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mod.rs
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pub use Integer::*;
pub use Primitive::*;
use crate::spec::Target;
use std::convert::{TryFrom, TryInto};
use std::num::NonZeroUsize;
use std::ops::{Add, AddAssign, Deref, Mul, Range, RangeInclusive, Sub};
use rustc_index::vec::{Idx, IndexVec};
use rustc_macros::HashStable_Generic;
use rustc_span::Span;
pub mod call;
/// Parsed [Data layout](http://llvm.org/docs/LangRef.html#data-layout)
/// for a target, which contains everything needed to compute layouts.
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,
}
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,
}
}
}
impl TargetDataLayout {
pub fn parse(target: &Target) -> Result<TargetDataLayout, String> {
// Parse an address space index from a string.
let parse_address_space = |s: &str, cause: &str| {
s.parse::<u32>().map(AddressSpace).map_err(|err| {
format!("invalid address space `{}` for `{}` in \"data-layout\": {}", s, cause, err)
})
};
// Parse a bit count from a string.
let parse_bits = |s: &str, kind: &str, cause: &str| {
s.parse::<u64>().map_err(|err| {
format!("invalid {} `{}` for `{}` in \"data-layout\": {}", kind, s, cause, err)
})
};
// Parse a size string.
let size = |s: &str, cause: &str| parse_bits(s, "size", cause).map(Size::from_bits);
// Parse an alignment string.
let align = |s: &[&str], cause: &str| {
if s.is_empty() {
return Err(format!("missing alignment for `{}` in \"data-layout\"", cause));
}
let align_from_bits = |bits| {
Align::from_bits(bits).map_err(|err| {
format!("invalid alignment for `{}` in \"data-layout\": {}", 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 target.data_layout.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 bits = match s[1..].parse::<u64>() {
Ok(bits) => bits,
Err(_) => {
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.
}
}
// Perform consistency checks against the Target information.
let endian_str = match dl.endian {
Endian::Little => "little",
Endian::Big => "big",
};
if endian_str != target.endian {
return Err(format!(
"inconsistent target specification: \"data-layout\" claims \
architecture is {}-endian, while \"target-endian\" is `{}`",
endian_str, target.endian
));
}
if dl.pointer_size.bits() != target.pointer_width.into() {
return Err(format!(
"inconsistent target specification: \"data-layout\" claims \
pointers are {}-bit, while \"target-pointer-width\" is `{}`",
dl.pointer_size.bits(),
target.pointer_width
));
}
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.
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),
}
}
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),
}
}
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 {
fn data_layout(&self) -> &TargetDataLayout {
self
}
}
/// Endianness of the target, which must match cfg(target-endian).
#[derive(Copy, Clone, PartialEq)]
pub enum Endian {
Little,
Big,
}
/// Size of a type in bytes.
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
#[derive(HashStable_Generic)]
pub struct Size {
raw: u64,
}
impl Size {
pub const ZERO: Size = Size { raw: 0 };
#[inline]
pub fn from_bits(bits: impl TryInto<u64>) -> Size {
let bits = bits.try_into().ok().unwrap();
// Avoid potential overflow from `bits + 7`.
Size::from_bytes(bits / 8 + ((bits % 8) + 7) / 8)
}
#[inline]
pub fn from_bytes(bytes: impl TryInto<u64>) -> Size {
Size { raw: bytes.try_into().ok().unwrap() }
}
#[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 {
self.bytes().checked_mul(8).unwrap_or_else(|| {
panic!("Size::bits: {} bytes in bits doesn't fit in u64", 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
}
}
// 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;
}
}
/// Alignment of a type in bytes (always a power of two).
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
#[derive(HashStable_Generic)]
pub struct Align {
pow2: u8,
}
impl Align {
pub fn from_bits(bits: u64) -> Result<Align, String> {
Align::from_bytes(Size::from_bits(bits).bytes())
}
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 { pow2: 0 });
}
let mut bytes = align;
let mut pow2: u8 = 0;
while (bytes & 1) == 0 {
pow2 += 1;
bytes >>= 1;
}
if bytes != 1 {
return Err(format!("`{}` is not a power of 2", align));
}
if pow2 > 29 {
return Err(format!("`{}` is too large", align));
}
Ok(Align { pow2 })
}
pub fn bytes(self) -> u64 {
1 << self.pow2
}
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`.
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).
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, Encodable, Decodable)]
#[derive(HashStable_Generic)]
pub struct AbiAndPrefAlign {
pub abi: Align,
pub pref: Align,
}
impl AbiAndPrefAlign {
pub fn new(align: Align) -> AbiAndPrefAlign {
AbiAndPrefAlign { abi: align, pref: align }
}
pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) }
}
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, HashStable_Generic)]
pub enum Integer {
I8,
I16,
I32,
I64,
I128,
}
impl Integer {
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),
}
}
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.
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.
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
}
}
/// Fundamental unit of memory access and layout.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, 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,
}
}
pub fn is_float(self) -> bool {
matches!(self, F32 | F64)
}
pub fn is_int(self) -> bool {
matches!(self, Int(..))
}
}
/// Information about one scalar component of a Rust type.
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
#[derive(HashStable_Generic)]
pub struct Scalar {
pub value: Primitive,
/// 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.
// 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.
pub valid_range: RangeInclusive<u128>,
}
impl Scalar {
pub fn is_bool(&self) -> bool {
if let Int(I8, _) = self.value { self.valid_range == (0..=1) } else { false }
}
/// Returns the valid range as a `x..y` range.
///
/// If `x` and `y` are equal, the range is full, not empty.
pub fn valid_range_exclusive<C: HasDataLayout>(&self, cx: &C) -> Range<u128> {
// For a (max) value of -1, max will be `-1 as usize`, which overflows.
// However, that is fine here (it would still represent the full range),
// i.e., if the range is everything.
let bits = self.value.size(cx).bits();
assert!(bits <= 128);
let mask = !0u128 >> (128 - bits);
let start = *self.valid_range.start();
let end = *self.valid_range.end();
assert_eq!(start, start & mask);
assert_eq!(end, end & mask);
start..(end.wrapping_add(1) & mask)
}
}
/// Describes how the fields of a type are located in memory.
#[derive(PartialEq, Eq, Hash, Debug, 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 {
pub fn count(&self) -> usize {
match *self {
FieldsShape::Primitive => 0,
FieldsShape::Union(count) => count.get(),
FieldsShape::Array { count, .. } => {
let usize_count = count as usize;
assert_eq!(usize_count as u64, count);
usize_count
}
FieldsShape::Arbitrary { ref offsets, .. } => offsets.len(),
}
}
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],
}
}
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, .. } => {
let r = memory_index[i];
assert_eq!(r as usize as u32, r);
r as usize
}
}
}
/// 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, PartialEq, Eq, Hash, Debug, 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.
pub fn is_unsized(&self) -> bool {
match *self {
Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
Abi::Aggregate { sized } => !sized,
}
}
/// Returns `true` if this is a single signed integer scalar
pub fn is_signed(&self) -> bool {
match *self {
Abi::Scalar(ref scal) => match scal.value {
Primitive::Int(_, signed) => signed,
_ => false,
},
_ => panic!("`is_signed` on non-scalar ABI {:?}", self),
}
}
/// Returns `true` if this is an uninhabited type
pub fn is_uninhabited(&self) -> bool {
matches!(*self, Abi::Uninhabited)
}
/// Returns `true` is this is a scalar type
pub fn is_scalar(&self) -> bool {
matches!(*self, Abi::Scalar(_))
}
}
rustc_index::newtype_index! {
pub struct VariantIdx {
derive [HashStable_Generic]
}
}
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub enum Variants {
/// Single enum variants, structs/tuples, unions, and all non-ADTs.
Single { index: VariantIdx },
/// 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,
tag_field: usize,
variants: IndexVec<VariantIdx, Layout>,
},
}
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub enum TagEncoding {
/// 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 `dataful_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 {
dataful_variant: VariantIdx,
niche_variants: RangeInclusive<VariantIdx>,
niche_start: u128,
},
}
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct Niche {
pub offset: Size,
pub scalar: Scalar,
}
impl Niche {
pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> {
let niche = Niche { offset, scalar };
if niche.available(cx) > 0 { Some(niche) } else { None }
}
pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 {
let Scalar { value, valid_range: ref v } = self.scalar;
let bits = value.size(cx).bits();
assert!(bits <= 128);
let max_value = !0u128 >> (128 - bits);
// 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 Scalar { value, valid_range: ref v } = self.scalar;
let bits = value.size(cx).bits();
assert!(bits <= 128);
let max_value = !0u128 >> (128 - bits);
if count > max_value {
return None;
}
// Compute the range of invalid values being reserved.
let start = v.end().wrapping_add(1) & max_value;
let end = v.end().wrapping_add(count) & max_value;
// If the `end` of our range is inside the valid range,
// then we ran out of invalid values.
// FIXME(eddyb) abstract this with a wraparound range type.
let valid_range_contains = |x| {
if v.start() <= v.end() {
*v.start() <= x && x <= *v.end()
} else {
*v.start() <= x || x <= *v.end()
}
};
if valid_range_contains(end) {
return None;
}
Some((start, Scalar { value, valid_range: *v.start()..=end }))
}
}
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct Layout {
/// 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,
/// 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 Layout {
pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self {
let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar.clone());
let size = scalar.value.size(cx);
let align = scalar.value.align(cx);
Layout {
variants: Variants::Single { index: VariantIdx::new(0) },
fields: FieldsShape::Primitive,
abi: Abi::Scalar(scalar),
largest_niche,
size,
align,
}
}
}
/// The layout of a type, alongside the type itself.
/// Provides various type traversal APIs (e.g., recursing into fields).
///
/// Note that the layout is NOT guaranteed to always be identical
/// to that obtained from `layout_of(ty)`, as we need to produce
/// layouts for which Rust types do not exist, such as enum variants
/// or synthetic fields of enums (i.e., discriminants) and fat pointers.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
pub struct TyAndLayout<'a, Ty> {
pub ty: Ty,
pub layout: &'a Layout,
}
impl<'a, Ty> Deref for TyAndLayout<'a, Ty> {
type Target = &'a Layout;
fn deref(&self) -> &&'a Layout {
&self.layout
}
}