1865 "print-type-size `{:#?}` adt general variants def {}",
1867 adt_def.variants.len()
1869 let variant_infos: Vec<_> = adt_def
1872 .map(|(i, variant_def)| {
1873 let fields: Vec<_> = variant_def.fields.iter().map(|f| f.name).collect();
1875 Some(variant_def.name),
1877 layout.for_variant(self, i),
1884 match tag_encoding {
1885 TagEncoding::Direct => Some(tag.value.size(self)),
1895 /// Type size "skeleton", i.e., the only information determining a type's size.
1896 /// While this is conservative, (aside from constant sizes, only pointers,
1897 /// newtypes thereof and null pointer optimized enums are allowed), it is
1898 /// enough to statically check common use cases of transmute.
1899 #[derive(Copy, Clone, Debug)]
1900 pub enum SizeSkeleton<'tcx> {
1901 /// Any statically computable Layout.
1904 /// A potentially-fat pointer.
1906 /// If true, this pointer is never null.
1908 /// The type which determines the unsized metadata, if any,
1909 /// of this pointer. Either a type parameter or a projection
1910 /// depending on one, with regions erased.
1915 impl<'tcx> SizeSkeleton<'tcx> {
1919 param_env: ty::ParamEnv<'tcx>,
1920 ) -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
1921 debug_assert!(!ty.has_infer_types_or_consts());
1923 // First try computing a static layout.
1924 let err = match tcx.layout_of(param_env.and(ty)) {
1926 return Ok(SizeSkeleton::Known(layout.size));
1932 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1933 let non_zero = !ty.is_unsafe_ptr();
1934 let tail = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
1936 ty::Param(_) | ty::Projection(_) => {
1937 debug_assert!(tail.has_param_types_or_consts());
1938 Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
1941 "SizeSkeleton::compute({}): layout errored ({}), yet \
1942 tail `{}` is not a type parameter or a projection",
1950 ty::Adt(def, substs) => {
1951 // Only newtypes and enums w/ nullable pointer optimization.
1952 if def.is_union() || def.variants.is_empty() || def.variants.len() > 2 {
1956 // Get a zero-sized variant or a pointer newtype.
1957 let zero_or_ptr_variant = |i| {
1958 let i = VariantIdx::new(i);
1959 let fields = def.variants[i]
1962 .map(|field| SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env));
1964 for field in fields {
1967 SizeSkeleton::Known(size) => {
1968 if size.bytes() > 0 {
1972 SizeSkeleton::Pointer { .. } => {
1983 let v0 = zero_or_ptr_variant(0)?;
1985 if def.variants.len() == 1 {
1986 if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
1987 return Ok(SizeSkeleton::Pointer {
1989 || match tcx.layout_scalar_valid_range(def.did) {
1990 (Bound::Included(start), Bound::Unbounded) => start > 0,
1991 (Bound::Included(start), Bound::Included(end)) => {
1992 0 < start && start < end
2003 let v1 = zero_or_ptr_variant(1)?;
2004 // Nullable pointer enum optimization.
2006 (Some(SizeSkeleton::Pointer { non_zero: true, tail }), None)
2007 | (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
2008 Ok(SizeSkeleton::Pointer { non_zero: false, tail })
2014 ty::Projection(_) | ty::Opaque(..) => {
2015 let normalized = tcx.normalize_erasing_regions(param_env, ty);
2016 if ty == normalized {
2019 SizeSkeleton::compute(normalized, tcx, param_env)
2027 pub fn same_size(self, other: SizeSkeleton<'_>) -> bool {
2028 match (self, other) {
2029 (SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
2030 (SizeSkeleton::Pointer { tail: a, .. }, SizeSkeleton::Pointer { tail: b, .. }) => {
2038 pub trait HasTyCtxt<'tcx>: HasDataLayout {
2039 fn tcx(&self) -> TyCtxt<'tcx>;
2042 pub trait HasParamEnv<'tcx> {
2043 fn param_env(&self) -> ty::ParamEnv<'tcx>;
2046 impl<'tcx> HasDataLayout for TyCtxt<'tcx> {
2048 fn data_layout(&self) -> &TargetDataLayout {
2053 impl<'tcx> HasTargetSpec for TyCtxt<'tcx> {
2054 fn target_spec(&self) -> &Target {
2059 impl<'tcx> HasTyCtxt<'tcx> for TyCtxt<'tcx> {
2061 fn tcx(&self) -> TyCtxt<'tcx> {
2066 impl<'tcx> HasDataLayout for ty::query::TyCtxtAt<'tcx> {
2068 fn data_layout(&self) -> &TargetDataLayout {
2073 impl<'tcx> HasTargetSpec for ty::query::TyCtxtAt<'tcx> {
2074 fn target_spec(&self) -> &Target {
2079 impl<'tcx> HasTyCtxt<'tcx> for ty::query::TyCtxtAt<'tcx> {
2081 fn tcx(&self) -> TyCtxt<'tcx> {
2086 impl<'tcx, C> HasParamEnv<'tcx> for LayoutCx<'tcx, C> {
2087 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2092 impl<'tcx, T: HasDataLayout> HasDataLayout for LayoutCx<'tcx, T> {
2093 fn data_layout(&self) -> &TargetDataLayout {
2094 self.tcx.data_layout()
2098 impl<'tcx, T: HasTargetSpec> HasTargetSpec for LayoutCx<'tcx, T> {
2099 fn target_spec(&self) -> &Target {
2100 self.tcx.target_spec()
2104 impl<'tcx, T: HasTyCtxt<'tcx>> HasTyCtxt<'tcx> for LayoutCx<'tcx, T> {
2105 fn tcx(&self) -> TyCtxt<'tcx> {
2110 pub trait MaybeResult<T> {
2113 fn from(x: Result<T, Self::Error>) -> Self;
2114 fn to_result(self) -> Result<T, Self::Error>;
2117 impl<T> MaybeResult<T> for T {
2120 fn from(Ok(x): Result<T, Self::Error>) -> Self {
2123 fn to_result(self) -> Result<T, Self::Error> {
2128 impl<T, E> MaybeResult<T> for Result<T, E> {
2131 fn from(x: Result<T, Self::Error>) -> Self {
2134 fn to_result(self) -> Result<T, Self::Error> {
2139 pub type TyAndLayout<'tcx> = rustc_target::abi::TyAndLayout<'tcx, Ty<'tcx>>;
2141 /// Trait for contexts that want to be able to compute layouts of types.
2142 /// This automatically gives access to `LayoutOf`, through a blanket `impl`.
2143 pub trait LayoutOfHelpers<'tcx>: HasDataLayout + HasTyCtxt<'tcx> + HasParamEnv<'tcx> {
2144 /// The `TyAndLayout`-wrapping type (or `TyAndLayout` itself), which will be
2145 /// returned from `layout_of` (see also `handle_layout_err`).
2146 type LayoutOfResult: MaybeResult<TyAndLayout<'tcx>>;
2148 /// `Span` to use for `tcx.at(span)`, from `layout_of`.
2149 // FIXME(eddyb) perhaps make this mandatory to get contexts to track it better?
2151 fn layout_tcx_at_span(&self) -> Span {
2155 /// Helper used for `layout_of`, to adapt `tcx.layout_of(...)` into a
2156 /// `Self::LayoutOfResult` (which does not need to be a `Result<...>`).
2158 /// Most `impl`s, which propagate `LayoutError`s, should simply return `err`,
2159 /// but this hook allows e.g. codegen to return only `TyAndLayout` from its
2160 /// `cx.layout_of(...)`, without any `Result<...>` around it to deal with
2161 /// (and any `LayoutError`s are turned into fatal errors or ICEs).
2162 fn handle_layout_err(
2164 err: LayoutError<'tcx>,
2167 ) -> <Self::LayoutOfResult as MaybeResult<TyAndLayout<'tcx>>>::Error;
2170 /// Blanket extension trait for contexts that can compute layouts of types.
2171 pub trait LayoutOf<'tcx>: LayoutOfHelpers<'tcx> {
2172 /// Computes the layout of a type. Note that this implicitly
2173 /// executes in "reveal all" mode, and will normalize the input type.
2175 fn layout_of(&self, ty: Ty<'tcx>) -> Self::LayoutOfResult {
2176 self.spanned_layout_of(ty, DUMMY_SP)
2179 /// Computes the layout of a type, at `span`. Note that this implicitly
2180 /// executes in "reveal all" mode, and will normalize the input type.
2181 // FIXME(eddyb) avoid passing information like this, and instead add more
2182 // `TyCtxt::at`-like APIs to be able to do e.g. `cx.at(span).layout_of(ty)`.
2184 fn spanned_layout_of(&self, ty: Ty<'tcx>, span: Span) -> Self::LayoutOfResult {
2185 let span = if !span.is_dummy() { span } else { self.layout_tcx_at_span() };
2186 let tcx = self.tcx().at(span);
2189 tcx.layout_of(self.param_env().and(ty))
2190 .map_err(|err| self.handle_layout_err(err, span, ty)),
2195 impl<'tcx, C: LayoutOfHelpers<'tcx>> LayoutOf<'tcx> for C {}
2197 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, TyCtxt<'tcx>> {
2198 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2201 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2206 impl<'tcx> LayoutOfHelpers<'tcx> for LayoutCx<'tcx, ty::query::TyCtxtAt<'tcx>> {
2207 type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
2210 fn layout_tcx_at_span(&self) -> Span {
2215 fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
2220 impl<'tcx, C> TyAbiInterface<'tcx, C> for Ty<'tcx>
2222 C: HasTyCtxt<'tcx> + HasParamEnv<'tcx>,
2224 fn ty_and_layout_for_variant(
2225 this: TyAndLayout<'tcx>,
2227 variant_index: VariantIdx,
2228 ) -> TyAndLayout<'tcx> {
2229 let layout = match this.variants {
2230 Variants::Single { index }
2231 // If all variants but one are uninhabited, the variant layout is the enum layout.
2232 if index == variant_index &&
2233 // Don't confuse variants of uninhabited enums with the enum itself.
2234 // For more details see https://github.com/rust-lang/rust/issues/69763.
2235 this.fields != FieldsShape::Primitive =>
2240 Variants::Single { index } => {
2242 let param_env = cx.param_env();
2244 // Deny calling for_variant more than once for non-Single enums.
2245 if let Ok(original_layout) = tcx.layout_of(param_env.and(this.ty)) {
2246 assert_eq!(original_layout.variants, Variants::Single { index });
2249 let fields = match this.ty.kind() {
2250 ty::Adt(def, _) if def.variants.is_empty() =>
2251 bug!("for_variant called on zero-variant enum"),
2252 ty::Adt(def, _) => def.variants[variant_index].fields.len(),
2255 tcx.intern_layout(Layout {
2256 variants: Variants::Single { index: variant_index },
2257 fields: match NonZeroUsize::new(fields) {
2258 Some(fields) => FieldsShape::Union(fields),
2259 None => FieldsShape::Arbitrary { offsets: vec![], memory_index: vec![] },
2261 abi: Abi::Uninhabited,
2262 largest_niche: None,
2263 align: tcx.data_layout.i8_align,
2268 Variants::Multiple { ref variants, .. } => &variants[variant_index],
2271 assert_eq!(layout.variants, Variants::Single { index: variant_index });
2273 TyAndLayout { ty: this.ty, layout }
2276 fn ty_and_layout_field(this: TyAndLayout<'tcx>, cx: &C, i: usize) -> TyAndLayout<'tcx> {
2277 enum TyMaybeWithLayout<'tcx> {
2279 TyAndLayout(TyAndLayout<'tcx>),
2282 fn field_ty_or_layout<'tcx>(
2283 this: TyAndLayout<'tcx>,
2284 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
2286 ) -> TyMaybeWithLayout<'tcx> {
2288 let tag_layout = |tag: Scalar| -> TyAndLayout<'tcx> {
2289 let layout = Layout::scalar(cx, tag);
2290 TyAndLayout { layout: tcx.intern_layout(layout), ty: tag.value.to_ty(tcx) }
2293 match *this.ty.kind() {
2302 | ty::GeneratorWitness(..)
2304 | ty::Dynamic(..) => bug!("TyAndLayout::field({:?}): not applicable", this),
2306 // Potentially-fat pointers.
2307 ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
2308 assert!(i < this.fields.count());
2310 // Reuse the fat `*T` type as its own thin pointer data field.
2311 // This provides information about, e.g., DST struct pointees
2312 // (which may have no non-DST form), and will work as long
2313 // as the `Abi` or `FieldsShape` is checked by users.
2315 let nil = tcx.mk_unit();
2316 let unit_ptr_ty = if this.ty.is_unsafe_ptr() {
2319 tcx.mk_mut_ref(tcx.lifetimes.re_static, nil)
2322 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing
2323 // the `Result` should always work because the type is
2324 // always either `*mut ()` or `&'static mut ()`.
2325 return TyMaybeWithLayout::TyAndLayout(TyAndLayout {
2327 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()
2331 match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() {
2332 ty::Slice(_) | ty::Str => TyMaybeWithLayout::Ty(tcx.types.usize),
2333 ty::Dynamic(_, _) => {
2334 TyMaybeWithLayout::Ty(tcx.mk_imm_ref(
2335 tcx.lifetimes.re_static,
2336 tcx.mk_array(tcx.types.usize, 3),
2338 /* FIXME: use actual fn pointers
2339 Warning: naively computing the number of entries in the
2340 vtable by counting the methods on the trait + methods on
2341 all parent traits does not work, because some methods can
2342 be not object safe and thus excluded from the vtable.
2343 Increase this counter if you tried to implement this but
2344 failed to do it without duplicating a lot of code from
2345 other places in the compiler: 2
2347 tcx.mk_array(tcx.types.usize, 3),
2348 tcx.mk_array(Option<fn()>),
2352 _ => bug!("TyAndLayout::field({:?}): not applicable", this),
2356 // Arrays and slices.
2357 ty::Array(element, _) | ty::Slice(element) => TyMaybeWithLayout::Ty(element),
2358 ty::Str => TyMaybeWithLayout::Ty(tcx.types.u8),
2360 // Tuples, generators and closures.
2361 ty::Closure(_, ref substs) => field_ty_or_layout(
2362 TyAndLayout { ty: substs.as_closure().tupled_upvars_ty(), ..this },
2367 ty::Generator(def_id, ref substs, _) => match this.variants {
2368 Variants::Single { index } => TyMaybeWithLayout::Ty(
2371 .state_tys(def_id, tcx)
2372 .nth(index.as_usize())
2377 Variants::Multiple { tag, tag_field, .. } => {
2379 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2381 TyMaybeWithLayout::Ty(substs.as_generator().prefix_tys().nth(i).unwrap())
2385 ty::Tuple(tys) => TyMaybeWithLayout::Ty(tys[i].expect_ty()),
2388 ty::Adt(def, substs) => {
2389 match this.variants {
2390 Variants::Single { index } => {
2391 TyMaybeWithLayout::Ty(def.variants[index].fields[i].ty(tcx, substs))
2394 // Discriminant field for enums (where applicable).
2395 Variants::Multiple { tag, .. } => {
2397 return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
2404 | ty::Placeholder(..)
2408 | ty::Error(_) => bug!("TyAndLayout::field: unexpected type `{}`", this.ty),
2412 match field_ty_or_layout(this, cx, i) {
2413 TyMaybeWithLayout::Ty(field_ty) => {
2414 cx.tcx().layout_of(cx.param_env().and(field_ty)).unwrap_or_else(|e| {
2416 "failed to get layout for `{}`: {},\n\
2417 despite it being a field (#{}) of an existing layout: {:#?}",
2425 TyMaybeWithLayout::TyAndLayout(field_layout) => field_layout,
2429 fn ty_and_layout_pointee_info_at(
2430 this: TyAndLayout<'tcx>,
2433 ) -> Option<PointeeInfo> {
2435 let param_env = cx.param_env();
2437 let addr_space_of_ty = |ty: Ty<'tcx>| {
2438 if ty.is_fn() { cx.data_layout().instruction_address_space } else { AddressSpace::DATA }
2441 let pointee_info = match *this.ty.kind() {
2442 ty::RawPtr(mt) if offset.bytes() == 0 => {
2443 tcx.layout_of(param_env.and(mt.ty)).ok().map(|layout| PointeeInfo {
2445 align: layout.align.abi,
2447 address_space: addr_space_of_ty(mt.ty),
2450 ty::FnPtr(fn_sig) if offset.bytes() == 0 => {
2451 tcx.layout_of(param_env.and(tcx.mk_fn_ptr(fn_sig))).ok().map(|layout| PointeeInfo {
2453 align: layout.align.abi,
2455 address_space: cx.data_layout().instruction_address_space,
2458 ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
2459 let address_space = addr_space_of_ty(ty);
2460 let kind = if tcx.sess.opts.optimize == OptLevel::No {
2461 // Use conservative pointer kind if not optimizing. This saves us the
2462 // Freeze/Unpin queries, and can save time in the codegen backend (noalias
2463 // attributes in LLVM have compile-time cost even in unoptimized builds).
2467 hir::Mutability::Not => {
2468 if ty.is_freeze(tcx.at(DUMMY_SP), cx.param_env()) {
2474 hir::Mutability::Mut => {
2475 // References to self-referential structures should not be considered
2476 // noalias, as another pointer to the structure can be obtained, that
2477 // is not based-on the original reference. We consider all !Unpin
2478 // types to be potentially self-referential here.
2479 if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) {
2480 PointerKind::UniqueBorrowed
2488 tcx.layout_of(param_env.and(ty)).ok().map(|layout| PointeeInfo {
2490 align: layout.align.abi,
2497 let mut data_variant = match this.variants {
2498 // Within the discriminant field, only the niche itself is
2499 // always initialized, so we only check for a pointer at its
2502 // If the niche is a pointer, it's either valid (according
2503 // to its type), or null (which the niche field's scalar
2504 // validity range encodes). This allows using
2505 // `dereferenceable_or_null` for e.g., `Option<&T>`, and
2506 // this will continue to work as long as we don't start
2507 // using more niches than just null (e.g., the first page of
2508 // the address space, or unaligned pointers).
2509 Variants::Multiple {
2510 tag_encoding: TagEncoding::Niche { dataful_variant, .. },
2513 } if this.fields.offset(tag_field) == offset => {
2514 Some(this.for_variant(cx, dataful_variant))
2519 if let Some(variant) = data_variant {
2520 // We're not interested in any unions.
2521 if let FieldsShape::Union(_) = variant.fields {
2522 data_variant = None;
2526 let mut result = None;
2528 if let Some(variant) = data_variant {
2529 let ptr_end = offset + Pointer.size(cx);
2530 for i in 0..variant.fields.count() {
2531 let field_start = variant.fields.offset(i);
2532 if field_start <= offset {
2533 let field = variant.field(cx, i);
2534 result = field.to_result().ok().and_then(|field| {
2535 if ptr_end <= field_start + field.size {
2536 // We found the right field, look inside it.
2538 field.pointee_info_at(cx, offset - field_start);
2544 if result.is_some() {
2551 // FIXME(eddyb) This should be for `ptr::Unique<T>`, not `Box<T>`.
2552 if let Some(ref mut pointee) = result {
2553 if let ty::Adt(def, _) = this.ty.kind() {
2554 if def.is_box() && offset.bytes() == 0 {
2555 pointee.safe = Some(PointerKind::UniqueOwned);
2565 "pointee_info_at (offset={:?}, type kind: {:?}) => {:?}",
2575 impl<'tcx> ty::Instance<'tcx> {
2576 // NOTE(eddyb) this is private to avoid using it from outside of
2577 // `fn_abi_of_instance` - any other uses are either too high-level
2578 // for `Instance` (e.g. typeck would use `Ty::fn_sig` instead),
2579 // or should go through `FnAbi` instead, to avoid losing any
2580 // adjustments `fn_abi_of_instance` might be performing.
2581 fn fn_sig_for_fn_abi(
2584 param_env: ty::ParamEnv<'tcx>,
2585 ) -> ty::PolyFnSig<'tcx> {
2586 let ty = self.ty(tcx, param_env);
2589 // HACK(davidtwco,eddyb): This is a workaround for polymorphization considering
2590 // parameters unused if they show up in the signature, but not in the `mir::Body`
2591 // (i.e. due to being inside a projection that got normalized, see
2592 // `src/test/ui/polymorphization/normalized_sig_types.rs`), and codegen not keeping
2593 // track of a polymorphization `ParamEnv` to allow normalizing later.
2594 let mut sig = match *ty.kind() {
2595 ty::FnDef(def_id, substs) => tcx
2596 .normalize_erasing_regions(tcx.param_env(def_id), tcx.fn_sig(def_id))
2597 .subst(tcx, substs),
2598 _ => unreachable!(),
2601 if let ty::InstanceDef::VtableShim(..) = self.def {
2602 // Modify `fn(self, ...)` to `fn(self: *mut Self, ...)`.
2603 sig = sig.map_bound(|mut sig| {
2604 let mut inputs_and_output = sig.inputs_and_output.to_vec();
2605 inputs_and_output[0] = tcx.mk_mut_ptr(inputs_and_output[0]);
2606 sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output);
2612 ty::Closure(def_id, substs) => {
2613 let sig = substs.as_closure().sig();
2615 let bound_vars = tcx.mk_bound_variable_kinds(
2618 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2620 let br = ty::BoundRegion {
2621 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2622 kind: ty::BoundRegionKind::BrEnv,
2624 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2625 let env_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
2627 let sig = sig.skip_binder();
2628 ty::Binder::bind_with_vars(
2630 iter::once(env_ty).chain(sig.inputs().iter().cloned()),
2639 ty::Generator(_, substs, _) => {
2640 let sig = substs.as_generator().poly_sig();
2642 let bound_vars = tcx.mk_bound_variable_kinds(
2645 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
2647 let br = ty::BoundRegion {
2648 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
2649 kind: ty::BoundRegionKind::BrEnv,
2651 let env_region = ty::ReLateBound(ty::INNERMOST, br);
2652 let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
2654 let pin_did = tcx.require_lang_item(LangItem::Pin, None);
2655 let pin_adt_ref = tcx.adt_def(pin_did);
2656 let pin_substs = tcx.intern_substs(&[env_ty.into()]);
2657 let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
2659 let sig = sig.skip_binder();
2660 let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
2661 let state_adt_ref = tcx.adt_def(state_did);
2662 let state_substs = tcx.intern_substs(&[sig.yield_ty.into(), sig.return_ty.into()]);
2663 let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);
2664 ty::Binder::bind_with_vars(
2666 [env_ty, sig.resume_ty].iter(),
2669 hir::Unsafety::Normal,
2670 rustc_target::spec::abi::Abi::Rust,
2675 _ => bug!("unexpected type {:?} in Instance::fn_sig", ty),
2680 /// Calculates whether a function's ABI can unwind or not.
2682 /// This takes two primary parameters:
2684 /// * `codegen_fn_attr_flags` - these are flags calculated as part of the
2685 /// codegen attrs for a defined function. For function pointers this set of
2686 /// flags is the empty set. This is only applicable for Rust-defined
2687 /// functions, and generally isn't needed except for small optimizations where
2688 /// we try to say a function which otherwise might look like it could unwind
2689 /// doesn't actually unwind (such as for intrinsics and such).
2691 /// * `abi` - this is the ABI that the function is defined with. This is the
2692 /// primary factor for determining whether a function can unwind or not.
2694 /// Note that in this case unwinding is not necessarily panicking in Rust. Rust
2695 /// panics are implemented with unwinds on most platform (when
2696 /// `-Cpanic=unwind`), but this also accounts for `-Cpanic=abort` build modes.
2697 /// Notably unwinding is disallowed for more non-Rust ABIs unless it's
2698 /// specifically in the name (e.g. `"C-unwind"`). Unwinding within each ABI is
2699 /// defined for each ABI individually, but it always corresponds to some form of
2700 /// stack-based unwinding (the exact mechanism of which varies
2701 /// platform-by-platform).
2703 /// Rust functions are classfied whether or not they can unwind based on the
2704 /// active "panic strategy". In other words Rust functions are considered to
2705 /// unwind in `-Cpanic=unwind` mode and cannot unwind in `-Cpanic=abort` mode.
2706 /// Note that Rust supports intermingling panic=abort and panic=unwind code, but
2707 /// only if the final panic mode is panic=abort. In this scenario any code
2708 /// previously compiled assuming that a function can unwind is still correct, it
2709 /// just never happens to actually unwind at runtime.
2711 /// This function's answer to whether or not a function can unwind is quite
2712 /// impactful throughout the compiler. This affects things like:
2714 /// * Calling a function which can't unwind means codegen simply ignores any
2715 /// associated unwinding cleanup.
2716 /// * Calling a function which can unwind from a function which can't unwind
2717 /// causes the `abort_unwinding_calls` MIR pass to insert a landing pad that
2718 /// aborts the process.
2719 /// * This affects whether functions have the LLVM `nounwind` attribute, which
2720 /// affects various optimizations and codegen.
2722 /// FIXME: this is actually buggy with respect to Rust functions. Rust functions
2723 /// compiled with `-Cpanic=unwind` and referenced from another crate compiled
2724 /// with `-Cpanic=abort` will look like they can't unwind when in fact they
2725 /// might (from a foreign exception or similar).
2727 pub fn fn_can_unwind<'tcx>(
2729 codegen_fn_attr_flags: CodegenFnAttrFlags,
2732 // Special attribute for functions which can't unwind.
2733 if codegen_fn_attr_flags.contains(CodegenFnAttrFlags::NEVER_UNWIND) {
2737 // Otherwise if this isn't special then unwinding is generally determined by
2738 // the ABI of the itself. ABIs like `C` have variants which also
2739 // specifically allow unwinding (`C-unwind`), but not all platform-specific
2740 // ABIs have such an option. Otherwise the only other thing here is Rust
2741 // itself, and those ABIs are determined by the panic strategy configured
2742 // for this compilation.
2744 // Unfortunately at this time there's also another caveat. Rust [RFC
2745 // 2945][rfc] has been accepted and is in the process of being implemented
2746 // and stabilized. In this interim state we need to deal with historical
2747 // rustc behavior as well as plan for future rustc behavior.
2749 // Historically functions declared with `extern "C"` were marked at the
2750 // codegen layer as `nounwind`. This happened regardless of `panic=unwind`
2751 // or not. This is UB for functions in `panic=unwind` mode that then
2752 // actually panic and unwind. Note that this behavior is true for both
2753 // externally declared functions as well as Rust-defined function.
2755 // To fix this UB rustc would like to change in the future to catch unwinds
2756 // from function calls that may unwind within a Rust-defined `extern "C"`
2757 // function and forcibly abort the process, thereby respecting the
2758 // `nounwind` attribut emitted for `extern "C"`. This behavior change isn't
2759 // ready to roll out, so determining whether or not the `C` family of ABIs
2760 // unwinds is conditional not only on their definition but also whether the
2761 // `#![feature(c_unwind)]` feature gate is active.
2763 // Note that this means that unlike historical compilers rustc now, by
2764 // default, unconditionally thinks that the `C` ABI may unwind. This will
2765 // prevent some optimization opportunities, however, so we try to scope this
2766 // change and only assume that `C` unwinds with `panic=unwind` (as opposed
2767 // to `panic=abort`).
2769 // Eventually the check against `c_unwind` here will ideally get removed and
2770 // this'll be a little cleaner as it'll be a straightforward check of the
2773 // [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
2776 C { unwind } | Stdcall { unwind } | System { unwind } | Thiscall { unwind } => {
2778 || (!tcx.features().c_unwind && tcx.sess.panic_strategy() == PanicStrategy::Unwind)
2792 | AvrNonBlockingInterrupt
2793 | CCmseNonSecureCall
2797 | Unadjusted => false,
2798 Rust | RustCall => tcx.sess.panic_strategy() == PanicStrategy::Unwind,
2803 pub fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv {
2804 use rustc_target::spec::abi::Abi::*;
2805 match tcx.sess.target.adjust_abi(abi) {
2806 RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
2808 // It's the ABI's job to select this, not ours.
2809 System { .. } => bug!("system abi should be selected elsewhere"),
2810 EfiApi => bug!("eficall abi should be selected elsewhere"),
2812 Stdcall { .. } => Conv::X86Stdcall,
2813 Fastcall => Conv::X86Fastcall,
2814 Vectorcall => Conv::X86VectorCall,
2815 Thiscall { .. } => Conv::X86ThisCall,
2816 C { .. } => Conv::C,
2817 Unadjusted => Conv::C,
2818 Win64 => Conv::X86_64Win64,
2819 SysV64 => Conv::X86_64SysV,
2820 Aapcs => Conv::ArmAapcs,
2821 CCmseNonSecureCall => Conv::CCmseNonSecureCall,
2822 PtxKernel => Conv::PtxKernel,
2823 Msp430Interrupt => Conv::Msp430Intr,
2824 X86Interrupt => Conv::X86Intr,
2825 AmdGpuKernel => Conv::AmdGpuKernel,
2826 AvrInterrupt => Conv::AvrInterrupt,
2827 AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt,
2830 // These API constants ought to be more specific...
2835 /// Error produced by attempting to compute or adjust a `FnAbi`.
2836 #[derive(Clone, Debug, HashStable)]
2837 pub enum FnAbiError<'tcx> {
2838 /// Error produced by a `layout_of` call, while computing `FnAbi` initially.
2839 Layout(LayoutError<'tcx>),
2841 /// Error produced by attempting to adjust a `FnAbi`, for a "foreign" ABI.
2842 AdjustForForeignAbi(call::AdjustForForeignAbiError),
2845 impl<'tcx> From<LayoutError<'tcx>> for FnAbiError<'tcx> {
2846 fn from(err: LayoutError<'tcx>) -> Self {
2851 impl From<call::AdjustForForeignAbiError> for FnAbiError<'_> {
2852 fn from(err: call::AdjustForForeignAbiError) -> Self {
2853 Self::AdjustForForeignAbi(err)
2857 impl<'tcx> fmt::Display for FnAbiError<'tcx> {
2858 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2860 Self::Layout(err) => err.fmt(f),
2861 Self::AdjustForForeignAbi(err) => err.fmt(f),
2866 // FIXME(eddyb) maybe use something like this for an unified `fn_abi_of`, not
2867 // just for error handling.
2869 pub enum FnAbiRequest<'tcx> {
2870 OfFnPtr { sig: ty::PolyFnSig<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2871 OfInstance { instance: ty::Instance<'tcx>, extra_args: &'tcx ty::List<Ty<'tcx>> },
2874 /// Trait for contexts that want to be able to compute `FnAbi`s.
2875 /// This automatically gives access to `FnAbiOf`, through a blanket `impl`.
2876 pub trait FnAbiOfHelpers<'tcx>: LayoutOfHelpers<'tcx> {
2877 /// The `&FnAbi`-wrapping type (or `&FnAbi` itself), which will be
2878 /// returned from `fn_abi_of_*` (see also `handle_fn_abi_err`).
2879 type FnAbiOfResult: MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>;
2881 /// Helper used for `fn_abi_of_*`, to adapt `tcx.fn_abi_of_*(...)` into a
2882 /// `Self::FnAbiOfResult` (which does not need to be a `Result<...>`).
2884 /// Most `impl`s, which propagate `FnAbiError`s, should simply return `err`,
2885 /// but this hook allows e.g. codegen to return only `&FnAbi` from its
2886 /// `cx.fn_abi_of_*(...)`, without any `Result<...>` around it to deal with
2887 /// (and any `FnAbiError`s are turned into fatal errors or ICEs).
2888 fn handle_fn_abi_err(
2890 err: FnAbiError<'tcx>,
2892 fn_abi_request: FnAbiRequest<'tcx>,
2893 ) -> <Self::FnAbiOfResult as MaybeResult<&'tcx FnAbi<'tcx, Ty<'tcx>>>>::Error;
2896 /// Blanket extension trait for contexts that can compute `FnAbi`s.
2897 pub trait FnAbiOf<'tcx>: FnAbiOfHelpers<'tcx> {
2898 /// Compute a `FnAbi` suitable for indirect calls, i.e. to `fn` pointers.
2900 /// NB: this doesn't handle virtual calls - those should use `fn_abi_of_instance`
2901 /// instead, where the instance is an `InstanceDef::Virtual`.
2903 fn fn_abi_of_fn_ptr(
2905 sig: ty::PolyFnSig<'tcx>,
2906 extra_args: &'tcx ty::List<Ty<'tcx>>,
2907 ) -> Self::FnAbiOfResult {
2908 // FIXME(eddyb) get a better `span` here.
2909 let span = self.layout_tcx_at_span();
2910 let tcx = self.tcx().at(span);
2912 MaybeResult::from(tcx.fn_abi_of_fn_ptr(self.param_env().and((sig, extra_args))).map_err(
2913 |err| self.handle_fn_abi_err(err, span, FnAbiRequest::OfFnPtr { sig, extra_args }),
2917 /// Compute a `FnAbi` suitable for declaring/defining an `fn` instance, and for
2918 /// direct calls to an `fn`.
2920 /// NB: that includes virtual calls, which are represented by "direct calls"
2921 /// to an `InstanceDef::Virtual` instance (of `<dyn Trait as Trait>::fn`).
2923 fn fn_abi_of_instance(
2925 instance: ty::Instance<'tcx>,
2926 extra_args: &'tcx ty::List<Ty<'tcx>>,
2927 ) -> Self::FnAbiOfResult {
2928 // FIXME(eddyb) get a better `span` here.
2929 let span = self.layout_tcx_at_span();
2930 let tcx = self.tcx().at(span);
2933 tcx.fn_abi_of_instance(self.param_env().and((instance, extra_args))).map_err(|err| {
2934 // HACK(eddyb) at least for definitions of/calls to `Instance`s,
2935 // we can get some kind of span even if one wasn't provided.
2936 // However, we don't do this early in order to avoid calling
2937 // `def_span` unconditionally (which may have a perf penalty).
2938 let span = if !span.is_dummy() { span } else { tcx.def_span(instance.def_id()) };
2939 self.handle_fn_abi_err(err, span, FnAbiRequest::OfInstance { instance, extra_args })
2945 impl<'tcx, C: FnAbiOfHelpers<'tcx>> FnAbiOf<'tcx> for C {}
2947 fn fn_abi_of_fn_ptr<'tcx>(
2949 query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2950 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2951 let (param_env, (sig, extra_args)) = query.into_parts();
2953 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
2957 CodegenFnAttrFlags::empty(),
2962 fn fn_abi_of_instance<'tcx>(
2964 query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
2965 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2966 let (param_env, (instance, extra_args)) = query.into_parts();
2968 let sig = instance.fn_sig_for_fn_abi(tcx, param_env);
2970 let caller_location = if instance.def.requires_caller_location(tcx) {
2971 Some(tcx.caller_location_ty())
2976 let attrs = tcx.codegen_fn_attrs(instance.def_id()).flags;
2978 LayoutCx { tcx, param_env }.fn_abi_new_uncached(
2983 matches!(instance.def, ty::InstanceDef::Virtual(..)),
2987 impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
2988 // FIXME(eddyb) perhaps group the signature/type-containing (or all of them?)
2989 // arguments of this method, into a separate `struct`.
2990 fn fn_abi_new_uncached(
2992 sig: ty::PolyFnSig<'tcx>,
2993 extra_args: &[Ty<'tcx>],
2994 caller_location: Option<Ty<'tcx>>,
2995 codegen_fn_attr_flags: CodegenFnAttrFlags,
2996 // FIXME(eddyb) replace this with something typed, like an `enum`.
2997 force_thin_self_ptr: bool,
2998 ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, FnAbiError<'tcx>> {
2999 debug!("fn_abi_new_uncached({:?}, {:?})", sig, extra_args);
3001 let sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, sig);
3003 let conv = conv_from_spec_abi(self.tcx(), sig.abi);
3005 let mut inputs = sig.inputs();
3006 let extra_args = if sig.abi == RustCall {
3007 assert!(!sig.c_variadic && extra_args.is_empty());
3009 if let Some(input) = sig.inputs().last() {
3010 if let ty::Tuple(tupled_arguments) = input.kind() {
3011 inputs = &sig.inputs()[0..sig.inputs().len() - 1];
3012 tupled_arguments.iter().map(|k| k.expect_ty()).collect()
3015 "argument to function with \"rust-call\" ABI \
3021 "argument to function with \"rust-call\" ABI \
3026 assert!(sig.c_variadic || extra_args.is_empty());
3030 let target = &self.tcx.sess.target;
3031 let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc");
3032 let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu";
3033 let linux_s390x_gnu_like =
3034 target.os == "linux" && target.arch == "s390x" && target_env_gnu_like;
3035 let linux_sparc64_gnu_like =
3036 target.os == "linux" && target.arch == "sparc64" && target_env_gnu_like;
3037 let linux_powerpc_gnu_like =
3038 target.os == "linux" && target.arch == "powerpc" && target_env_gnu_like;
3040 let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall);
3042 // Handle safe Rust thin and fat pointers.
3043 let adjust_for_rust_scalar = |attrs: &mut ArgAttributes,
3045 layout: TyAndLayout<'tcx>,
3048 // Booleans are always an i1 that needs to be zero-extended.
3049 if scalar.is_bool() {
3050 attrs.ext(ArgExtension::Zext);
3054 // Only pointer types handled below.
3055 if scalar.value != Pointer {
3059 if !scalar.valid_range.contains(0) {
3060 attrs.set(ArgAttribute::NonNull);
3063 if let Some(pointee) = layout.pointee_info_at(self, offset) {
3064 if let Some(kind) = pointee.safe {
3065 attrs.pointee_align = Some(pointee.align);
3067 // `Box` (`UniqueBorrowed`) are not necessarily dereferenceable
3068 // for the entire duration of the function as they can be deallocated
3069 // at any time. Set their valid size to 0.
3070 attrs.pointee_size = match kind {
3071 PointerKind::UniqueOwned => Size::ZERO,
3075 // `Box` pointer parameters never alias because ownership is transferred
3076 // `&mut` pointer parameters never alias other parameters,
3077 // or mutable global data
3079 // `&T` where `T` contains no `UnsafeCell<U>` is immutable,
3080 // and can be marked as both `readonly` and `noalias`, as
3081 // LLVM's definition of `noalias` is based solely on memory
3082 // dependencies rather than pointer equality
3084 // Due to past miscompiles in LLVM, we apply a separate NoAliasMutRef attribute
3085 // for UniqueBorrowed arguments, so that the codegen backend can decide whether
3086 // or not to actually emit the attribute. It can also be controlled with the
3087 // `-Zmutable-noalias` debugging option.
3088 let no_alias = match kind {
3089 PointerKind::Shared | PointerKind::UniqueBorrowed => false,
3090 PointerKind::UniqueOwned => true,
3091 PointerKind::Frozen => !is_return,
3094 attrs.set(ArgAttribute::NoAlias);
3097 if kind == PointerKind::Frozen && !is_return {
3098 attrs.set(ArgAttribute::ReadOnly);
3101 if kind == PointerKind::UniqueBorrowed && !is_return {
3102 attrs.set(ArgAttribute::NoAliasMutRef);
3108 let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, FnAbiError<'tcx>> {
3109 let is_return = arg_idx.is_none();
3111 let layout = self.layout_of(ty)?;
3112 let layout = if force_thin_self_ptr && arg_idx == Some(0) {
3113 // Don't pass the vtable, it's not an argument of the virtual fn.
3114 // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait`
3115 // or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen
3116 make_thin_self_ptr(self, layout)
3121 let mut arg = ArgAbi::new(self, layout, |layout, scalar, offset| {
3122 let mut attrs = ArgAttributes::new();
3123 adjust_for_rust_scalar(&mut attrs, scalar, *layout, offset, is_return);
3127 if arg.layout.is_zst() {
3128 // For some forsaken reason, x86_64-pc-windows-gnu
3129 // doesn't ignore zero-sized struct arguments.
3130 // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}.
3134 && !linux_s390x_gnu_like
3135 && !linux_sparc64_gnu_like
3136 && !linux_powerpc_gnu_like)
3138 arg.mode = PassMode::Ignore;
3145 let mut fn_abi = FnAbi {
3146 ret: arg_of(sig.output(), None)?,
3151 .chain(caller_location)
3153 .map(|(i, ty)| arg_of(ty, Some(i)))
3154 .collect::<Result<_, _>>()?,
3155 c_variadic: sig.c_variadic,
3156 fixed_count: inputs.len(),
3158 can_unwind: fn_can_unwind(self.tcx(), codegen_fn_attr_flags, sig.abi),
3160 self.fn_abi_adjust_for_abi(&mut fn_abi, sig.abi)?;
3161 debug!("fn_abi_new_uncached = {:?}", fn_abi);
3162 Ok(self.tcx.arena.alloc(fn_abi))
3165 fn fn_abi_adjust_for_abi(
3167 fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>,
3169 ) -> Result<(), FnAbiError<'tcx>> {
3170 if abi == SpecAbi::Unadjusted {
3174 if abi == SpecAbi::Rust
3175 || abi == SpecAbi::RustCall
3176 || abi == SpecAbi::RustIntrinsic
3177 || abi == SpecAbi::PlatformIntrinsic
3179 let fixup = |arg: &mut ArgAbi<'tcx, Ty<'tcx>>| {
3180 if arg.is_ignore() {
3184 match arg.layout.abi {
3185 Abi::Aggregate { .. } => {}
3187 // This is a fun case! The gist of what this is doing is
3188 // that we want callers and callees to always agree on the
3189 // ABI of how they pass SIMD arguments. If we were to *not*
3190 // make these arguments indirect then they'd be immediates
3191 // in LLVM, which means that they'd used whatever the
3192 // appropriate ABI is for the callee and the caller. That
3193 // means, for example, if the caller doesn't have AVX
3194 // enabled but the callee does, then passing an AVX argument
3195 // across this boundary would cause corrupt data to show up.
3197 // This problem is fixed by unconditionally passing SIMD
3198 // arguments through memory between callers and callees
3199 // which should get them all to agree on ABI regardless of
3200 // target feature sets. Some more information about this
3201 // issue can be found in #44367.
3203 // Note that the platform intrinsic ABI is exempt here as
3204 // that's how we connect up to LLVM and it's unstable
3205 // anyway, we control all calls to it in libstd.
3207 if abi != SpecAbi::PlatformIntrinsic
3208 && self.tcx.sess.target.simd_types_indirect =>
3210 arg.make_indirect();
3217 // Pass and return structures up to 2 pointers in size by value, matching `ScalarPair`.
3218 // LLVM will usually pass these in 2 registers, which is more efficient than by-ref.
3219 let max_by_val_size = Pointer.size(self) * 2;
3220 let size = arg.layout.size;
3222 if arg.layout.is_unsized() || size > max_by_val_size {
3223 arg.make_indirect();
3225 // We want to pass small aggregates as immediates, but using
3226 // a LLVM aggregate type for this leads to bad optimizations,
3227 // so we pick an appropriately sized integer type instead.
3228 arg.cast_to(Reg { kind: RegKind::Integer, size });
3231 fixup(&mut fn_abi.ret);
3232 for arg in &mut fn_abi.args {
3236 fn_abi.adjust_for_foreign_abi(self, abi)?;
3243 fn make_thin_self_ptr<'tcx>(
3244 cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>),
3245 layout: TyAndLayout<'tcx>,
3246 ) -> TyAndLayout<'tcx> {
3248 let fat_pointer_ty = if layout.is_unsized() {
3249 // unsized `self` is passed as a pointer to `self`
3250 // FIXME (mikeyhew) change this to use &own if it is ever added to the language
3251 tcx.mk_mut_ptr(layout.ty)
3254 Abi::ScalarPair(..) => (),
3255 _ => bug!("receiver type has unsupported layout: {:?}", layout),
3258 // In the case of Rc<Self>, we need to explicitly pass a *mut RcBox<Self>
3259 // with a Scalar (not ScalarPair) ABI. This is a hack that is understood
3260 // elsewhere in the compiler as a method on a `dyn Trait`.
3261 // To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we
3262 // get a built-in pointer type
3263 let mut fat_pointer_layout = layout;
3264 'descend_newtypes: while !fat_pointer_layout.ty.is_unsafe_ptr()
3265 && !fat_pointer_layout.ty.is_region_ptr()
3267 for i in 0..fat_pointer_layout.fields.count() {
3268 let field_layout = fat_pointer_layout.field(cx, i);
3270 if !field_layout.is_zst() {
3271 fat_pointer_layout = field_layout;
3272 continue 'descend_newtypes;
3276 bug!("receiver has no non-zero-sized fields {:?}", fat_pointer_layout);
3279 fat_pointer_layout.ty
3282 // we now have a type like `*mut RcBox<dyn Trait>`
3283 // change its layout to that of `*mut ()`, a thin pointer, but keep the same type
3284 // this is understood as a special case elsewhere in the compiler
3285 let unit_ptr_ty = tcx.mk_mut_ptr(tcx.mk_unit());
3290 // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result`
3291 // should always work because the type is always `*mut ()`.
3292 ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap()