1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 pub use self::Integer::*;
12 pub use self::Layout::*;
13 pub use self::Primitive::*;
18 use ty::{self, Ty, TyCtxt, TypeFoldable, ReprOptions};
20 use syntax::ast::{FloatTy, IntTy, UintTy};
22 use syntax_pos::DUMMY_SP;
29 /// Parsed [Data layout](http://llvm.org/docs/LangRef.html#data-layout)
30 /// for a target, which contains everything needed to compute layouts.
31 pub struct TargetDataLayout {
38 pub i128_align: Align,
41 pub pointer_size: Size,
42 pub pointer_align: Align,
43 pub aggregate_align: Align,
45 /// Alignments for vector types.
46 pub vector_align: Vec<(Size, Align)>
49 impl Default for TargetDataLayout {
50 /// Creates an instance of `TargetDataLayout`.
51 fn default() -> TargetDataLayout {
54 i1_align: Align::from_bits(8, 8).unwrap(),
55 i8_align: Align::from_bits(8, 8).unwrap(),
56 i16_align: Align::from_bits(16, 16).unwrap(),
57 i32_align: Align::from_bits(32, 32).unwrap(),
58 i64_align: Align::from_bits(32, 64).unwrap(),
59 i128_align: Align::from_bits(32, 64).unwrap(),
60 f32_align: Align::from_bits(32, 32).unwrap(),
61 f64_align: Align::from_bits(64, 64).unwrap(),
62 pointer_size: Size::from_bits(64),
63 pointer_align: Align::from_bits(64, 64).unwrap(),
64 aggregate_align: Align::from_bits(0, 64).unwrap(),
66 (Size::from_bits(64), Align::from_bits(64, 64).unwrap()),
67 (Size::from_bits(128), Align::from_bits(128, 128).unwrap())
73 impl TargetDataLayout {
74 pub fn parse(sess: &Session) -> TargetDataLayout {
75 // Parse a bit count from a string.
76 let parse_bits = |s: &str, kind: &str, cause: &str| {
77 s.parse::<u64>().unwrap_or_else(|err| {
78 sess.err(&format!("invalid {} `{}` for `{}` in \"data-layout\": {}",
79 kind, s, cause, err));
84 // Parse a size string.
85 let size = |s: &str, cause: &str| {
86 Size::from_bits(parse_bits(s, "size", cause))
89 // Parse an alignment string.
90 let align = |s: &[&str], cause: &str| {
92 sess.err(&format!("missing alignment for `{}` in \"data-layout\"", cause));
94 let abi = parse_bits(s[0], "alignment", cause);
95 let pref = s.get(1).map_or(abi, |pref| parse_bits(pref, "alignment", cause));
96 Align::from_bits(abi, pref).unwrap_or_else(|err| {
97 sess.err(&format!("invalid alignment for `{}` in \"data-layout\": {}",
99 Align::from_bits(8, 8).unwrap()
103 let mut dl = TargetDataLayout::default();
104 let mut i128_align_src = 64;
105 for spec in sess.target.target.data_layout.split("-") {
106 match &spec.split(":").collect::<Vec<_>>()[..] {
107 &["e"] => dl.endian = Endian::Little,
108 &["E"] => dl.endian = Endian::Big,
109 &["a", ref a..] => dl.aggregate_align = align(a, "a"),
110 &["f32", ref a..] => dl.f32_align = align(a, "f32"),
111 &["f64", ref a..] => dl.f64_align = align(a, "f64"),
112 &[p @ "p", s, ref a..] | &[p @ "p0", s, ref a..] => {
113 dl.pointer_size = size(s, p);
114 dl.pointer_align = align(a, p);
116 &[s, ref a..] if s.starts_with("i") => {
117 let bits = match s[1..].parse::<u64>() {
120 size(&s[1..], "i"); // For the user error.
126 1 => dl.i1_align = a,
127 8 => dl.i8_align = a,
128 16 => dl.i16_align = a,
129 32 => dl.i32_align = a,
130 64 => dl.i64_align = a,
133 if bits >= i128_align_src && bits <= 128 {
134 // Default alignment for i128 is decided by taking the alignment of
135 // largest-sized i{64...128}.
136 i128_align_src = bits;
140 &[s, ref a..] if s.starts_with("v") => {
141 let v_size = size(&s[1..], "v");
143 if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
147 // No existing entry, add a new one.
148 dl.vector_align.push((v_size, a));
150 _ => {} // Ignore everything else.
154 // Perform consistency checks against the Target information.
155 let endian_str = match dl.endian {
156 Endian::Little => "little",
159 if endian_str != sess.target.target.target_endian {
160 sess.err(&format!("inconsistent target specification: \"data-layout\" claims \
161 architecture is {}-endian, while \"target-endian\" is `{}`",
162 endian_str, sess.target.target.target_endian));
165 if dl.pointer_size.bits().to_string() != sess.target.target.target_pointer_width {
166 sess.err(&format!("inconsistent target specification: \"data-layout\" claims \
167 pointers are {}-bit, while \"target-pointer-width\" is `{}`",
168 dl.pointer_size.bits(), sess.target.target.target_pointer_width));
174 /// Return exclusive upper bound on object size.
176 /// The theoretical maximum object size is defined as the maximum positive `isize` value.
177 /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
178 /// index every address within an object along with one byte past the end, along with allowing
179 /// `isize` to store the difference between any two pointers into an object.
181 /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
182 /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
183 /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
184 /// address space on 64-bit ARMv8 and x86_64.
185 pub fn obj_size_bound(&self) -> u64 {
186 match self.pointer_size.bits() {
190 bits => bug!("obj_size_bound: unknown pointer bit size {}", bits)
194 pub fn ptr_sized_integer(&self) -> Integer {
195 match self.pointer_size.bits() {
199 bits => bug!("ptr_sized_integer: unknown pointer bit size {}", bits)
204 /// Endianness of the target, which must match cfg(target-endian).
205 #[derive(Copy, Clone)]
211 /// Size of a type in bytes.
212 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
218 pub fn from_bits(bits: u64) -> Size {
219 Size::from_bytes((bits + 7) / 8)
222 pub fn from_bytes(bytes: u64) -> Size {
223 if bytes >= (1 << 61) {
224 bug!("Size::from_bytes: {} bytes in bits doesn't fit in u64", bytes)
231 pub fn bytes(self) -> u64 {
235 pub fn bits(self) -> u64 {
239 pub fn abi_align(self, align: Align) -> Size {
240 let mask = align.abi() - 1;
241 Size::from_bytes((self.bytes() + mask) & !mask)
244 pub fn checked_add(self, offset: Size, dl: &TargetDataLayout) -> Option<Size> {
245 // Each Size is less than dl.obj_size_bound(), so the sum is
246 // also less than 1 << 62 (and therefore can't overflow).
247 let bytes = self.bytes() + offset.bytes();
249 if bytes < dl.obj_size_bound() {
250 Some(Size::from_bytes(bytes))
256 pub fn checked_mul(self, count: u64, dl: &TargetDataLayout) -> Option<Size> {
257 // Each Size is less than dl.obj_size_bound(), so the sum is
258 // also less than 1 << 62 (and therefore can't overflow).
259 match self.bytes().checked_mul(count) {
260 Some(bytes) if bytes < dl.obj_size_bound() => {
261 Some(Size::from_bytes(bytes))
268 /// Alignment of a type in bytes, both ABI-mandated and preferred.
269 /// Since alignments are always powers of 2, we can pack both in one byte,
270 /// giving each a nibble (4 bits) for a maximum alignment of 2<sup>15</sup> = 32768.
271 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
277 pub fn from_bits(abi: u64, pref: u64) -> Result<Align, String> {
278 Align::from_bytes((abi + 7) / 8, (pref + 7) / 8)
281 pub fn from_bytes(abi: u64, pref: u64) -> Result<Align, String> {
282 let pack = |align: u64| {
283 // Treat an alignment of 0 bytes like 1-byte alignment.
288 let mut bytes = align;
290 while (bytes & 1) == 0 {
295 Err(format!("`{}` is not a power of 2", align))
296 } else if pow > 0x0f {
297 Err(format!("`{}` is too large", align))
304 raw: pack(abi)? | (pack(pref)? << 4)
308 pub fn abi(self) -> u64 {
309 1 << (self.raw & 0xf)
312 pub fn pref(self) -> u64 {
316 pub fn min(self, other: Align) -> Align {
317 let abi = cmp::min(self.raw & 0x0f, other.raw & 0x0f);
318 let pref = cmp::min(self.raw & 0xf0, other.raw & 0xf0);
324 pub fn max(self, other: Align) -> Align {
325 let abi = cmp::max(self.raw & 0x0f, other.raw & 0x0f);
326 let pref = cmp::max(self.raw & 0xf0, other.raw & 0xf0);
333 /// Integers, also used for enum discriminants.
334 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
345 pub fn size(&self) -> Size {
347 I1 => Size::from_bits(1),
348 I8 => Size::from_bytes(1),
349 I16 => Size::from_bytes(2),
350 I32 => Size::from_bytes(4),
351 I64 => Size::from_bytes(8),
352 I128 => Size::from_bytes(16),
356 pub fn align(&self, dl: &TargetDataLayout)-> Align {
363 I128 => dl.i128_align,
367 pub fn to_ty<'a, 'tcx>(&self, tcx: &ty::TyCtxt<'a, 'tcx, 'tcx>,
368 signed: bool) -> Ty<'tcx> {
369 match (*self, signed) {
370 (I1, false) => tcx.types.u8,
371 (I8, false) => tcx.types.u8,
372 (I16, false) => tcx.types.u16,
373 (I32, false) => tcx.types.u32,
374 (I64, false) => tcx.types.u64,
375 (I128, false) => tcx.types.u128,
376 (I1, true) => tcx.types.i8,
377 (I8, true) => tcx.types.i8,
378 (I16, true) => tcx.types.i16,
379 (I32, true) => tcx.types.i32,
380 (I64, true) => tcx.types.i64,
381 (I128, true) => tcx.types.i128,
385 /// Find the smallest Integer type which can represent the signed value.
386 pub fn fit_signed(x: i64) -> Integer {
388 -0x0000_0000_0000_0001...0x0000_0000_0000_0000 => I1,
389 -0x0000_0000_0000_0080...0x0000_0000_0000_007f => I8,
390 -0x0000_0000_0000_8000...0x0000_0000_0000_7fff => I16,
391 -0x0000_0000_8000_0000...0x0000_0000_7fff_ffff => I32,
392 -0x8000_0000_0000_0000...0x7fff_ffff_ffff_ffff => I64,
397 /// Find the smallest Integer type which can represent the unsigned value.
398 pub fn fit_unsigned(x: u64) -> Integer {
400 0...0x0000_0000_0000_0001 => I1,
401 0...0x0000_0000_0000_00ff => I8,
402 0...0x0000_0000_0000_ffff => I16,
403 0...0x0000_0000_ffff_ffff => I32,
404 0...0xffff_ffff_ffff_ffff => I64,
409 /// Find the smallest integer with the given alignment.
410 pub fn for_abi_align(dl: &TargetDataLayout, align: Align) -> Option<Integer> {
411 let wanted = align.abi();
412 for &candidate in &[I8, I16, I32, I64] {
413 let ty = Int(candidate);
414 if wanted == ty.align(dl).abi() && wanted == ty.size(dl).bytes() {
415 return Some(candidate);
421 /// Get the Integer type from an attr::IntType.
422 pub fn from_attr(dl: &TargetDataLayout, ity: attr::IntType) -> Integer {
424 attr::SignedInt(IntTy::I8) | attr::UnsignedInt(UintTy::U8) => I8,
425 attr::SignedInt(IntTy::I16) | attr::UnsignedInt(UintTy::U16) => I16,
426 attr::SignedInt(IntTy::I32) | attr::UnsignedInt(UintTy::U32) => I32,
427 attr::SignedInt(IntTy::I64) | attr::UnsignedInt(UintTy::U64) => I64,
428 attr::SignedInt(IntTy::I128) | attr::UnsignedInt(UintTy::U128) => I128,
429 attr::SignedInt(IntTy::Is) | attr::UnsignedInt(UintTy::Us) => {
430 dl.ptr_sized_integer()
435 /// Find the appropriate Integer type and signedness for the given
436 /// signed discriminant range and #[repr] attribute.
437 /// N.B.: u64 values above i64::MAX will be treated as signed, but
438 /// that shouldn't affect anything, other than maybe debuginfo.
439 fn repr_discr(tcx: TyCtxt, ty: Ty, repr: &ReprOptions, min: i64, max: i64)
441 // Theoretically, negative values could be larger in unsigned representation
442 // than the unsigned representation of the signed minimum. However, if there
443 // are any negative values, the only valid unsigned representation is u64
444 // which can fit all i64 values, so the result remains unaffected.
445 let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u64, max as u64));
446 let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
448 let mut min_from_extern = None;
449 let min_default = I8;
451 if let Some(ity) = repr.int {
452 let discr = Integer::from_attr(&tcx.data_layout, ity);
453 let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
455 bug!("Integer::repr_discr: `#[repr]` hint too small for \
456 discriminant range of enum `{}", ty)
458 return (discr, ity.is_signed());
462 match &tcx.sess.target.target.arch[..] {
463 // WARNING: the ARM EABI has two variants; the one corresponding
464 // to `at_least == I32` appears to be used on Linux and NetBSD,
465 // but some systems may use the variant corresponding to no
466 // lower bound. However, we don't run on those yet...?
467 "arm" => min_from_extern = Some(I32),
468 _ => min_from_extern = Some(I32),
472 let at_least = min_from_extern.unwrap_or(min_default);
474 // If there are no negative values, we can use the unsigned fit.
476 (cmp::max(unsigned_fit, at_least), false)
478 (cmp::max(signed_fit, at_least), true)
483 /// Fundamental unit of memory access and layout.
484 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
493 pub fn size(self, dl: &TargetDataLayout) -> Size {
495 Int(I1) | Int(I8) => Size::from_bits(8),
496 Int(I16) => Size::from_bits(16),
497 Int(I32) | F32 => Size::from_bits(32),
498 Int(I64) | F64 => Size::from_bits(64),
499 Int(I128) => Size::from_bits(128),
500 Pointer => dl.pointer_size
504 pub fn align(self, dl: &TargetDataLayout) -> Align {
506 Int(I1) => dl.i1_align,
507 Int(I8) => dl.i8_align,
508 Int(I16) => dl.i16_align,
509 Int(I32) => dl.i32_align,
510 Int(I64) => dl.i64_align,
511 Int(I128) => dl.i128_align,
514 Pointer => dl.pointer_align
519 /// Path through fields of nested structures.
520 // FIXME(eddyb) use small vector optimization for the common case.
521 pub type FieldPath = Vec<u32>;
523 /// A structure, a product type in ADT terms.
524 #[derive(PartialEq, Eq, Hash, Debug)]
528 /// If true, no alignment padding is used.
531 /// If true, the size is exact, otherwise it's only a lower bound.
534 /// Offsets for the first byte of each field, ordered to match the source definition order.
535 /// This vector does not go in increasing order.
536 /// FIXME(eddyb) use small vector optimization for the common case.
537 pub offsets: Vec<Size>,
539 /// Maps source order field indices to memory order indices, depending how fields were permuted.
540 /// FIXME (camlorn) also consider small vector optimization here.
541 pub memory_index: Vec<u32>,
546 // Info required to optimize struct layout.
547 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
549 // A tuple, closure, or univariant which cannot be coerced to unsized.
550 AlwaysSizedUnivariant,
551 // A univariant, the last field of which may be coerced to unsized.
552 MaybeUnsizedUnivariant,
553 // A univariant, but part of an enum.
557 impl<'a, 'gcx, 'tcx> Struct {
558 // FIXME(camlorn): reprs need a better representation to deal with multiple reprs on one type.
559 fn new(dl: &TargetDataLayout, fields: &Vec<&'a Layout>,
560 repr: &ReprOptions, kind: StructKind,
561 scapegoat: Ty<'gcx>) -> Result<Struct, LayoutError<'gcx>> {
562 let packed = repr.packed;
563 let mut ret = Struct {
564 align: if packed { dl.i8_align } else { dl.aggregate_align },
568 memory_index: vec![],
569 min_size: Size::from_bytes(0),
572 // Anything with repr(C) or repr(packed) doesn't optimize.
573 // Neither do 1-member and 2-member structs.
574 // In addition, code in trans assume that 2-element structs can become pairs.
575 // It's easier to just short-circuit here.
576 let mut can_optimize = (fields.len() > 2 || StructKind::EnumVariant == kind)
577 && ! (repr.c || repr.packed);
579 // Disable field reordering until we can decide what to do.
580 // The odd pattern here avoids a warning about the value never being read.
581 if can_optimize { can_optimize = false; }
583 let (optimize, sort_ascending) = match kind {
584 StructKind::AlwaysSizedUnivariant => (can_optimize, false),
585 StructKind::MaybeUnsizedUnivariant => (can_optimize, false),
586 StructKind::EnumVariant => {
587 assert!(fields.len() >= 1, "Enum variants must have discriminants.");
588 (can_optimize && fields[0].size(dl).bytes() == 1, true)
592 ret.offsets = vec![Size::from_bytes(0); fields.len()];
593 let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
596 let start = if let StructKind::EnumVariant = kind { 1 } else { 0 };
597 let end = if let StructKind::MaybeUnsizedUnivariant = kind {
603 let optimizing = &mut inverse_memory_index[start..end];
605 optimizing.sort_by_key(|&x| fields[x as usize].align(dl).abi());
607 optimizing.sort_by(| &a, &b | {
608 let a = fields[a as usize].align(dl).abi();
609 let b = fields[b as usize].align(dl).abi();
616 // inverse_memory_index holds field indices by increasing memory offset.
617 // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
618 // We now write field offsets to the corresponding offset slot;
619 // field 5 with offset 0 puts 0 in offsets[5].
620 // At the bottom of this function, we use inverse_memory_index to produce memory_index.
622 if let StructKind::EnumVariant = kind {
623 assert_eq!(inverse_memory_index[0], 0,
624 "Enum variant discriminants must have the lowest offset.");
627 let mut offset = Size::from_bytes(0);
629 for i in inverse_memory_index.iter() {
630 let field = fields[*i as usize];
632 bug!("Struct::new: field #{} of `{}` comes after unsized field",
633 ret.offsets.len(), scapegoat);
636 if field.is_unsized() {
640 // Invariant: offset < dl.obj_size_bound() <= 1<<61
642 let align = field.align(dl);
643 ret.align = ret.align.max(align);
644 offset = offset.abi_align(align);
647 debug!("Struct::new offset: {:?} field: {:?} {:?}", offset, field, field.size(dl));
648 ret.offsets[*i as usize] = offset;
650 offset = offset.checked_add(field.size(dl), dl)
651 .map_or(Err(LayoutError::SizeOverflow(scapegoat)), Ok)?;
655 debug!("Struct::new min_size: {:?}", offset);
656 ret.min_size = offset;
658 // As stated above, inverse_memory_index holds field indices by increasing offset.
659 // This makes it an already-sorted view of the offsets vec.
660 // To invert it, consider:
661 // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
662 // Field 5 would be the first element, so memory_index is i:
663 // Note: if we didn't optimize, it's already right.
666 ret.memory_index = vec![0; inverse_memory_index.len()];
668 for i in 0..inverse_memory_index.len() {
669 ret.memory_index[inverse_memory_index[i] as usize] = i as u32;
672 ret.memory_index = inverse_memory_index;
678 /// Get the size with trailing alignment padding.
679 pub fn stride(&self) -> Size {
680 self.min_size.abi_align(self.align)
683 /// Determine whether a structure would be zero-sized, given its fields.
684 pub fn would_be_zero_sized<I>(dl: &TargetDataLayout, fields: I)
685 -> Result<bool, LayoutError<'gcx>>
686 where I: Iterator<Item=Result<&'a Layout, LayoutError<'gcx>>> {
687 for field in fields {
689 if field.is_unsized() || field.size(dl).bytes() > 0 {
696 /// Get indices of the tys that made this struct by increasing offset.
698 pub fn field_index_by_increasing_offset<'b>(&'b self) -> impl iter::Iterator<Item=usize>+'b {
699 let mut inverse_small = [0u8; 64];
700 let mut inverse_big = vec![];
701 let use_small = self.memory_index.len() <= inverse_small.len();
703 // We have to write this logic twice in order to keep the array small.
705 for i in 0..self.memory_index.len() {
706 inverse_small[self.memory_index[i] as usize] = i as u8;
709 inverse_big = vec![0; self.memory_index.len()];
710 for i in 0..self.memory_index.len() {
711 inverse_big[self.memory_index[i] as usize] = i as u32;
715 (0..self.memory_index.len()).map(move |i| {
716 if use_small { inverse_small[i] as usize }
717 else { inverse_big[i] as usize }
721 /// Find the path leading to a non-zero leaf field, starting from
722 /// the given type and recursing through aggregates.
723 /// The tuple is `(path, source_path)`,
724 /// where `path` is in memory order and `source_path` in source order.
725 // FIXME(eddyb) track value ranges and traverse already optimized enums.
726 fn non_zero_field_in_type(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
728 -> Result<Option<(FieldPath, FieldPath)>, LayoutError<'gcx>> {
729 let tcx = infcx.tcx.global_tcx();
730 match (ty.layout(infcx)?, &ty.sty) {
731 (&Scalar { non_zero: true, .. }, _) |
732 (&CEnum { non_zero: true, .. }, _) => Ok(Some((vec![], vec![]))),
733 (&FatPointer { non_zero: true, .. }, _) => {
734 Ok(Some((vec![FAT_PTR_ADDR as u32], vec![FAT_PTR_ADDR as u32])))
737 // Is this the NonZero lang item wrapping a pointer or integer type?
738 (&Univariant { non_zero: true, .. }, &ty::TyAdt(def, substs)) => {
739 let fields = &def.struct_variant().fields;
740 assert_eq!(fields.len(), 1);
741 match *fields[0].ty(tcx, substs).layout(infcx)? {
742 // FIXME(eddyb) also allow floating-point types here.
743 Scalar { value: Int(_), non_zero: false } |
744 Scalar { value: Pointer, non_zero: false } => {
745 Ok(Some((vec![0], vec![0])))
747 FatPointer { non_zero: false, .. } => {
748 let tmp = vec![FAT_PTR_ADDR as u32, 0];
749 Ok(Some((tmp.clone(), tmp)))
755 // Perhaps one of the fields of this struct is non-zero
756 // let's recurse and find out
757 (&Univariant { ref variant, .. }, &ty::TyAdt(def, substs)) if def.is_struct() => {
758 Struct::non_zero_field_paths(infcx, def.struct_variant().fields
759 .iter().map(|field| {
760 field.ty(tcx, substs)
762 Some(&variant.memory_index[..]))
765 // Perhaps one of the upvars of this closure is non-zero
766 (&Univariant { ref variant, .. }, &ty::TyClosure(def, substs)) => {
767 let upvar_tys = substs.upvar_tys(def, tcx);
768 Struct::non_zero_field_paths(infcx, upvar_tys,
769 Some(&variant.memory_index[..]))
771 // Can we use one of the fields in this tuple?
772 (&Univariant { ref variant, .. }, &ty::TyTuple(tys, _)) => {
773 Struct::non_zero_field_paths(infcx, tys.iter().cloned(),
774 Some(&variant.memory_index[..]))
777 // Is this a fixed-size array of something non-zero
778 // with at least one element?
779 (_, &ty::TyArray(ety, d)) if d > 0 => {
780 Struct::non_zero_field_paths(infcx, Some(ety).into_iter(), None)
783 (_, &ty::TyProjection(_)) | (_, &ty::TyAnon(..)) => {
784 let normalized = normalize_associated_type(infcx, ty);
785 if ty == normalized {
788 return Struct::non_zero_field_in_type(infcx, normalized);
791 // Anything else is not a non-zero type.
796 /// Find the path leading to a non-zero leaf field, starting from
797 /// the given set of fields and recursing through aggregates.
798 /// Returns Some((path, source_path)) on success.
799 /// `path` is translated to memory order. `source_path` is not.
800 fn non_zero_field_paths<I>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
802 permutation: Option<&[u32]>)
803 -> Result<Option<(FieldPath, FieldPath)>, LayoutError<'gcx>>
804 where I: Iterator<Item=Ty<'gcx>> {
805 for (i, ty) in fields.enumerate() {
806 if let Some((mut path, mut source_path)) = Struct::non_zero_field_in_type(infcx, ty)? {
807 source_path.push(i as u32);
808 let index = if let Some(p) = permutation {
813 path.push(index as u32);
814 return Ok(Some((path, source_path)));
821 /// An untagged union.
822 #[derive(PartialEq, Eq, Hash, Debug)]
828 /// If true, no alignment padding is used.
832 impl<'a, 'gcx, 'tcx> Union {
833 pub fn new(dl: &TargetDataLayout, packed: bool) -> Union {
835 align: if packed { dl.i8_align } else { dl.aggregate_align },
836 min_size: Size::from_bytes(0),
841 /// Extend the Struct with more fields.
842 pub fn extend<I>(&mut self, dl: &TargetDataLayout,
845 -> Result<(), LayoutError<'gcx>>
846 where I: Iterator<Item=Result<&'a Layout, LayoutError<'gcx>>> {
847 for (index, field) in fields.enumerate() {
849 if field.is_unsized() {
850 bug!("Union::extend: field #{} of `{}` is unsized",
854 debug!("Union::extend field: {:?} {:?}", field, field.size(dl));
857 self.align = self.align.max(field.align(dl));
859 self.min_size = cmp::max(self.min_size, field.size(dl));
862 debug!("Union::extend min-size: {:?}", self.min_size);
867 /// Get the size with trailing alignment padding.
868 pub fn stride(&self) -> Size {
869 self.min_size.abi_align(self.align)
873 /// The first half of a fat pointer.
874 /// - For a trait object, this is the address of the box.
875 /// - For a slice, this is the base address.
876 pub const FAT_PTR_ADDR: usize = 0;
878 /// The second half of a fat pointer.
879 /// - For a trait object, this is the address of the vtable.
880 /// - For a slice, this is the length.
881 pub const FAT_PTR_EXTRA: usize = 1;
883 /// Type layout, from which size and alignment can be cheaply computed.
884 /// For ADTs, it also includes field placement and enum optimizations.
885 /// NOTE: Because Layout is interned, redundant information should be
886 /// kept to a minimum, e.g. it includes no sub-component Ty or Layout.
887 #[derive(Debug, PartialEq, Eq, Hash)]
889 /// TyBool, TyChar, TyInt, TyUint, TyFloat, TyRawPtr, TyRef or TyFnPtr.
892 // If true, the value cannot represent a bit pattern of all zeroes.
896 /// SIMD vectors, from structs marked with #[repr(simd)].
902 /// TyArray, TySlice or TyStr.
904 /// If true, the size is exact, otherwise it's only a lower bound.
910 /// TyRawPtr or TyRef with a !Sized pointee.
913 // If true, the pointer cannot be null.
917 // Remaining variants are all ADTs such as structs, enums or tuples.
919 /// C-like enums; basically an integer.
924 // Inclusive discriminant range.
925 // If min > max, it represents min...u64::MAX followed by 0...max.
926 // FIXME(eddyb) always use the shortest range, e.g. by finding
927 // the largest space between two consecutive discriminants and
928 // taking everything else as the (shortest) discriminant range.
933 /// Single-case enums, and structs/tuples.
936 // If true, the structure is NonZero.
937 // FIXME(eddyb) use a newtype Layout kind for this.
946 /// General-case enums: for each case there is a struct, and they
947 /// all start with a field for the discriminant.
950 variants: Vec<Struct>,
955 /// Two cases distinguished by a nullable pointer: the case with discriminant
956 /// `nndiscr` must have single field which is known to be nonnull due to its type.
957 /// The other case is known to be zero sized. Hence we represent the enum
958 /// as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
959 /// otherwise it indicates the other case.
961 /// For example, `std::option::Option` instantiated at a safe pointer type
962 /// is represented such that `None` is a null pointer and `Some` is the
963 /// identity function.
969 /// Two cases distinguished by a nullable pointer: the case with discriminant
970 /// `nndiscr` is represented by the struct `nonnull`, where the `discrfield`th
971 /// field is known to be nonnull due to its type; if that field is null, then
972 /// it represents the other case, which is known to be zero sized.
973 StructWrappedNullablePointer {
976 // N.B. There is a 0 at the start, for LLVM GEP through a pointer.
977 discrfield: FieldPath,
978 // Like discrfield, but in source order. For debuginfo.
979 discrfield_source: FieldPath
983 #[derive(Copy, Clone, Debug)]
984 pub enum LayoutError<'tcx> {
986 SizeOverflow(Ty<'tcx>)
989 impl<'tcx> fmt::Display for LayoutError<'tcx> {
990 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
992 LayoutError::Unknown(ty) => {
993 write!(f, "the type `{:?}` has an unknown layout", ty)
995 LayoutError::SizeOverflow(ty) => {
996 write!(f, "the type `{:?}` is too big for the current architecture", ty)
1002 /// Helper function for normalizing associated types in an inference context.
1003 fn normalize_associated_type<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
1006 if !ty.has_projection_types() {
1010 let mut selcx = traits::SelectionContext::new(infcx);
1011 let cause = traits::ObligationCause::dummy();
1012 let traits::Normalized { value: result, obligations } =
1013 traits::normalize(&mut selcx, cause, &ty);
1015 let mut fulfill_cx = traits::FulfillmentContext::new();
1017 for obligation in obligations {
1018 fulfill_cx.register_predicate_obligation(infcx, obligation);
1021 infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
1024 impl<'a, 'gcx, 'tcx> Layout {
1025 pub fn compute_uncached(ty: Ty<'gcx>,
1026 infcx: &InferCtxt<'a, 'gcx, 'tcx>)
1027 -> Result<&'gcx Layout, LayoutError<'gcx>> {
1028 let tcx = infcx.tcx.global_tcx();
1029 let success = |layout| Ok(tcx.intern_layout(layout));
1030 let dl = &tcx.data_layout;
1031 assert!(!ty.has_infer_types());
1033 let ptr_layout = |pointee: Ty<'gcx>| {
1034 let non_zero = !ty.is_unsafe_ptr();
1035 let pointee = normalize_associated_type(infcx, pointee);
1036 if pointee.is_sized(tcx, &infcx.parameter_environment, DUMMY_SP) {
1037 Ok(Scalar { value: Pointer, non_zero: non_zero })
1039 let unsized_part = tcx.struct_tail(pointee);
1040 let meta = match unsized_part.sty {
1041 ty::TySlice(_) | ty::TyStr => {
1042 Int(dl.ptr_sized_integer())
1044 ty::TyDynamic(..) => Pointer,
1045 _ => return Err(LayoutError::Unknown(unsized_part))
1047 Ok(FatPointer { metadata: meta, non_zero: non_zero })
1051 let layout = match ty.sty {
1053 ty::TyBool => Scalar { value: Int(I1), non_zero: false },
1054 ty::TyChar => Scalar { value: Int(I32), non_zero: false },
1057 value: Int(Integer::from_attr(dl, attr::SignedInt(ity))),
1061 ty::TyUint(ity) => {
1063 value: Int(Integer::from_attr(dl, attr::UnsignedInt(ity))),
1067 ty::TyFloat(FloatTy::F32) => Scalar { value: F32, non_zero: false },
1068 ty::TyFloat(FloatTy::F64) => Scalar { value: F64, non_zero: false },
1069 ty::TyFnPtr(_) => Scalar { value: Pointer, non_zero: true },
1072 ty::TyNever => Univariant {
1073 variant: Struct::new(dl, &vec![], &ReprOptions::default(),
1074 StructKind::AlwaysSizedUnivariant, ty)?,
1078 // Potentially-fat pointers.
1079 ty::TyRef(_, ty::TypeAndMut { ty: pointee, .. }) |
1080 ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1081 ptr_layout(pointee)?
1083 ty::TyAdt(def, _) if def.is_box() => {
1084 ptr_layout(ty.boxed_ty())?
1087 // Arrays and slices.
1088 ty::TyArray(element, count) => {
1089 let element = element.layout(infcx)?;
1092 align: element.align(dl),
1093 size: element.size(dl).checked_mul(count as u64, dl)
1094 .map_or(Err(LayoutError::SizeOverflow(ty)), Ok)?
1097 ty::TySlice(element) => {
1100 align: element.layout(infcx)?.align(dl),
1101 size: Size::from_bytes(0)
1108 size: Size::from_bytes(0)
1113 ty::TyFnDef(..) => {
1115 variant: Struct::new(dl, &vec![],
1116 &ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?,
1120 ty::TyDynamic(..) => {
1121 let mut unit = Struct::new(dl, &vec![], &ReprOptions::default(),
1122 StructKind::AlwaysSizedUnivariant, ty)?;
1124 Univariant { variant: unit, non_zero: false }
1127 // Tuples and closures.
1128 ty::TyClosure(def_id, ref substs) => {
1129 let tys = substs.upvar_tys(def_id, tcx);
1130 let st = Struct::new(dl,
1131 &tys.map(|ty| ty.layout(infcx))
1132 .collect::<Result<Vec<_>, _>>()?,
1133 &ReprOptions::default(),
1134 StructKind::AlwaysSizedUnivariant, ty)?;
1135 Univariant { variant: st, non_zero: false }
1138 ty::TyTuple(tys, _) => {
1139 // FIXME(camlorn): if we ever allow unsized tuples, this needs to be checked.
1140 // See the univariant case below to learn how.
1141 let st = Struct::new(dl,
1142 &tys.iter().map(|ty| ty.layout(infcx))
1143 .collect::<Result<Vec<_>, _>>()?,
1144 &ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?;
1145 Univariant { variant: st, non_zero: false }
1148 // SIMD vector types.
1149 ty::TyAdt(def, ..) if def.repr.simd => {
1150 let element = ty.simd_type(tcx);
1151 match *element.layout(infcx)? {
1152 Scalar { value, .. } => {
1153 return success(Vector {
1155 count: ty.simd_size(tcx) as u64
1159 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` with \
1160 a non-machine element type `{}`",
1167 ty::TyAdt(def, substs) => {
1168 if def.variants.is_empty() {
1169 // Uninhabitable; represent as unit
1170 // (Typechecking will reject discriminant-sizing attrs.)
1172 return success(Univariant {
1173 variant: Struct::new(dl, &vec![],
1174 &def.repr, StructKind::AlwaysSizedUnivariant, ty)?,
1179 if def.is_enum() && def.variants.iter().all(|v| v.fields.is_empty()) {
1180 // All bodies empty -> intlike
1181 let (mut min, mut max, mut non_zero) = (i64::max_value(),
1184 for discr in def.discriminants(tcx) {
1185 let x = discr.to_u128_unchecked() as i64;
1186 if x == 0 { non_zero = false; }
1187 if x < min { min = x; }
1188 if x > max { max = x; }
1191 // FIXME: should handle i128? signed-value based impl is weird and hard to
1193 let (discr, signed) = Integer::repr_discr(tcx, ty, &def.repr, min, max);
1194 return success(CEnum {
1198 // FIXME: should be u128?
1204 if !def.is_enum() || (def.variants.len() == 1 &&
1205 !def.repr.inhibit_enum_layout_opt()) {
1206 // Struct, or union, or univariant enum equivalent to a struct.
1207 // (Typechecking will reject discriminant-sizing attrs.)
1209 let kind = if def.is_enum() || def.variants[0].fields.len() == 0{
1210 StructKind::AlwaysSizedUnivariant
1212 use middle::region::ROOT_CODE_EXTENT;
1213 let param_env = tcx.construct_parameter_environment(DUMMY_SP,
1214 def.did, ROOT_CODE_EXTENT);
1215 let fields = &def.variants[0].fields;
1216 let last_field = &fields[fields.len()-1];
1217 let always_sized = last_field.ty(tcx, param_env.free_substs)
1218 .is_sized(tcx, ¶m_env, DUMMY_SP);
1219 if !always_sized { StructKind::MaybeUnsizedUnivariant }
1220 else { StructKind::AlwaysSizedUnivariant }
1223 let fields = def.variants[0].fields.iter().map(|field| {
1224 field.ty(tcx, substs).layout(infcx)
1225 }).collect::<Result<Vec<_>, _>>()?;
1226 let layout = if def.is_union() {
1227 let mut un = Union::new(dl, def.repr.packed);
1228 un.extend(dl, fields.iter().map(|&f| Ok(f)), ty)?;
1229 UntaggedUnion { variants: un }
1231 let st = Struct::new(dl, &fields, &def.repr,
1233 let non_zero = Some(def.did) == tcx.lang_items.non_zero();
1234 Univariant { variant: st, non_zero: non_zero }
1236 return success(layout);
1239 // Since there's at least one
1240 // non-empty body, explicit discriminants should have
1241 // been rejected by a checker before this point.
1242 for (i, v) in def.variants.iter().enumerate() {
1243 if v.discr != ty::VariantDiscr::Relative(i) {
1244 bug!("non-C-like enum {} with specified discriminants",
1245 tcx.item_path_str(def.did));
1249 // Cache the substituted and normalized variant field types.
1250 let variants = def.variants.iter().map(|v| {
1251 v.fields.iter().map(|field| field.ty(tcx, substs)).collect::<Vec<_>>()
1252 }).collect::<Vec<_>>();
1254 if variants.len() == 2 && !def.repr.inhibit_enum_layout_opt() {
1255 // Nullable pointer optimization
1257 let other_fields = variants[1 - discr].iter().map(|ty| {
1260 if !Struct::would_be_zero_sized(dl, other_fields)? {
1263 let paths = Struct::non_zero_field_paths(infcx,
1264 variants[discr].iter().cloned(),
1266 let (mut path, mut path_source) = if let Some(p) = paths { p }
1269 // FIXME(eddyb) should take advantage of a newtype.
1270 if path == &[0] && variants[discr].len() == 1 {
1271 let value = match *variants[discr][0].layout(infcx)? {
1272 Scalar { value, .. } => value,
1273 CEnum { discr, .. } => Int(discr),
1274 _ => bug!("Layout::compute: `{}`'s non-zero \
1275 `{}` field not scalar?!",
1276 ty, variants[discr][0])
1278 return success(RawNullablePointer {
1279 nndiscr: discr as u64,
1284 let st = Struct::new(dl,
1285 &variants[discr].iter().map(|ty| ty.layout(infcx))
1286 .collect::<Result<Vec<_>, _>>()?,
1287 &def.repr, StructKind::AlwaysSizedUnivariant, ty)?;
1289 // We have to fix the last element of path here.
1290 let mut i = *path.last().unwrap();
1291 i = st.memory_index[i as usize];
1292 *path.last_mut().unwrap() = i;
1293 path.push(0); // For GEP through a pointer.
1295 path_source.push(0);
1296 path_source.reverse();
1298 return success(StructWrappedNullablePointer {
1299 nndiscr: discr as u64,
1302 discrfield_source: path_source
1307 // The general case.
1308 let discr_max = (variants.len() - 1) as i64;
1309 assert!(discr_max >= 0);
1310 let (min_ity, _) = Integer::repr_discr(tcx, ty, &def.repr, 0, discr_max);
1311 let mut align = dl.aggregate_align;
1312 let mut size = Size::from_bytes(0);
1314 // We're interested in the smallest alignment, so start large.
1315 let mut start_align = Align::from_bytes(256, 256).unwrap();
1317 // Create the set of structs that represent each variant
1318 // Use the minimum integer type we figured out above
1319 let discr = Scalar { value: Int(min_ity), non_zero: false };
1320 let mut variants = variants.into_iter().map(|fields| {
1321 let mut fields = fields.into_iter().map(|field| {
1323 }).collect::<Result<Vec<_>, _>>()?;
1324 fields.insert(0, &discr);
1325 let st = Struct::new(dl,
1327 &def.repr, StructKind::EnumVariant, ty)?;
1328 // Find the first field we can't move later
1329 // to make room for a larger discriminant.
1330 // It is important to skip the first field.
1331 for i in st.field_index_by_increasing_offset().skip(1) {
1332 let field = fields[i];
1333 let field_align = field.align(dl);
1334 if field.size(dl).bytes() != 0 || field_align.abi() != 1 {
1335 start_align = start_align.min(field_align);
1339 size = cmp::max(size, st.min_size);
1340 align = align.max(st.align);
1342 }).collect::<Result<Vec<_>, _>>()?;
1344 // Align the maximum variant size to the largest alignment.
1345 size = size.abi_align(align);
1347 if size.bytes() >= dl.obj_size_bound() {
1348 return Err(LayoutError::SizeOverflow(ty));
1351 let typeck_ity = Integer::from_attr(dl, def.repr.discr_type());
1352 if typeck_ity < min_ity {
1353 // It is a bug if Layout decided on a greater discriminant size than typeck for
1354 // some reason at this point (based on values discriminant can take on). Mostly
1355 // because this discriminant will be loaded, and then stored into variable of
1356 // type calculated by typeck. Consider such case (a bug): typeck decided on
1357 // byte-sized discriminant, but layout thinks we need a 16-bit to store all
1358 // discriminant values. That would be a bug, because then, in trans, in order
1359 // to store this 16-bit discriminant into 8-bit sized temporary some of the
1360 // space necessary to represent would have to be discarded (or layout is wrong
1361 // on thinking it needs 16 bits)
1362 bug!("layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
1363 min_ity, typeck_ity);
1364 // However, it is fine to make discr type however large (as an optimisation)
1365 // after this point – we’ll just truncate the value we load in trans.
1368 // Check to see if we should use a different type for the
1369 // discriminant. We can safely use a type with the same size
1370 // as the alignment of the first field of each variant.
1371 // We increase the size of the discriminant to avoid LLVM copying
1372 // padding when it doesn't need to. This normally causes unaligned
1373 // load/stores and excessive memcpy/memset operations. By using a
1374 // bigger integer size, LLVM can be sure about it's contents and
1375 // won't be so conservative.
1377 // Use the initial field alignment
1378 let mut ity = Integer::for_abi_align(dl, start_align).unwrap_or(min_ity);
1380 // If the alignment is not larger than the chosen discriminant size,
1381 // don't use the alignment as the final size.
1385 // Patch up the variants' first few fields.
1386 let old_ity_size = Int(min_ity).size(dl);
1387 let new_ity_size = Int(ity).size(dl);
1388 for variant in &mut variants {
1389 for i in variant.offsets.iter_mut() {
1390 // The first field is the discrimminant, at offset 0.
1391 // These aren't in order, and we need to skip it.
1392 if *i <= old_ity_size && *i > Size::from_bytes(0) {
1396 // We might be making the struct larger.
1397 if variant.min_size <= old_ity_size {
1398 variant.min_size = new_ity_size;
1411 // Types with no meaningful known layout.
1412 ty::TyProjection(_) | ty::TyAnon(..) => {
1413 let normalized = normalize_associated_type(infcx, ty);
1414 if ty == normalized {
1415 return Err(LayoutError::Unknown(ty));
1417 return normalized.layout(infcx);
1420 return Err(LayoutError::Unknown(ty));
1422 ty::TyInfer(_) | ty::TyError => {
1423 bug!("Layout::compute: unexpected type `{}`", ty)
1430 /// Returns true if the layout corresponds to an unsized type.
1431 pub fn is_unsized(&self) -> bool {
1433 Scalar {..} | Vector {..} | FatPointer {..} |
1434 CEnum {..} | UntaggedUnion {..} | General {..} |
1435 RawNullablePointer {..} |
1436 StructWrappedNullablePointer {..} => false,
1438 Array { sized, .. } |
1439 Univariant { variant: Struct { sized, .. }, .. } => !sized
1443 pub fn size(&self, dl: &TargetDataLayout) -> Size {
1445 Scalar { value, .. } | RawNullablePointer { value, .. } => {
1449 Vector { element, count } => {
1450 let elem_size = element.size(dl);
1451 let vec_size = match elem_size.checked_mul(count, dl) {
1453 None => bug!("Layout::size({:?}): {} * {} overflowed",
1454 self, elem_size.bytes(), count)
1456 vec_size.abi_align(self.align(dl))
1459 FatPointer { metadata, .. } => {
1460 // Effectively a (ptr, meta) tuple.
1461 Pointer.size(dl).abi_align(metadata.align(dl))
1462 .checked_add(metadata.size(dl), dl).unwrap()
1463 .abi_align(self.align(dl))
1466 CEnum { discr, .. } => Int(discr).size(dl),
1467 Array { size, .. } | General { size, .. } => size,
1468 UntaggedUnion { ref variants } => variants.stride(),
1470 Univariant { ref variant, .. } |
1471 StructWrappedNullablePointer { nonnull: ref variant, .. } => {
1477 pub fn align(&self, dl: &TargetDataLayout) -> Align {
1479 Scalar { value, .. } | RawNullablePointer { value, .. } => {
1483 Vector { element, count } => {
1484 let elem_size = element.size(dl);
1485 let vec_size = match elem_size.checked_mul(count, dl) {
1487 None => bug!("Layout::align({:?}): {} * {} overflowed",
1488 self, elem_size.bytes(), count)
1490 for &(size, align) in &dl.vector_align {
1491 if size == vec_size {
1495 // Default to natural alignment, which is what LLVM does.
1496 // That is, use the size, rounded up to a power of 2.
1497 let align = vec_size.bytes().next_power_of_two();
1498 Align::from_bytes(align, align).unwrap()
1501 FatPointer { metadata, .. } => {
1502 // Effectively a (ptr, meta) tuple.
1503 Pointer.align(dl).max(metadata.align(dl))
1506 CEnum { discr, .. } => Int(discr).align(dl),
1507 Array { align, .. } | General { align, .. } => align,
1508 UntaggedUnion { ref variants } => variants.align,
1510 Univariant { ref variant, .. } |
1511 StructWrappedNullablePointer { nonnull: ref variant, .. } => {
1518 /// Type size "skeleton", i.e. the only information determining a type's size.
1519 /// While this is conservative, (aside from constant sizes, only pointers,
1520 /// newtypes thereof and null pointer optimized enums are allowed), it is
1521 /// enough to statically check common usecases of transmute.
1522 #[derive(Copy, Clone, Debug)]
1523 pub enum SizeSkeleton<'tcx> {
1524 /// Any statically computable Layout.
1527 /// A potentially-fat pointer.
1529 // If true, this pointer is never null.
1531 // The type which determines the unsized metadata, if any,
1532 // of this pointer. Either a type parameter or a projection
1533 // depending on one, with regions erased.
1538 impl<'a, 'gcx, 'tcx> SizeSkeleton<'gcx> {
1539 pub fn compute(ty: Ty<'gcx>, infcx: &InferCtxt<'a, 'gcx, 'tcx>)
1540 -> Result<SizeSkeleton<'gcx>, LayoutError<'gcx>> {
1541 let tcx = infcx.tcx.global_tcx();
1542 assert!(!ty.has_infer_types());
1544 // First try computing a static layout.
1545 let err = match ty.layout(infcx) {
1547 return Ok(SizeSkeleton::Known(layout.size(&tcx.data_layout)));
1552 let ptr_skeleton = |pointee: Ty<'gcx>| {
1553 let non_zero = !ty.is_unsafe_ptr();
1554 let tail = tcx.struct_tail(pointee);
1556 ty::TyParam(_) | ty::TyProjection(_) => {
1557 assert!(tail.has_param_types() || tail.has_self_ty());
1558 Ok(SizeSkeleton::Pointer {
1560 tail: tcx.erase_regions(&tail)
1564 bug!("SizeSkeleton::compute({}): layout errored ({}), yet \
1565 tail `{}` is not a type parameter or a projection",
1572 ty::TyRef(_, ty::TypeAndMut { ty: pointee, .. }) |
1573 ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1574 ptr_skeleton(pointee)
1576 ty::TyAdt(def, _) if def.is_box() => {
1577 ptr_skeleton(ty.boxed_ty())
1580 ty::TyAdt(def, substs) => {
1581 // Only newtypes and enums w/ nullable pointer optimization.
1582 if def.is_union() || def.variants.is_empty() || def.variants.len() > 2 {
1586 // Get a zero-sized variant or a pointer newtype.
1587 let zero_or_ptr_variant = |i: usize| {
1588 let fields = def.variants[i].fields.iter().map(|field| {
1589 SizeSkeleton::compute(field.ty(tcx, substs), infcx)
1592 for field in fields {
1595 SizeSkeleton::Known(size) => {
1596 if size.bytes() > 0 {
1600 SizeSkeleton::Pointer {..} => {
1611 let v0 = zero_or_ptr_variant(0)?;
1613 if def.variants.len() == 1 {
1614 if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
1615 return Ok(SizeSkeleton::Pointer {
1616 non_zero: non_zero ||
1617 Some(def.did) == tcx.lang_items.non_zero(),
1625 let v1 = zero_or_ptr_variant(1)?;
1626 // Nullable pointer enum optimization.
1628 (Some(SizeSkeleton::Pointer { non_zero: true, tail }), None) |
1629 (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
1630 Ok(SizeSkeleton::Pointer {
1639 ty::TyProjection(_) | ty::TyAnon(..) => {
1640 let normalized = normalize_associated_type(infcx, ty);
1641 if ty == normalized {
1644 SizeSkeleton::compute(normalized, infcx)
1652 pub fn same_size(self, other: SizeSkeleton) -> bool {
1653 match (self, other) {
1654 (SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
1655 (SizeSkeleton::Pointer { tail: a, .. },
1656 SizeSkeleton::Pointer { tail: b, .. }) => a == b,