1574 lines
52 KiB
Rust
1574 lines
52 KiB
Rust
#![cfg_attr(feature = "nightly", feature(step_trait, rustc_attrs, min_specialization))]
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use std::fmt;
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#[cfg(feature = "nightly")]
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use std::iter::Step;
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use std::num::{NonZeroUsize, ParseIntError};
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use std::ops::{Add, AddAssign, Mul, RangeInclusive, Sub};
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use std::str::FromStr;
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use bitflags::bitflags;
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use rustc_data_structures::intern::Interned;
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#[cfg(feature = "nightly")]
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use rustc_data_structures::stable_hasher::StableOrd;
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use rustc_index::vec::{Idx, IndexSlice, IndexVec};
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#[cfg(feature = "nightly")]
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use rustc_macros::HashStable_Generic;
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#[cfg(feature = "nightly")]
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use rustc_macros::{Decodable, Encodable};
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mod layout;
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pub use layout::LayoutCalculator;
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/// Requirements for a `StableHashingContext` to be used in this crate.
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/// This is a hack to allow using the `HashStable_Generic` derive macro
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/// instead of implementing everything in `rustc_middle`.
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pub trait HashStableContext {}
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use Integer::*;
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use Primitive::*;
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bitflags! {
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#[derive(Default)]
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#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
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pub struct ReprFlags: u8 {
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const IS_C = 1 << 0;
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const IS_SIMD = 1 << 1;
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const IS_TRANSPARENT = 1 << 2;
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// Internal only for now. If true, don't reorder fields.
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const IS_LINEAR = 1 << 3;
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// If true, the type's layout can be randomized using
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// the seed stored in `ReprOptions.layout_seed`
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const RANDOMIZE_LAYOUT = 1 << 4;
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// Any of these flags being set prevent field reordering optimisation.
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const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
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| ReprFlags::IS_SIMD.bits
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| ReprFlags::IS_LINEAR.bits;
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}
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}
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#[derive(Copy, Clone, Debug, Eq, PartialEq)]
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#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
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pub enum IntegerType {
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/// Pointer sized integer type, i.e. isize and usize. The field shows signedness, that
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/// is, `Pointer(true)` is isize.
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Pointer(bool),
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/// Fix sized integer type, e.g. i8, u32, i128 The bool field shows signedness, `Fixed(I8, false)` means `u8`
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Fixed(Integer, bool),
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}
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impl IntegerType {
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pub fn is_signed(&self) -> bool {
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match self {
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IntegerType::Pointer(b) => *b,
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IntegerType::Fixed(_, b) => *b,
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}
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}
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}
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/// Represents the repr options provided by the user,
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#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
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#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
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pub struct ReprOptions {
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pub int: Option<IntegerType>,
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pub align: Option<Align>,
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pub pack: Option<Align>,
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pub flags: ReprFlags,
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/// The seed to be used for randomizing a type's layout
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///
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/// Note: This could technically be a `[u8; 16]` (a `u128`) which would
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/// be the "most accurate" hash as it'd encompass the item and crate
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/// hash without loss, but it does pay the price of being larger.
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/// Everything's a tradeoff, a `u64` seed should be sufficient for our
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/// purposes (primarily `-Z randomize-layout`)
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pub field_shuffle_seed: u64,
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}
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impl ReprOptions {
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#[inline]
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pub fn simd(&self) -> bool {
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self.flags.contains(ReprFlags::IS_SIMD)
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}
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#[inline]
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pub fn c(&self) -> bool {
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self.flags.contains(ReprFlags::IS_C)
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}
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#[inline]
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pub fn packed(&self) -> bool {
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self.pack.is_some()
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}
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#[inline]
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pub fn transparent(&self) -> bool {
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self.flags.contains(ReprFlags::IS_TRANSPARENT)
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}
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#[inline]
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pub fn linear(&self) -> bool {
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self.flags.contains(ReprFlags::IS_LINEAR)
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}
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/// Returns the discriminant type, given these `repr` options.
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/// This must only be called on enums!
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pub fn discr_type(&self) -> IntegerType {
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self.int.unwrap_or(IntegerType::Pointer(true))
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}
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/// Returns `true` if this `#[repr()]` should inhabit "smart enum
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/// layout" optimizations, such as representing `Foo<&T>` as a
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/// single pointer.
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pub fn inhibit_enum_layout_opt(&self) -> bool {
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self.c() || self.int.is_some()
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}
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/// Returns `true` if this `#[repr()]` should inhibit struct field reordering
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/// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
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pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
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if let Some(pack) = self.pack {
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if pack.bytes() == 1 {
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return true;
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}
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}
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self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
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}
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/// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
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/// was enabled for its declaration crate
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pub fn can_randomize_type_layout(&self) -> bool {
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!self.inhibit_struct_field_reordering_opt()
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&& self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
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}
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/// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
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pub fn inhibit_union_abi_opt(&self) -> bool {
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self.c()
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}
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}
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/// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout)
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/// for a target, which contains everything needed to compute layouts.
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#[derive(Debug, PartialEq, Eq)]
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pub struct TargetDataLayout {
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pub endian: Endian,
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pub i1_align: AbiAndPrefAlign,
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pub i8_align: AbiAndPrefAlign,
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pub i16_align: AbiAndPrefAlign,
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pub i32_align: AbiAndPrefAlign,
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pub i64_align: AbiAndPrefAlign,
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pub i128_align: AbiAndPrefAlign,
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pub f32_align: AbiAndPrefAlign,
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pub f64_align: AbiAndPrefAlign,
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pub pointer_size: Size,
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pub pointer_align: AbiAndPrefAlign,
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pub aggregate_align: AbiAndPrefAlign,
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/// Alignments for vector types.
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pub vector_align: Vec<(Size, AbiAndPrefAlign)>,
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pub instruction_address_space: AddressSpace,
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/// Minimum size of #[repr(C)] enums (default c_int::BITS, usually 32)
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/// Note: This isn't in LLVM's data layout string, it is `short_enum`
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/// so the only valid spec for LLVM is c_int::BITS or 8
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pub c_enum_min_size: Integer,
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}
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impl Default for TargetDataLayout {
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/// Creates an instance of `TargetDataLayout`.
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fn default() -> TargetDataLayout {
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let align = |bits| Align::from_bits(bits).unwrap();
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TargetDataLayout {
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endian: Endian::Big,
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i1_align: AbiAndPrefAlign::new(align(8)),
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i8_align: AbiAndPrefAlign::new(align(8)),
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i16_align: AbiAndPrefAlign::new(align(16)),
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i32_align: AbiAndPrefAlign::new(align(32)),
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i64_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
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i128_align: AbiAndPrefAlign { abi: align(32), pref: align(64) },
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f32_align: AbiAndPrefAlign::new(align(32)),
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f64_align: AbiAndPrefAlign::new(align(64)),
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pointer_size: Size::from_bits(64),
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pointer_align: AbiAndPrefAlign::new(align(64)),
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aggregate_align: AbiAndPrefAlign { abi: align(0), pref: align(64) },
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vector_align: vec![
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(Size::from_bits(64), AbiAndPrefAlign::new(align(64))),
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(Size::from_bits(128), AbiAndPrefAlign::new(align(128))),
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],
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instruction_address_space: AddressSpace::DATA,
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c_enum_min_size: Integer::I32,
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}
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}
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}
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pub enum TargetDataLayoutErrors<'a> {
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InvalidAddressSpace { addr_space: &'a str, cause: &'a str, err: ParseIntError },
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InvalidBits { kind: &'a str, bit: &'a str, cause: &'a str, err: ParseIntError },
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MissingAlignment { cause: &'a str },
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InvalidAlignment { cause: &'a str, err: String },
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InconsistentTargetArchitecture { dl: &'a str, target: &'a str },
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InconsistentTargetPointerWidth { pointer_size: u64, target: u32 },
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InvalidBitsSize { err: String },
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}
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impl TargetDataLayout {
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/// Parse data layout from an [llvm data layout string](https://llvm.org/docs/LangRef.html#data-layout)
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///
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/// This function doesn't fill `c_enum_min_size` and it will always be `I32` since it can not be
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/// determined from llvm string.
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pub fn parse_from_llvm_datalayout_string<'a>(
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input: &'a str,
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) -> Result<TargetDataLayout, TargetDataLayoutErrors<'a>> {
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// Parse an address space index from a string.
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let parse_address_space = |s: &'a str, cause: &'a str| {
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s.parse::<u32>().map(AddressSpace).map_err(|err| {
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TargetDataLayoutErrors::InvalidAddressSpace { addr_space: s, cause, err }
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})
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};
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// Parse a bit count from a string.
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let parse_bits = |s: &'a str, kind: &'a str, cause: &'a str| {
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s.parse::<u64>().map_err(|err| TargetDataLayoutErrors::InvalidBits {
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kind,
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bit: s,
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cause,
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err,
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})
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};
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// Parse a size string.
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let size = |s: &'a str, cause: &'a str| parse_bits(s, "size", cause).map(Size::from_bits);
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// Parse an alignment string.
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let align = |s: &[&'a str], cause: &'a str| {
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if s.is_empty() {
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return Err(TargetDataLayoutErrors::MissingAlignment { cause });
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}
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let align_from_bits = |bits| {
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Align::from_bits(bits)
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.map_err(|err| TargetDataLayoutErrors::InvalidAlignment { cause, err })
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};
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let abi = parse_bits(s[0], "alignment", cause)?;
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let pref = s.get(1).map_or(Ok(abi), |pref| parse_bits(pref, "alignment", cause))?;
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Ok(AbiAndPrefAlign { abi: align_from_bits(abi)?, pref: align_from_bits(pref)? })
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};
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let mut dl = TargetDataLayout::default();
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let mut i128_align_src = 64;
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for spec in input.split('-') {
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let spec_parts = spec.split(':').collect::<Vec<_>>();
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match &*spec_parts {
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["e"] => dl.endian = Endian::Little,
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["E"] => dl.endian = Endian::Big,
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[p] if p.starts_with('P') => {
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dl.instruction_address_space = parse_address_space(&p[1..], "P")?
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}
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["a", ref a @ ..] => dl.aggregate_align = align(a, "a")?,
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["f32", ref a @ ..] => dl.f32_align = align(a, "f32")?,
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["f64", ref a @ ..] => dl.f64_align = align(a, "f64")?,
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// FIXME(erikdesjardins): we should be parsing nonzero address spaces
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// this will require replacing TargetDataLayout::{pointer_size,pointer_align}
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// with e.g. `fn pointer_size_in(AddressSpace)`
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[p @ "p", s, ref a @ ..] | [p @ "p0", s, ref a @ ..] => {
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dl.pointer_size = size(s, p)?;
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dl.pointer_align = align(a, p)?;
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}
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[s, ref a @ ..] if s.starts_with('i') => {
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let Ok(bits) = s[1..].parse::<u64>() else {
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size(&s[1..], "i")?; // For the user error.
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continue;
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};
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let a = align(a, s)?;
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match bits {
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1 => dl.i1_align = a,
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8 => dl.i8_align = a,
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16 => dl.i16_align = a,
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32 => dl.i32_align = a,
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64 => dl.i64_align = a,
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_ => {}
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}
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if bits >= i128_align_src && bits <= 128 {
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// Default alignment for i128 is decided by taking the alignment of
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// largest-sized i{64..=128}.
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i128_align_src = bits;
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dl.i128_align = a;
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}
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}
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[s, ref a @ ..] if s.starts_with('v') => {
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let v_size = size(&s[1..], "v")?;
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let a = align(a, s)?;
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if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) {
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v.1 = a;
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continue;
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}
|
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// No existing entry, add a new one.
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dl.vector_align.push((v_size, a));
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}
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_ => {} // Ignore everything else.
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}
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}
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Ok(dl)
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}
|
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|
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/// Returns exclusive upper bound on object size.
|
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///
|
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/// 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.
|
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///
|
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/// 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.
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#[inline]
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pub fn obj_size_bound(&self) -> u64 {
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match self.pointer_size.bits() {
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16 => 1 << 15,
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32 => 1 << 31,
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64 => 1 << 47,
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bits => panic!("obj_size_bound: unknown pointer bit size {}", bits),
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}
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}
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|
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#[inline]
|
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pub fn ptr_sized_integer(&self) -> Integer {
|
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match self.pointer_size.bits() {
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16 => I16,
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32 => I32,
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||
64 => I64,
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bits => panic!("ptr_sized_integer: unknown pointer bit size {}", bits),
|
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}
|
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}
|
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|
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#[inline]
|
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pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign {
|
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for &(size, align) in &self.vector_align {
|
||
if size == vec_size {
|
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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())
|
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}
|
||
}
|
||
|
||
pub trait HasDataLayout {
|
||
fn data_layout(&self) -> &TargetDataLayout;
|
||
}
|
||
|
||
impl HasDataLayout for TargetDataLayout {
|
||
#[inline]
|
||
fn data_layout(&self) -> &TargetDataLayout {
|
||
self
|
||
}
|
||
}
|
||
|
||
/// Endianness of the target, which must match cfg(target-endian).
|
||
#[derive(Copy, Clone, PartialEq, Eq)]
|
||
pub enum Endian {
|
||
Little,
|
||
Big,
|
||
}
|
||
|
||
impl Endian {
|
||
pub fn as_str(&self) -> &'static str {
|
||
match self {
|
||
Self::Little => "little",
|
||
Self::Big => "big",
|
||
}
|
||
}
|
||
}
|
||
|
||
impl fmt::Debug for Endian {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
f.write_str(self.as_str())
|
||
}
|
||
}
|
||
|
||
impl FromStr for Endian {
|
||
type Err = String;
|
||
|
||
fn from_str(s: &str) -> Result<Self, Self::Err> {
|
||
match s {
|
||
"little" => Ok(Self::Little),
|
||
"big" => Ok(Self::Big),
|
||
_ => Err(format!(r#"unknown endian: "{}""#, s)),
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Size of a type in bytes.
|
||
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
|
||
#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
|
||
pub struct Size {
|
||
raw: u64,
|
||
}
|
||
|
||
// Safety: Ord is implement as just comparing numerical values and numerical values
|
||
// are not changed by (de-)serialization.
|
||
#[cfg(feature = "nightly")]
|
||
unsafe impl StableOrd for Size {}
|
||
|
||
// This is debug-printed a lot in larger structs, don't waste too much space there
|
||
impl fmt::Debug for Size {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
write!(f, "Size({} bytes)", self.bytes())
|
||
}
|
||
}
|
||
|
||
impl Size {
|
||
pub const ZERO: Size = Size { raw: 0 };
|
||
|
||
/// Rounds `bits` up to the next-higher byte boundary, if `bits` is
|
||
/// not a multiple of 8.
|
||
pub fn from_bits(bits: impl TryInto<u64>) -> Size {
|
||
let bits = bits.try_into().ok().unwrap();
|
||
// Avoid potential overflow from `bits + 7`.
|
||
Size { raw: bits / 8 + ((bits % 8) + 7) / 8 }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn from_bytes(bytes: impl TryInto<u64>) -> Size {
|
||
let bytes: u64 = bytes.try_into().ok().unwrap();
|
||
Size { raw: bytes }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bytes(self) -> u64 {
|
||
self.raw
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bytes_usize(self) -> usize {
|
||
self.bytes().try_into().unwrap()
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bits(self) -> u64 {
|
||
#[cold]
|
||
fn overflow(bytes: u64) -> ! {
|
||
panic!("Size::bits: {} bytes in bits doesn't fit in u64", bytes)
|
||
}
|
||
|
||
self.bytes().checked_mul(8).unwrap_or_else(|| overflow(self.bytes()))
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bits_usize(self) -> usize {
|
||
self.bits().try_into().unwrap()
|
||
}
|
||
|
||
#[inline]
|
||
pub fn align_to(self, align: Align) -> Size {
|
||
let mask = align.bytes() - 1;
|
||
Size::from_bytes((self.bytes() + mask) & !mask)
|
||
}
|
||
|
||
#[inline]
|
||
pub fn is_aligned(self, align: Align) -> bool {
|
||
let mask = align.bytes() - 1;
|
||
self.bytes() & mask == 0
|
||
}
|
||
|
||
#[inline]
|
||
pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size> {
|
||
let dl = cx.data_layout();
|
||
|
||
let bytes = self.bytes().checked_add(offset.bytes())?;
|
||
|
||
if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size> {
|
||
let dl = cx.data_layout();
|
||
|
||
let bytes = self.bytes().checked_mul(count)?;
|
||
if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None }
|
||
}
|
||
|
||
/// Truncates `value` to `self` bits and then sign-extends it to 128 bits
|
||
/// (i.e., if it is negative, fill with 1's on the left).
|
||
#[inline]
|
||
pub fn sign_extend(self, value: u128) -> u128 {
|
||
let size = self.bits();
|
||
if size == 0 {
|
||
// Truncated until nothing is left.
|
||
return 0;
|
||
}
|
||
// Sign-extend it.
|
||
let shift = 128 - size;
|
||
// Shift the unsigned value to the left, then shift back to the right as signed
|
||
// (essentially fills with sign bit on the left).
|
||
(((value << shift) as i128) >> shift) as u128
|
||
}
|
||
|
||
/// Truncates `value` to `self` bits.
|
||
#[inline]
|
||
pub fn truncate(self, value: u128) -> u128 {
|
||
let size = self.bits();
|
||
if size == 0 {
|
||
// Truncated until nothing is left.
|
||
return 0;
|
||
}
|
||
let shift = 128 - size;
|
||
// Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
|
||
(value << shift) >> shift
|
||
}
|
||
|
||
#[inline]
|
||
pub fn signed_int_min(&self) -> i128 {
|
||
self.sign_extend(1_u128 << (self.bits() - 1)) as i128
|
||
}
|
||
|
||
#[inline]
|
||
pub fn signed_int_max(&self) -> i128 {
|
||
i128::MAX >> (128 - self.bits())
|
||
}
|
||
|
||
#[inline]
|
||
pub fn unsigned_int_max(&self) -> u128 {
|
||
u128::MAX >> (128 - self.bits())
|
||
}
|
||
}
|
||
|
||
// Panicking addition, subtraction and multiplication for convenience.
|
||
// Avoid during layout computation, return `LayoutError` instead.
|
||
|
||
impl Add for Size {
|
||
type Output = Size;
|
||
#[inline]
|
||
fn add(self, other: Size) -> Size {
|
||
Size::from_bytes(self.bytes().checked_add(other.bytes()).unwrap_or_else(|| {
|
||
panic!("Size::add: {} + {} doesn't fit in u64", self.bytes(), other.bytes())
|
||
}))
|
||
}
|
||
}
|
||
|
||
impl Sub for Size {
|
||
type Output = Size;
|
||
#[inline]
|
||
fn sub(self, other: Size) -> Size {
|
||
Size::from_bytes(self.bytes().checked_sub(other.bytes()).unwrap_or_else(|| {
|
||
panic!("Size::sub: {} - {} would result in negative size", self.bytes(), other.bytes())
|
||
}))
|
||
}
|
||
}
|
||
|
||
impl Mul<Size> for u64 {
|
||
type Output = Size;
|
||
#[inline]
|
||
fn mul(self, size: Size) -> Size {
|
||
size * self
|
||
}
|
||
}
|
||
|
||
impl Mul<u64> for Size {
|
||
type Output = Size;
|
||
#[inline]
|
||
fn mul(self, count: u64) -> Size {
|
||
match self.bytes().checked_mul(count) {
|
||
Some(bytes) => Size::from_bytes(bytes),
|
||
None => panic!("Size::mul: {} * {} doesn't fit in u64", self.bytes(), count),
|
||
}
|
||
}
|
||
}
|
||
|
||
impl AddAssign for Size {
|
||
#[inline]
|
||
fn add_assign(&mut self, other: Size) {
|
||
*self = *self + other;
|
||
}
|
||
}
|
||
|
||
#[cfg(feature = "nightly")]
|
||
impl Step for Size {
|
||
#[inline]
|
||
fn steps_between(start: &Self, end: &Self) -> Option<usize> {
|
||
u64::steps_between(&start.bytes(), &end.bytes())
|
||
}
|
||
|
||
#[inline]
|
||
fn forward_checked(start: Self, count: usize) -> Option<Self> {
|
||
u64::forward_checked(start.bytes(), count).map(Self::from_bytes)
|
||
}
|
||
|
||
#[inline]
|
||
fn forward(start: Self, count: usize) -> Self {
|
||
Self::from_bytes(u64::forward(start.bytes(), count))
|
||
}
|
||
|
||
#[inline]
|
||
unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
|
||
Self::from_bytes(u64::forward_unchecked(start.bytes(), count))
|
||
}
|
||
|
||
#[inline]
|
||
fn backward_checked(start: Self, count: usize) -> Option<Self> {
|
||
u64::backward_checked(start.bytes(), count).map(Self::from_bytes)
|
||
}
|
||
|
||
#[inline]
|
||
fn backward(start: Self, count: usize) -> Self {
|
||
Self::from_bytes(u64::backward(start.bytes(), count))
|
||
}
|
||
|
||
#[inline]
|
||
unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
|
||
Self::from_bytes(u64::backward_unchecked(start.bytes(), count))
|
||
}
|
||
}
|
||
|
||
/// Alignment of a type in bytes (always a power of two).
|
||
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
|
||
#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
|
||
pub struct Align {
|
||
pow2: u8,
|
||
}
|
||
|
||
// This is debug-printed a lot in larger structs, don't waste too much space there
|
||
impl fmt::Debug for Align {
|
||
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
write!(f, "Align({} bytes)", self.bytes())
|
||
}
|
||
}
|
||
|
||
impl Align {
|
||
pub const ONE: Align = Align { pow2: 0 };
|
||
pub const MAX: Align = Align { pow2: 29 };
|
||
|
||
#[inline]
|
||
pub fn from_bits(bits: u64) -> Result<Align, String> {
|
||
Align::from_bytes(Size::from_bits(bits).bytes())
|
||
}
|
||
|
||
#[inline]
|
||
pub fn from_bytes(align: u64) -> Result<Align, String> {
|
||
// Treat an alignment of 0 bytes like 1-byte alignment.
|
||
if align == 0 {
|
||
return Ok(Align::ONE);
|
||
}
|
||
|
||
#[cold]
|
||
fn not_power_of_2(align: u64) -> String {
|
||
format!("`{}` is not a power of 2", align)
|
||
}
|
||
|
||
#[cold]
|
||
fn too_large(align: u64) -> String {
|
||
format!("`{}` is too large", align)
|
||
}
|
||
|
||
let mut bytes = align;
|
||
let mut pow2: u8 = 0;
|
||
while (bytes & 1) == 0 {
|
||
pow2 += 1;
|
||
bytes >>= 1;
|
||
}
|
||
if bytes != 1 {
|
||
return Err(not_power_of_2(align));
|
||
}
|
||
if pow2 > Self::MAX.pow2 {
|
||
return Err(too_large(align));
|
||
}
|
||
|
||
Ok(Align { pow2 })
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bytes(self) -> u64 {
|
||
1 << self.pow2
|
||
}
|
||
|
||
#[inline]
|
||
pub fn bits(self) -> u64 {
|
||
self.bytes() * 8
|
||
}
|
||
|
||
/// Computes the best alignment possible for the given offset
|
||
/// (the largest power of two that the offset is a multiple of).
|
||
///
|
||
/// N.B., for an offset of `0`, this happens to return `2^64`.
|
||
#[inline]
|
||
pub fn max_for_offset(offset: Size) -> Align {
|
||
Align { pow2: offset.bytes().trailing_zeros() as u8 }
|
||
}
|
||
|
||
/// Lower the alignment, if necessary, such that the given offset
|
||
/// is aligned to it (the offset is a multiple of the alignment).
|
||
#[inline]
|
||
pub fn restrict_for_offset(self, offset: Size) -> Align {
|
||
self.min(Align::max_for_offset(offset))
|
||
}
|
||
}
|
||
|
||
/// A pair of alignments, ABI-mandated and preferred.
|
||
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
|
||
pub struct AbiAndPrefAlign {
|
||
pub abi: Align,
|
||
pub pref: Align,
|
||
}
|
||
|
||
impl AbiAndPrefAlign {
|
||
#[inline]
|
||
pub fn new(align: Align) -> AbiAndPrefAlign {
|
||
AbiAndPrefAlign { abi: align, pref: align }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
|
||
AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign {
|
||
AbiAndPrefAlign { abi: self.abi.max(other.abi), pref: self.pref.max(other.pref) }
|
||
}
|
||
}
|
||
|
||
/// Integers, also used for enum discriminants.
|
||
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))]
|
||
|
||
pub enum Integer {
|
||
I8,
|
||
I16,
|
||
I32,
|
||
I64,
|
||
I128,
|
||
}
|
||
|
||
impl Integer {
|
||
#[inline]
|
||
pub fn size(self) -> Size {
|
||
match self {
|
||
I8 => Size::from_bytes(1),
|
||
I16 => Size::from_bytes(2),
|
||
I32 => Size::from_bytes(4),
|
||
I64 => Size::from_bytes(8),
|
||
I128 => Size::from_bytes(16),
|
||
}
|
||
}
|
||
|
||
/// Gets the Integer type from an IntegerType.
|
||
pub fn from_attr<C: HasDataLayout>(cx: &C, ity: IntegerType) -> Integer {
|
||
let dl = cx.data_layout();
|
||
|
||
match ity {
|
||
IntegerType::Pointer(_) => dl.ptr_sized_integer(),
|
||
IntegerType::Fixed(x, _) => x,
|
||
}
|
||
}
|
||
|
||
pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign {
|
||
let dl = cx.data_layout();
|
||
|
||
match self {
|
||
I8 => dl.i8_align,
|
||
I16 => dl.i16_align,
|
||
I32 => dl.i32_align,
|
||
I64 => dl.i64_align,
|
||
I128 => dl.i128_align,
|
||
}
|
||
}
|
||
|
||
/// Returns the largest signed value that can be represented by this Integer.
|
||
#[inline]
|
||
pub fn signed_max(self) -> i128 {
|
||
match self {
|
||
I8 => i8::MAX as i128,
|
||
I16 => i16::MAX as i128,
|
||
I32 => i32::MAX as i128,
|
||
I64 => i64::MAX as i128,
|
||
I128 => i128::MAX,
|
||
}
|
||
}
|
||
|
||
/// 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();
|
||
|
||
[I8, I16, I32, I64, I128].into_iter().find(|&candidate| {
|
||
wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes()
|
||
})
|
||
}
|
||
|
||
/// Find the largest integer with the given alignment or less.
|
||
pub fn approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer {
|
||
let dl = cx.data_layout();
|
||
|
||
// FIXME(eddyb) maybe include I128 in the future, when it works everywhere.
|
||
for candidate in [I64, I32, I16] {
|
||
if wanted >= candidate.align(dl).abi && wanted.bytes() >= candidate.size().bytes() {
|
||
return candidate;
|
||
}
|
||
}
|
||
I8
|
||
}
|
||
|
||
// FIXME(eddyb) consolidate this and other methods that find the appropriate
|
||
// `Integer` given some requirements.
|
||
#[inline]
|
||
pub fn from_size(size: Size) -> Result<Self, String> {
|
||
match size.bits() {
|
||
8 => Ok(Integer::I8),
|
||
16 => Ok(Integer::I16),
|
||
32 => Ok(Integer::I32),
|
||
64 => Ok(Integer::I64),
|
||
128 => Ok(Integer::I128),
|
||
_ => Err(format!("rust does not support integers with {} bits", size.bits())),
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Fundamental unit of memory access and layout.
|
||
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub enum Primitive {
|
||
/// The `bool` is the signedness of the `Integer` type.
|
||
///
|
||
/// One would think we would not care about such details this low down,
|
||
/// but some ABIs are described in terms of C types and ISAs where the
|
||
/// integer arithmetic is done on {sign,zero}-extended registers, e.g.
|
||
/// a negative integer passed by zero-extension will appear positive in
|
||
/// the callee, and most operations on it will produce the wrong values.
|
||
Int(Integer, bool),
|
||
F32,
|
||
F64,
|
||
Pointer(AddressSpace),
|
||
}
|
||
|
||
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),
|
||
// FIXME(erikdesjardins): ignoring address space is technically wrong, pointers in
|
||
// different address spaces can have different sizes
|
||
// (but TargetDataLayout doesn't currently parse that part of the DL string)
|
||
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,
|
||
// FIXME(erikdesjardins): ignoring address space is technically wrong, pointers in
|
||
// different address spaces can have different alignments
|
||
// (but TargetDataLayout doesn't currently parse that part of the DL string)
|
||
Pointer(_) => dl.pointer_align,
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Inclusive wrap-around range of valid values, that is, if
|
||
/// start > end, it represents `start..=MAX`,
|
||
/// followed by `0..=end`.
|
||
///
|
||
/// That is, for an i8 primitive, a range of `254..=2` means following
|
||
/// sequence:
|
||
///
|
||
/// 254 (-2), 255 (-1), 0, 1, 2
|
||
///
|
||
/// This is intended specifically to mirror LLVM’s `!range` metadata semantics.
|
||
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub struct WrappingRange {
|
||
pub start: u128,
|
||
pub end: u128,
|
||
}
|
||
|
||
impl WrappingRange {
|
||
pub fn full(size: Size) -> Self {
|
||
Self { start: 0, end: size.unsigned_int_max() }
|
||
}
|
||
|
||
/// Returns `true` if `v` is contained in the range.
|
||
#[inline(always)]
|
||
pub fn contains(&self, v: u128) -> bool {
|
||
if self.start <= self.end {
|
||
self.start <= v && v <= self.end
|
||
} else {
|
||
self.start <= v || v <= self.end
|
||
}
|
||
}
|
||
|
||
/// Returns `self` with replaced `start`
|
||
#[inline(always)]
|
||
pub fn with_start(mut self, start: u128) -> Self {
|
||
self.start = start;
|
||
self
|
||
}
|
||
|
||
/// Returns `self` with replaced `end`
|
||
#[inline(always)]
|
||
pub fn with_end(mut self, end: u128) -> Self {
|
||
self.end = end;
|
||
self
|
||
}
|
||
|
||
/// Returns `true` if `size` completely fills the range.
|
||
#[inline]
|
||
pub fn is_full_for(&self, size: Size) -> bool {
|
||
let max_value = size.unsigned_int_max();
|
||
debug_assert!(self.start <= max_value && self.end <= max_value);
|
||
self.start == (self.end.wrapping_add(1) & max_value)
|
||
}
|
||
}
|
||
|
||
impl fmt::Debug for WrappingRange {
|
||
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
if self.start > self.end {
|
||
write!(fmt, "(..={}) | ({}..)", self.end, self.start)?;
|
||
} else {
|
||
write!(fmt, "{}..={}", self.start, self.end)?;
|
||
}
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
/// Information about one scalar component of a Rust type.
|
||
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub enum Scalar {
|
||
Initialized {
|
||
value: Primitive,
|
||
|
||
// FIXME(eddyb) always use the shortest range, e.g., by finding
|
||
// the largest space between two consecutive valid values and
|
||
// taking everything else as the (shortest) valid range.
|
||
valid_range: WrappingRange,
|
||
},
|
||
Union {
|
||
/// Even for unions, we need to use the correct registers for the kind of
|
||
/// values inside the union, so we keep the `Primitive` type around. We
|
||
/// also use it to compute the size of the scalar.
|
||
/// However, unions never have niches and even allow undef,
|
||
/// so there is no `valid_range`.
|
||
value: Primitive,
|
||
},
|
||
}
|
||
|
||
impl Scalar {
|
||
#[inline]
|
||
pub fn is_bool(&self) -> bool {
|
||
matches!(
|
||
self,
|
||
Scalar::Initialized {
|
||
value: Int(I8, false),
|
||
valid_range: WrappingRange { start: 0, end: 1 }
|
||
}
|
||
)
|
||
}
|
||
|
||
/// Get the primitive representation of this type, ignoring the valid range and whether the
|
||
/// value is allowed to be undefined (due to being a union).
|
||
pub fn primitive(&self) -> Primitive {
|
||
match *self {
|
||
Scalar::Initialized { value, .. } | Scalar::Union { value } => value,
|
||
}
|
||
}
|
||
|
||
pub fn align(self, cx: &impl HasDataLayout) -> AbiAndPrefAlign {
|
||
self.primitive().align(cx)
|
||
}
|
||
|
||
pub fn size(self, cx: &impl HasDataLayout) -> Size {
|
||
self.primitive().size(cx)
|
||
}
|
||
|
||
#[inline]
|
||
pub fn to_union(&self) -> Self {
|
||
Self::Union { value: self.primitive() }
|
||
}
|
||
|
||
#[inline]
|
||
pub fn valid_range(&self, cx: &impl HasDataLayout) -> WrappingRange {
|
||
match *self {
|
||
Scalar::Initialized { valid_range, .. } => valid_range,
|
||
Scalar::Union { value } => WrappingRange::full(value.size(cx)),
|
||
}
|
||
}
|
||
|
||
#[inline]
|
||
/// Allows the caller to mutate the valid range. This operation will panic if attempted on a union.
|
||
pub fn valid_range_mut(&mut self) -> &mut WrappingRange {
|
||
match self {
|
||
Scalar::Initialized { valid_range, .. } => valid_range,
|
||
Scalar::Union { .. } => panic!("cannot change the valid range of a union"),
|
||
}
|
||
}
|
||
|
||
/// Returns `true` if all possible numbers are valid, i.e `valid_range` covers the whole layout
|
||
#[inline]
|
||
pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool {
|
||
match *self {
|
||
Scalar::Initialized { valid_range, .. } => valid_range.is_full_for(self.size(cx)),
|
||
Scalar::Union { .. } => true,
|
||
}
|
||
}
|
||
|
||
/// Returns `true` if this type can be left uninit.
|
||
#[inline]
|
||
pub fn is_uninit_valid(&self) -> bool {
|
||
match *self {
|
||
Scalar::Initialized { .. } => false,
|
||
Scalar::Union { .. } => true,
|
||
}
|
||
}
|
||
}
|
||
|
||
rustc_index::newtype_index! {
|
||
/// The *source-order* index of a field in a variant.
|
||
///
|
||
/// This is how most code after type checking refers to fields, rather than
|
||
/// using names (as names have hygiene complications and more complex lookup).
|
||
///
|
||
/// Particularly for `repr(Rust)` types, this may not be the same as *layout* order.
|
||
/// (It is for `repr(C)` `struct`s, however.)
|
||
///
|
||
/// For example, in the following types,
|
||
/// ```rust
|
||
/// # enum Never {}
|
||
/// # #[repr(u16)]
|
||
/// enum Demo1 {
|
||
/// Variant0 { a: Never, b: i32 } = 100,
|
||
/// Variant1 { c: u8, d: u64 } = 10,
|
||
/// }
|
||
/// struct Demo2 { e: u8, f: u16, g: u8 }
|
||
/// ```
|
||
/// `b` is `FieldIdx(1)` in `VariantIdx(0)`,
|
||
/// `d` is `FieldIdx(1)` in `VariantIdx(1)`, and
|
||
/// `f` is `FieldIdx(1)` in `VariantIdx(0)`.
|
||
#[derive(HashStable_Generic)]
|
||
pub struct FieldIdx {}
|
||
}
|
||
|
||
/// Describes how the fields of a type are located in memory.
|
||
#[derive(PartialEq, Eq, Hash, Clone, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub enum FieldsShape {
|
||
/// Scalar primitives and `!`, which never have fields.
|
||
Primitive,
|
||
|
||
/// All fields start at no offset. The `usize` is the field count.
|
||
Union(NonZeroUsize),
|
||
|
||
/// Array/vector-like placement, with all fields of identical types.
|
||
Array { stride: Size, count: u64 },
|
||
|
||
/// Struct-like placement, with precomputed offsets.
|
||
///
|
||
/// Fields are guaranteed to not overlap, but note that gaps
|
||
/// before, between and after all the fields are NOT always
|
||
/// padding, and as such their contents may not be discarded.
|
||
/// For example, enum variants leave a gap at the start,
|
||
/// where the discriminant field in the enum layout goes.
|
||
Arbitrary {
|
||
/// Offsets for the first byte of each field,
|
||
/// ordered to match the source definition order.
|
||
/// This vector does not go in increasing order.
|
||
// FIXME(eddyb) use small vector optimization for the common case.
|
||
offsets: IndexVec<FieldIdx, 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: IndexVec<FieldIdx, 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[FieldIdx::from_usize(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[FieldIdx::from_usize(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 = IndexVec::new();
|
||
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 (field_idx, &mem_idx) in memory_index.iter_enumerated() {
|
||
inverse_small[mem_idx as usize] = field_idx.as_u32() as u8;
|
||
}
|
||
} else {
|
||
inverse_big = memory_index.invert_bijective_mapping();
|
||
}
|
||
}
|
||
|
||
(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 u32].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, Hash)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub struct AddressSpace(pub u32);
|
||
|
||
impl AddressSpace {
|
||
/// The default address space, corresponding to data space.
|
||
pub const DATA: Self = AddressSpace(0);
|
||
}
|
||
|
||
/// Describes how values of the type are passed by target ABIs,
|
||
/// in terms of categories of C types there are ABI rules for.
|
||
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
|
||
pub enum Abi {
|
||
Uninhabited,
|
||
Scalar(Scalar),
|
||
ScalarPair(Scalar, Scalar),
|
||
Vector {
|
||
element: Scalar,
|
||
count: u64,
|
||
},
|
||
Aggregate {
|
||
/// If true, the size is exact, otherwise it's only a lower bound.
|
||
sized: bool,
|
||
},
|
||
}
|
||
|
||
impl Abi {
|
||
/// Returns `true` if the layout corresponds to an unsized type.
|
||
#[inline]
|
||
pub fn is_unsized(&self) -> bool {
|
||
match *self {
|
||
Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
|
||
Abi::Aggregate { sized } => !sized,
|
||
}
|
||
}
|
||
|
||
#[inline]
|
||
pub fn is_sized(&self) -> bool {
|
||
!self.is_unsized()
|
||
}
|
||
|
||
/// Returns `true` if this is a single signed integer scalar
|
||
#[inline]
|
||
pub fn is_signed(&self) -> bool {
|
||
match self {
|
||
Abi::Scalar(scal) => match scal.primitive() {
|
||
Primitive::Int(_, signed) => signed,
|
||
_ => false,
|
||
},
|
||
_ => panic!("`is_signed` on non-scalar ABI {:?}", self),
|
||
}
|
||
}
|
||
|
||
/// Returns `true` if this is an uninhabited type
|
||
#[inline]
|
||
pub fn is_uninhabited(&self) -> bool {
|
||
matches!(*self, Abi::Uninhabited)
|
||
}
|
||
|
||
/// Returns `true` is this is a scalar type
|
||
#[inline]
|
||
pub fn is_scalar(&self) -> bool {
|
||
matches!(*self, Abi::Scalar(_))
|
||
}
|
||
}
|
||
|
||
#[derive(PartialEq, Eq, Hash, Clone, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub enum Variants {
|
||
/// 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, LayoutS>,
|
||
},
|
||
}
|
||
|
||
#[derive(PartialEq, Eq, Hash, Clone, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(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 `untagged_variant` contains a niche at an arbitrary
|
||
/// offset (field `tag_field` of the enum), which for a variant with
|
||
/// discriminant `d` is set to
|
||
/// `(d - niche_variants.start).wrapping_add(niche_start)`.
|
||
///
|
||
/// For example, `Option<(usize, &T)>` is represented such that
|
||
/// `None` has a null pointer for the second tuple field, and
|
||
/// `Some` is the identity function (with a non-null reference).
|
||
Niche {
|
||
untagged_variant: VariantIdx,
|
||
niche_variants: RangeInclusive<VariantIdx>,
|
||
niche_start: u128,
|
||
},
|
||
}
|
||
|
||
#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub struct Niche {
|
||
pub offset: Size,
|
||
pub value: Primitive,
|
||
pub valid_range: WrappingRange,
|
||
}
|
||
|
||
impl Niche {
|
||
pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> {
|
||
let Scalar::Initialized { value, valid_range } = scalar else { return None };
|
||
let niche = Niche { offset, value, valid_range };
|
||
if niche.available(cx) > 0 { Some(niche) } else { None }
|
||
}
|
||
|
||
pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 {
|
||
let Self { value, valid_range: v, .. } = *self;
|
||
let size = value.size(cx);
|
||
assert!(size.bits() <= 128);
|
||
let max_value = size.unsigned_int_max();
|
||
|
||
// Find out how many values are outside the valid range.
|
||
let niche = v.end.wrapping_add(1)..v.start;
|
||
niche.end.wrapping_sub(niche.start) & max_value
|
||
}
|
||
|
||
pub fn reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)> {
|
||
assert!(count > 0);
|
||
|
||
let Self { value, valid_range: v, .. } = *self;
|
||
let size = value.size(cx);
|
||
assert!(size.bits() <= 128);
|
||
let max_value = size.unsigned_int_max();
|
||
|
||
let niche = v.end.wrapping_add(1)..v.start;
|
||
let available = niche.end.wrapping_sub(niche.start) & max_value;
|
||
if count > available {
|
||
return None;
|
||
}
|
||
|
||
// Extend the range of valid values being reserved by moving either `v.start` or `v.end` bound.
|
||
// Given an eventual `Option<T>`, we try to maximize the chance for `None` to occupy the niche of zero.
|
||
// This is accomplished by preferring enums with 2 variants(`count==1`) and always taking the shortest path to niche zero.
|
||
// Having `None` in niche zero can enable some special optimizations.
|
||
//
|
||
// Bound selection criteria:
|
||
// 1. Select closest to zero given wrapping semantics.
|
||
// 2. Avoid moving past zero if possible.
|
||
//
|
||
// In practice this means that enums with `count > 1` are unlikely to claim niche zero, since they have to fit perfectly.
|
||
// If niche zero is already reserved, the selection of bounds are of little interest.
|
||
let move_start = |v: WrappingRange| {
|
||
let start = v.start.wrapping_sub(count) & max_value;
|
||
Some((start, Scalar::Initialized { value, valid_range: v.with_start(start) }))
|
||
};
|
||
let move_end = |v: WrappingRange| {
|
||
let start = v.end.wrapping_add(1) & max_value;
|
||
let end = v.end.wrapping_add(count) & max_value;
|
||
Some((start, Scalar::Initialized { value, valid_range: v.with_end(end) }))
|
||
};
|
||
let distance_end_zero = max_value - v.end;
|
||
if v.start > v.end {
|
||
// zero is unavailable because wrapping occurs
|
||
move_end(v)
|
||
} else if v.start <= distance_end_zero {
|
||
if count <= v.start {
|
||
move_start(v)
|
||
} else {
|
||
// moved past zero, use other bound
|
||
move_end(v)
|
||
}
|
||
} else {
|
||
let end = v.end.wrapping_add(count) & max_value;
|
||
let overshot_zero = (1..=v.end).contains(&end);
|
||
if overshot_zero {
|
||
// moved past zero, use other bound
|
||
move_start(v)
|
||
} else {
|
||
move_end(v)
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
rustc_index::newtype_index! {
|
||
/// The *source-order* index of a variant in a type.
|
||
///
|
||
/// For enums, these are always `0..variant_count`, regardless of any
|
||
/// custom discriminants that may have been defined, and including any
|
||
/// variants that may end up uninhabited due to field types. (Some of the
|
||
/// variants may not be present in a monomorphized ABI [`Variants`], but
|
||
/// those skipped variants are always counted when determining the *index*.)
|
||
///
|
||
/// `struct`s, `tuples`, and `unions`s are considered to have a single variant
|
||
/// with variant index zero, aka [`FIRST_VARIANT`].
|
||
#[derive(HashStable_Generic)]
|
||
pub struct VariantIdx {
|
||
/// Equivalent to `VariantIdx(0)`.
|
||
const FIRST_VARIANT = 0;
|
||
}
|
||
}
|
||
|
||
#[derive(PartialEq, Eq, Hash, Clone)]
|
||
#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
|
||
pub struct LayoutS {
|
||
/// 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 LayoutS {
|
||
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: FIRST_VARIANT },
|
||
fields: FieldsShape::Primitive,
|
||
abi: Abi::Scalar(scalar),
|
||
largest_niche,
|
||
size,
|
||
align,
|
||
}
|
||
}
|
||
}
|
||
|
||
impl fmt::Debug for LayoutS {
|
||
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>);
|
||
|
||
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 {
|
||
&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
|
||
}
|
||
}
|
||
|
||
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
|
||
pub enum PointerKind {
|
||
/// Shared reference. `frozen` indicates the absence of any `UnsafeCell`.
|
||
SharedRef { frozen: bool },
|
||
/// Mutable reference. `unpin` indicates the absence of any pinned data.
|
||
MutableRef { unpin: bool },
|
||
/// Box. `unpin` indicates the absence of any pinned data.
|
||
Box { unpin: bool },
|
||
}
|
||
|
||
/// Note that this information is advisory only, and backends are free to ignore it.
|
||
/// It can only be used to encode potential optimizations, but no critical information.
|
||
#[derive(Copy, Clone, Debug)]
|
||
pub struct PointeeInfo {
|
||
pub size: Size,
|
||
pub align: Align,
|
||
pub safe: Option<PointerKind>,
|
||
}
|
||
|
||
impl LayoutS {
|
||
/// Returns `true` if the layout corresponds to an unsized type.
|
||
pub fn is_unsized(&self) -> bool {
|
||
self.abi.is_unsized()
|
||
}
|
||
|
||
pub fn is_sized(&self) -> bool {
|
||
self.abi.is_sized()
|
||
}
|
||
|
||
/// Returns `true` if the type is a ZST and not unsized.
|
||
pub fn is_zst(&self) -> bool {
|
||
match self.abi {
|
||
Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false,
|
||
Abi::Uninhabited => self.size.bytes() == 0,
|
||
Abi::Aggregate { sized } => sized && self.size.bytes() == 0,
|
||
}
|
||
}
|
||
}
|
||
|
||
#[derive(Copy, Clone, Debug)]
|
||
pub enum StructKind {
|
||
/// A tuple, closure, or univariant which cannot be coerced to unsized.
|
||
AlwaysSized,
|
||
/// A univariant, the last field of which may be coerced to unsized.
|
||
MaybeUnsized,
|
||
/// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
|
||
Prefixed(Size, Align),
|
||
}
|