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 { // Parse an address space index from a string. let parse_address_space = |s: &str, cause: &str| { s.parse::().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::().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::>(); 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::() 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 { 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) -> 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) -> 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(self, offset: Size, cx: &C) -> Option { 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(self, count: u64, cx: &C) -> Option { 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 for u64 { type Output = Size; #[inline] fn mul(self, size: Size) -> Size { size * self } } impl Mul 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 { u64::steps_between(&start.bytes(), &end.bytes()) } #[inline] fn forward_checked(start: Self, count: usize) -> Option { 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 { 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::from_bytes(Size::from_bits(bits).bytes()) } #[inline] pub fn from_bytes(align: u64) -> Result { // 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(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(cx: &C, wanted: Align) -> Option { 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(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 { 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(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(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(&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, /// 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, }, } 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 + '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>, }, } #[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, 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(cx: &C, offset: Size, scalar: Scalar) -> Option { 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(&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(&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`, 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>` 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, pub align: AbiAndPrefAlign, pub size: Size, } impl<'a> LayoutS<'a> { pub fn scalar(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`. 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 `::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 { 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`, 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, 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; 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(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(self, cx: &C, i: usize) -> Self where Ty: TyAbiInterface<'a, C>, { Ty::ty_and_layout_field(self, cx, i) } pub fn pointee_info_at(self, cx: &C, offset: Size) -> Option where Ty: TyAbiInterface<'a, C>, { Ty::ty_and_layout_pointee_info_at(self, cx, offset) } pub fn is_single_fp_element(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(self) -> bool where Ty: TyAbiInterface<'a, C>, { Ty::is_adt(self) } pub fn is_never(self) -> bool where Ty: TyAbiInterface<'a, C>, { Ty::is_never(self) } pub fn is_tuple(self) -> bool where Ty: TyAbiInterface<'a, C>, { Ty::is_tuple(self) } pub fn is_unit(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 . /// /// 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(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 } }