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Diffstat (limited to 'compiler/rustc_target/src/abi/mod.rs')
| -rw-r--r-- | compiler/rustc_target/src/abi/mod.rs | 1558 |
1 files changed, 1558 insertions, 0 deletions
diff --git a/compiler/rustc_target/src/abi/mod.rs b/compiler/rustc_target/src/abi/mod.rs new file mode 100644 index 000000000..92ce4d91d --- /dev/null +++ b/compiler/rustc_target/src/abi/mod.rs @@ -0,0 +1,1558 @@ +pub use Integer::*; +pub use Primitive::*; + +use crate::json::{Json, ToJson}; +use crate::spec::Target; + +use std::convert::{TryFrom, TryInto}; +use std::fmt; +use std::iter::Step; +use std::num::NonZeroUsize; +use std::ops::{Add, AddAssign, Deref, Mul, RangeInclusive, Sub}; +use std::str::FromStr; + +use rustc_data_structures::intern::Interned; +use rustc_index::vec::{Idx, IndexVec}; +use rustc_macros::HashStable_Generic; + +pub mod call; + +/// Parsed [Data layout](https://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, + + /// 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, + } + } +} + +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 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. + } + } + + // Perform consistency checks against the Target information. + if dl.endian != target.endian { + return Err(format!( + "inconsistent target specification: \"data-layout\" claims \ + architecture is {}-endian, while \"target-endian\" is `{}`", + dl.endian.as_str(), + target.endian.as_str(), + )); + } + + let target_pointer_width: u64 = target.pointer_width.into(); + if dl.pointer_size.bits() != target_pointer_width { + return Err(format!( + "inconsistent target specification: \"data-layout\" claims \ + pointers are {}-bit, while \"target-pointer-width\" is `{}`", + dl.pointer_size.bits(), + target.pointer_width + )); + } + + dl.c_enum_min_size = Integer::from_size(Size::from_bits(target.c_enum_min_bits))?; + + 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)] +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)), + } + } +} + +impl ToJson for Endian { + fn to_json(&self) -> Json { + self.as_str().to_json() + } +} + +/// Size of a type in bytes. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)] +#[derive(HashStable_Generic)] +pub struct Size { + raw: u64, +} + +// 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; + } +} + +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, Encodable, Decodable)] +#[derive(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)] +#[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, 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), + } + } + + 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] + 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, 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)] +#[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)] +#[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, 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 { + #[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, 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, + } + } + + /// 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(_)) + } +} + +rustc_index::newtype_index! { + pub struct VariantIdx { + derive [HashStable_Generic] + } +} + +#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)] +pub enum Variants<'a> { + /// 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<'a>>, + }, +} + +#[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, Copy, PartialEq, Eq, Hash, Debug, 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, HashStable_Generic)] +pub struct LayoutS<'a> { + /// 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<'a>, + + /// 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<'a> LayoutS<'a> { + 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: VariantIdx::new(0) }, + fields: FieldsShape::Primitive, + abi: Abi::Scalar(scalar), + largest_niche, + size, + align, + } + } +} + +impl<'a> fmt::Debug for LayoutS<'a> { + 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, Hash, HashStable_Generic)] +#[rustc_pass_by_value] +pub struct Layout<'a>(pub Interned<'a, LayoutS<'a>>); + +impl<'a> fmt::Debug for Layout<'a> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + // See comment on `<LayoutS as Debug>::fmt` above. + self.0.0.fmt(f) + } +} + +impl<'a> Layout<'a> { + pub fn fields(self) -> &'a FieldsShape { + &self.0.0.fields + } + + pub fn variants(self) -> &'a Variants<'a> { + &self.0.0.variants + } + + pub fn abi(self) -> Abi { + self.0.0.abi + } + + pub fn largest_niche(self) -> Option<Niche> { + self.0.0.largest_niche + } + + pub fn align(self) -> AbiAndPrefAlign { + self.0.0.align + } + + pub fn size(self) -> Size { + self.0.0.size + } +} + +/// 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, HashStable_Generic)] +pub struct TyAndLayout<'a, Ty> { + pub ty: Ty, + pub layout: Layout<'a>, +} + +impl<'a, Ty> Deref for TyAndLayout<'a, Ty> { + type Target = &'a LayoutS<'a>; + fn deref(&self) -> &&'a LayoutS<'a> { + &self.layout.0.0 + } +} + +#[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, + Uninit, +} + +/// Trait that needs to be implemented by the higher-level type representation +/// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality. +pub trait TyAbiInterface<'a, C>: Sized { + fn ty_and_layout_for_variant( + this: TyAndLayout<'a, Self>, + cx: &C, + variant_index: VariantIdx, + ) -> TyAndLayout<'a, Self>; + fn ty_and_layout_field(this: TyAndLayout<'a, Self>, cx: &C, i: usize) -> TyAndLayout<'a, Self>; + fn ty_and_layout_pointee_info_at( + this: TyAndLayout<'a, Self>, + cx: &C, + offset: Size, + ) -> Option<PointeeInfo>; + fn is_adt(this: TyAndLayout<'a, Self>) -> bool; + fn is_never(this: TyAndLayout<'a, Self>) -> bool; + fn is_tuple(this: TyAndLayout<'a, Self>) -> bool; + fn is_unit(this: TyAndLayout<'a, Self>) -> bool; +} + +impl<'a, Ty> TyAndLayout<'a, Ty> { + pub fn for_variant<C>(self, cx: &C, variant_index: VariantIdx) -> Self + where + Ty: TyAbiInterface<'a, C>, + { + Ty::ty_and_layout_for_variant(self, cx, variant_index) + } + + pub fn field<C>(self, cx: &C, i: usize) -> Self + where + Ty: TyAbiInterface<'a, C>, + { + Ty::ty_and_layout_field(self, cx, i) + } + + pub fn pointee_info_at<C>(self, cx: &C, offset: Size) -> Option<PointeeInfo> + where + Ty: TyAbiInterface<'a, C>, + { + Ty::ty_and_layout_pointee_info_at(self, cx, offset) + } + + pub fn is_single_fp_element<C>(self, cx: &C) -> bool + where + Ty: TyAbiInterface<'a, C>, + C: HasDataLayout, + { + match self.abi { + Abi::Scalar(scalar) => scalar.primitive().is_float(), + Abi::Aggregate { .. } => { + if self.fields.count() == 1 && self.fields.offset(0).bytes() == 0 { + self.field(cx, 0).is_single_fp_element(cx) + } else { + false + } + } + _ => false, + } + } + + pub fn is_adt<C>(self) -> bool + where + Ty: TyAbiInterface<'a, C>, + { + Ty::is_adt(self) + } + + pub fn is_never<C>(self) -> bool + where + Ty: TyAbiInterface<'a, C>, + { + Ty::is_never(self) + } + + pub fn is_tuple<C>(self) -> bool + where + Ty: TyAbiInterface<'a, C>, + { + Ty::is_tuple(self) + } + + pub fn is_unit<C>(self) -> bool + where + Ty: TyAbiInterface<'a, C>, + { + Ty::is_unit(self) + } +} + +impl<'a, Ty> TyAndLayout<'a, Ty> { + /// Returns `true` if the layout corresponds to an unsized type. + pub fn is_unsized(&self) -> bool { + self.abi.is_unsized() + } + + /// 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, + } + } + + /// Determines if this type permits "raw" initialization by just transmuting some + /// memory into an instance of `T`. + /// + /// `init_kind` indicates if the memory is zero-initialized or left uninitialized. + /// + /// This code is intentionally conservative, and will not detect + /// * zero init of an enum whose 0 variant does not allow zero initialization + /// * making uninitialized types who have a full valid range (ints, floats, raw pointers) + /// * Any form of invalid value being made inside an array (unless the value is uninhabited) + /// + /// A strict form of these checks that uses const evaluation exists in + /// `rustc_const_eval::might_permit_raw_init`, and a tracking issue for making these checks + /// stricter is <https://github.com/rust-lang/rust/issues/66151>. + /// + /// FIXME: Once all the conservatism is removed from here, and the checks are ran by default, + /// we can use the const evaluation checks always instead. + pub fn might_permit_raw_init<C>(self, cx: &C, init_kind: InitKind) -> bool + where + Self: Copy, + Ty: TyAbiInterface<'a, C>, + C: HasDataLayout, + { + let scalar_allows_raw_init = move |s: Scalar| -> bool { + match init_kind { + InitKind::Zero => { + // The range must contain 0. + s.valid_range(cx).contains(0) + } + InitKind::Uninit => { + // The range must include all values. + s.is_always_valid(cx) + } + } + }; + + // Check the ABI. + let valid = match self.abi { + Abi::Uninhabited => false, // definitely UB + Abi::Scalar(s) => scalar_allows_raw_init(s), + Abi::ScalarPair(s1, s2) => scalar_allows_raw_init(s1) && scalar_allows_raw_init(s2), + Abi::Vector { element: s, count } => count == 0 || scalar_allows_raw_init(s), + Abi::Aggregate { .. } => true, // Fields are checked below. + }; + if !valid { + // This is definitely not okay. + return false; + } + + // If we have not found an error yet, we need to recursively descend into fields. + match &self.fields { + FieldsShape::Primitive | FieldsShape::Union { .. } => {} + FieldsShape::Array { .. } => { + // FIXME(#66151): For now, we are conservative and do not check arrays by default. + } + FieldsShape::Arbitrary { offsets, .. } => { + for idx in 0..offsets.len() { + if !self.field(cx, idx).might_permit_raw_init(cx, init_kind) { + // We found a field that is unhappy with this kind of initialization. + return false; + } + } + } + } + + // FIXME(#66151): For now, we are conservative and do not check `self.variants`. + true + } +} |