4 use crate::spec::Target;
6 use std::convert::{TryFrom, TryInto};
9 use std::num::NonZeroUsize;
10 use std::ops::{Add, AddAssign, Deref, Mul, RangeInclusive, Sub};
11 use std::str::FromStr;
13 use rustc_data_structures::intern::Interned;
14 use rustc_index::vec::{Idx, IndexVec};
15 use rustc_macros::HashStable_Generic;
16 use rustc_serialize::json::{Json, ToJson};
20 /// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout)
21 /// for a target, which contains everything needed to compute layouts.
22 pub struct TargetDataLayout {
24 pub i1_align: AbiAndPrefAlign,
25 pub i8_align: AbiAndPrefAlign,
26 pub i16_align: AbiAndPrefAlign,
27 pub i32_align: AbiAndPrefAlign,
28 pub i64_align: AbiAndPrefAlign,
29 pub i128_align: AbiAndPrefAlign,
30 pub f32_align: AbiAndPrefAlign,
31 pub f64_align: AbiAndPrefAlign,
32 pub pointer_size: Size,
33 pub pointer_align: AbiAndPrefAlign,
34 pub aggregate_align: AbiAndPrefAlign,
36 /// Alignments for vector types.
37 pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
39 pub instruction_address_space: AddressSpace,
41 /// Minimum size of #[repr(C)] enums (default I32 bits)
42 pub c_enum_min_size: Integer,
45 impl Default for TargetDataLayout {
46 /// Creates an instance of `TargetDataLayout`.
47 fn default() -> TargetDataLayout {
48 let align = |bits| Align::from_bits(bits).unwrap();
51 i1_align: AbiAndPrefAlign::new(align(8)),
52 i8_align: AbiAndPrefAlign::new(align(8)),
53 i16_align: AbiAndPrefAlign::new(align(16)),
54 i32_align: AbiAndPrefAlign::new(align(32)),
55 i64_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
56 i128_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
57 f32_align: AbiAndPrefAlign::new(align(32)),
58 f64_align: AbiAndPrefAlign::new(align(64)),
59 pointer_size: Size::from_bits(64),
60 pointer_align: AbiAndPrefAlign::new(align(64)),
61 aggregate_align: AbiAndPrefAlign { abi: align(0), pref: align(64) },
63 (Size::from_bits(64), AbiAndPrefAlign::new(align(64))),
64 (Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
66 instruction_address_space: AddressSpace::DATA,
67 c_enum_min_size: Integer::I32,
72 impl TargetDataLayout {
73 pub fn parse(target: &Target) -> Result<TargetDataLayout, String> {
74 // Parse an address space index from a string.
75 let parse_address_space = |s: &str, cause: &str| {
76 s.parse::<u32>().map(AddressSpace).map_err(|err| {
77 format!("invalid address space `{}` for `{}` in \"data-layout\": {}", s, cause, err)
81 // Parse a bit count from a string.
82 let parse_bits = |s: &str, kind: &str, cause: &str| {
83 s.parse::<u64>().map_err(|err| {
84 format!("invalid {} `{}` for `{}` in \"data-layout\": {}", kind, s, cause, err)
88 // Parse a size string.
89 let size = |s: &str, cause: &str| parse_bits(s, "size", cause).map(Size::from_bits);
91 // Parse an alignment string.
92 let align = |s: &[&str], cause: &str| {
94 return Err(format!("missing alignment for `{}` in \"data-layout\"", cause));
96 let align_from_bits = |bits| {
97 Align::from_bits(bits).map_err(|err| {
98 format!("invalid alignment for `{}` in \"data-layout\": {}", cause, err)
101 let abi = parse_bits(s[0], "alignment", cause)?;
102 let pref = s.get(1).map_or(Ok(abi), |pref| parse_bits(pref, "alignment", cause))?;
103 Ok(AbiAndPrefAlign { abi: align_from_bits(abi)?, pref: align_from_bits(pref)? })
106 let mut dl = TargetDataLayout::default();
107 let mut i128_align_src = 64;
108 for spec in target.data_layout.split('-') {
109 let spec_parts = spec.split(':').collect::<Vec<_>>();
112 ["e"] => dl.endian = Endian::Little,
113 ["E"] => dl.endian = Endian::Big,
114 [p] if p.starts_with('P') => {
115 dl.instruction_address_space = parse_address_space(&p[1..], "P")?
117 ["a", ref a @ ..] => dl.aggregate_align = align(a, "a")?,
118 ["f32", ref a @ ..] => dl.f32_align = align(a, "f32")?,
119 ["f64", ref a @ ..] => dl.f64_align = align(a, "f64")?,
120 [p @ "p", s, ref a @ ..] | [p @ "p0", s, ref a @ ..] => {
121 dl.pointer_size = size(s, p)?;
122 dl.pointer_align = align(a, p)?;
124 [s, ref a @ ..] if s.starts_with('i') => {
125 let Ok(bits) = s[1..].parse::<u64>() else {
126 size(&s[1..], "i")?; // For the user error.
129 let a = align(a, s)?;
131 1 => dl.i1_align = a,
132 8 => dl.i8_align = a,
133 16 => dl.i16_align = a,
134 32 => dl.i32_align = a,
135 64 => dl.i64_align = a,
138 if bits >= i128_align_src && bits <= 128 {
139 // Default alignment for i128 is decided by taking the alignment of
140 // largest-sized i{64..=128}.
141 i128_align_src = bits;
145 [s, ref a @ ..] if s.starts_with('v') => {
146 let v_size = size(&s[1..], "v")?;
147 let a = align(a, s)?;
148 if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
152 // No existing entry, add a new one.
153 dl.vector_align.push((v_size, a));
155 _ => {} // Ignore everything else.
159 // Perform consistency checks against the Target information.
160 if dl.endian != target.endian {
162 "inconsistent target specification: \"data-layout\" claims \
163 architecture is {}-endian, while \"target-endian\" is `{}`",
165 target.endian.as_str(),
169 if dl.pointer_size.bits() != target.pointer_width.into() {
171 "inconsistent target specification: \"data-layout\" claims \
172 pointers are {}-bit, while \"target-pointer-width\" is `{}`",
173 dl.pointer_size.bits(),
178 dl.c_enum_min_size = Integer::from_size(Size::from_bits(target.c_enum_min_bits))?;
183 /// Returns exclusive upper bound on object size.
185 /// The theoretical maximum object size is defined as the maximum positive `isize` value.
186 /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
187 /// index every address within an object along with one byte past the end, along with allowing
188 /// `isize` to store the difference between any two pointers into an object.
190 /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
191 /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
192 /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
193 /// address space on 64-bit ARMv8 and x86_64.
195 pub fn obj_size_bound(&self) -> u64 {
196 match self.pointer_size.bits() {
200 bits => panic!("obj_size_bound: unknown pointer bit size {}", bits),
205 pub fn ptr_sized_integer(&self) -> Integer {
206 match self.pointer_size.bits() {
210 bits => panic!("ptr_sized_integer: unknown pointer bit size {}", bits),
215 pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
216 for &(size, align) in &self.vector_align {
217 if size == vec_size {
221 // Default to natural alignment, which is what LLVM does.
222 // That is, use the size, rounded up to a power of 2.
223 AbiAndPrefAlign::new(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap())
227 pub trait HasDataLayout {
228 fn data_layout(&self) -> &TargetDataLayout;
231 impl HasDataLayout for TargetDataLayout {
233 fn data_layout(&self) -> &TargetDataLayout {
238 /// Endianness of the target, which must match cfg(target-endian).
239 #[derive(Copy, Clone, PartialEq)]
246 pub fn as_str(&self) -> &'static str {
248 Self::Little => "little",
254 impl fmt::Debug for Endian {
255 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
256 f.write_str(self.as_str())
260 impl FromStr for Endian {
263 fn from_str(s: &str) -> Result<Self, Self::Err> {
265 "little" => Ok(Self::Little),
266 "big" => Ok(Self::Big),
267 _ => Err(format!(r#"unknown endian: "{}""#, s)),
272 impl ToJson for Endian {
273 fn to_json(&self) -> Json {
274 self.as_str().to_json()
278 /// Size of a type in bytes.
279 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
280 #[derive(HashStable_Generic)]
286 pub const ZERO: Size = Size { raw: 0 };
288 /// Rounds `bits` up to the next-higher byte boundary, if `bits` is
289 /// not a multiple of 8.
290 pub fn from_bits(bits: impl TryInto<u64>) -> Size {
291 let bits = bits.try_into().ok().unwrap();
292 // Avoid potential overflow from `bits + 7`.
293 Size { raw: bits / 8 + ((bits % 8) + 7) / 8 }
297 pub fn from_bytes(bytes: impl TryInto<u64>) -> Size {
298 let bytes: u64 = bytes.try_into().ok().unwrap();
303 pub fn bytes(self) -> u64 {
308 pub fn bytes_usize(self) -> usize {
309 self.bytes().try_into().unwrap()
313 pub fn bits(self) -> u64 {
315 fn overflow(bytes: u64) -> ! {
316 panic!("Size::bits: {} bytes in bits doesn't fit in u64", bytes)
319 self.bytes().checked_mul(8).unwrap_or_else(|| overflow(self.bytes()))
323 pub fn bits_usize(self) -> usize {
324 self.bits().try_into().unwrap()
328 pub fn align_to(self, align: Align) -> Size {
329 let mask = align.bytes() - 1;
330 Size::from_bytes((self.bytes() + mask) & !mask)
334 pub fn is_aligned(self, align: Align) -> bool {
335 let mask = align.bytes() - 1;
336 self.bytes() & mask == 0
340 pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size> {
341 let dl = cx.data_layout();
343 let bytes = self.bytes().checked_add(offset.bytes())?;
345 if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
349 pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size> {
350 let dl = cx.data_layout();
352 let bytes = self.bytes().checked_mul(count)?;
353 if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
356 /// Truncates `value` to `self` bits and then sign-extends it to 128 bits
357 /// (i.e., if it is negative, fill with 1's on the left).
359 pub fn sign_extend(self, value: u128) -> u128 {
360 let size = self.bits();
362 // Truncated until nothing is left.
366 let shift = 128 - size;
367 // Shift the unsigned value to the left, then shift back to the right as signed
368 // (essentially fills with sign bit on the left).
369 (((value << shift) as i128) >> shift) as u128
372 /// Truncates `value` to `self` bits.
374 pub fn truncate(self, value: u128) -> u128 {
375 let size = self.bits();
377 // Truncated until nothing is left.
380 let shift = 128 - size;
381 // Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
382 (value << shift) >> shift
386 pub fn signed_int_min(&self) -> i128 {
387 self.sign_extend(1_u128 << (self.bits() - 1)) as i128
391 pub fn signed_int_max(&self) -> i128 {
392 i128::MAX >> (128 - self.bits())
396 pub fn unsigned_int_max(&self) -> u128 {
397 u128::MAX >> (128 - self.bits())
401 // Panicking addition, subtraction and multiplication for convenience.
402 // Avoid during layout computation, return `LayoutError` instead.
407 fn add(self, other: Size) -> Size {
408 Size::from_bytes(self.bytes().checked_add(other.bytes()).unwrap_or_else(|| {
409 panic!("Size::add: {} + {} doesn't fit in u64", self.bytes(), other.bytes())
417 fn sub(self, other: Size) -> Size {
418 Size::from_bytes(self.bytes().checked_sub(other.bytes()).unwrap_or_else(|| {
419 panic!("Size::sub: {} - {} would result in negative size", self.bytes(), other.bytes())
424 impl Mul<Size> for u64 {
427 fn mul(self, size: Size) -> Size {
432 impl Mul<u64> for Size {
435 fn mul(self, count: u64) -> Size {
436 match self.bytes().checked_mul(count) {
437 Some(bytes) => Size::from_bytes(bytes),
438 None => panic!("Size::mul: {} * {} doesn't fit in u64", self.bytes(), count),
443 impl AddAssign for Size {
445 fn add_assign(&mut self, other: Size) {
446 *self = *self + other;
452 fn steps_between(start: &Self, end: &Self) -> Option<usize> {
453 u64::steps_between(&start.bytes(), &end.bytes())
457 fn forward_checked(start: Self, count: usize) -> Option<Self> {
458 u64::forward_checked(start.bytes(), count).map(Self::from_bytes)
462 fn forward(start: Self, count: usize) -> Self {
463 Self::from_bytes(u64::forward(start.bytes(), count))
467 unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
468 Self::from_bytes(u64::forward_unchecked(start.bytes(), count))
472 fn backward_checked(start: Self, count: usize) -> Option<Self> {
473 u64::backward_checked(start.bytes(), count).map(Self::from_bytes)
477 fn backward(start: Self, count: usize) -> Self {
478 Self::from_bytes(u64::backward(start.bytes(), count))
482 unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
483 Self::from_bytes(u64::backward_unchecked(start.bytes(), count))
487 /// Alignment of a type in bytes (always a power of two).
488 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
489 #[derive(HashStable_Generic)]
495 pub const ONE: Align = Align { pow2: 0 };
498 pub fn from_bits(bits: u64) -> Result<Align, String> {
499 Align::from_bytes(Size::from_bits(bits).bytes())
503 pub fn from_bytes(align: u64) -> Result<Align, String> {
504 // Treat an alignment of 0 bytes like 1-byte alignment.
506 return Ok(Align::ONE);
510 fn not_power_of_2(align: u64) -> String {
511 format!("`{}` is not a power of 2", align)
515 fn too_large(align: u64) -> String {
516 format!("`{}` is too large", align)
519 let mut bytes = align;
520 let mut pow2: u8 = 0;
521 while (bytes & 1) == 0 {
526 return Err(not_power_of_2(align));
529 return Err(too_large(align));
536 pub fn bytes(self) -> u64 {
541 pub fn bits(self) -> u64 {
545 /// Computes the best alignment possible for the given offset
546 /// (the largest power of two that the offset is a multiple of).
548 /// N.B., for an offset of `0`, this happens to return `2^64`.
550 pub fn max_for_offset(offset: Size) -> Align {
551 Align { pow2: offset.bytes().trailing_zeros() as u8 }
554 /// Lower the alignment, if necessary, such that the given offset
555 /// is aligned to it (the offset is a multiple of the alignment).
557 pub fn restrict_for_offset(self, offset: Size) -> Align {
558 self.min(Align::max_for_offset(offset))
562 /// A pair of alignments, ABI-mandated and preferred.
563 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Encodable, Decodable)]
564 #[derive(HashStable_Generic)]
565 pub struct AbiAndPrefAlign {
570 impl AbiAndPrefAlign {
572 pub fn new(align: Align) -> AbiAndPrefAlign {
573 AbiAndPrefAlign { abi: align, pref: align }
577 pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
578 AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) }
582 pub fn max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
583 AbiAndPrefAlign { abi: self.abi.max(other.abi), pref: self.pref.max(other.pref) }
587 /// Integers, also used for enum discriminants.
588 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, HashStable_Generic)]
599 pub fn size(self) -> Size {
601 I8 => Size::from_bytes(1),
602 I16 => Size::from_bytes(2),
603 I32 => Size::from_bytes(4),
604 I64 => Size::from_bytes(8),
605 I128 => Size::from_bytes(16),
609 pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
610 let dl = cx.data_layout();
617 I128 => dl.i128_align,
621 /// Finds the smallest Integer type which can represent the signed value.
623 pub fn fit_signed(x: i128) -> Integer {
625 -0x0000_0000_0000_0080..=0x0000_0000_0000_007f => I8,
626 -0x0000_0000_0000_8000..=0x0000_0000_0000_7fff => I16,
627 -0x0000_0000_8000_0000..=0x0000_0000_7fff_ffff => I32,
628 -0x8000_0000_0000_0000..=0x7fff_ffff_ffff_ffff => I64,
633 /// Finds the smallest Integer type which can represent the unsigned value.
635 pub fn fit_unsigned(x: u128) -> Integer {
637 0..=0x0000_0000_0000_00ff => I8,
638 0..=0x0000_0000_0000_ffff => I16,
639 0..=0x0000_0000_ffff_ffff => I32,
640 0..=0xffff_ffff_ffff_ffff => I64,
645 /// Finds the smallest integer with the given alignment.
646 pub fn for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer> {
647 let dl = cx.data_layout();
649 for candidate in [I8, I16, I32, I64, I128] {
650 if wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes() {
651 return Some(candidate);
657 /// Find the largest integer with the given alignment or less.
658 pub fn approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer {
659 let dl = cx.data_layout();
661 // FIXME(eddyb) maybe include I128 in the future, when it works everywhere.
662 for candidate in [I64, I32, I16] {
663 if wanted >= candidate.align(dl).abi && wanted.bytes() >= candidate.size().bytes() {
670 // FIXME(eddyb) consolidate this and other methods that find the appropriate
671 // `Integer` given some requirements.
673 fn from_size(size: Size) -> Result<Self, String> {
675 8 => Ok(Integer::I8),
676 16 => Ok(Integer::I16),
677 32 => Ok(Integer::I32),
678 64 => Ok(Integer::I64),
679 128 => Ok(Integer::I128),
680 _ => Err(format!("rust does not support integers with {} bits", size.bits())),
685 /// Fundamental unit of memory access and layout.
686 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
688 /// The `bool` is the signedness of the `Integer` type.
690 /// One would think we would not care about such details this low down,
691 /// but some ABIs are described in terms of C types and ISAs where the
692 /// integer arithmetic is done on {sign,zero}-extended registers, e.g.
693 /// a negative integer passed by zero-extension will appear positive in
694 /// the callee, and most operations on it will produce the wrong values.
702 pub fn size<C: HasDataLayout>(self, cx: &C) -> Size {
703 let dl = cx.data_layout();
706 Int(i, _) => i.size(),
707 F32 => Size::from_bits(32),
708 F64 => Size::from_bits(64),
709 Pointer => dl.pointer_size,
713 pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
714 let dl = cx.data_layout();
717 Int(i, _) => i.align(dl),
720 Pointer => dl.pointer_align,
724 // FIXME(eddyb) remove, it's trivial thanks to `matches!`.
726 pub fn is_float(self) -> bool {
727 matches!(self, F32 | F64)
730 // FIXME(eddyb) remove, it's completely unused.
732 pub fn is_int(self) -> bool {
733 matches!(self, Int(..))
737 /// Inclusive wrap-around range of valid values, that is, if
738 /// start > end, it represents `start..=MAX`,
739 /// followed by `0..=end`.
741 /// That is, for an i8 primitive, a range of `254..=2` means following
744 /// 254 (-2), 255 (-1), 0, 1, 2
746 /// This is intended specifically to mirror LLVM’s `!range` metadata semantics.
747 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
748 #[derive(HashStable_Generic)]
749 pub struct WrappingRange {
755 pub fn full(size: Size) -> Self {
756 Self { start: 0, end: size.unsigned_int_max() }
759 /// Returns `true` if `v` is contained in the range.
761 pub fn contains(&self, v: u128) -> bool {
762 if self.start <= self.end {
763 self.start <= v && v <= self.end
765 self.start <= v || v <= self.end
769 /// Returns `self` with replaced `start`
771 pub fn with_start(mut self, start: u128) -> Self {
776 /// Returns `self` with replaced `end`
778 pub fn with_end(mut self, end: u128) -> Self {
783 /// Returns `true` if `size` completely fills the range.
785 pub fn is_full_for(&self, size: Size) -> bool {
786 let max_value = size.unsigned_int_max();
787 debug_assert!(self.start <= max_value && self.end <= max_value);
788 self.start == (self.end.wrapping_add(1) & max_value)
792 impl fmt::Debug for WrappingRange {
793 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
794 if self.start > self.end {
795 write!(fmt, "(..={}) | ({}..)", self.end, self.start)?;
797 write!(fmt, "{}..={}", self.start, self.end)?;
803 /// Information about one scalar component of a Rust type.
804 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
805 #[derive(HashStable_Generic)]
810 // FIXME(eddyb) always use the shortest range, e.g., by finding
811 // the largest space between two consecutive valid values and
812 // taking everything else as the (shortest) valid range.
813 valid_range: WrappingRange,
816 /// Even for unions, we need to use the correct registers for the kind of
817 /// values inside the union, so we keep the `Primitive` type around. We
818 /// also use it to compute the size of the scalar.
819 /// However, unions never have niches and even allow undef,
820 /// so there is no `valid_range`.
827 pub fn is_bool(&self) -> bool {
830 Scalar::Initialized {
831 value: Int(I8, false),
832 valid_range: WrappingRange { start: 0, end: 1 }
837 /// Get the primitive representation of this type, ignoring the valid range and whether the
838 /// value is allowed to be undefined (due to being a union).
839 pub fn primitive(&self) -> Primitive {
841 Scalar::Initialized { value, .. } | Scalar::Union { value } => value,
845 pub fn align(self, cx: &impl HasDataLayout) -> AbiAndPrefAlign {
846 self.primitive().align(cx)
849 pub fn size(self, cx: &impl HasDataLayout) -> Size {
850 self.primitive().size(cx)
854 pub fn to_union(&self) -> Self {
855 Self::Union { value: self.primitive() }
859 pub fn valid_range(&self, cx: &impl HasDataLayout) -> WrappingRange {
861 Scalar::Initialized { valid_range, .. } => valid_range,
862 Scalar::Union { value } => WrappingRange::full(value.size(cx)),
867 /// Allows the caller to mutate the valid range. This operation will panic if attempted on a union.
868 pub fn valid_range_mut(&mut self) -> &mut WrappingRange {
870 Scalar::Initialized { valid_range, .. } => valid_range,
871 Scalar::Union { .. } => panic!("cannot change the valid range of a union"),
875 /// Returns `true` if all possible numbers are valid, i.e `valid_range` covers the whole layout
877 pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool {
879 Scalar::Initialized { valid_range, .. } => valid_range.is_full_for(self.size(cx)),
880 Scalar::Union { .. } => true,
885 /// Describes how the fields of a type are located in memory.
886 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
887 pub enum FieldsShape {
888 /// Scalar primitives and `!`, which never have fields.
891 /// All fields start at no offset. The `usize` is the field count.
894 /// Array/vector-like placement, with all fields of identical types.
895 Array { stride: Size, count: u64 },
897 /// Struct-like placement, with precomputed offsets.
899 /// Fields are guaranteed to not overlap, but note that gaps
900 /// before, between and after all the fields are NOT always
901 /// padding, and as such their contents may not be discarded.
902 /// For example, enum variants leave a gap at the start,
903 /// where the discriminant field in the enum layout goes.
905 /// Offsets for the first byte of each field,
906 /// ordered to match the source definition order.
907 /// This vector does not go in increasing order.
908 // FIXME(eddyb) use small vector optimization for the common case.
911 /// Maps source order field indices to memory order indices,
912 /// depending on how the fields were reordered (if at all).
913 /// This is a permutation, with both the source order and the
914 /// memory order using the same (0..n) index ranges.
916 /// Note that during computation of `memory_index`, sometimes
917 /// it is easier to operate on the inverse mapping (that is,
918 /// from memory order to source order), and that is usually
919 /// named `inverse_memory_index`.
921 // FIXME(eddyb) build a better abstraction for permutations, if possible.
922 // FIXME(camlorn) also consider small vector optimization here.
923 memory_index: Vec<u32>,
929 pub fn count(&self) -> usize {
931 FieldsShape::Primitive => 0,
932 FieldsShape::Union(count) => count.get(),
933 FieldsShape::Array { count, .. } => count.try_into().unwrap(),
934 FieldsShape::Arbitrary { ref offsets, .. } => offsets.len(),
939 pub fn offset(&self, i: usize) -> Size {
941 FieldsShape::Primitive => {
942 unreachable!("FieldsShape::offset: `Primitive`s have no fields")
944 FieldsShape::Union(count) => {
947 "tried to access field {} of union with {} fields",
953 FieldsShape::Array { stride, count } => {
954 let i = u64::try_from(i).unwrap();
958 FieldsShape::Arbitrary { ref offsets, .. } => offsets[i],
963 pub fn memory_index(&self, i: usize) -> usize {
965 FieldsShape::Primitive => {
966 unreachable!("FieldsShape::memory_index: `Primitive`s have no fields")
968 FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
969 FieldsShape::Arbitrary { ref memory_index, .. } => memory_index[i].try_into().unwrap(),
973 /// Gets source indices of the fields by increasing offsets.
975 pub fn index_by_increasing_offset<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
976 let mut inverse_small = [0u8; 64];
977 let mut inverse_big = vec![];
978 let use_small = self.count() <= inverse_small.len();
980 // We have to write this logic twice in order to keep the array small.
981 if let FieldsShape::Arbitrary { ref memory_index, .. } = *self {
983 for i in 0..self.count() {
984 inverse_small[memory_index[i] as usize] = i as u8;
987 inverse_big = vec![0; self.count()];
988 for i in 0..self.count() {
989 inverse_big[memory_index[i] as usize] = i as u32;
994 (0..self.count()).map(move |i| match *self {
995 FieldsShape::Primitive | FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
996 FieldsShape::Arbitrary { .. } => {
998 inverse_small[i] as usize
1000 inverse_big[i] as usize
1007 /// An identifier that specifies the address space that some operation
1008 /// should operate on. Special address spaces have an effect on code generation,
1009 /// depending on the target and the address spaces it implements.
1010 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
1011 pub struct AddressSpace(pub u32);
1014 /// The default address space, corresponding to data space.
1015 pub const DATA: Self = AddressSpace(0);
1018 /// Describes how values of the type are passed by target ABIs,
1019 /// in terms of categories of C types there are ABI rules for.
1020 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
1024 ScalarPair(Scalar, Scalar),
1030 /// If true, the size is exact, otherwise it's only a lower bound.
1036 /// Returns `true` if the layout corresponds to an unsized type.
1038 pub fn is_unsized(&self) -> bool {
1040 Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
1041 Abi::Aggregate { sized } => !sized,
1045 /// Returns `true` if this is a single signed integer scalar
1047 pub fn is_signed(&self) -> bool {
1049 Abi::Scalar(scal) => match scal.primitive() {
1050 Primitive::Int(_, signed) => signed,
1053 _ => panic!("`is_signed` on non-scalar ABI {:?}", self),
1057 /// Returns `true` if this is an uninhabited type
1059 pub fn is_uninhabited(&self) -> bool {
1060 matches!(*self, Abi::Uninhabited)
1063 /// Returns `true` is this is a scalar type
1065 pub fn is_scalar(&self) -> bool {
1066 matches!(*self, Abi::Scalar(_))
1070 rustc_index::newtype_index! {
1071 pub struct VariantIdx {
1072 derive [HashStable_Generic]
1076 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
1077 pub enum Variants<'a> {
1078 /// Single enum variants, structs/tuples, unions, and all non-ADTs.
1079 Single { index: VariantIdx },
1081 /// Enum-likes with more than one inhabited variant: each variant comes with
1082 /// a *discriminant* (usually the same as the variant index but the user can
1083 /// assign explicit discriminant values). That discriminant is encoded
1084 /// as a *tag* on the machine. The layout of each variant is
1085 /// a struct, and they all have space reserved for the tag.
1086 /// For enums, the tag is the sole field of the layout.
1089 tag_encoding: TagEncoding,
1091 variants: IndexVec<VariantIdx, Layout<'a>>,
1095 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
1096 pub enum TagEncoding {
1097 /// The tag directly stores the discriminant, but possibly with a smaller layout
1098 /// (so converting the tag to the discriminant can require sign extension).
1101 /// Niche (values invalid for a type) encoding the discriminant:
1102 /// Discriminant and variant index coincide.
1103 /// The variant `dataful_variant` contains a niche at an arbitrary
1104 /// offset (field `tag_field` of the enum), which for a variant with
1105 /// discriminant `d` is set to
1106 /// `(d - niche_variants.start).wrapping_add(niche_start)`.
1108 /// For example, `Option<(usize, &T)>` is represented such that
1109 /// `None` has a null pointer for the second tuple field, and
1110 /// `Some` is the identity function (with a non-null reference).
1112 dataful_variant: VariantIdx,
1113 niche_variants: RangeInclusive<VariantIdx>,
1118 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
1121 pub value: Primitive,
1122 pub valid_range: WrappingRange,
1126 pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> {
1127 let Scalar::Initialized { value, valid_range } = scalar else { return None };
1128 let niche = Niche { offset, value, valid_range };
1129 if niche.available(cx) > 0 { Some(niche) } else { None }
1132 pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 {
1133 let Self { value, valid_range: v, .. } = *self;
1134 let size = value.size(cx);
1135 assert!(size.bits() <= 128);
1136 let max_value = size.unsigned_int_max();
1138 // Find out how many values are outside the valid range.
1139 let niche = v.end.wrapping_add(1)..v.start;
1140 niche.end.wrapping_sub(niche.start) & max_value
1143 pub fn reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)> {
1146 let Self { value, valid_range: v, .. } = *self;
1147 let size = value.size(cx);
1148 assert!(size.bits() <= 128);
1149 let max_value = size.unsigned_int_max();
1151 let niche = v.end.wrapping_add(1)..v.start;
1152 let available = niche.end.wrapping_sub(niche.start) & max_value;
1153 if count > available {
1157 // Extend the range of valid values being reserved by moving either `v.start` or `v.end` bound.
1158 // Given an eventual `Option<T>`, we try to maximize the chance for `None` to occupy the niche of zero.
1159 // This is accomplished by preferring enums with 2 variants(`count==1`) and always taking the shortest path to niche zero.
1160 // Having `None` in niche zero can enable some special optimizations.
1162 // Bound selection criteria:
1163 // 1. Select closest to zero given wrapping semantics.
1164 // 2. Avoid moving past zero if possible.
1166 // In practice this means that enums with `count > 1` are unlikely to claim niche zero, since they have to fit perfectly.
1167 // If niche zero is already reserved, the selection of bounds are of little interest.
1168 let move_start = |v: WrappingRange| {
1169 let start = v.start.wrapping_sub(count) & max_value;
1170 Some((start, Scalar::Initialized { value, valid_range: v.with_start(start) }))
1172 let move_end = |v: WrappingRange| {
1173 let start = v.end.wrapping_add(1) & max_value;
1174 let end = v.end.wrapping_add(count) & max_value;
1175 Some((start, Scalar::Initialized { value, valid_range: v.with_end(end) }))
1177 let distance_end_zero = max_value - v.end;
1178 if v.start > v.end {
1179 // zero is unavailable because wrapping occurs
1181 } else if v.start <= distance_end_zero {
1182 if count <= v.start {
1185 // moved past zero, use other bound
1189 let end = v.end.wrapping_add(count) & max_value;
1190 let overshot_zero = (1..=v.end).contains(&end);
1192 // moved past zero, use other bound
1201 #[derive(PartialEq, Eq, Hash, HashStable_Generic)]
1202 pub struct LayoutS<'a> {
1203 /// Says where the fields are located within the layout.
1204 pub fields: FieldsShape,
1206 /// Encodes information about multi-variant layouts.
1207 /// Even with `Multiple` variants, a layout still has its own fields! Those are then
1208 /// shared between all variants. One of them will be the discriminant,
1209 /// but e.g. generators can have more.
1211 /// To access all fields of this layout, both `fields` and the fields of the active variant
1212 /// must be taken into account.
1213 pub variants: Variants<'a>,
1215 /// The `abi` defines how this data is passed between functions, and it defines
1216 /// value restrictions via `valid_range`.
1218 /// Note that this is entirely orthogonal to the recursive structure defined by
1219 /// `variants` and `fields`; for example, `ManuallyDrop<Result<isize, isize>>` has
1220 /// `Abi::ScalarPair`! So, even with non-`Aggregate` `abi`, `fields` and `variants`
1221 /// have to be taken into account to find all fields of this layout.
1224 /// The leaf scalar with the largest number of invalid values
1225 /// (i.e. outside of its `valid_range`), if it exists.
1226 pub largest_niche: Option<Niche>,
1228 pub align: AbiAndPrefAlign,
1232 impl<'a> LayoutS<'a> {
1233 pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
1234 let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
1235 let size = scalar.size(cx);
1236 let align = scalar.align(cx);
1238 variants: Variants::Single { index: VariantIdx::new(0) },
1239 fields: FieldsShape::Primitive,
1240 abi: Abi::Scalar(scalar),
1248 impl<'a> fmt::Debug for LayoutS<'a> {
1249 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1250 // This is how `Layout` used to print before it become
1251 // `Interned<LayoutS>`. We print it like this to avoid having to update
1252 // expected output in a lot of tests.
1253 f.debug_struct("Layout")
1254 .field("fields", &self.fields)
1255 .field("variants", &self.variants)
1256 .field("abi", &self.abi)
1257 .field("largest_niche", &self.largest_niche)
1258 .field("align", &self.align)
1259 .field("size", &self.size)
1264 #[derive(Copy, Clone, PartialEq, Eq, Hash, HashStable_Generic)]
1265 #[rustc_pass_by_value]
1266 pub struct Layout<'a>(pub Interned<'a, LayoutS<'a>>);
1268 impl<'a> fmt::Debug for Layout<'a> {
1269 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1270 // See comment on `<LayoutS as Debug>::fmt` above.
1275 impl<'a> Layout<'a> {
1276 pub fn fields(self) -> &'a FieldsShape {
1280 pub fn variants(self) -> &'a Variants<'a> {
1284 pub fn abi(self) -> Abi {
1288 pub fn largest_niche(self) -> Option<Niche> {
1289 self.0.0.largest_niche
1292 pub fn align(self) -> AbiAndPrefAlign {
1296 pub fn size(self) -> Size {
1301 /// The layout of a type, alongside the type itself.
1302 /// Provides various type traversal APIs (e.g., recursing into fields).
1304 /// Note that the layout is NOT guaranteed to always be identical
1305 /// to that obtained from `layout_of(ty)`, as we need to produce
1306 /// layouts for which Rust types do not exist, such as enum variants
1307 /// or synthetic fields of enums (i.e., discriminants) and fat pointers.
1308 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable_Generic)]
1309 pub struct TyAndLayout<'a, Ty> {
1311 pub layout: Layout<'a>,
1314 impl<'a, Ty> Deref for TyAndLayout<'a, Ty> {
1315 type Target = &'a LayoutS<'a>;
1316 fn deref(&self) -> &&'a LayoutS<'a> {
1321 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
1322 pub enum PointerKind {
1323 /// Most general case, we know no restrictions to tell LLVM.
1326 /// `&T` where `T` contains no `UnsafeCell`, is `noalias` and `readonly`.
1329 /// `&mut T` which is `noalias` but not `readonly`.
1332 /// `Box<T>`, unlike `UniqueBorrowed`, it also has `noalias` on returns.
1336 #[derive(Copy, Clone, Debug)]
1337 pub struct PointeeInfo {
1340 pub safe: Option<PointerKind>,
1341 pub address_space: AddressSpace,
1344 /// Trait that needs to be implemented by the higher-level type representation
1345 /// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality.
1346 pub trait TyAbiInterface<'a, C>: Sized {
1347 fn ty_and_layout_for_variant(
1348 this: TyAndLayout<'a, Self>,
1350 variant_index: VariantIdx,
1351 ) -> TyAndLayout<'a, Self>;
1352 fn ty_and_layout_field(this: TyAndLayout<'a, Self>, cx: &C, i: usize) -> TyAndLayout<'a, Self>;
1353 fn ty_and_layout_pointee_info_at(
1354 this: TyAndLayout<'a, Self>,
1357 ) -> Option<PointeeInfo>;
1358 fn is_adt(this: TyAndLayout<'a, Self>) -> bool;
1359 fn is_never(this: TyAndLayout<'a, Self>) -> bool;
1360 fn is_tuple(this: TyAndLayout<'a, Self>) -> bool;
1361 fn is_unit(this: TyAndLayout<'a, Self>) -> bool;
1364 impl<'a, Ty> TyAndLayout<'a, Ty> {
1365 pub fn for_variant<C>(self, cx: &C, variant_index: VariantIdx) -> Self
1367 Ty: TyAbiInterface<'a, C>,
1369 Ty::ty_and_layout_for_variant(self, cx, variant_index)
1372 pub fn field<C>(self, cx: &C, i: usize) -> Self
1374 Ty: TyAbiInterface<'a, C>,
1376 Ty::ty_and_layout_field(self, cx, i)
1379 pub fn pointee_info_at<C>(self, cx: &C, offset: Size) -> Option<PointeeInfo>
1381 Ty: TyAbiInterface<'a, C>,
1383 Ty::ty_and_layout_pointee_info_at(self, cx, offset)
1386 pub fn is_single_fp_element<C>(self, cx: &C) -> bool
1388 Ty: TyAbiInterface<'a, C>,
1392 Abi::Scalar(scalar) => scalar.primitive().is_float(),
1393 Abi::Aggregate { .. } => {
1394 if self.fields.count() == 1 && self.fields.offset(0).bytes() == 0 {
1395 self.field(cx, 0).is_single_fp_element(cx)
1404 pub fn is_adt<C>(self) -> bool
1406 Ty: TyAbiInterface<'a, C>,
1411 pub fn is_never<C>(self) -> bool
1413 Ty: TyAbiInterface<'a, C>,
1418 pub fn is_tuple<C>(self) -> bool
1420 Ty: TyAbiInterface<'a, C>,
1425 pub fn is_unit<C>(self) -> bool
1427 Ty: TyAbiInterface<'a, C>,
1433 impl<'a, Ty> TyAndLayout<'a, Ty> {
1434 /// Returns `true` if the layout corresponds to an unsized type.
1435 pub fn is_unsized(&self) -> bool {
1436 self.abi.is_unsized()
1439 /// Returns `true` if the type is a ZST and not unsized.
1440 pub fn is_zst(&self) -> bool {
1442 Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
1443 Abi::Uninhabited => self.size.bytes() == 0,
1444 Abi::Aggregate { sized } => sized && self.size.bytes() == 0,
1448 /// Determines if this type permits "raw" initialization by just transmuting some
1449 /// memory into an instance of `T`.
1450 /// `zero` indicates if the memory is zero-initialized, or alternatively
1451 /// left entirely uninitialized.
1452 /// This is conservative: in doubt, it will answer `true`.
1454 /// FIXME: Once we removed all the conservatism, we could alternatively
1455 /// create an all-0/all-undef constant and run the const value validator to see if
1456 /// this is a valid value for the given type.
1457 pub fn might_permit_raw_init<C>(self, cx: &C, zero: bool) -> bool
1460 Ty: TyAbiInterface<'a, C>,
1463 let scalar_allows_raw_init = move |s: Scalar| -> bool {
1465 // The range must contain 0.
1466 s.valid_range(cx).contains(0)
1468 // The range must include all values.
1469 s.is_always_valid(cx)
1474 let valid = match self.abi {
1475 Abi::Uninhabited => false, // definitely UB
1476 Abi::Scalar(s) => scalar_allows_raw_init(s),
1477 Abi::ScalarPair(s1, s2) => scalar_allows_raw_init(s1) && scalar_allows_raw_init(s2),
1478 Abi::Vector { element: s, count } => count == 0 || scalar_allows_raw_init(s),
1479 Abi::Aggregate { .. } => true, // Fields are checked below.
1482 // This is definitely not okay.
1486 // If we have not found an error yet, we need to recursively descend into fields.
1487 match &self.fields {
1488 FieldsShape::Primitive | FieldsShape::Union { .. } => {}
1489 FieldsShape::Array { .. } => {
1490 // FIXME(#66151): For now, we are conservative and do not check arrays.
1492 FieldsShape::Arbitrary { offsets, .. } => {
1493 for idx in 0..offsets.len() {
1494 if !self.field(cx, idx).might_permit_raw_init(cx, zero) {
1495 // We found a field that is unhappy with this kind of initialization.
1502 // FIXME(#66151): For now, we are conservative and do not check `self.variants`.