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-rw-r--r--compiler/rustc_abi/src/lib.rs1502
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diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
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+++ b/compiler/rustc_abi/src/lib.rs
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+#![cfg_attr(feature = "nightly", feature(step_trait, rustc_attrs, min_specialization))]
+
+use std::convert::{TryFrom, TryInto};
+use std::fmt;
+#[cfg(feature = "nightly")]
+use std::iter::Step;
+use std::num::{NonZeroUsize, ParseIntError};
+use std::ops::{Add, AddAssign, Mul, RangeInclusive, Sub};
+use std::str::FromStr;
+
+use bitflags::bitflags;
+#[cfg(feature = "nightly")]
+use rustc_data_structures::stable_hasher::StableOrd;
+use rustc_index::vec::{Idx, IndexVec};
+#[cfg(feature = "nightly")]
+use rustc_macros::HashStable_Generic;
+#[cfg(feature = "nightly")]
+use rustc_macros::{Decodable, Encodable};
+
+mod layout;
+
+pub use layout::LayoutCalculator;
+
+/// Requirements for a `StableHashingContext` to be used in this crate.
+/// This is a hack to allow using the `HashStable_Generic` derive macro
+/// instead of implementing everything in `rustc_middle`.
+pub trait HashStableContext {}
+
+use Integer::*;
+use Primitive::*;
+
+bitflags! {
+ #[derive(Default)]
+ #[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+ pub struct ReprFlags: u8 {
+ const IS_C = 1 << 0;
+ const IS_SIMD = 1 << 1;
+ const IS_TRANSPARENT = 1 << 2;
+ // Internal only for now. If true, don't reorder fields.
+ const IS_LINEAR = 1 << 3;
+ // If true, the type's layout can be randomized using
+ // the seed stored in `ReprOptions.layout_seed`
+ const RANDOMIZE_LAYOUT = 1 << 4;
+ // Any of these flags being set prevent field reordering optimisation.
+ const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
+ | ReprFlags::IS_SIMD.bits
+ | ReprFlags::IS_LINEAR.bits;
+ }
+}
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub enum IntegerType {
+ /// Pointer sized integer type, i.e. isize and usize. The field shows signedness, that
+ /// is, `Pointer(true)` is isize.
+ Pointer(bool),
+ /// Fix sized integer type, e.g. i8, u32, i128 The bool field shows signedness, `Fixed(I8, false)` means `u8`
+ Fixed(Integer, bool),
+}
+
+impl IntegerType {
+ pub fn is_signed(&self) -> bool {
+ match self {
+ IntegerType::Pointer(b) => *b,
+ IntegerType::Fixed(_, b) => *b,
+ }
+ }
+}
+
+/// Represents the repr options provided by the user,
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct ReprOptions {
+ pub int: Option<IntegerType>,
+ pub align: Option<Align>,
+ pub pack: Option<Align>,
+ pub flags: ReprFlags,
+ /// The seed to be used for randomizing a type's layout
+ ///
+ /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
+ /// be the "most accurate" hash as it'd encompass the item and crate
+ /// hash without loss, but it does pay the price of being larger.
+ /// Everything's a tradeoff, a `u64` seed should be sufficient for our
+ /// purposes (primarily `-Z randomize-layout`)
+ pub field_shuffle_seed: u64,
+}
+
+impl ReprOptions {
+ #[inline]
+ pub fn simd(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_SIMD)
+ }
+
+ #[inline]
+ pub fn c(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_C)
+ }
+
+ #[inline]
+ pub fn packed(&self) -> bool {
+ self.pack.is_some()
+ }
+
+ #[inline]
+ pub fn transparent(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_TRANSPARENT)
+ }
+
+ #[inline]
+ pub fn linear(&self) -> bool {
+ self.flags.contains(ReprFlags::IS_LINEAR)
+ }
+
+ /// Returns the discriminant type, given these `repr` options.
+ /// This must only be called on enums!
+ pub fn discr_type(&self) -> IntegerType {
+ self.int.unwrap_or(IntegerType::Pointer(true))
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhabit "smart enum
+ /// layout" optimizations, such as representing `Foo<&T>` as a
+ /// single pointer.
+ pub fn inhibit_enum_layout_opt(&self) -> bool {
+ self.c() || self.int.is_some()
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
+ /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
+ pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
+ if let Some(pack) = self.pack {
+ if pack.bytes() == 1 {
+ return true;
+ }
+ }
+
+ self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
+ }
+
+ /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
+ /// was enabled for its declaration crate
+ pub fn can_randomize_type_layout(&self) -> bool {
+ !self.inhibit_struct_field_reordering_opt()
+ && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
+ }
+
+ /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
+ pub fn inhibit_union_abi_opt(&self) -> bool {
+ self.c()
+ }
+}
+
+/// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout)
+/// for a target, which contains everything needed to compute layouts.
+#[derive(Debug, PartialEq, Eq)]
+pub struct TargetDataLayout {
+ pub endian: Endian,
+ pub i1_align: AbiAndPrefAlign,
+ pub i8_align: AbiAndPrefAlign,
+ pub i16_align: AbiAndPrefAlign,
+ pub i32_align: AbiAndPrefAlign,
+ pub i64_align: AbiAndPrefAlign,
+ pub i128_align: AbiAndPrefAlign,
+ pub f32_align: AbiAndPrefAlign,
+ pub f64_align: AbiAndPrefAlign,
+ pub pointer_size: Size,
+ pub pointer_align: AbiAndPrefAlign,
+ pub aggregate_align: AbiAndPrefAlign,
+
+ /// Alignments for vector types.
+ pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
+
+ pub instruction_address_space: AddressSpace,
+
+ /// Minimum size of #[repr(C)] enums (default I32 bits)
+ pub c_enum_min_size: Integer,
+}
+
+impl Default for TargetDataLayout {
+ /// Creates an instance of `TargetDataLayout`.
+ fn default() -> TargetDataLayout {
+ let align = |bits| Align::from_bits(bits).unwrap();
+ TargetDataLayout {
+ endian: Endian::Big,
+ i1_align: AbiAndPrefAlign::new(align(8)),
+ i8_align: AbiAndPrefAlign::new(align(8)),
+ i16_align: AbiAndPrefAlign::new(align(16)),
+ i32_align: AbiAndPrefAlign::new(align(32)),
+ i64_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
+ i128_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
+ f32_align: AbiAndPrefAlign::new(align(32)),
+ f64_align: AbiAndPrefAlign::new(align(64)),
+ pointer_size: Size::from_bits(64),
+ pointer_align: AbiAndPrefAlign::new(align(64)),
+ aggregate_align: AbiAndPrefAlign { abi: align(0), pref: align(64) },
+ vector_align: vec![
+ (Size::from_bits(64), AbiAndPrefAlign::new(align(64))),
+ (Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
+ ],
+ instruction_address_space: AddressSpace::DATA,
+ c_enum_min_size: Integer::I32,
+ }
+ }
+}
+
+pub enum TargetDataLayoutErrors<'a> {
+ InvalidAddressSpace { addr_space: &'a str, cause: &'a str, err: ParseIntError },
+ InvalidBits { kind: &'a str, bit: &'a str, cause: &'a str, err: ParseIntError },
+ MissingAlignment { cause: &'a str },
+ InvalidAlignment { cause: &'a str, err: String },
+ InconsistentTargetArchitecture { dl: &'a str, target: &'a str },
+ InconsistentTargetPointerWidth { pointer_size: u64, target: u32 },
+ InvalidBitsSize { err: String },
+}
+
+impl TargetDataLayout {
+ /// Parse data layout from an [llvm data layout string](https://llvm.org/docs/LangRef.html#data-layout)
+ ///
+ /// This function doesn't fill `c_enum_min_size` and it will always be `I32` since it can not be
+ /// determined from llvm string.
+ pub fn parse_from_llvm_datalayout_string<'a>(
+ input: &'a str,
+ ) -> Result<TargetDataLayout, TargetDataLayoutErrors<'a>> {
+ // Parse an address space index from a string.
+ let parse_address_space = |s: &'a str, cause: &'a str| {
+ s.parse::<u32>().map(AddressSpace).map_err(|err| {
+ TargetDataLayoutErrors::InvalidAddressSpace { addr_space: s, cause, err }
+ })
+ };
+
+ // Parse a bit count from a string.
+ let parse_bits = |s: &'a str, kind: &'a str, cause: &'a str| {
+ s.parse::<u64>().map_err(|err| TargetDataLayoutErrors::InvalidBits {
+ kind,
+ bit: s,
+ cause,
+ err,
+ })
+ };
+
+ // Parse a size string.
+ let size = |s: &'a str, cause: &'a str| parse_bits(s, "size", cause).map(Size::from_bits);
+
+ // Parse an alignment string.
+ let align = |s: &[&'a str], cause: &'a str| {
+ if s.is_empty() {
+ return Err(TargetDataLayoutErrors::MissingAlignment { cause });
+ }
+ let align_from_bits = |bits| {
+ Align::from_bits(bits)
+ .map_err(|err| TargetDataLayoutErrors::InvalidAlignment { cause, err })
+ };
+ let abi = parse_bits(s[0], "alignment", cause)?;
+ let pref = s.get(1).map_or(Ok(abi), |pref| parse_bits(pref, "alignment", cause))?;
+ Ok(AbiAndPrefAlign { abi: align_from_bits(abi)?, pref: align_from_bits(pref)? })
+ };
+
+ let mut dl = TargetDataLayout::default();
+ let mut i128_align_src = 64;
+ for spec in input.split('-') {
+ let spec_parts = spec.split(':').collect::<Vec<_>>();
+
+ match &*spec_parts {
+ ["e"] => dl.endian = Endian::Little,
+ ["E"] => dl.endian = Endian::Big,
+ [p] if p.starts_with('P') => {
+ dl.instruction_address_space = parse_address_space(&p[1..], "P")?
+ }
+ ["a", ref a @ ..] => dl.aggregate_align = align(a, "a")?,
+ ["f32", ref a @ ..] => dl.f32_align = align(a, "f32")?,
+ ["f64", ref a @ ..] => dl.f64_align = align(a, "f64")?,
+ [p @ "p", s, ref a @ ..] | [p @ "p0", s, ref a @ ..] => {
+ dl.pointer_size = size(s, p)?;
+ dl.pointer_align = align(a, p)?;
+ }
+ [s, ref a @ ..] if s.starts_with('i') => {
+ let Ok(bits) = s[1..].parse::<u64>() else {
+ size(&s[1..], "i")?; // For the user error.
+ continue;
+ };
+ let a = align(a, s)?;
+ match bits {
+ 1 => dl.i1_align = a,
+ 8 => dl.i8_align = a,
+ 16 => dl.i16_align = a,
+ 32 => dl.i32_align = a,
+ 64 => dl.i64_align = a,
+ _ => {}
+ }
+ if bits >= i128_align_src && bits <= 128 {
+ // Default alignment for i128 is decided by taking the alignment of
+ // largest-sized i{64..=128}.
+ i128_align_src = bits;
+ dl.i128_align = a;
+ }
+ }
+ [s, ref a @ ..] if s.starts_with('v') => {
+ let v_size = size(&s[1..], "v")?;
+ let a = align(a, s)?;
+ if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
+ v.1 = a;
+ continue;
+ }
+ // No existing entry, add a new one.
+ dl.vector_align.push((v_size, a));
+ }
+ _ => {} // Ignore everything else.
+ }
+ }
+ Ok(dl)
+ }
+
+ /// Returns exclusive upper bound on object size.
+ ///
+ /// The theoretical maximum object size is defined as the maximum positive `isize` value.
+ /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly
+ /// index every address within an object along with one byte past the end, along with allowing
+ /// `isize` to store the difference between any two pointers into an object.
+ ///
+ /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer
+ /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is
+ /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable
+ /// address space on 64-bit ARMv8 and x86_64.
+ #[inline]
+ pub fn obj_size_bound(&self) -> u64 {
+ match self.pointer_size.bits() {
+ 16 => 1 << 15,
+ 32 => 1 << 31,
+ 64 => 1 << 47,
+ bits => panic!("obj_size_bound: unknown pointer bit size {}", bits),
+ }
+ }
+
+ #[inline]
+ pub fn ptr_sized_integer(&self) -> Integer {
+ match self.pointer_size.bits() {
+ 16 => I16,
+ 32 => I32,
+ 64 => I64,
+ bits => panic!("ptr_sized_integer: unknown pointer bit size {}", bits),
+ }
+ }
+
+ #[inline]
+ pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
+ for &(size, align) in &self.vector_align {
+ if size == vec_size {
+ return align;
+ }
+ }
+ // Default to natural alignment, which is what LLVM does.
+ // That is, use the size, rounded up to a power of 2.
+ AbiAndPrefAlign::new(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap())
+ }
+}
+
+pub trait HasDataLayout {
+ fn data_layout(&self) -> &TargetDataLayout;
+}
+
+impl HasDataLayout for TargetDataLayout {
+ #[inline]
+ fn data_layout(&self) -> &TargetDataLayout {
+ self
+ }
+}
+
+/// Endianness of the target, which must match cfg(target-endian).
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Endian {
+ Little,
+ Big,
+}
+
+impl Endian {
+ pub fn as_str(&self) -> &'static str {
+ match self {
+ Self::Little => "little",
+ Self::Big => "big",
+ }
+ }
+}
+
+impl fmt::Debug for Endian {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.write_str(self.as_str())
+ }
+}
+
+impl FromStr for Endian {
+ type Err = String;
+
+ fn from_str(s: &str) -> Result<Self, Self::Err> {
+ match s {
+ "little" => Ok(Self::Little),
+ "big" => Ok(Self::Big),
+ _ => Err(format!(r#"unknown endian: "{}""#, s)),
+ }
+ }
+}
+
+/// Size of a type in bytes.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct Size {
+ raw: u64,
+}
+
+// Safety: Ord is implement as just comparing numerical values and numerical values
+// are not changed by (de-)serialization.
+#[cfg(feature = "nightly")]
+unsafe impl StableOrd for Size {}
+
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Size {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "Size({} bytes)", self.bytes())
+ }
+}
+
+impl Size {
+ pub const ZERO: Size = Size { raw: 0 };
+
+ /// Rounds `bits` up to the next-higher byte boundary, if `bits` is
+ /// not a multiple of 8.
+ pub fn from_bits(bits: impl TryInto<u64>) -> Size {
+ let bits = bits.try_into().ok().unwrap();
+ // Avoid potential overflow from `bits + 7`.
+ Size { raw: bits / 8 + ((bits % 8) + 7) / 8 }
+ }
+
+ #[inline]
+ pub fn from_bytes(bytes: impl TryInto<u64>) -> Size {
+ let bytes: u64 = bytes.try_into().ok().unwrap();
+ Size { raw: bytes }
+ }
+
+ #[inline]
+ pub fn bytes(self) -> u64 {
+ self.raw
+ }
+
+ #[inline]
+ pub fn bytes_usize(self) -> usize {
+ self.bytes().try_into().unwrap()
+ }
+
+ #[inline]
+ pub fn bits(self) -> u64 {
+ #[cold]
+ fn overflow(bytes: u64) -> ! {
+ panic!("Size::bits: {} bytes in bits doesn't fit in u64", bytes)
+ }
+
+ self.bytes().checked_mul(8).unwrap_or_else(|| overflow(self.bytes()))
+ }
+
+ #[inline]
+ pub fn bits_usize(self) -> usize {
+ self.bits().try_into().unwrap()
+ }
+
+ #[inline]
+ pub fn align_to(self, align: Align) -> Size {
+ let mask = align.bytes() - 1;
+ Size::from_bytes((self.bytes() + mask) & !mask)
+ }
+
+ #[inline]
+ pub fn is_aligned(self, align: Align) -> bool {
+ let mask = align.bytes() - 1;
+ self.bytes() & mask == 0
+ }
+
+ #[inline]
+ pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size> {
+ let dl = cx.data_layout();
+
+ let bytes = self.bytes().checked_add(offset.bytes())?;
+
+ if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
+ }
+
+ #[inline]
+ pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size> {
+ let dl = cx.data_layout();
+
+ let bytes = self.bytes().checked_mul(count)?;
+ if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
+ }
+
+ /// Truncates `value` to `self` bits and then sign-extends it to 128 bits
+ /// (i.e., if it is negative, fill with 1's on the left).
+ #[inline]
+ pub fn sign_extend(self, value: u128) -> u128 {
+ let size = self.bits();
+ if size == 0 {
+ // Truncated until nothing is left.
+ return 0;
+ }
+ // Sign-extend it.
+ let shift = 128 - size;
+ // Shift the unsigned value to the left, then shift back to the right as signed
+ // (essentially fills with sign bit on the left).
+ (((value << shift) as i128) >> shift) as u128
+ }
+
+ /// Truncates `value` to `self` bits.
+ #[inline]
+ pub fn truncate(self, value: u128) -> u128 {
+ let size = self.bits();
+ if size == 0 {
+ // Truncated until nothing is left.
+ return 0;
+ }
+ let shift = 128 - size;
+ // Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
+ (value << shift) >> shift
+ }
+
+ #[inline]
+ pub fn signed_int_min(&self) -> i128 {
+ self.sign_extend(1_u128 << (self.bits() - 1)) as i128
+ }
+
+ #[inline]
+ pub fn signed_int_max(&self) -> i128 {
+ i128::MAX >> (128 - self.bits())
+ }
+
+ #[inline]
+ pub fn unsigned_int_max(&self) -> u128 {
+ u128::MAX >> (128 - self.bits())
+ }
+}
+
+// Panicking addition, subtraction and multiplication for convenience.
+// Avoid during layout computation, return `LayoutError` instead.
+
+impl Add for Size {
+ type Output = Size;
+ #[inline]
+ fn add(self, other: Size) -> Size {
+ Size::from_bytes(self.bytes().checked_add(other.bytes()).unwrap_or_else(|| {
+ panic!("Size::add: {} + {} doesn't fit in u64", self.bytes(), other.bytes())
+ }))
+ }
+}
+
+impl Sub for Size {
+ type Output = Size;
+ #[inline]
+ fn sub(self, other: Size) -> Size {
+ Size::from_bytes(self.bytes().checked_sub(other.bytes()).unwrap_or_else(|| {
+ panic!("Size::sub: {} - {} would result in negative size", self.bytes(), other.bytes())
+ }))
+ }
+}
+
+impl Mul<Size> for u64 {
+ type Output = Size;
+ #[inline]
+ fn mul(self, size: Size) -> Size {
+ size * self
+ }
+}
+
+impl Mul<u64> for Size {
+ type Output = Size;
+ #[inline]
+ fn mul(self, count: u64) -> Size {
+ match self.bytes().checked_mul(count) {
+ Some(bytes) => Size::from_bytes(bytes),
+ None => panic!("Size::mul: {} * {} doesn't fit in u64", self.bytes(), count),
+ }
+ }
+}
+
+impl AddAssign for Size {
+ #[inline]
+ fn add_assign(&mut self, other: Size) {
+ *self = *self + other;
+ }
+}
+
+#[cfg(feature = "nightly")]
+impl Step for Size {
+ #[inline]
+ fn steps_between(start: &Self, end: &Self) -> Option<usize> {
+ u64::steps_between(&start.bytes(), &end.bytes())
+ }
+
+ #[inline]
+ fn forward_checked(start: Self, count: usize) -> Option<Self> {
+ u64::forward_checked(start.bytes(), count).map(Self::from_bytes)
+ }
+
+ #[inline]
+ fn forward(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::forward(start.bytes(), count))
+ }
+
+ #[inline]
+ unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::forward_unchecked(start.bytes(), count))
+ }
+
+ #[inline]
+ fn backward_checked(start: Self, count: usize) -> Option<Self> {
+ u64::backward_checked(start.bytes(), count).map(Self::from_bytes)
+ }
+
+ #[inline]
+ fn backward(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::backward(start.bytes(), count))
+ }
+
+ #[inline]
+ unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
+ Self::from_bytes(u64::backward_unchecked(start.bytes(), count))
+ }
+}
+
+/// Alignment of a type in bytes (always a power of two).
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+pub struct Align {
+ pow2: u8,
+}
+
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Align {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "Align({} bytes)", self.bytes())
+ }
+}
+
+impl Align {
+ pub const ONE: Align = Align { pow2: 0 };
+ pub const MAX: Align = Align { pow2: 29 };
+
+ #[inline]
+ pub fn from_bits(bits: u64) -> Result<Align, String> {
+ Align::from_bytes(Size::from_bits(bits).bytes())
+ }
+
+ #[inline]
+ pub fn from_bytes(align: u64) -> Result<Align, String> {
+ // Treat an alignment of 0 bytes like 1-byte alignment.
+ if align == 0 {
+ return Ok(Align::ONE);
+ }
+
+ #[cold]
+ fn not_power_of_2(align: u64) -> String {
+ format!("`{}` is not a power of 2", align)
+ }
+
+ #[cold]
+ fn too_large(align: u64) -> String {
+ format!("`{}` is too large", align)
+ }
+
+ let mut bytes = align;
+ let mut pow2: u8 = 0;
+ while (bytes & 1) == 0 {
+ pow2 += 1;
+ bytes >>= 1;
+ }
+ if bytes != 1 {
+ return Err(not_power_of_2(align));
+ }
+ if pow2 > Self::MAX.pow2 {
+ return Err(too_large(align));
+ }
+
+ Ok(Align { pow2 })
+ }
+
+ #[inline]
+ pub fn bytes(self) -> u64 {
+ 1 << self.pow2
+ }
+
+ #[inline]
+ pub fn bits(self) -> u64 {
+ self.bytes() * 8
+ }
+
+ /// Computes the best alignment possible for the given offset
+ /// (the largest power of two that the offset is a multiple of).
+ ///
+ /// N.B., for an offset of `0`, this happens to return `2^64`.
+ #[inline]
+ pub fn max_for_offset(offset: Size) -> Align {
+ Align { pow2: offset.bytes().trailing_zeros() as u8 }
+ }
+
+ /// Lower the alignment, if necessary, such that the given offset
+ /// is aligned to it (the offset is a multiple of the alignment).
+ #[inline]
+ pub fn restrict_for_offset(self, offset: Size) -> Align {
+ self.min(Align::max_for_offset(offset))
+ }
+}
+
+/// A pair of alignments, ABI-mandated and preferred.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+
+pub struct AbiAndPrefAlign {
+ pub abi: Align,
+ pub pref: Align,
+}
+
+impl AbiAndPrefAlign {
+ #[inline]
+ pub fn new(align: Align) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: align, pref: align }
+ }
+
+ #[inline]
+ pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) }
+ }
+
+ #[inline]
+ pub fn max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
+ AbiAndPrefAlign { abi: self.abi.max(other.abi), pref: self.pref.max(other.pref) }
+ }
+}
+
+/// Integers, also used for enum discriminants.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
+
+pub enum Integer {
+ I8,
+ I16,
+ I32,
+ I64,
+ I128,
+}
+
+impl Integer {
+ #[inline]
+ pub fn size(self) -> Size {
+ match self {
+ I8 => Size::from_bytes(1),
+ I16 => Size::from_bytes(2),
+ I32 => Size::from_bytes(4),
+ I64 => Size::from_bytes(8),
+ I128 => Size::from_bytes(16),
+ }
+ }
+
+ /// Gets the Integer type from an IntegerType.
+ pub fn from_attr<C: HasDataLayout>(cx: &C, ity: IntegerType) -> Integer {
+ let dl = cx.data_layout();
+
+ match ity {
+ IntegerType::Pointer(_) => dl.ptr_sized_integer(),
+ IntegerType::Fixed(x, _) => x,
+ }
+ }
+
+ pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
+ let dl = cx.data_layout();
+
+ match self {
+ I8 => dl.i8_align,
+ I16 => dl.i16_align,
+ I32 => dl.i32_align,
+ I64 => dl.i64_align,
+ I128 => dl.i128_align,
+ }
+ }
+
+ /// Finds the smallest Integer type which can represent the signed value.
+ #[inline]
+ pub fn fit_signed(x: i128) -> Integer {
+ match x {
+ -0x0000_0000_0000_0080..=0x0000_0000_0000_007f => I8,
+ -0x0000_0000_0000_8000..=0x0000_0000_0000_7fff => I16,
+ -0x0000_0000_8000_0000..=0x0000_0000_7fff_ffff => I32,
+ -0x8000_0000_0000_0000..=0x7fff_ffff_ffff_ffff => I64,
+ _ => I128,
+ }
+ }
+
+ /// Finds the smallest Integer type which can represent the unsigned value.
+ #[inline]
+ pub fn fit_unsigned(x: u128) -> Integer {
+ match x {
+ 0..=0x0000_0000_0000_00ff => I8,
+ 0..=0x0000_0000_0000_ffff => I16,
+ 0..=0x0000_0000_ffff_ffff => I32,
+ 0..=0xffff_ffff_ffff_ffff => I64,
+ _ => I128,
+ }
+ }
+
+ /// Finds the smallest integer with the given alignment.
+ pub fn for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer> {
+ let dl = cx.data_layout();
+
+ for candidate in [I8, I16, I32, I64, I128] {
+ if wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes() {
+ return Some(candidate);
+ }
+ }
+ None
+ }
+
+ /// Find the largest integer with the given alignment or less.
+ pub fn approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer {
+ let dl = cx.data_layout();
+
+ // FIXME(eddyb) maybe include I128 in the future, when it works everywhere.
+ for candidate in [I64, I32, I16] {
+ if wanted >= candidate.align(dl).abi && wanted.bytes() >= candidate.size().bytes() {
+ return candidate;
+ }
+ }
+ I8
+ }
+
+ // FIXME(eddyb) consolidate this and other methods that find the appropriate
+ // `Integer` given some requirements.
+ #[inline]
+ pub fn from_size(size: Size) -> Result<Self, String> {
+ match size.bits() {
+ 8 => Ok(Integer::I8),
+ 16 => Ok(Integer::I16),
+ 32 => Ok(Integer::I32),
+ 64 => Ok(Integer::I64),
+ 128 => Ok(Integer::I128),
+ _ => Err(format!("rust does not support integers with {} bits", size.bits())),
+ }
+ }
+}
+
+/// Fundamental unit of memory access and layout.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Primitive {
+ /// The `bool` is the signedness of the `Integer` type.
+ ///
+ /// One would think we would not care about such details this low down,
+ /// but some ABIs are described in terms of C types and ISAs where the
+ /// integer arithmetic is done on {sign,zero}-extended registers, e.g.
+ /// a negative integer passed by zero-extension will appear positive in
+ /// the callee, and most operations on it will produce the wrong values.
+ Int(Integer, bool),
+ F32,
+ F64,
+ Pointer,
+}
+
+impl Primitive {
+ pub fn size<C: HasDataLayout>(self, cx: &C) -> Size {
+ let dl = cx.data_layout();
+
+ match self {
+ Int(i, _) => i.size(),
+ F32 => Size::from_bits(32),
+ F64 => Size::from_bits(64),
+ Pointer => dl.pointer_size,
+ }
+ }
+
+ pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
+ let dl = cx.data_layout();
+
+ match self {
+ Int(i, _) => i.align(dl),
+ F32 => dl.f32_align,
+ F64 => dl.f64_align,
+ Pointer => dl.pointer_align,
+ }
+ }
+
+ // FIXME(eddyb) remove, it's trivial thanks to `matches!`.
+ #[inline]
+ pub fn is_float(self) -> bool {
+ matches!(self, F32 | F64)
+ }
+
+ // FIXME(eddyb) remove, it's completely unused.
+ #[inline]
+ pub fn is_int(self) -> bool {
+ matches!(self, Int(..))
+ }
+
+ #[inline]
+ pub fn is_ptr(self) -> bool {
+ matches!(self, Pointer)
+ }
+}
+
+/// Inclusive wrap-around range of valid values, that is, if
+/// start > end, it represents `start..=MAX`,
+/// followed by `0..=end`.
+///
+/// That is, for an i8 primitive, a range of `254..=2` means following
+/// sequence:
+///
+/// 254 (-2), 255 (-1), 0, 1, 2
+///
+/// This is intended specifically to mirror LLVM’s `!range` metadata semantics.
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct WrappingRange {
+ pub start: u128,
+ pub end: u128,
+}
+
+impl WrappingRange {
+ pub fn full(size: Size) -> Self {
+ Self { start: 0, end: size.unsigned_int_max() }
+ }
+
+ /// Returns `true` if `v` is contained in the range.
+ #[inline(always)]
+ pub fn contains(&self, v: u128) -> bool {
+ if self.start <= self.end {
+ self.start <= v && v <= self.end
+ } else {
+ self.start <= v || v <= self.end
+ }
+ }
+
+ /// Returns `self` with replaced `start`
+ #[inline(always)]
+ pub fn with_start(mut self, start: u128) -> Self {
+ self.start = start;
+ self
+ }
+
+ /// Returns `self` with replaced `end`
+ #[inline(always)]
+ pub fn with_end(mut self, end: u128) -> Self {
+ self.end = end;
+ self
+ }
+
+ /// Returns `true` if `size` completely fills the range.
+ #[inline]
+ pub fn is_full_for(&self, size: Size) -> bool {
+ let max_value = size.unsigned_int_max();
+ debug_assert!(self.start <= max_value && self.end <= max_value);
+ self.start == (self.end.wrapping_add(1) & max_value)
+ }
+}
+
+impl fmt::Debug for WrappingRange {
+ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ if self.start > self.end {
+ write!(fmt, "(..={}) | ({}..)", self.end, self.start)?;
+ } else {
+ write!(fmt, "{}..={}", self.start, self.end)?;
+ }
+ Ok(())
+ }
+}
+
+/// Information about one scalar component of a Rust type.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Scalar {
+ Initialized {
+ value: Primitive,
+
+ // FIXME(eddyb) always use the shortest range, e.g., by finding
+ // the largest space between two consecutive valid values and
+ // taking everything else as the (shortest) valid range.
+ valid_range: WrappingRange,
+ },
+ Union {
+ /// Even for unions, we need to use the correct registers for the kind of
+ /// values inside the union, so we keep the `Primitive` type around. We
+ /// also use it to compute the size of the scalar.
+ /// However, unions never have niches and even allow undef,
+ /// so there is no `valid_range`.
+ value: Primitive,
+ },
+}
+
+impl Scalar {
+ #[inline]
+ pub fn is_bool(&self) -> bool {
+ matches!(
+ self,
+ Scalar::Initialized {
+ value: Int(I8, false),
+ valid_range: WrappingRange { start: 0, end: 1 }
+ }
+ )
+ }
+
+ /// Get the primitive representation of this type, ignoring the valid range and whether the
+ /// value is allowed to be undefined (due to being a union).
+ pub fn primitive(&self) -> Primitive {
+ match *self {
+ Scalar::Initialized { value, .. } | Scalar::Union { value } => value,
+ }
+ }
+
+ pub fn align(self, cx: &impl HasDataLayout) -> AbiAndPrefAlign {
+ self.primitive().align(cx)
+ }
+
+ pub fn size(self, cx: &impl HasDataLayout) -> Size {
+ self.primitive().size(cx)
+ }
+
+ #[inline]
+ pub fn to_union(&self) -> Self {
+ Self::Union { value: self.primitive() }
+ }
+
+ #[inline]
+ pub fn valid_range(&self, cx: &impl HasDataLayout) -> WrappingRange {
+ match *self {
+ Scalar::Initialized { valid_range, .. } => valid_range,
+ Scalar::Union { value } => WrappingRange::full(value.size(cx)),
+ }
+ }
+
+ #[inline]
+ /// Allows the caller to mutate the valid range. This operation will panic if attempted on a union.
+ pub fn valid_range_mut(&mut self) -> &mut WrappingRange {
+ match self {
+ Scalar::Initialized { valid_range, .. } => valid_range,
+ Scalar::Union { .. } => panic!("cannot change the valid range of a union"),
+ }
+ }
+
+ /// Returns `true` if all possible numbers are valid, i.e `valid_range` covers the whole layout
+ #[inline]
+ pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool {
+ match *self {
+ Scalar::Initialized { valid_range, .. } => valid_range.is_full_for(self.size(cx)),
+ Scalar::Union { .. } => true,
+ }
+ }
+
+ /// Returns `true` if this type can be left uninit.
+ #[inline]
+ pub fn is_uninit_valid(&self) -> bool {
+ match *self {
+ Scalar::Initialized { .. } => false,
+ Scalar::Union { .. } => true,
+ }
+ }
+}
+
+/// Describes how the fields of a type are located in memory.
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum FieldsShape {
+ /// Scalar primitives and `!`, which never have fields.
+ Primitive,
+
+ /// All fields start at no offset. The `usize` is the field count.
+ Union(NonZeroUsize),
+
+ /// Array/vector-like placement, with all fields of identical types.
+ Array { stride: Size, count: u64 },
+
+ /// Struct-like placement, with precomputed offsets.
+ ///
+ /// Fields are guaranteed to not overlap, but note that gaps
+ /// before, between and after all the fields are NOT always
+ /// padding, and as such their contents may not be discarded.
+ /// For example, enum variants leave a gap at the start,
+ /// where the discriminant field in the enum layout goes.
+ Arbitrary {
+ /// Offsets for the first byte of each field,
+ /// ordered to match the source definition order.
+ /// This vector does not go in increasing order.
+ // FIXME(eddyb) use small vector optimization for the common case.
+ offsets: Vec<Size>,
+
+ /// Maps source order field indices to memory order indices,
+ /// depending on how the fields were reordered (if at all).
+ /// This is a permutation, with both the source order and the
+ /// memory order using the same (0..n) index ranges.
+ ///
+ /// Note that during computation of `memory_index`, sometimes
+ /// it is easier to operate on the inverse mapping (that is,
+ /// from memory order to source order), and that is usually
+ /// named `inverse_memory_index`.
+ ///
+ // FIXME(eddyb) build a better abstraction for permutations, if possible.
+ // FIXME(camlorn) also consider small vector optimization here.
+ memory_index: Vec<u32>,
+ },
+}
+
+impl FieldsShape {
+ #[inline]
+ pub fn count(&self) -> usize {
+ match *self {
+ FieldsShape::Primitive => 0,
+ FieldsShape::Union(count) => count.get(),
+ FieldsShape::Array { count, .. } => count.try_into().unwrap(),
+ FieldsShape::Arbitrary { ref offsets, .. } => offsets.len(),
+ }
+ }
+
+ #[inline]
+ pub fn offset(&self, i: usize) -> Size {
+ match *self {
+ FieldsShape::Primitive => {
+ unreachable!("FieldsShape::offset: `Primitive`s have no fields")
+ }
+ FieldsShape::Union(count) => {
+ assert!(
+ i < count.get(),
+ "tried to access field {} of union with {} fields",
+ i,
+ count
+ );
+ Size::ZERO
+ }
+ FieldsShape::Array { stride, count } => {
+ let i = u64::try_from(i).unwrap();
+ assert!(i < count);
+ stride * i
+ }
+ FieldsShape::Arbitrary { ref offsets, .. } => offsets[i],
+ }
+ }
+
+ #[inline]
+ pub fn memory_index(&self, i: usize) -> usize {
+ match *self {
+ FieldsShape::Primitive => {
+ unreachable!("FieldsShape::memory_index: `Primitive`s have no fields")
+ }
+ FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
+ FieldsShape::Arbitrary { ref memory_index, .. } => memory_index[i].try_into().unwrap(),
+ }
+ }
+
+ /// Gets source indices of the fields by increasing offsets.
+ #[inline]
+ pub fn index_by_increasing_offset<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
+ let mut inverse_small = [0u8; 64];
+ let mut inverse_big = vec![];
+ let use_small = self.count() <= inverse_small.len();
+
+ // We have to write this logic twice in order to keep the array small.
+ if let FieldsShape::Arbitrary { ref memory_index, .. } = *self {
+ if use_small {
+ for i in 0..self.count() {
+ inverse_small[memory_index[i] as usize] = i as u8;
+ }
+ } else {
+ inverse_big = vec![0; self.count()];
+ for i in 0..self.count() {
+ inverse_big[memory_index[i] as usize] = i as u32;
+ }
+ }
+ }
+
+ (0..self.count()).map(move |i| match *self {
+ FieldsShape::Primitive | FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
+ FieldsShape::Arbitrary { .. } => {
+ if use_small {
+ inverse_small[i] as usize
+ } else {
+ inverse_big[i] as usize
+ }
+ }
+ })
+ }
+}
+
+/// An identifier that specifies the address space that some operation
+/// should operate on. Special address spaces have an effect on code generation,
+/// depending on the target and the address spaces it implements.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct AddressSpace(pub u32);
+
+impl AddressSpace {
+ /// The default address space, corresponding to data space.
+ pub const DATA: Self = AddressSpace(0);
+}
+
+/// Describes how values of the type are passed by target ABIs,
+/// in terms of categories of C types there are ABI rules for.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+
+pub enum Abi {
+ Uninhabited,
+ Scalar(Scalar),
+ ScalarPair(Scalar, Scalar),
+ Vector {
+ element: Scalar,
+ count: u64,
+ },
+ Aggregate {
+ /// If true, the size is exact, otherwise it's only a lower bound.
+ sized: bool,
+ },
+}
+
+impl Abi {
+ /// Returns `true` if the layout corresponds to an unsized type.
+ #[inline]
+ pub fn is_unsized(&self) -> bool {
+ match *self {
+ Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
+ Abi::Aggregate { sized } => !sized,
+ }
+ }
+
+ #[inline]
+ pub fn is_sized(&self) -> bool {
+ !self.is_unsized()
+ }
+
+ /// Returns `true` if this is a single signed integer scalar
+ #[inline]
+ pub fn is_signed(&self) -> bool {
+ match self {
+ Abi::Scalar(scal) => match scal.primitive() {
+ Primitive::Int(_, signed) => signed,
+ _ => false,
+ },
+ _ => panic!("`is_signed` on non-scalar ABI {:?}", self),
+ }
+ }
+
+ /// Returns `true` if this is an uninhabited type
+ #[inline]
+ pub fn is_uninhabited(&self) -> bool {
+ matches!(*self, Abi::Uninhabited)
+ }
+
+ /// Returns `true` is this is a scalar type
+ #[inline]
+ pub fn is_scalar(&self) -> bool {
+ matches!(*self, Abi::Scalar(_))
+ }
+}
+
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum Variants<V: Idx> {
+ /// Single enum variants, structs/tuples, unions, and all non-ADTs.
+ Single { index: V },
+
+ /// Enum-likes with more than one inhabited variant: each variant comes with
+ /// a *discriminant* (usually the same as the variant index but the user can
+ /// assign explicit discriminant values). That discriminant is encoded
+ /// as a *tag* on the machine. The layout of each variant is
+ /// a struct, and they all have space reserved for the tag.
+ /// For enums, the tag is the sole field of the layout.
+ Multiple {
+ tag: Scalar,
+ tag_encoding: TagEncoding<V>,
+ tag_field: usize,
+ variants: IndexVec<V, LayoutS<V>>,
+ },
+}
+
+#[derive(PartialEq, Eq, Hash, Clone, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum TagEncoding<V: Idx> {
+ /// The tag directly stores the discriminant, but possibly with a smaller layout
+ /// (so converting the tag to the discriminant can require sign extension).
+ Direct,
+
+ /// Niche (values invalid for a type) encoding the discriminant:
+ /// Discriminant and variant index coincide.
+ /// The variant `untagged_variant` contains a niche at an arbitrary
+ /// offset (field `tag_field` of the enum), which for a variant with
+ /// discriminant `d` is set to
+ /// `(d - niche_variants.start).wrapping_add(niche_start)`.
+ ///
+ /// For example, `Option<(usize, &T)>` is represented such that
+ /// `None` has a null pointer for the second tuple field, and
+ /// `Some` is the identity function (with a non-null reference).
+ Niche { untagged_variant: V, niche_variants: RangeInclusive<V>, niche_start: u128 },
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct Niche {
+ pub offset: Size,
+ pub value: Primitive,
+ pub valid_range: WrappingRange,
+}
+
+impl Niche {
+ pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> {
+ let Scalar::Initialized { value, valid_range } = scalar else { return None };
+ let niche = Niche { offset, value, valid_range };
+ if niche.available(cx) > 0 { Some(niche) } else { None }
+ }
+
+ pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 {
+ let Self { value, valid_range: v, .. } = *self;
+ let size = value.size(cx);
+ assert!(size.bits() <= 128);
+ let max_value = size.unsigned_int_max();
+
+ // Find out how many values are outside the valid range.
+ let niche = v.end.wrapping_add(1)..v.start;
+ niche.end.wrapping_sub(niche.start) & max_value
+ }
+
+ pub fn reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)> {
+ assert!(count > 0);
+
+ let Self { value, valid_range: v, .. } = *self;
+ let size = value.size(cx);
+ assert!(size.bits() <= 128);
+ let max_value = size.unsigned_int_max();
+
+ let niche = v.end.wrapping_add(1)..v.start;
+ let available = niche.end.wrapping_sub(niche.start) & max_value;
+ if count > available {
+ return None;
+ }
+
+ // Extend the range of valid values being reserved by moving either `v.start` or `v.end` bound.
+ // Given an eventual `Option<T>`, we try to maximize the chance for `None` to occupy the niche of zero.
+ // This is accomplished by preferring enums with 2 variants(`count==1`) and always taking the shortest path to niche zero.
+ // Having `None` in niche zero can enable some special optimizations.
+ //
+ // Bound selection criteria:
+ // 1. Select closest to zero given wrapping semantics.
+ // 2. Avoid moving past zero if possible.
+ //
+ // In practice this means that enums with `count > 1` are unlikely to claim niche zero, since they have to fit perfectly.
+ // If niche zero is already reserved, the selection of bounds are of little interest.
+ let move_start = |v: WrappingRange| {
+ let start = v.start.wrapping_sub(count) & max_value;
+ Some((start, Scalar::Initialized { value, valid_range: v.with_start(start) }))
+ };
+ let move_end = |v: WrappingRange| {
+ let start = v.end.wrapping_add(1) & max_value;
+ let end = v.end.wrapping_add(count) & max_value;
+ Some((start, Scalar::Initialized { value, valid_range: v.with_end(end) }))
+ };
+ let distance_end_zero = max_value - v.end;
+ if v.start > v.end {
+ // zero is unavailable because wrapping occurs
+ move_end(v)
+ } else if v.start <= distance_end_zero {
+ if count <= v.start {
+ move_start(v)
+ } else {
+ // moved past zero, use other bound
+ move_end(v)
+ }
+ } else {
+ let end = v.end.wrapping_add(count) & max_value;
+ let overshot_zero = (1..=v.end).contains(&end);
+ if overshot_zero {
+ // moved past zero, use other bound
+ move_start(v)
+ } else {
+ move_end(v)
+ }
+ }
+ }
+}
+
+#[derive(PartialEq, Eq, Hash, Clone)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub struct LayoutS<V: Idx> {
+ /// Says where the fields are located within the layout.
+ pub fields: FieldsShape,
+
+ /// Encodes information about multi-variant layouts.
+ /// Even with `Multiple` variants, a layout still has its own fields! Those are then
+ /// shared between all variants. One of them will be the discriminant,
+ /// but e.g. generators can have more.
+ ///
+ /// To access all fields of this layout, both `fields` and the fields of the active variant
+ /// must be taken into account.
+ pub variants: Variants<V>,
+
+ /// The `abi` defines how this data is passed between functions, and it defines
+ /// value restrictions via `valid_range`.
+ ///
+ /// Note that this is entirely orthogonal to the recursive structure defined by
+ /// `variants` and `fields`; for example, `ManuallyDrop<Result<isize, isize>>` has
+ /// `Abi::ScalarPair`! So, even with non-`Aggregate` `abi`, `fields` and `variants`
+ /// have to be taken into account to find all fields of this layout.
+ pub abi: Abi,
+
+ /// The leaf scalar with the largest number of invalid values
+ /// (i.e. outside of its `valid_range`), if it exists.
+ pub largest_niche: Option<Niche>,
+
+ pub align: AbiAndPrefAlign,
+ pub size: Size,
+}
+
+impl<V: Idx> LayoutS<V> {
+ pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
+ let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar);
+ let size = scalar.size(cx);
+ let align = scalar.align(cx);
+ LayoutS {
+ variants: Variants::Single { index: V::new(0) },
+ fields: FieldsShape::Primitive,
+ abi: Abi::Scalar(scalar),
+ largest_niche,
+ size,
+ align,
+ }
+ }
+}
+
+impl<V: Idx> fmt::Debug for LayoutS<V> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ // This is how `Layout` used to print before it become
+ // `Interned<LayoutS>`. We print it like this to avoid having to update
+ // expected output in a lot of tests.
+ let LayoutS { size, align, abi, fields, largest_niche, variants } = self;
+ f.debug_struct("Layout")
+ .field("size", size)
+ .field("align", align)
+ .field("abi", abi)
+ .field("fields", fields)
+ .field("largest_niche", largest_niche)
+ .field("variants", variants)
+ .finish()
+ }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+pub enum PointerKind {
+ /// Most general case, we know no restrictions to tell LLVM.
+ SharedMutable,
+
+ /// `&T` where `T` contains no `UnsafeCell`, is `dereferenceable`, `noalias` and `readonly`.
+ Frozen,
+
+ /// `&mut T` which is `dereferenceable` and `noalias` but not `readonly`.
+ UniqueBorrowed,
+
+ /// `&mut !Unpin`, which is `dereferenceable` but neither `noalias` nor `readonly`.
+ UniqueBorrowedPinned,
+
+ /// `Box<T>`, which is `noalias` (even on return types, unlike the above) but neither `readonly`
+ /// nor `dereferenceable`.
+ UniqueOwned,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct PointeeInfo {
+ pub size: Size,
+ pub align: Align,
+ pub safe: Option<PointerKind>,
+ pub address_space: AddressSpace,
+}
+
+/// Used in `might_permit_raw_init` to indicate the kind of initialisation
+/// that is checked to be valid
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum InitKind {
+ Zero,
+ UninitMitigated0x01Fill,
+}
+
+impl<V: Idx> LayoutS<V> {
+ /// Returns `true` if the layout corresponds to an unsized type.
+ pub fn is_unsized(&self) -> bool {
+ self.abi.is_unsized()
+ }
+
+ pub fn is_sized(&self) -> bool {
+ self.abi.is_sized()
+ }
+
+ /// Returns `true` if the type is a ZST and not unsized.
+ pub fn is_zst(&self) -> bool {
+ match self.abi {
+ Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
+ Abi::Uninhabited => self.size.bytes() == 0,
+ Abi::Aggregate { sized } => sized && self.size.bytes() == 0,
+ }
+ }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum StructKind {
+ /// A tuple, closure, or univariant which cannot be coerced to unsized.
+ AlwaysSized,
+ /// A univariant, the last field of which may be coerced to unsized.
+ MaybeUnsized,
+ /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
+ Prefixed(Size, Align),
+}