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::*;
15 use session::{self, DataTypeKind, Session};
16 use ty::{self, Ty, TyCtxt, TypeFoldable, ReprOptions, ReprFlags};
18 use syntax::ast::{self, FloatTy, IntTy, UintTy};
20 use syntax_pos::DUMMY_SP;
28 /// Parsed [Data layout](http://llvm.org/docs/LangRef.html#data-layout)
29 /// for a target, which contains everything needed to compute layouts.
30 pub struct TargetDataLayout {
37 pub i128_align: Align,
40 pub pointer_size: Size,
41 pub pointer_align: Align,
42 pub aggregate_align: Align,
44 /// Alignments for vector types.
45 pub vector_align: Vec<(Size, Align)>
48 impl Default for TargetDataLayout {
49 /// Creates an instance of `TargetDataLayout`.
50 fn default() -> TargetDataLayout {
53 i1_align: Align::from_bits(8, 8).unwrap(),
54 i8_align: Align::from_bits(8, 8).unwrap(),
55 i16_align: Align::from_bits(16, 16).unwrap(),
56 i32_align: Align::from_bits(32, 32).unwrap(),
57 i64_align: Align::from_bits(32, 64).unwrap(),
58 i128_align: Align::from_bits(32, 64).unwrap(),
59 f32_align: Align::from_bits(32, 32).unwrap(),
60 f64_align: Align::from_bits(64, 64).unwrap(),
61 pointer_size: Size::from_bits(64),
62 pointer_align: Align::from_bits(64, 64).unwrap(),
63 aggregate_align: Align::from_bits(0, 64).unwrap(),
65 (Size::from_bits(64), Align::from_bits(64, 64).unwrap()),
66 (Size::from_bits(128), Align::from_bits(128, 128).unwrap())
72 impl TargetDataLayout {
73 pub fn parse(sess: &Session) -> TargetDataLayout {
74 // Parse a bit count from a string.
75 let parse_bits = |s: &str, kind: &str, cause: &str| {
76 s.parse::<u64>().unwrap_or_else(|err| {
77 sess.err(&format!("invalid {} `{}` for `{}` in \"data-layout\": {}",
78 kind, s, cause, err));
83 // Parse a size string.
84 let size = |s: &str, cause: &str| {
85 Size::from_bits(parse_bits(s, "size", cause))
88 // Parse an alignment string.
89 let align = |s: &[&str], cause: &str| {
91 sess.err(&format!("missing alignment for `{}` in \"data-layout\"", cause));
93 let abi = parse_bits(s[0], "alignment", cause);
94 let pref = s.get(1).map_or(abi, |pref| parse_bits(pref, "alignment", cause));
95 Align::from_bits(abi, pref).unwrap_or_else(|err| {
96 sess.err(&format!("invalid alignment for `{}` in \"data-layout\": {}",
98 Align::from_bits(8, 8).unwrap()
102 let mut dl = TargetDataLayout::default();
103 let mut i128_align_src = 64;
104 for spec in sess.target.target.data_layout.split("-") {
105 match &spec.split(":").collect::<Vec<_>>()[..] {
106 &["e"] => dl.endian = Endian::Little,
107 &["E"] => dl.endian = Endian::Big,
108 &["a", ref a..] => dl.aggregate_align = align(a, "a"),
109 &["f32", ref a..] => dl.f32_align = align(a, "f32"),
110 &["f64", ref a..] => dl.f64_align = align(a, "f64"),
111 &[p @ "p", s, ref a..] | &[p @ "p0", s, ref a..] => {
112 dl.pointer_size = size(s, p);
113 dl.pointer_align = align(a, p);
115 &[s, ref a..] if s.starts_with("i") => {
116 let bits = match s[1..].parse::<u64>() {
119 size(&s[1..], "i"); // For the user error.
125 1 => dl.i1_align = a,
126 8 => dl.i8_align = a,
127 16 => dl.i16_align = a,
128 32 => dl.i32_align = a,
129 64 => dl.i64_align = a,
132 if bits >= i128_align_src && bits <= 128 {
133 // Default alignment for i128 is decided by taking the alignment of
134 // largest-sized i{64...128}.
135 i128_align_src = bits;
139 &[s, ref a..] if s.starts_with("v") => {
140 let v_size = size(&s[1..], "v");
142 if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
146 // No existing entry, add a new one.
147 dl.vector_align.push((v_size, a));
149 _ => {} // Ignore everything else.
153 // Perform consistency checks against the Target information.
154 let endian_str = match dl.endian {
155 Endian::Little => "little",
158 if endian_str != sess.target.target.target_endian {
159 sess.err(&format!("inconsistent target specification: \"data-layout\" claims \
160 architecture is {}-endian, while \"target-endian\" is `{}`",
161 endian_str, sess.target.target.target_endian));
164 if dl.pointer_size.bits().to_string() != sess.target.target.target_pointer_width {
165 sess.err(&format!("inconsistent target specification: \"data-layout\" claims \
166 pointers are {}-bit, while \"target-pointer-width\" is `{}`",
167 dl.pointer_size.bits(), sess.target.target.target_pointer_width));
173 /// Return exclusive upper bound on object size.
175 /// The theoretical maximum object size is defined as the maximum positive `isize` value.
176 /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
177 /// index every address within an object along with one byte past the end, along with allowing
178 /// `isize` to store the difference between any two pointers into an object.
180 /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
181 /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
182 /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
183 /// address space on 64-bit ARMv8 and x86_64.
184 pub fn obj_size_bound(&self) -> u64 {
185 match self.pointer_size.bits() {
189 bits => bug!("obj_size_bound: unknown pointer bit size {}", bits)
193 pub fn ptr_sized_integer(&self) -> Integer {
194 match self.pointer_size.bits() {
198 bits => bug!("ptr_sized_integer: unknown pointer bit size {}", bits)
203 pub trait HasDataLayout: Copy {
204 fn data_layout(&self) -> &TargetDataLayout;
207 impl<'a> HasDataLayout for &'a TargetDataLayout {
208 fn data_layout(&self) -> &TargetDataLayout {
213 impl<'a, 'tcx> HasDataLayout for TyCtxt<'a, 'tcx, 'tcx> {
214 fn data_layout(&self) -> &TargetDataLayout {
219 /// Endianness of the target, which must match cfg(target-endian).
220 #[derive(Copy, Clone)]
226 /// Size of a type in bytes.
227 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
233 pub fn from_bits(bits: u64) -> Size {
234 Size::from_bytes((bits + 7) / 8)
237 pub fn from_bytes(bytes: u64) -> Size {
238 if bytes >= (1 << 61) {
239 bug!("Size::from_bytes: {} bytes in bits doesn't fit in u64", bytes)
246 pub fn bytes(self) -> u64 {
250 pub fn bits(self) -> u64 {
254 pub fn abi_align(self, align: Align) -> Size {
255 let mask = align.abi() - 1;
256 Size::from_bytes((self.bytes() + mask) & !mask)
259 pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: C) -> Option<Size> {
260 let dl = cx.data_layout();
262 // Each Size is less than dl.obj_size_bound(), so the sum is
263 // also less than 1 << 62 (and therefore can't overflow).
264 let bytes = self.bytes() + offset.bytes();
266 if bytes < dl.obj_size_bound() {
267 Some(Size::from_bytes(bytes))
273 pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: C) -> Option<Size> {
274 let dl = cx.data_layout();
276 // Each Size is less than dl.obj_size_bound(), so the sum is
277 // also less than 1 << 62 (and therefore can't overflow).
278 match self.bytes().checked_mul(count) {
279 Some(bytes) if bytes < dl.obj_size_bound() => {
280 Some(Size::from_bytes(bytes))
287 /// Alignment of a type in bytes, both ABI-mandated and preferred.
288 /// Each field is a power of two, giving the alignment a maximum
289 /// value of 2^(2^8 - 1), which is limited by LLVM to a i32, with
290 /// a maximum capacity of 2^31 - 1 or 2147483647.
291 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
298 pub fn from_bits(abi: u64, pref: u64) -> Result<Align, String> {
299 Align::from_bytes((abi + 7) / 8, (pref + 7) / 8)
302 pub fn from_bytes(abi: u64, pref: u64) -> Result<Align, String> {
303 let log2 = |align: u64| {
304 // Treat an alignment of 0 bytes like 1-byte alignment.
309 let mut bytes = align;
311 while (bytes & 1) == 0 {
316 Err(format!("`{}` is not a power of 2", align))
318 Err(format!("`{}` is too large", align))
330 pub fn abi(self) -> u64 {
334 pub fn pref(self) -> u64 {
338 pub fn min(self, other: Align) -> Align {
340 abi: cmp::min(self.abi, other.abi),
341 pref: cmp::min(self.pref, other.pref),
345 pub fn max(self, other: Align) -> Align {
347 abi: cmp::max(self.abi, other.abi),
348 pref: cmp::max(self.pref, other.pref),
353 /// Integers, also used for enum discriminants.
354 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
365 pub fn size(&self) -> Size {
367 I1 => Size::from_bits(1),
368 I8 => Size::from_bytes(1),
369 I16 => Size::from_bytes(2),
370 I32 => Size::from_bytes(4),
371 I64 => Size::from_bytes(8),
372 I128 => Size::from_bytes(16),
376 pub fn align<C: HasDataLayout>(&self, cx: C) -> Align {
377 let dl = cx.data_layout();
385 I128 => dl.i128_align,
389 pub fn to_ty<'a, 'tcx>(&self, tcx: &ty::TyCtxt<'a, 'tcx, 'tcx>,
390 signed: bool) -> Ty<'tcx> {
391 match (*self, signed) {
392 (I1, false) => tcx.types.u8,
393 (I8, false) => tcx.types.u8,
394 (I16, false) => tcx.types.u16,
395 (I32, false) => tcx.types.u32,
396 (I64, false) => tcx.types.u64,
397 (I128, false) => tcx.types.u128,
398 (I1, true) => tcx.types.i8,
399 (I8, true) => tcx.types.i8,
400 (I16, true) => tcx.types.i16,
401 (I32, true) => tcx.types.i32,
402 (I64, true) => tcx.types.i64,
403 (I128, true) => tcx.types.i128,
407 /// Find the smallest Integer type which can represent the signed value.
408 pub fn fit_signed(x: i64) -> Integer {
410 -0x0000_0000_0000_0001...0x0000_0000_0000_0000 => I1,
411 -0x0000_0000_0000_0080...0x0000_0000_0000_007f => I8,
412 -0x0000_0000_0000_8000...0x0000_0000_0000_7fff => I16,
413 -0x0000_0000_8000_0000...0x0000_0000_7fff_ffff => I32,
414 -0x8000_0000_0000_0000...0x7fff_ffff_ffff_ffff => I64,
419 /// Find the smallest Integer type which can represent the unsigned value.
420 pub fn fit_unsigned(x: u64) -> Integer {
422 0...0x0000_0000_0000_0001 => I1,
423 0...0x0000_0000_0000_00ff => I8,
424 0...0x0000_0000_0000_ffff => I16,
425 0...0x0000_0000_ffff_ffff => I32,
426 0...0xffff_ffff_ffff_ffff => I64,
431 /// Find the smallest integer with the given alignment.
432 pub fn for_abi_align<C: HasDataLayout>(cx: C, align: Align) -> Option<Integer> {
433 let dl = cx.data_layout();
435 let wanted = align.abi();
436 for &candidate in &[I8, I16, I32, I64] {
437 let ty = Int(candidate);
438 if wanted == ty.align(dl).abi() && wanted == ty.size(dl).bytes() {
439 return Some(candidate);
445 /// Get the Integer type from an attr::IntType.
446 pub fn from_attr<C: HasDataLayout>(cx: C, ity: attr::IntType) -> Integer {
447 let dl = cx.data_layout();
450 attr::SignedInt(IntTy::I8) | attr::UnsignedInt(UintTy::U8) => I8,
451 attr::SignedInt(IntTy::I16) | attr::UnsignedInt(UintTy::U16) => I16,
452 attr::SignedInt(IntTy::I32) | attr::UnsignedInt(UintTy::U32) => I32,
453 attr::SignedInt(IntTy::I64) | attr::UnsignedInt(UintTy::U64) => I64,
454 attr::SignedInt(IntTy::I128) | attr::UnsignedInt(UintTy::U128) => I128,
455 attr::SignedInt(IntTy::Is) | attr::UnsignedInt(UintTy::Us) => {
456 dl.ptr_sized_integer()
461 /// Find the appropriate Integer type and signedness for the given
462 /// signed discriminant range and #[repr] attribute.
463 /// N.B.: u64 values above i64::MAX will be treated as signed, but
464 /// that shouldn't affect anything, other than maybe debuginfo.
465 fn repr_discr<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
471 // Theoretically, negative values could be larger in unsigned representation
472 // than the unsigned representation of the signed minimum. However, if there
473 // are any negative values, the only valid unsigned representation is u64
474 // which can fit all i64 values, so the result remains unaffected.
475 let unsigned_fit = Integer::fit_unsigned(cmp::max(min as u64, max as u64));
476 let signed_fit = cmp::max(Integer::fit_signed(min), Integer::fit_signed(max));
478 let mut min_from_extern = None;
479 let min_default = I8;
481 if let Some(ity) = repr.int {
482 let discr = Integer::from_attr(tcx, ity);
483 let fit = if ity.is_signed() { signed_fit } else { unsigned_fit };
485 bug!("Integer::repr_discr: `#[repr]` hint too small for \
486 discriminant range of enum `{}", ty)
488 return (discr, ity.is_signed());
492 match &tcx.sess.target.target.arch[..] {
493 // WARNING: the ARM EABI has two variants; the one corresponding
494 // to `at_least == I32` appears to be used on Linux and NetBSD,
495 // but some systems may use the variant corresponding to no
496 // lower bound. However, we don't run on those yet...?
497 "arm" => min_from_extern = Some(I32),
498 _ => min_from_extern = Some(I32),
502 let at_least = min_from_extern.unwrap_or(min_default);
504 // If there are no negative values, we can use the unsigned fit.
506 (cmp::max(unsigned_fit, at_least), false)
508 (cmp::max(signed_fit, at_least), true)
513 /// Fundamental unit of memory access and layout.
514 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
523 pub fn size<C: HasDataLayout>(self, cx: C) -> Size {
524 let dl = cx.data_layout();
527 Int(I1) | Int(I8) => Size::from_bits(8),
528 Int(I16) => Size::from_bits(16),
529 Int(I32) | F32 => Size::from_bits(32),
530 Int(I64) | F64 => Size::from_bits(64),
531 Int(I128) => Size::from_bits(128),
532 Pointer => dl.pointer_size
536 pub fn align<C: HasDataLayout>(self, cx: C) -> Align {
537 let dl = cx.data_layout();
540 Int(I1) => dl.i1_align,
541 Int(I8) => dl.i8_align,
542 Int(I16) => dl.i16_align,
543 Int(I32) => dl.i32_align,
544 Int(I64) => dl.i64_align,
545 Int(I128) => dl.i128_align,
548 Pointer => dl.pointer_align
553 /// Path through fields of nested structures.
554 // FIXME(eddyb) use small vector optimization for the common case.
555 pub type FieldPath = Vec<u32>;
557 /// A structure, a product type in ADT terms.
558 #[derive(PartialEq, Eq, Hash, Debug)]
560 /// Maximum alignment of fields and repr alignment.
563 /// Primitive alignment of fields without repr alignment.
564 pub primitive_align: Align,
566 /// If true, no alignment padding is used.
569 /// If true, the size is exact, otherwise it's only a lower bound.
572 /// Offsets for the first byte of each field, ordered to match the source definition order.
573 /// This vector does not go in increasing order.
574 /// FIXME(eddyb) use small vector optimization for the common case.
575 pub offsets: Vec<Size>,
577 /// Maps source order field indices to memory order indices, depending how fields were permuted.
578 /// FIXME (camlorn) also consider small vector optimization here.
579 pub memory_index: Vec<u32>,
584 /// Info required to optimize struct layout.
585 #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
587 /// A tuple, closure, or univariant which cannot be coerced to unsized.
588 AlwaysSizedUnivariant,
589 /// A univariant, the last field of which may be coerced to unsized.
590 MaybeUnsizedUnivariant,
591 /// A univariant, but part of an enum.
595 impl<'a, 'tcx> Struct {
596 fn new(dl: &TargetDataLayout,
597 fields: &Vec<&'a Layout>,
601 -> Result<Struct, LayoutError<'tcx>> {
602 if repr.packed() && repr.align > 0 {
603 bug!("Struct cannot be packed and aligned");
606 let align = if repr.packed() {
612 let mut ret = Struct {
614 primitive_align: align,
615 packed: repr.packed(),
618 memory_index: vec![],
619 min_size: Size::from_bytes(0),
622 // Anything with repr(C) or repr(packed) doesn't optimize.
623 // Neither do 1-member and 2-member structs.
624 // In addition, code in trans assume that 2-element structs can become pairs.
625 // It's easier to just short-circuit here.
626 let can_optimize = (fields.len() > 2 || StructKind::EnumVariant == kind)
627 && (repr.flags & ReprFlags::IS_UNOPTIMISABLE).is_empty();
629 let (optimize, sort_ascending) = match kind {
630 StructKind::AlwaysSizedUnivariant => (can_optimize, false),
631 StructKind::MaybeUnsizedUnivariant => (can_optimize, false),
632 StructKind::EnumVariant => {
633 assert!(fields.len() >= 1, "Enum variants must have discriminants.");
634 (can_optimize && fields[0].size(dl).bytes() == 1, true)
638 ret.offsets = vec![Size::from_bytes(0); fields.len()];
639 let mut inverse_memory_index: Vec<u32> = (0..fields.len() as u32).collect();
642 let start = if let StructKind::EnumVariant = kind { 1 } else { 0 };
643 let end = if let StructKind::MaybeUnsizedUnivariant = kind {
649 let optimizing = &mut inverse_memory_index[start..end];
651 optimizing.sort_by_key(|&x| fields[x as usize].align(dl).abi());
653 optimizing.sort_by(| &a, &b | {
654 let a = fields[a as usize].align(dl).abi();
655 let b = fields[b as usize].align(dl).abi();
662 // inverse_memory_index holds field indices by increasing memory offset.
663 // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5.
664 // We now write field offsets to the corresponding offset slot;
665 // field 5 with offset 0 puts 0 in offsets[5].
666 // At the bottom of this function, we use inverse_memory_index to produce memory_index.
668 if let StructKind::EnumVariant = kind {
669 assert_eq!(inverse_memory_index[0], 0,
670 "Enum variant discriminants must have the lowest offset.");
673 let mut offset = Size::from_bytes(0);
675 for i in inverse_memory_index.iter() {
676 let field = fields[*i as usize];
678 bug!("Struct::new: field #{} of `{}` comes after unsized field",
679 ret.offsets.len(), scapegoat);
682 if field.is_unsized() {
686 // Invariant: offset < dl.obj_size_bound() <= 1<<61
688 let align = field.align(dl);
689 let primitive_align = field.primitive_align(dl);
690 ret.align = ret.align.max(align);
691 ret.primitive_align = ret.primitive_align.max(primitive_align);
692 offset = offset.abi_align(align);
695 debug!("Struct::new offset: {:?} field: {:?} {:?}", offset, field, field.size(dl));
696 ret.offsets[*i as usize] = offset;
698 offset = offset.checked_add(field.size(dl), dl)
699 .map_or(Err(LayoutError::SizeOverflow(scapegoat)), Ok)?;
703 let repr_align = repr.align as u64;
704 ret.align = ret.align.max(Align::from_bytes(repr_align, repr_align).unwrap());
705 debug!("Struct::new repr_align: {:?}", repr_align);
708 debug!("Struct::new min_size: {:?}", offset);
709 ret.min_size = offset;
711 // As stated above, inverse_memory_index holds field indices by increasing offset.
712 // This makes it an already-sorted view of the offsets vec.
713 // To invert it, consider:
714 // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0.
715 // Field 5 would be the first element, so memory_index is i:
716 // Note: if we didn't optimize, it's already right.
719 ret.memory_index = vec![0; inverse_memory_index.len()];
721 for i in 0..inverse_memory_index.len() {
722 ret.memory_index[inverse_memory_index[i] as usize] = i as u32;
725 ret.memory_index = inverse_memory_index;
731 /// Get the size with trailing alignment padding.
732 pub fn stride(&self) -> Size {
733 self.min_size.abi_align(self.align)
736 /// Determine whether a structure would be zero-sized, given its fields.
737 fn would_be_zero_sized<I>(dl: &TargetDataLayout, fields: I)
738 -> Result<bool, LayoutError<'tcx>>
739 where I: Iterator<Item=Result<&'a Layout, LayoutError<'tcx>>> {
740 for field in fields {
742 if field.is_unsized() || field.size(dl).bytes() > 0 {
749 /// Get indices of the tys that made this struct by increasing offset.
751 pub fn field_index_by_increasing_offset<'b>(&'b self) -> impl iter::Iterator<Item=usize>+'b {
752 let mut inverse_small = [0u8; 64];
753 let mut inverse_big = vec![];
754 let use_small = self.memory_index.len() <= inverse_small.len();
756 // We have to write this logic twice in order to keep the array small.
758 for i in 0..self.memory_index.len() {
759 inverse_small[self.memory_index[i] as usize] = i as u8;
762 inverse_big = vec![0; self.memory_index.len()];
763 for i in 0..self.memory_index.len() {
764 inverse_big[self.memory_index[i] as usize] = i as u32;
768 (0..self.memory_index.len()).map(move |i| {
769 if use_small { inverse_small[i] as usize }
770 else { inverse_big[i] as usize }
774 /// Find the path leading to a non-zero leaf field, starting from
775 /// the given type and recursing through aggregates.
776 /// The tuple is `(path, source_path)`,
777 /// where `path` is in memory order and `source_path` in source order.
778 // FIXME(eddyb) track value ranges and traverse already optimized enums.
779 fn non_zero_field_in_type(tcx: TyCtxt<'a, 'tcx, 'tcx>,
780 param_env: ty::ParamEnv<'tcx>,
782 -> Result<Option<(FieldPath, FieldPath)>, LayoutError<'tcx>> {
783 match (ty.layout(tcx, param_env)?, &ty.sty) {
784 (&Scalar { non_zero: true, .. }, _) |
785 (&CEnum { non_zero: true, .. }, _) => Ok(Some((vec![], vec![]))),
786 (&FatPointer { non_zero: true, .. }, _) => {
787 Ok(Some((vec![FAT_PTR_ADDR as u32], vec![FAT_PTR_ADDR as u32])))
790 // Is this the NonZero lang item wrapping a pointer or integer type?
791 (&Univariant { non_zero: true, .. }, &ty::TyAdt(def, substs)) => {
792 let fields = &def.struct_variant().fields;
793 assert_eq!(fields.len(), 1);
794 match *fields[0].ty(tcx, substs).layout(tcx, param_env)? {
795 // FIXME(eddyb) also allow floating-point types here.
796 Scalar { value: Int(_), non_zero: false } |
797 Scalar { value: Pointer, non_zero: false } => {
798 Ok(Some((vec![0], vec![0])))
800 FatPointer { non_zero: false, .. } => {
801 let tmp = vec![FAT_PTR_ADDR as u32, 0];
802 Ok(Some((tmp.clone(), tmp)))
808 // Perhaps one of the fields of this struct is non-zero
809 // let's recurse and find out
810 (&Univariant { ref variant, .. }, &ty::TyAdt(def, substs)) if def.is_struct() => {
811 Struct::non_zero_field_paths(
814 def.struct_variant().fields.iter().map(|field| {
815 field.ty(tcx, substs)
817 Some(&variant.memory_index[..]))
820 // Perhaps one of the upvars of this closure is non-zero
821 (&Univariant { ref variant, .. }, &ty::TyClosure(def, substs)) => {
822 let upvar_tys = substs.upvar_tys(def, tcx);
823 Struct::non_zero_field_paths(
827 Some(&variant.memory_index[..]))
829 // Can we use one of the fields in this tuple?
830 (&Univariant { ref variant, .. }, &ty::TyTuple(tys, _)) => {
831 Struct::non_zero_field_paths(
835 Some(&variant.memory_index[..]))
838 // Is this a fixed-size array of something non-zero
839 // with at least one element?
840 (_, &ty::TyArray(ety, d)) if d > 0 => {
841 Struct::non_zero_field_paths(
844 Some(ety).into_iter(),
848 (_, &ty::TyProjection(_)) | (_, &ty::TyAnon(..)) => {
849 let normalized = tcx.normalize_associated_type_in_env(&ty, param_env);
850 if ty == normalized {
853 return Struct::non_zero_field_in_type(tcx, param_env, normalized);
856 // Anything else is not a non-zero type.
861 /// Find the path leading to a non-zero leaf field, starting from
862 /// the given set of fields and recursing through aggregates.
863 /// Returns Some((path, source_path)) on success.
864 /// `path` is translated to memory order. `source_path` is not.
865 fn non_zero_field_paths<I>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
866 param_env: ty::ParamEnv<'tcx>,
868 permutation: Option<&[u32]>)
869 -> Result<Option<(FieldPath, FieldPath)>, LayoutError<'tcx>>
870 where I: Iterator<Item=Ty<'tcx>> {
871 for (i, ty) in fields.enumerate() {
872 let r = Struct::non_zero_field_in_type(tcx, param_env, ty)?;
873 if let Some((mut path, mut source_path)) = r {
874 source_path.push(i as u32);
875 let index = if let Some(p) = permutation {
880 path.push(index as u32);
881 return Ok(Some((path, source_path)));
887 pub fn over_align(&self) -> Option<u32> {
888 let align = self.align.abi();
889 let primitive_align = self.primitive_align.abi();
890 if align > primitive_align {
898 /// An untagged union.
899 #[derive(PartialEq, Eq, Hash, Debug)]
902 pub primitive_align: Align,
906 /// If true, no alignment padding is used.
910 impl<'a, 'tcx> Union {
911 fn new(dl: &TargetDataLayout, repr: &ReprOptions) -> Union {
912 if repr.packed() && repr.align > 0 {
913 bug!("Union cannot be packed and aligned");
916 let primitive_align = if repr.packed() {
922 let align = if repr.align > 0 {
923 let repr_align = repr.align as u64;
924 debug!("Union::new repr_align: {:?}", repr_align);
925 primitive_align.max(Align::from_bytes(repr_align, repr_align).unwrap())
933 min_size: Size::from_bytes(0),
934 packed: repr.packed(),
938 /// Extend the Struct with more fields.
939 fn extend<I>(&mut self, dl: &TargetDataLayout,
942 -> Result<(), LayoutError<'tcx>>
943 where I: Iterator<Item=Result<&'a Layout, LayoutError<'tcx>>> {
944 for (index, field) in fields.enumerate() {
946 if field.is_unsized() {
947 bug!("Union::extend: field #{} of `{}` is unsized",
951 debug!("Union::extend field: {:?} {:?}", field, field.size(dl));
954 self.align = self.align.max(field.align(dl));
955 self.primitive_align = self.primitive_align.max(field.primitive_align(dl));
957 self.min_size = cmp::max(self.min_size, field.size(dl));
960 debug!("Union::extend min-size: {:?}", self.min_size);
965 /// Get the size with trailing alignment padding.
966 pub fn stride(&self) -> Size {
967 self.min_size.abi_align(self.align)
970 pub fn over_align(&self) -> Option<u32> {
971 let align = self.align.abi();
972 let primitive_align = self.primitive_align.abi();
973 if align > primitive_align {
981 /// The first half of a fat pointer.
982 /// - For a trait object, this is the address of the box.
983 /// - For a slice, this is the base address.
984 pub const FAT_PTR_ADDR: usize = 0;
986 /// The second half of a fat pointer.
987 /// - For a trait object, this is the address of the vtable.
988 /// - For a slice, this is the length.
989 pub const FAT_PTR_EXTRA: usize = 1;
991 /// Type layout, from which size and alignment can be cheaply computed.
992 /// For ADTs, it also includes field placement and enum optimizations.
993 /// NOTE: Because Layout is interned, redundant information should be
994 /// kept to a minimum, e.g. it includes no sub-component Ty or Layout.
995 #[derive(Debug, PartialEq, Eq, Hash)]
997 /// TyBool, TyChar, TyInt, TyUint, TyFloat, TyRawPtr, TyRef or TyFnPtr.
1000 // If true, the value cannot represent a bit pattern of all zeroes.
1004 /// SIMD vectors, from structs marked with #[repr(simd)].
1010 /// TyArray, TySlice or TyStr.
1012 /// If true, the size is exact, otherwise it's only a lower bound.
1015 primitive_align: Align,
1020 /// TyRawPtr or TyRef with a !Sized pointee.
1022 metadata: Primitive,
1023 /// If true, the pointer cannot be null.
1027 // Remaining variants are all ADTs such as structs, enums or tuples.
1029 /// C-like enums; basically an integer.
1034 /// Inclusive discriminant range.
1035 /// If min > max, it represents min...u64::MAX followed by 0...max.
1036 // FIXME(eddyb) always use the shortest range, e.g. by finding
1037 // the largest space between two consecutive discriminants and
1038 // taking everything else as the (shortest) discriminant range.
1043 /// Single-case enums, and structs/tuples.
1046 /// If true, the structure is NonZero.
1047 // FIXME(eddyb) use a newtype Layout kind for this.
1051 /// Untagged unions.
1056 /// General-case enums: for each case there is a struct, and they
1057 /// all start with a field for the discriminant.
1060 variants: Vec<Struct>,
1063 primitive_align: Align,
1066 /// Two cases distinguished by a nullable pointer: the case with discriminant
1067 /// `nndiscr` must have single field which is known to be nonnull due to its type.
1068 /// The other case is known to be zero sized. Hence we represent the enum
1069 /// as simply a nullable pointer: if not null it indicates the `nndiscr` variant,
1070 /// otherwise it indicates the other case.
1072 /// For example, `std::option::Option` instantiated at a safe pointer type
1073 /// is represented such that `None` is a null pointer and `Some` is the
1074 /// identity function.
1075 RawNullablePointer {
1080 /// Two cases distinguished by a nullable pointer: the case with discriminant
1081 /// `nndiscr` is represented by the struct `nonnull`, where the `discrfield`th
1082 /// field is known to be nonnull due to its type; if that field is null, then
1083 /// it represents the other case, which is known to be zero sized.
1084 StructWrappedNullablePointer {
1087 /// N.B. There is a 0 at the start, for LLVM GEP through a pointer.
1088 discrfield: FieldPath,
1089 /// Like discrfield, but in source order. For debuginfo.
1090 discrfield_source: FieldPath
1094 #[derive(Copy, Clone, Debug)]
1095 pub enum LayoutError<'tcx> {
1097 SizeOverflow(Ty<'tcx>)
1100 impl<'tcx> fmt::Display for LayoutError<'tcx> {
1101 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1103 LayoutError::Unknown(ty) => {
1104 write!(f, "the type `{:?}` has an unknown layout", ty)
1106 LayoutError::SizeOverflow(ty) => {
1107 write!(f, "the type `{:?}` is too big for the current architecture", ty)
1113 impl<'a, 'tcx> Layout {
1114 pub fn compute_uncached(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1115 param_env: ty::ParamEnv<'tcx>,
1117 -> Result<&'tcx Layout, LayoutError<'tcx>> {
1118 let success = |layout| Ok(tcx.intern_layout(layout));
1119 let dl = &tcx.data_layout;
1120 assert!(!ty.has_infer_types());
1122 let ptr_layout = |pointee: Ty<'tcx>| {
1123 let non_zero = !ty.is_unsafe_ptr();
1124 let pointee = tcx.normalize_associated_type_in_env(&pointee, param_env);
1125 if pointee.is_sized(tcx, param_env, DUMMY_SP) {
1126 Ok(Scalar { value: Pointer, non_zero: non_zero })
1128 let unsized_part = tcx.struct_tail(pointee);
1129 let meta = match unsized_part.sty {
1130 ty::TySlice(_) | ty::TyStr => {
1131 Int(dl.ptr_sized_integer())
1133 ty::TyDynamic(..) => Pointer,
1134 _ => return Err(LayoutError::Unknown(unsized_part))
1136 Ok(FatPointer { metadata: meta, non_zero: non_zero })
1140 let layout = match ty.sty {
1142 ty::TyBool => Scalar { value: Int(I1), non_zero: false },
1143 ty::TyChar => Scalar { value: Int(I32), non_zero: false },
1146 value: Int(Integer::from_attr(dl, attr::SignedInt(ity))),
1150 ty::TyUint(ity) => {
1152 value: Int(Integer::from_attr(dl, attr::UnsignedInt(ity))),
1156 ty::TyFloat(FloatTy::F32) => Scalar { value: F32, non_zero: false },
1157 ty::TyFloat(FloatTy::F64) => Scalar { value: F64, non_zero: false },
1158 ty::TyFnPtr(_) => Scalar { value: Pointer, non_zero: true },
1161 ty::TyNever => Univariant {
1162 variant: Struct::new(dl, &vec![], &ReprOptions::default(),
1163 StructKind::AlwaysSizedUnivariant, ty)?,
1167 // Potentially-fat pointers.
1168 ty::TyRef(_, ty::TypeAndMut { ty: pointee, .. }) |
1169 ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
1170 ptr_layout(pointee)?
1172 ty::TyAdt(def, _) if def.is_box() => {
1173 ptr_layout(ty.boxed_ty())?
1176 // Arrays and slices.
1177 ty::TyArray(element, count) => {
1178 let element = element.layout(tcx, param_env)?;
1179 let element_size = element.size(dl);
1180 // FIXME(eddyb) Don't use host `usize` for array lengths.
1181 let usize_count: usize = count;
1182 let count = usize_count as u64;
1183 if element_size.checked_mul(count, dl).is_none() {
1184 return Err(LayoutError::SizeOverflow(ty));
1188 align: element.align(dl),
1189 primitive_align: element.primitive_align(dl),
1194 ty::TySlice(element) => {
1195 let element = element.layout(tcx, param_env)?;
1198 align: element.align(dl),
1199 primitive_align: element.primitive_align(dl),
1200 element_size: element.size(dl),
1208 primitive_align: dl.i8_align,
1209 element_size: Size::from_bytes(1),
1215 ty::TyFnDef(..) => {
1217 variant: Struct::new(dl, &vec![],
1218 &ReprOptions::default(), StructKind::AlwaysSizedUnivariant, ty)?,
1222 ty::TyDynamic(..) => {
1223 let mut unit = Struct::new(dl, &vec![], &ReprOptions::default(),
1224 StructKind::AlwaysSizedUnivariant, ty)?;
1226 Univariant { variant: unit, non_zero: false }
1229 // Tuples, generators and closures.
1230 ty::TyGenerator(def_id, ref substs, _) => {
1231 let tys = substs.field_tys(def_id, tcx);
1232 let st = Struct::new(dl,
1233 &tys.map(|ty| ty.layout(tcx, param_env))
1234 .collect::<Result<Vec<_>, _>>()?,
1235 &ReprOptions::default(),
1236 StructKind::AlwaysSizedUnivariant, ty)?;
1237 Univariant { variant: st, non_zero: false }
1240 ty::TyClosure(def_id, ref substs) => {
1241 let tys = substs.upvar_tys(def_id, tcx);
1242 let st = Struct::new(dl,
1243 &tys.map(|ty| ty.layout(tcx, param_env))
1244 .collect::<Result<Vec<_>, _>>()?,
1245 &ReprOptions::default(),
1246 StructKind::AlwaysSizedUnivariant, ty)?;
1247 Univariant { variant: st, non_zero: false }
1250 ty::TyTuple(tys, _) => {
1251 let kind = if tys.len() == 0 {
1252 StructKind::AlwaysSizedUnivariant
1254 StructKind::MaybeUnsizedUnivariant
1257 let st = Struct::new(dl,
1258 &tys.iter().map(|ty| ty.layout(tcx, param_env))
1259 .collect::<Result<Vec<_>, _>>()?,
1260 &ReprOptions::default(), kind, ty)?;
1261 Univariant { variant: st, non_zero: false }
1264 // SIMD vector types.
1265 ty::TyAdt(def, ..) if def.repr.simd() => {
1266 let element = ty.simd_type(tcx);
1267 match *element.layout(tcx, param_env)? {
1268 Scalar { value, .. } => {
1269 return success(Vector {
1271 count: ty.simd_size(tcx) as u64
1275 tcx.sess.fatal(&format!("monomorphising SIMD type `{}` with \
1276 a non-machine element type `{}`",
1283 ty::TyAdt(def, substs) => {
1284 if def.variants.is_empty() {
1285 // Uninhabitable; represent as unit
1286 // (Typechecking will reject discriminant-sizing attrs.)
1288 return success(Univariant {
1289 variant: Struct::new(dl, &vec![],
1290 &def.repr, StructKind::AlwaysSizedUnivariant, ty)?,
1295 if def.is_enum() && def.variants.iter().all(|v| v.fields.is_empty()) {
1296 // All bodies empty -> intlike
1297 let (mut min, mut max, mut non_zero) = (i64::max_value(),
1300 for discr in def.discriminants(tcx) {
1301 let x = discr.to_u128_unchecked() as i64;
1302 if x == 0 { non_zero = false; }
1303 if x < min { min = x; }
1304 if x > max { max = x; }
1307 // FIXME: should handle i128? signed-value based impl is weird and hard to
1309 let (discr, signed) = Integer::repr_discr(tcx, ty, &def.repr, min, max);
1310 return success(CEnum {
1314 // FIXME: should be u128?
1320 if !def.is_enum() || (def.variants.len() == 1 &&
1321 !def.repr.inhibit_enum_layout_opt()) {
1322 // Struct, or union, or univariant enum equivalent to a struct.
1323 // (Typechecking will reject discriminant-sizing attrs.)
1325 let kind = if def.is_enum() || def.variants[0].fields.len() == 0{
1326 StructKind::AlwaysSizedUnivariant
1328 let param_env = tcx.param_env(def.did);
1329 let fields = &def.variants[0].fields;
1330 let last_field = &fields[fields.len()-1];
1331 let always_sized = tcx.type_of(last_field.did)
1332 .is_sized(tcx, param_env, DUMMY_SP);
1333 if !always_sized { StructKind::MaybeUnsizedUnivariant }
1334 else { StructKind::AlwaysSizedUnivariant }
1337 let fields = def.variants[0].fields.iter().map(|field| {
1338 field.ty(tcx, substs).layout(tcx, param_env)
1339 }).collect::<Result<Vec<_>, _>>()?;
1340 let layout = if def.is_union() {
1341 let mut un = Union::new(dl, &def.repr);
1342 un.extend(dl, fields.iter().map(|&f| Ok(f)), ty)?;
1343 UntaggedUnion { variants: un }
1345 let st = Struct::new(dl, &fields, &def.repr,
1347 let non_zero = Some(def.did) == tcx.lang_items().non_zero();
1348 Univariant { variant: st, non_zero: non_zero }
1350 return success(layout);
1353 // Since there's at least one
1354 // non-empty body, explicit discriminants should have
1355 // been rejected by a checker before this point.
1356 for (i, v) in def.variants.iter().enumerate() {
1357 if v.discr != ty::VariantDiscr::Relative(i) {
1358 bug!("non-C-like enum {} with specified discriminants",
1359 tcx.item_path_str(def.did));
1363 // Cache the substituted and normalized variant field types.
1364 let variants = def.variants.iter().map(|v| {
1365 v.fields.iter().map(|field| field.ty(tcx, substs)).collect::<Vec<_>>()
1366 }).collect::<Vec<_>>();
1368 if variants.len() == 2 && !def.repr.inhibit_enum_layout_opt() {
1369 // Nullable pointer optimization
1371 let other_fields = variants[1 - discr].iter().map(|ty| {
1372 ty.layout(tcx, param_env)
1374 if !Struct::would_be_zero_sized(dl, other_fields)? {
1377 let paths = Struct::non_zero_field_paths(tcx,
1379 variants[discr].iter().cloned(),
1381 let (mut path, mut path_source) = if let Some(p) = paths { p }
1384 // FIXME(eddyb) should take advantage of a newtype.
1385 if path == &[0] && variants[discr].len() == 1 {
1386 let value = match *variants[discr][0].layout(tcx, param_env)? {
1387 Scalar { value, .. } => value,
1388 CEnum { discr, .. } => Int(discr),
1389 _ => bug!("Layout::compute: `{}`'s non-zero \
1390 `{}` field not scalar?!",
1391 ty, variants[discr][0])
1393 return success(RawNullablePointer {
1394 nndiscr: discr as u64,
1399 let st = Struct::new(dl,
1400 &variants[discr].iter().map(|ty| ty.layout(tcx, param_env))
1401 .collect::<Result<Vec<_>, _>>()?,
1402 &def.repr, StructKind::AlwaysSizedUnivariant, ty)?;
1404 // We have to fix the last element of path here.
1405 let mut i = *path.last().unwrap();
1406 i = st.memory_index[i as usize];
1407 *path.last_mut().unwrap() = i;
1408 path.push(0); // For GEP through a pointer.
1410 path_source.push(0);
1411 path_source.reverse();
1413 return success(StructWrappedNullablePointer {
1414 nndiscr: discr as u64,
1417 discrfield_source: path_source
1422 // The general case.
1423 let discr_max = (variants.len() - 1) as i64;
1424 assert!(discr_max >= 0);
1425 let (min_ity, _) = Integer::repr_discr(tcx, ty, &def.repr, 0, discr_max);
1426 let mut align = dl.aggregate_align;
1427 let mut primitive_align = dl.aggregate_align;
1428 let mut size = Size::from_bytes(0);
1430 // We're interested in the smallest alignment, so start large.
1431 let mut start_align = Align::from_bytes(256, 256).unwrap();
1433 // Create the set of structs that represent each variant
1434 // Use the minimum integer type we figured out above
1435 let discr = Scalar { value: Int(min_ity), non_zero: false };
1436 let mut variants = variants.into_iter().map(|fields| {
1437 let mut fields = fields.into_iter().map(|field| {
1438 field.layout(tcx, param_env)
1439 }).collect::<Result<Vec<_>, _>>()?;
1440 fields.insert(0, &discr);
1441 let st = Struct::new(dl,
1443 &def.repr, StructKind::EnumVariant, ty)?;
1444 // Find the first field we can't move later
1445 // to make room for a larger discriminant.
1446 // It is important to skip the first field.
1447 for i in st.field_index_by_increasing_offset().skip(1) {
1448 let field = fields[i];
1449 let field_align = field.align(dl);
1450 if field.size(dl).bytes() != 0 || field_align.abi() != 1 {
1451 start_align = start_align.min(field_align);
1455 size = cmp::max(size, st.min_size);
1456 align = align.max(st.align);
1457 primitive_align = primitive_align.max(st.primitive_align);
1459 }).collect::<Result<Vec<_>, _>>()?;
1461 // Align the maximum variant size to the largest alignment.
1462 size = size.abi_align(align);
1464 if size.bytes() >= dl.obj_size_bound() {
1465 return Err(LayoutError::SizeOverflow(ty));
1468 let typeck_ity = Integer::from_attr(dl, def.repr.discr_type());
1469 if typeck_ity < min_ity {
1470 // It is a bug if Layout decided on a greater discriminant size than typeck for
1471 // some reason at this point (based on values discriminant can take on). Mostly
1472 // because this discriminant will be loaded, and then stored into variable of
1473 // type calculated by typeck. Consider such case (a bug): typeck decided on
1474 // byte-sized discriminant, but layout thinks we need a 16-bit to store all
1475 // discriminant values. That would be a bug, because then, in trans, in order
1476 // to store this 16-bit discriminant into 8-bit sized temporary some of the
1477 // space necessary to represent would have to be discarded (or layout is wrong
1478 // on thinking it needs 16 bits)
1479 bug!("layout decided on a larger discriminant type ({:?}) than typeck ({:?})",
1480 min_ity, typeck_ity);
1481 // However, it is fine to make discr type however large (as an optimisation)
1482 // after this point – we’ll just truncate the value we load in trans.
1485 // Check to see if we should use a different type for the
1486 // discriminant. We can safely use a type with the same size
1487 // as the alignment of the first field of each variant.
1488 // We increase the size of the discriminant to avoid LLVM copying
1489 // padding when it doesn't need to. This normally causes unaligned
1490 // load/stores and excessive memcpy/memset operations. By using a
1491 // bigger integer size, LLVM can be sure about it's contents and
1492 // won't be so conservative.
1494 // Use the initial field alignment
1495 let mut ity = Integer::for_abi_align(dl, start_align).unwrap_or(min_ity);
1497 // If the alignment is not larger than the chosen discriminant size,
1498 // don't use the alignment as the final size.
1502 // Patch up the variants' first few fields.
1503 let old_ity_size = Int(min_ity).size(dl);
1504 let new_ity_size = Int(ity).size(dl);
1505 for variant in &mut variants {
1506 for i in variant.offsets.iter_mut() {
1507 // The first field is the discrimminant, at offset 0.
1508 // These aren't in order, and we need to skip it.
1509 if *i <= old_ity_size && *i > Size::from_bytes(0) {
1513 // We might be making the struct larger.
1514 if variant.min_size <= old_ity_size {
1515 variant.min_size = new_ity_size;
1529 // Types with no meaningful known layout.
1530 ty::TyProjection(_) | ty::TyAnon(..) => {
1531 let normalized = tcx.normalize_associated_type_in_env(&ty, param_env);
1532 if ty == normalized {
1533 return Err(LayoutError::Unknown(ty));
1535 return normalized.layout(tcx, param_env);
1538 return Err(LayoutError::Unknown(ty));
1540 ty::TyInfer(_) | ty::TyError => {
1541 bug!("Layout::compute: unexpected type `{}`", ty)
1548 /// Returns true if the layout corresponds to an unsized type.
1549 pub fn is_unsized(&self) -> bool {
1551 Scalar {..} | Vector {..} | FatPointer {..} |
1552 CEnum {..} | UntaggedUnion {..} | General {..} |
1553 RawNullablePointer {..} |
1554 StructWrappedNullablePointer {..} => false,
1556 Array { sized, .. } |
1557 Univariant { variant: Struct { sized, .. }, .. } => !sized
1561 pub fn size<C: HasDataLayout>(&self, cx: C) -> Size {
1562 let dl = cx.data_layout();
1565 Scalar { value, .. } | RawNullablePointer { value, .. } => {
1569 Vector { element, count } => {
1570 let element_size = element.size(dl);
1571 let vec_size = match element_size.checked_mul(count, dl) {
1573 None => bug!("Layout::size({:?}): {} * {} overflowed",
1574 self, element_size.bytes(), count)
1576 vec_size.abi_align(self.align(dl))
1579 Array { element_size, count, .. } => {
1580 match element_size.checked_mul(count, dl) {
1582 None => bug!("Layout::size({:?}): {} * {} overflowed",
1583 self, element_size.bytes(), count)
1587 FatPointer { metadata, .. } => {
1588 // Effectively a (ptr, meta) tuple.
1589 Pointer.size(dl).abi_align(metadata.align(dl))
1590 .checked_add(metadata.size(dl), dl).unwrap()
1591 .abi_align(self.align(dl))
1594 CEnum { discr, .. } => Int(discr).size(dl),
1595 General { size, .. } => size,
1596 UntaggedUnion { ref variants } => variants.stride(),
1598 Univariant { ref variant, .. } |
1599 StructWrappedNullablePointer { nonnull: ref variant, .. } => {
1605 pub fn align<C: HasDataLayout>(&self, cx: C) -> Align {
1606 let dl = cx.data_layout();
1609 Scalar { value, .. } | RawNullablePointer { value, .. } => {
1613 Vector { element, count } => {
1614 let elem_size = element.size(dl);
1615 let vec_size = match elem_size.checked_mul(count, dl) {
1617 None => bug!("Layout::align({:?}): {} * {} overflowed",
1618 self, elem_size.bytes(), count)
1620 for &(size, align) in &dl.vector_align {
1621 if size == vec_size {
1625 // Default to natural alignment, which is what LLVM does.
1626 // That is, use the size, rounded up to a power of 2.
1627 let align = vec_size.bytes().next_power_of_two();
1628 Align::from_bytes(align, align).unwrap()
1631 FatPointer { metadata, .. } => {
1632 // Effectively a (ptr, meta) tuple.
1633 Pointer.align(dl).max(metadata.align(dl))
1636 CEnum { discr, .. } => Int(discr).align(dl),
1637 Array { align, .. } | General { align, .. } => align,
1638 UntaggedUnion { ref variants } => variants.align,
1640 Univariant { ref variant, .. } |
1641 StructWrappedNullablePointer { nonnull: ref variant, .. } => {
1647 /// Returns alignment before repr alignment is applied
1648 pub fn primitive_align(&self, dl: &TargetDataLayout) -> Align {
1650 Array { primitive_align, .. } | General { primitive_align, .. } => primitive_align,
1651 Univariant { ref variant, .. } |
1652 StructWrappedNullablePointer { nonnull: ref variant, .. } => {
1653 variant.primitive_align
1660 /// Returns repr alignment if it is greater than the primitive alignment.
1661 pub fn over_align(&self, dl: &TargetDataLayout) -> Option<u32> {
1662 let align = self.align(dl);
1663 let primitive_align = self.primitive_align(dl);
1664 if align.abi() > primitive_align.abi() {
1665 Some(align.abi() as u32)
1671 pub fn field_offset<C: HasDataLayout>(&self,
1674 variant_index: Option<usize>)
1676 let dl = cx.data_layout();
1681 UntaggedUnion { .. } |
1682 RawNullablePointer { .. } => {
1686 Vector { element, count } => {
1687 let element_size = element.size(dl);
1690 Size::from_bytes(element_size.bytes() * count)
1693 Array { element_size, count, .. } => {
1696 Size::from_bytes(element_size.bytes() * count)
1699 FatPointer { metadata, .. } => {
1700 // Effectively a (ptr, meta) tuple.
1705 Pointer.size(dl).abi_align(metadata.align(dl))
1709 Univariant { ref variant, .. } => variant.offsets[i],
1711 General { ref variants, .. } => {
1712 let v = variant_index.expect("variant index required");
1713 variants[v].offsets[i + 1]
1716 StructWrappedNullablePointer { nndiscr, ref nonnull, .. } => {
1717 if Some(nndiscr as usize) == variant_index {
1726 /// This is invoked by the `layout_raw` query to record the final
1727 /// layout of each type.
1729 pub fn record_layout_for_printing(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1731 param_env: ty::ParamEnv<'tcx>,
1733 // If we are running with `-Zprint-type-sizes`, record layouts for
1734 // dumping later. Ignore layouts that are done with non-empty
1735 // environments or non-monomorphic layouts, as the user only wants
1736 // to see the stuff resulting from the final trans session.
1738 !tcx.sess.opts.debugging_opts.print_type_sizes ||
1739 ty.has_param_types() ||
1741 !param_env.caller_bounds.is_empty()
1746 Self::record_layout_for_printing_outlined(tcx, ty, param_env, layout)
1749 fn record_layout_for_printing_outlined(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1751 param_env: ty::ParamEnv<'tcx>,
1753 // (delay format until we actually need it)
1754 let record = |kind, opt_discr_size, variants| {
1755 let type_desc = format!("{:?}", ty);
1756 let overall_size = layout.size(tcx);
1757 let align = layout.align(tcx);
1758 tcx.sess.code_stats.borrow_mut().record_type_size(kind,
1766 let (adt_def, substs) = match ty.sty {
1767 ty::TyAdt(ref adt_def, substs) => {
1768 debug!("print-type-size t: `{:?}` process adt", ty);
1772 ty::TyClosure(..) => {
1773 debug!("print-type-size t: `{:?}` record closure", ty);
1774 record(DataTypeKind::Closure, None, vec![]);
1779 debug!("print-type-size t: `{:?}` skip non-nominal", ty);
1784 let adt_kind = adt_def.adt_kind();
1786 let build_field_info = |(field_name, field_ty): (ast::Name, Ty<'tcx>), offset: &Size| {
1787 let layout = field_ty.layout(tcx, param_env);
1789 Err(_) => bug!("no layout found for field {} type: `{:?}`", field_name, field_ty),
1790 Ok(field_layout) => {
1791 session::FieldInfo {
1792 name: field_name.to_string(),
1793 offset: offset.bytes(),
1794 size: field_layout.size(tcx).bytes(),
1795 align: field_layout.align(tcx).abi(),
1801 let build_primitive_info = |name: ast::Name, value: &Primitive| {
1802 session::VariantInfo {
1803 name: Some(name.to_string()),
1804 kind: session::SizeKind::Exact,
1805 align: value.align(tcx).abi(),
1806 size: value.size(tcx).bytes(),
1812 WithDiscrim(&'a Struct),
1813 NoDiscrim(&'a Struct),
1816 let build_variant_info = |n: Option<ast::Name>,
1817 flds: &[(ast::Name, Ty<'tcx>)],
1819 let (s, field_offsets) = match layout {
1820 Fields::WithDiscrim(s) => (s, &s.offsets[1..]),
1821 Fields::NoDiscrim(s) => (s, &s.offsets[0..]),
1823 let field_info: Vec<_> =
1825 .zip(field_offsets.iter())
1826 .map(|(&field_name_ty, offset)| build_field_info(field_name_ty, offset))
1829 session::VariantInfo {
1830 name: n.map(|n|n.to_string()),
1832 session::SizeKind::Exact
1834 session::SizeKind::Min
1836 align: s.align.abi(),
1837 size: s.min_size.bytes(),
1843 Layout::StructWrappedNullablePointer { nonnull: ref variant_layout,
1846 discrfield_source: _ } => {
1847 debug!("print-type-size t: `{:?}` adt struct-wrapped nullable nndiscr {} is {:?}",
1848 ty, nndiscr, variant_layout);
1849 let variant_def = &adt_def.variants[nndiscr as usize];
1850 let fields: Vec<_> =
1851 variant_def.fields.iter()
1852 .map(|field_def| (field_def.name, field_def.ty(tcx, substs)))
1854 record(adt_kind.into(),
1856 vec![build_variant_info(Some(variant_def.name),
1858 Fields::NoDiscrim(variant_layout))]);
1860 Layout::RawNullablePointer { nndiscr, value } => {
1861 debug!("print-type-size t: `{:?}` adt raw nullable nndiscr {} is {:?}",
1862 ty, nndiscr, value);
1863 let variant_def = &adt_def.variants[nndiscr as usize];
1864 record(adt_kind.into(), None,
1865 vec![build_primitive_info(variant_def.name, &value)]);
1867 Layout::Univariant { variant: ref variant_layout, non_zero: _ } => {
1868 let variant_names = || {
1869 adt_def.variants.iter().map(|v|format!("{}", v.name)).collect::<Vec<_>>()
1871 debug!("print-type-size t: `{:?}` adt univariant {:?} variants: {:?}",
1872 ty, variant_layout, variant_names());
1873 assert!(adt_def.variants.len() <= 1,
1874 "univariant with variants {:?}", variant_names());
1875 if adt_def.variants.len() == 1 {
1876 let variant_def = &adt_def.variants[0];
1877 let fields: Vec<_> =
1878 variant_def.fields.iter()
1879 .map(|f| (f.name, f.ty(tcx, substs)))
1881 record(adt_kind.into(),
1883 vec![build_variant_info(Some(variant_def.name),
1885 Fields::NoDiscrim(variant_layout))]);
1887 // (This case arises for *empty* enums; so give it
1889 record(adt_kind.into(), None, vec![]);
1893 Layout::General { ref variants, discr, .. } => {
1894 debug!("print-type-size t: `{:?}` adt general variants def {} layouts {} {:?}",
1895 ty, adt_def.variants.len(), variants.len(), variants);
1896 let variant_infos: Vec<_> =
1897 adt_def.variants.iter()
1898 .zip(variants.iter())
1899 .map(|(variant_def, variant_layout)| {
1900 let fields: Vec<_> =
1903 .map(|f| (f.name, f.ty(tcx, substs)))
1905 build_variant_info(Some(variant_def.name),
1907 Fields::WithDiscrim(variant_layout))
1910 record(adt_kind.into(), Some(discr.size()), variant_infos);
1913 Layout::UntaggedUnion { ref variants } => {
1914 debug!("print-type-size t: `{:?}` adt union variants {:?}",
1916 // layout does not currently store info about each
1918 record(adt_kind.into(), None, Vec::new());
1921 Layout::CEnum { discr, .. } => {
1922 debug!("print-type-size t: `{:?}` adt c-like enum", ty);
1923 let variant_infos: Vec<_> =
1924 adt_def.variants.iter()
1925 .map(|variant_def| {
1926 build_primitive_info(variant_def.name,
1927 &Primitive::Int(discr))
1930 record(adt_kind.into(), Some(discr.size()), variant_infos);
1933 // other cases provide little interesting (i.e. adjustable
1934 // via representation tweaks) size info beyond total size.
1935 Layout::Scalar { .. } |
1936 Layout::Vector { .. } |
1937 Layout::Array { .. } |
1938 Layout::FatPointer { .. } => {
1939 debug!("print-type-size t: `{:?}` adt other", ty);
1940 record(adt_kind.into(), None, Vec::new())
1946 /// Type size "skeleton", i.e. the only information determining a type's size.
1947 /// While this is conservative, (aside from constant sizes, only pointers,
1948 /// newtypes thereof and null pointer optimized enums are allowed), it is
1949 /// enough to statically check common usecases of transmute.
1950 #[derive(Copy, Clone, Debug)]
1951 pub enum SizeSkeleton<'tcx> {
1952 /// Any statically computable Layout.
1955 /// A potentially-fat pointer.
1957 /// If true, this pointer is never null.
1959 /// The type which determines the unsized metadata, if any,
1960 /// of this pointer. Either a type parameter or a projection
1961 /// depending on one, with regions erased.
1966 impl<'a, 'tcx> SizeSkeleton<'tcx> {
1967 pub fn compute(ty: Ty<'tcx>,
1968 tcx: TyCtxt<'a, 'tcx, 'tcx>,
1969 param_env: ty::ParamEnv<'tcx>)
1970 -> Result<SizeSkeleton<'tcx>, LayoutError<'tcx>> {
1971 assert!(!ty.has_infer_types());
1973 // First try computing a static layout.
1974 let err = match ty.layout(tcx, param_env) {
1976 return Ok(SizeSkeleton::Known(layout.size(tcx)));
1981 let ptr_skeleton = |pointee: Ty<'tcx>| {
1982 let non_zero = !ty.is_unsafe_ptr();
1983 let tail = tcx.struct_tail(pointee);
1985 ty::TyParam(_) | ty::TyProjection(_) => {
1986 assert!(tail.has_param_types() || tail.has_self_ty());
1987 Ok(SizeSkeleton::Pointer {
1989 tail: tcx.erase_regions(&tail)
1993 bug!("SizeSkeleton::compute({}): layout errored ({}), yet \
1994 tail `{}` is not a type parameter or a projection",
2001 ty::TyRef(_, ty::TypeAndMut { ty: pointee, .. }) |
2002 ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
2003 ptr_skeleton(pointee)
2005 ty::TyAdt(def, _) if def.is_box() => {
2006 ptr_skeleton(ty.boxed_ty())
2009 ty::TyAdt(def, substs) => {
2010 // Only newtypes and enums w/ nullable pointer optimization.
2011 if def.is_union() || def.variants.is_empty() || def.variants.len() > 2 {
2015 // Get a zero-sized variant or a pointer newtype.
2016 let zero_or_ptr_variant = |i: usize| {
2017 let fields = def.variants[i].fields.iter().map(|field| {
2018 SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env)
2021 for field in fields {
2024 SizeSkeleton::Known(size) => {
2025 if size.bytes() > 0 {
2029 SizeSkeleton::Pointer {..} => {
2040 let v0 = zero_or_ptr_variant(0)?;
2042 if def.variants.len() == 1 {
2043 if let Some(SizeSkeleton::Pointer { non_zero, tail }) = v0 {
2044 return Ok(SizeSkeleton::Pointer {
2045 non_zero: non_zero ||
2046 Some(def.did) == tcx.lang_items().non_zero(),
2054 let v1 = zero_or_ptr_variant(1)?;
2055 // Nullable pointer enum optimization.
2057 (Some(SizeSkeleton::Pointer { non_zero: true, tail }), None) |
2058 (None, Some(SizeSkeleton::Pointer { non_zero: true, tail })) => {
2059 Ok(SizeSkeleton::Pointer {
2068 ty::TyProjection(_) | ty::TyAnon(..) => {
2069 let normalized = tcx.normalize_associated_type_in_env(&ty, param_env);
2070 if ty == normalized {
2073 SizeSkeleton::compute(normalized, tcx, param_env)
2081 pub fn same_size(self, other: SizeSkeleton) -> bool {
2082 match (self, other) {
2083 (SizeSkeleton::Known(a), SizeSkeleton::Known(b)) => a == b,
2084 (SizeSkeleton::Pointer { tail: a, .. },
2085 SizeSkeleton::Pointer { tail: b, .. }) => a == b,
2091 /// A pair of a type and its layout. Implements various
2092 /// type traversal APIs (e.g. recursing into fields).
2093 #[derive(Copy, Clone, Debug)]
2094 pub struct TyLayout<'tcx> {
2096 pub layout: &'tcx Layout,
2097 pub variant_index: Option<usize>,
2100 impl<'tcx> Deref for TyLayout<'tcx> {
2101 type Target = Layout;
2102 fn deref(&self) -> &Layout {
2107 pub trait LayoutTyper<'tcx>: HasDataLayout {
2110 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx>;
2111 fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout;
2112 fn normalize_projections(self, ty: Ty<'tcx>) -> Ty<'tcx>;
2115 /// Combines a tcx with the parameter environment so that you can
2116 /// compute layout operations.
2117 #[derive(Copy, Clone)]
2118 pub struct LayoutCx<'a, 'tcx: 'a> {
2119 tcx: TyCtxt<'a, 'tcx, 'tcx>,
2120 param_env: ty::ParamEnv<'tcx>,
2123 impl<'a, 'tcx> LayoutCx<'a, 'tcx> {
2124 pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
2125 LayoutCx { tcx, param_env }
2129 impl<'a, 'tcx> HasDataLayout for LayoutCx<'a, 'tcx> {
2130 fn data_layout(&self) -> &TargetDataLayout {
2131 &self.tcx.data_layout
2135 impl<'a, 'tcx> LayoutTyper<'tcx> for LayoutCx<'a, 'tcx> {
2136 type TyLayout = Result<TyLayout<'tcx>, LayoutError<'tcx>>;
2138 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'tcx, 'tcx> {
2142 fn layout_of(self, ty: Ty<'tcx>) -> Self::TyLayout {
2143 let ty = self.normalize_projections(ty);
2147 layout: ty.layout(self.tcx, self.param_env)?,
2152 fn normalize_projections(self, ty: Ty<'tcx>) -> Ty<'tcx> {
2153 self.tcx.normalize_associated_type_in_env(&ty, self.param_env)
2157 impl<'a, 'tcx> TyLayout<'tcx> {
2158 pub fn for_variant(&self, variant_index: usize) -> Self {
2160 variant_index: Some(variant_index),
2165 pub fn field_offset<C: HasDataLayout>(&self, cx: C, i: usize) -> Size {
2166 self.layout.field_offset(cx, i, self.variant_index)
2169 pub fn field_count(&self) -> usize {
2170 // Handle enum/union through the type rather than Layout.
2171 if let ty::TyAdt(def, _) = self.ty.sty {
2172 let v = self.variant_index.unwrap_or(0);
2173 if def.variants.is_empty() {
2177 return def.variants[v].fields.len();
2181 match *self.layout {
2183 bug!("TyLayout::field_count({:?}): not applicable", self)
2186 // Handled above (the TyAdt case).
2189 UntaggedUnion { .. } |
2190 RawNullablePointer { .. } |
2191 StructWrappedNullablePointer { .. } => bug!(),
2193 FatPointer { .. } => 2,
2195 Vector { count, .. } |
2196 Array { count, .. } => {
2197 let usize_count = count as usize;
2198 assert_eq!(usize_count as u64, count);
2202 Univariant { ref variant, .. } => variant.offsets.len(),
2206 pub fn field_type<C: LayoutTyper<'tcx>>(&self, cx: C, i: usize) -> Ty<'tcx> {
2209 let ptr_field_type = |pointee: Ty<'tcx>| {
2211 let slice = |element: Ty<'tcx>| {
2213 tcx.mk_mut_ptr(element)
2218 match tcx.struct_tail(pointee).sty {
2219 ty::TySlice(element) => slice(element),
2220 ty::TyStr => slice(tcx.types.u8),
2221 ty::TyDynamic(..) => tcx.mk_mut_ptr(tcx.mk_nil()),
2222 _ => bug!("TyLayout::field_type({:?}): not applicable", self)
2235 ty::TyDynamic(..) => {
2236 bug!("TyLayout::field_type({:?}): not applicable", self)
2239 // Potentially-fat pointers.
2240 ty::TyRef(_, ty::TypeAndMut { ty: pointee, .. }) |
2241 ty::TyRawPtr(ty::TypeAndMut { ty: pointee, .. }) => {
2242 ptr_field_type(pointee)
2244 ty::TyAdt(def, _) if def.is_box() => {
2245 ptr_field_type(self.ty.boxed_ty())
2248 // Arrays and slices.
2249 ty::TyArray(element, _) |
2250 ty::TySlice(element) => element,
2251 ty::TyStr => tcx.types.u8,
2253 // Tuples, generators and closures.
2254 ty::TyClosure(def_id, ref substs) => {
2255 substs.upvar_tys(def_id, tcx).nth(i).unwrap()
2258 ty::TyGenerator(def_id, ref substs, _) => {
2259 substs.field_tys(def_id, tcx).nth(i).unwrap()
2262 ty::TyTuple(tys, _) => tys[i],
2264 // SIMD vector types.
2265 ty::TyAdt(def, ..) if def.repr.simd() => {
2266 self.ty.simd_type(tcx)
2270 ty::TyAdt(def, substs) => {
2271 def.variants[self.variant_index.unwrap_or(0)].fields[i].ty(tcx, substs)
2274 ty::TyProjection(_) | ty::TyAnon(..) | ty::TyParam(_) |
2275 ty::TyInfer(_) | ty::TyError => {
2276 bug!("TyLayout::field_type: unexpected type `{}`", self.ty)
2281 pub fn field<C: LayoutTyper<'tcx>>(&self,
2285 cx.layout_of(cx.normalize_projections(self.field_type(cx, i)))