From 27fb904d680996fe48e04aef65d4d655bdab843b Mon Sep 17 00:00:00 2001 From: hkalbasi Date: Tue, 1 Nov 2022 19:50:30 +0330 Subject: [PATCH] move some layout logic to rustc_target::abi::layout --- Cargo.lock | 3 + compiler/rustc_hir_analysis/src/collect.rs | 4 +- compiler/rustc_lint/src/types.rs | 6 +- compiler/rustc_middle/src/ty/adt.rs | 6 +- compiler/rustc_middle/src/ty/layout.rs | 31 +- compiler/rustc_middle/src/ty/mod.rs | 210 ++-- compiler/rustc_middle/src/ty/util.rs | 23 +- compiler/rustc_target/Cargo.toml | 4 +- compiler/rustc_target/src/abi/layout.rs | 943 +++++++++++++++++ compiler/rustc_target/src/abi/mod.rs | 151 ++- compiler/rustc_traits/Cargo.toml | 1 + compiler/rustc_traits/src/chalk/db.rs | 30 +- compiler/rustc_ty_utils/src/layout.rs | 972 +----------------- .../src/casts/cast_possible_truncation.rs | 5 +- src/tools/clippy/clippy_lints/src/lib.rs | 1 - 15 files changed, 1232 insertions(+), 1158 deletions(-) create mode 100644 compiler/rustc_target/src/abi/layout.rs diff --git a/Cargo.lock b/Cargo.lock index c987bf44ec00..13d37c933753 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -4281,6 +4281,8 @@ name = "rustc_target" version = "0.0.0" dependencies = [ "bitflags", + "rand 0.8.5", + "rand_xoshiro", "rustc_data_structures", "rustc_feature", "rustc_index", @@ -4336,6 +4338,7 @@ dependencies = [ "rustc_infer", "rustc_middle", "rustc_span", + "rustc_target", "rustc_trait_selection", "smallvec", "tracing", diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs index 5d63d90f304b..6bdd55114599 100644 --- a/compiler/rustc_hir_analysis/src/collect.rs +++ b/compiler/rustc_hir_analysis/src/collect.rs @@ -32,8 +32,8 @@ use rustc_middle::hir::nested_filter; use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs}; use rustc_middle::mir::mono::Linkage; use rustc_middle::ty::query::Providers; +use rustc_middle::ty::repr_options_of_def; use rustc_middle::ty::util::{Discr, IntTypeExt}; -use rustc_middle::ty::ReprOptions; use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, IsSuggestable, Ty, TyCtxt}; use rustc_session::lint; use rustc_session::parse::feature_err; @@ -860,7 +860,7 @@ fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> { bug!(); }; - let repr = ReprOptions::new(tcx, def_id.to_def_id()); + let repr = repr_options_of_def(tcx, def_id.to_def_id()); let (kind, variants) = match item.kind { ItemKind::Enum(ref def, _) => { let mut distance_from_explicit = 0; diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs index afc568f3a505..fadd47eed723 100644 --- a/compiler/rustc_lint/src/types.rs +++ b/compiler/rustc_lint/src/types.rs @@ -12,7 +12,7 @@ use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeSuperVisitable, use rustc_span::source_map; use rustc_span::symbol::sym; use rustc_span::{Span, Symbol}; -use rustc_target::abi::{Abi, WrappingRange}; +use rustc_target::abi::{Abi, Size, WrappingRange}; use rustc_target::abi::{Integer, TagEncoding, Variants}; use rustc_target::spec::abi::Abi as SpecAbi; @@ -225,11 +225,11 @@ fn report_bin_hex_error( cx: &LateContext<'_>, expr: &hir::Expr<'_>, ty: attr::IntType, + size: Size, repr_str: String, val: u128, negative: bool, ) { - let size = Integer::from_attr(&cx.tcx, ty).size(); cx.struct_span_lint( OVERFLOWING_LITERALS, expr.span, @@ -352,6 +352,7 @@ fn lint_int_literal<'tcx>( cx, e, attr::IntType::SignedInt(ty::ast_int_ty(t)), + Integer::from_int_ty(cx, t).size(), repr_str, v, negative, @@ -437,6 +438,7 @@ fn lint_uint_literal<'tcx>( cx, e, attr::IntType::UnsignedInt(ty::ast_uint_ty(t)), + Integer::from_uint_ty(cx, t).size(), repr_str, lit_val, false, diff --git a/compiler/rustc_middle/src/ty/adt.rs b/compiler/rustc_middle/src/ty/adt.rs index 6b6aa40a1604..d3d667f68407 100644 --- a/compiler/rustc_middle/src/ty/adt.rs +++ b/compiler/rustc_middle/src/ty/adt.rs @@ -14,7 +14,7 @@ use rustc_index::vec::{Idx, IndexVec}; use rustc_query_system::ich::StableHashingContext; use rustc_session::DataTypeKind; use rustc_span::symbol::sym; -use rustc_target::abi::VariantIdx; +use rustc_target::abi::{ReprOptions, VariantIdx}; use std::cell::RefCell; use std::cmp::Ordering; @@ -22,9 +22,7 @@ use std::hash::{Hash, Hasher}; use std::ops::Range; use std::str; -use super::{ - Destructor, FieldDef, GenericPredicates, ReprOptions, Ty, TyCtxt, VariantDef, VariantDiscr, -}; +use super::{Destructor, FieldDef, GenericPredicates, Ty, TyCtxt, VariantDef, VariantDiscr}; bitflags! { #[derive(HashStable, TyEncodable, TyDecodable)] diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs index fea2aa8cbf82..488fd567846a 100644 --- a/compiler/rustc_middle/src/ty/layout.rs +++ b/compiler/rustc_middle/src/ty/layout.rs @@ -1,8 +1,6 @@ use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags; use crate::ty::normalize_erasing_regions::NormalizationError; use crate::ty::{self, ReprOptions, Ty, TyCtxt, TypeVisitable}; -use rustc_ast as ast; -use rustc_attr as attr; use rustc_errors::{DiagnosticBuilder, Handler, IntoDiagnostic}; use rustc_hir as hir; use rustc_hir::def_id::DefId; @@ -20,7 +18,6 @@ use std::ops::Bound; pub trait IntegerExt { fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>, signed: bool) -> Ty<'tcx>; - fn from_attr(cx: &C, ity: attr::IntType) -> Integer; fn from_int_ty(cx: &C, ity: ty::IntTy) -> Integer; fn from_uint_ty(cx: &C, uty: ty::UintTy) -> Integer; fn repr_discr<'tcx>( @@ -49,22 +46,6 @@ impl IntegerExt for Integer { } } - /// Gets the Integer type from an attr::IntType. - fn from_attr(cx: &C, ity: attr::IntType) -> Integer { - let dl = cx.data_layout(); - - match ity { - attr::SignedInt(ast::IntTy::I8) | attr::UnsignedInt(ast::UintTy::U8) => I8, - attr::SignedInt(ast::IntTy::I16) | attr::UnsignedInt(ast::UintTy::U16) => I16, - attr::SignedInt(ast::IntTy::I32) | attr::UnsignedInt(ast::UintTy::U32) => I32, - attr::SignedInt(ast::IntTy::I64) | attr::UnsignedInt(ast::UintTy::U64) => I64, - attr::SignedInt(ast::IntTy::I128) | attr::UnsignedInt(ast::UintTy::U128) => I128, - attr::SignedInt(ast::IntTy::Isize) | attr::UnsignedInt(ast::UintTy::Usize) => { - dl.ptr_sized_integer() - } - } - } - fn from_int_ty(cx: &C, ity: ty::IntTy) -> Integer { match ity { ty::IntTy::I8 => I8, @@ -237,6 +218,18 @@ pub struct LayoutCx<'tcx, C> { pub param_env: ty::ParamEnv<'tcx>, } +impl<'tcx> LayoutCalculator for LayoutCx<'tcx, TyCtxt<'tcx>> { + type TargetDataLayoutRef = &'tcx TargetDataLayout; + + fn delay_bug(&self, txt: &str) { + self.tcx.sess.delay_span_bug(DUMMY_SP, txt); + } + + fn current_data_layout(&self) -> Self::TargetDataLayoutRef { + &self.tcx.data_layout + } +} + /// Type size "skeleton", i.e., the only information determining a type's size. /// While this is conservative, (aside from constant sizes, only pointers, /// newtypes thereof and null pointer optimized enums are allowed), it is diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs index 0458c4abd3d4..e3421ab9ce0b 100644 --- a/compiler/rustc_middle/src/ty/mod.rs +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -48,7 +48,8 @@ use rustc_session::cstore::CrateStoreDyn; use rustc_span::hygiene::MacroKind; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::{ExpnId, Span}; -use rustc_target::abi::{Align, VariantIdx}; +use rustc_target::abi::{Align, Integer, IntegerType, VariantIdx}; +pub use rustc_target::abi::{ReprFlags, ReprOptions}; pub use subst::*; pub use vtable::*; @@ -1994,161 +1995,76 @@ impl Hash for FieldDef { } } -bitflags! { - #[derive(TyEncodable, TyDecodable, Default, HashStable)] - pub struct ReprFlags: u8 { - const IS_C = 1 << 0; - const IS_SIMD = 1 << 1; - const IS_TRANSPARENT = 1 << 2; - // Internal only for now. If true, don't reorder fields. - const IS_LINEAR = 1 << 3; - // If true, the type's layout can be randomized using - // the seed stored in `ReprOptions.layout_seed` - const RANDOMIZE_LAYOUT = 1 << 4; - // Any of these flags being set prevent field reordering optimisation. - const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits - | ReprFlags::IS_SIMD.bits - | ReprFlags::IS_LINEAR.bits; +pub fn repr_options_of_def(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions { + let mut flags = ReprFlags::empty(); + let mut size = None; + let mut max_align: Option = None; + let mut min_pack: Option = None; + + // Generate a deterministically-derived seed from the item's path hash + // to allow for cross-crate compilation to actually work + let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash(); + + // If the user defined a custom seed for layout randomization, xor the item's + // path hash with the user defined seed, this will allowing determinism while + // still allowing users to further randomize layout generation for e.g. fuzzing + if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed { + field_shuffle_seed ^= user_seed; } -} -/// Represents the repr options provided by the user, -#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)] -pub struct ReprOptions { - pub int: Option, - pub align: Option, - pub pack: Option, - pub flags: ReprFlags, - /// The seed to be used for randomizing a type's layout - /// - /// Note: This could technically be a `[u8; 16]` (a `u128`) which would - /// be the "most accurate" hash as it'd encompass the item and crate - /// hash without loss, but it does pay the price of being larger. - /// Everything's a tradeoff, a `u64` seed should be sufficient for our - /// purposes (primarily `-Z randomize-layout`) - pub field_shuffle_seed: u64, -} - -impl ReprOptions { - pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions { - let mut flags = ReprFlags::empty(); - let mut size = None; - let mut max_align: Option = None; - let mut min_pack: Option = None; - - // Generate a deterministically-derived seed from the item's path hash - // to allow for cross-crate compilation to actually work - let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash(); - - // If the user defined a custom seed for layout randomization, xor the item's - // path hash with the user defined seed, this will allowing determinism while - // still allowing users to further randomize layout generation for e.g. fuzzing - if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed { - field_shuffle_seed ^= user_seed; + for attr in tcx.get_attrs(did, sym::repr) { + for r in attr::parse_repr_attr(&tcx.sess, attr) { + flags.insert(match r { + attr::ReprC => ReprFlags::IS_C, + attr::ReprPacked(pack) => { + let pack = Align::from_bytes(pack as u64).unwrap(); + min_pack = + Some(if let Some(min_pack) = min_pack { min_pack.min(pack) } else { pack }); + ReprFlags::empty() + } + attr::ReprTransparent => ReprFlags::IS_TRANSPARENT, + attr::ReprSimd => ReprFlags::IS_SIMD, + attr::ReprInt(i) => { + size = Some(match i { + attr::IntType::SignedInt(x) => match x { + ast::IntTy::Isize => IntegerType::Pointer(true), + ast::IntTy::I8 => IntegerType::Fixed(Integer::I8, true), + ast::IntTy::I16 => IntegerType::Fixed(Integer::I16, true), + ast::IntTy::I32 => IntegerType::Fixed(Integer::I32, true), + ast::IntTy::I64 => IntegerType::Fixed(Integer::I64, true), + ast::IntTy::I128 => IntegerType::Fixed(Integer::I128, true), + }, + attr::IntType::UnsignedInt(x) => match x { + ast::UintTy::Usize => IntegerType::Pointer(false), + ast::UintTy::U8 => IntegerType::Fixed(Integer::I8, false), + ast::UintTy::U16 => IntegerType::Fixed(Integer::I16, false), + ast::UintTy::U32 => IntegerType::Fixed(Integer::I32, false), + ast::UintTy::U64 => IntegerType::Fixed(Integer::I64, false), + ast::UintTy::U128 => IntegerType::Fixed(Integer::I128, false), + }, + }); + ReprFlags::empty() + } + attr::ReprAlign(align) => { + max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap())); + ReprFlags::empty() + } + }); } - - for attr in tcx.get_attrs(did, sym::repr) { - for r in attr::parse_repr_attr(&tcx.sess, attr) { - flags.insert(match r { - attr::ReprC => ReprFlags::IS_C, - attr::ReprPacked(pack) => { - let pack = Align::from_bytes(pack as u64).unwrap(); - min_pack = Some(if let Some(min_pack) = min_pack { - min_pack.min(pack) - } else { - pack - }); - ReprFlags::empty() - } - attr::ReprTransparent => ReprFlags::IS_TRANSPARENT, - attr::ReprSimd => ReprFlags::IS_SIMD, - attr::ReprInt(i) => { - size = Some(i); - ReprFlags::empty() - } - attr::ReprAlign(align) => { - max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap())); - ReprFlags::empty() - } - }); - } - } - - // If `-Z randomize-layout` was enabled for the type definition then we can - // consider performing layout randomization - if tcx.sess.opts.unstable_opts.randomize_layout { - flags.insert(ReprFlags::RANDOMIZE_LAYOUT); - } - - // This is here instead of layout because the choice must make it into metadata. - if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) { - flags.insert(ReprFlags::IS_LINEAR); - } - - Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed } } - #[inline] - pub fn simd(&self) -> bool { - self.flags.contains(ReprFlags::IS_SIMD) + // If `-Z randomize-layout` was enabled for the type definition then we can + // consider performing layout randomization + if tcx.sess.opts.unstable_opts.randomize_layout { + flags.insert(ReprFlags::RANDOMIZE_LAYOUT); } - #[inline] - pub fn c(&self) -> bool { - self.flags.contains(ReprFlags::IS_C) + // This is here instead of layout because the choice must make it into metadata. + if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) { + flags.insert(ReprFlags::IS_LINEAR); } - #[inline] - pub fn packed(&self) -> bool { - self.pack.is_some() - } - - #[inline] - pub fn transparent(&self) -> bool { - self.flags.contains(ReprFlags::IS_TRANSPARENT) - } - - #[inline] - pub fn linear(&self) -> bool { - self.flags.contains(ReprFlags::IS_LINEAR) - } - - /// Returns the discriminant type, given these `repr` options. - /// This must only be called on enums! - pub fn discr_type(&self) -> attr::IntType { - self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize)) - } - - /// Returns `true` if this `#[repr()]` should inhabit "smart enum - /// layout" optimizations, such as representing `Foo<&T>` as a - /// single pointer. - pub fn inhibit_enum_layout_opt(&self) -> bool { - self.c() || self.int.is_some() - } - - /// Returns `true` if this `#[repr()]` should inhibit struct field reordering - /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr()`. - pub fn inhibit_struct_field_reordering_opt(&self) -> bool { - if let Some(pack) = self.pack { - if pack.bytes() == 1 { - return true; - } - } - - self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some() - } - - /// Returns `true` if this type is valid for reordering and `-Z randomize-layout` - /// was enabled for its declaration crate - pub fn can_randomize_type_layout(&self) -> bool { - !self.inhibit_struct_field_reordering_opt() - && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT) - } - - /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations. - pub fn inhibit_union_abi_opt(&self) -> bool { - self.c() - } + ReprOptions { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed } } impl<'tcx> FieldDef { diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs index f72e236eda13..6561c4c278d0 100644 --- a/compiler/rustc_middle/src/ty/util.rs +++ b/compiler/rustc_middle/src/ty/util.rs @@ -8,8 +8,6 @@ use crate::ty::{ }; use crate::ty::{GenericArgKind, SubstsRef}; use rustc_apfloat::Float as _; -use rustc_ast as ast; -use rustc_attr::{self as attr, SignedInt, UnsignedInt}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; use rustc_errors::ErrorGuaranteed; @@ -19,7 +17,7 @@ use rustc_hir::def_id::DefId; use rustc_index::bit_set::GrowableBitSet; use rustc_macros::HashStable; use rustc_span::{sym, DUMMY_SP}; -use rustc_target::abi::{Integer, Size, TargetDataLayout}; +use rustc_target::abi::{Integer, IntegerType, Size, TargetDataLayout}; use rustc_target::spec::abi::Abi; use smallvec::SmallVec; use std::{fmt, iter}; @@ -104,21 +102,12 @@ pub trait IntTypeExt { fn initial_discriminant<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Discr<'tcx>; } -impl IntTypeExt for attr::IntType { +impl IntTypeExt for IntegerType { fn to_ty<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> { - match *self { - SignedInt(ast::IntTy::I8) => tcx.types.i8, - SignedInt(ast::IntTy::I16) => tcx.types.i16, - SignedInt(ast::IntTy::I32) => tcx.types.i32, - SignedInt(ast::IntTy::I64) => tcx.types.i64, - SignedInt(ast::IntTy::I128) => tcx.types.i128, - SignedInt(ast::IntTy::Isize) => tcx.types.isize, - UnsignedInt(ast::UintTy::U8) => tcx.types.u8, - UnsignedInt(ast::UintTy::U16) => tcx.types.u16, - UnsignedInt(ast::UintTy::U32) => tcx.types.u32, - UnsignedInt(ast::UintTy::U64) => tcx.types.u64, - UnsignedInt(ast::UintTy::U128) => tcx.types.u128, - UnsignedInt(ast::UintTy::Usize) => tcx.types.usize, + match self { + IntegerType::Pointer(true) => tcx.types.isize, + IntegerType::Pointer(false) => tcx.types.usize, + IntegerType::Fixed(i, s) => i.to_ty(tcx, *s), } } diff --git a/compiler/rustc_target/Cargo.toml b/compiler/rustc_target/Cargo.toml index 58eb4f69c44f..f2e21078b446 100644 --- a/compiler/rustc_target/Cargo.toml +++ b/compiler/rustc_target/Cargo.toml @@ -6,6 +6,8 @@ edition = "2021" [dependencies] bitflags = "1.2.1" tracing = "0.1" +rand = "0.8.4" +rand_xoshiro = "0.6.0" serde_json = "1.0.59" rustc_data_structures = { path = "../rustc_data_structures", optional = true } rustc_feature = { path = "../rustc_feature", optional = true } @@ -23,4 +25,4 @@ nightly = [ "rustc_macros", "rustc_serialize", "rustc_span", -] \ No newline at end of file +] diff --git a/compiler/rustc_target/src/abi/layout.rs b/compiler/rustc_target/src/abi/layout.rs new file mode 100644 index 000000000000..cf4843e9d6cb --- /dev/null +++ b/compiler/rustc_target/src/abi/layout.rs @@ -0,0 +1,943 @@ +use super::*; +use std::{ + borrow::Borrow, + cmp, + fmt::Debug, + iter, + ops::{Bound, Deref}, +}; + +use rand::{seq::SliceRandom, SeedableRng}; +use rand_xoshiro::Xoshiro128StarStar; + +use tracing::debug; + +// Invert a bijective mapping, i.e. `invert(map)[y] = x` if `map[x] = y`. +// This is used to go between `memory_index` (source field order to memory order) +// and `inverse_memory_index` (memory order to source field order). +// See also `FieldsShape::Arbitrary::memory_index` for more details. +// FIXME(eddyb) build a better abstraction for permutations, if possible. +fn invert_mapping(map: &[u32]) -> Vec { + let mut inverse = vec![0; map.len()]; + for i in 0..map.len() { + inverse[map[i] as usize] = i as u32; + } + inverse +} + +pub trait LayoutCalculator { + type TargetDataLayoutRef: Borrow; + + fn delay_bug(&self, txt: &str); + fn current_data_layout(&self) -> Self::TargetDataLayoutRef; + + fn scalar_pair(&self, a: Scalar, b: Scalar) -> LayoutS { + let dl = self.current_data_layout(); + let dl = dl.borrow(); + let b_align = b.align(dl); + let align = a.align(dl).max(b_align).max(dl.aggregate_align); + let b_offset = a.size(dl).align_to(b_align.abi); + let size = (b_offset + b.size(dl)).align_to(align.abi); + + // HACK(nox): We iter on `b` and then `a` because `max_by_key` + // returns the last maximum. + let largest_niche = Niche::from_scalar(dl, b_offset, b) + .into_iter() + .chain(Niche::from_scalar(dl, Size::ZERO, a)) + .max_by_key(|niche| niche.available(dl)); + + LayoutS { + variants: Variants::Single { index: V::new(0) }, + fields: FieldsShape::Arbitrary { + offsets: vec![Size::ZERO, b_offset], + memory_index: vec![0, 1], + }, + abi: Abi::ScalarPair(a, b), + largest_niche, + align, + size, + } + } + + fn univariant<'a, V: Idx, F: Deref> + Debug>( + &self, + dl: &TargetDataLayout, + fields: &[F], + repr: &ReprOptions, + kind: StructKind, + ) -> Option> { + let pack = repr.pack; + let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align }; + let mut inverse_memory_index: Vec = (0..fields.len() as u32).collect(); + let optimize = !repr.inhibit_struct_field_reordering_opt(); + if optimize { + let end = + if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() }; + let optimizing = &mut inverse_memory_index[..end]; + let effective_field_align = |f: &F| { + if let Some(pack) = pack { + // return the packed alignment in bytes + f.align.abi.min(pack).bytes() + } else { + // returns log2(effective-align). + // This is ok since `pack` applies to all fields equally. + // The calculation assumes that size is an integer multiple of align, except for ZSTs. + // + // group [u8; 4] with align-4 or [u8; 6] with align-2 fields + f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64 + } + }; + + // If `-Z randomize-layout` was enabled for the type definition we can shuffle + // the field ordering to try and catch some code making assumptions about layouts + // we don't guarantee + if repr.can_randomize_type_layout() { + // `ReprOptions.layout_seed` is a deterministic seed that we can use to + // randomize field ordering with + let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed); + + // Shuffle the ordering of the fields + optimizing.shuffle(&mut rng); + + // Otherwise we just leave things alone and actually optimize the type's fields + } else { + match kind { + StructKind::AlwaysSized | StructKind::MaybeUnsized => { + optimizing.sort_by_key(|&x| { + // Place ZSTs first to avoid "interesting offsets", + // especially with only one or two non-ZST fields. + // Then place largest alignments first, largest niches within an alignment group last + let f = &fields[x as usize]; + let niche_size = f.largest_niche.map_or(0, |n| n.available(dl)); + (!f.is_zst(), cmp::Reverse(effective_field_align(f)), niche_size) + }); + } + + StructKind::Prefixed(..) => { + // Sort in ascending alignment so that the layout stays optimal + // regardless of the prefix. + // And put the largest niche in an alignment group at the end + // so it can be used as discriminant in jagged enums + optimizing.sort_by_key(|&x| { + let f = &fields[x as usize]; + let niche_size = f.largest_niche.map_or(0, |n| n.available(dl)); + (effective_field_align(f), niche_size) + }); + } + } + + // FIXME(Kixiron): We can always shuffle fields within a given alignment class + // regardless of the status of `-Z randomize-layout` + } + } + // inverse_memory_index holds field indices by increasing memory offset. + // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5. + // We now write field offsets to the corresponding offset slot; + // field 5 with offset 0 puts 0 in offsets[5]. + // At the bottom of this function, we invert `inverse_memory_index` to + // produce `memory_index` (see `invert_mapping`). + let mut sized = true; + let mut offsets = vec![Size::ZERO; fields.len()]; + let mut offset = Size::ZERO; + let mut largest_niche = None; + let mut largest_niche_available = 0; + if let StructKind::Prefixed(prefix_size, prefix_align) = kind { + let prefix_align = + if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align }; + align = align.max(AbiAndPrefAlign::new(prefix_align)); + offset = prefix_size.align_to(prefix_align); + } + for &i in &inverse_memory_index { + let field = &fields[i as usize]; + if !sized { + self.delay_bug(&format!( + "univariant: field #{} comes after unsized field", + offsets.len(), + )); + } + + if field.is_unsized() { + sized = false; + } + + // Invariant: offset < dl.obj_size_bound() <= 1<<61 + let field_align = if let Some(pack) = pack { + field.align.min(AbiAndPrefAlign::new(pack)) + } else { + field.align + }; + offset = offset.align_to(field_align.abi); + align = align.max(field_align); + + debug!("univariant offset: {:?} field: {:#?}", offset, field); + offsets[i as usize] = offset; + + if let Some(mut niche) = field.largest_niche { + let available = niche.available(dl); + if available > largest_niche_available { + largest_niche_available = available; + niche.offset += offset; + largest_niche = Some(niche); + } + } + + offset = offset.checked_add(field.size, dl)?; + } + if let Some(repr_align) = repr.align { + align = align.max(AbiAndPrefAlign::new(repr_align)); + } + debug!("univariant min_size: {:?}", offset); + let min_size = offset; + // As stated above, inverse_memory_index holds field indices by increasing offset. + // This makes it an already-sorted view of the offsets vec. + // To invert it, consider: + // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0. + // Field 5 would be the first element, so memory_index is i: + // Note: if we didn't optimize, it's already right. + let memory_index = + if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index }; + let size = min_size.align_to(align.abi); + let mut abi = Abi::Aggregate { sized }; + // Unpack newtype ABIs and find scalar pairs. + if sized && size.bytes() > 0 { + // All other fields must be ZSTs. + let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst()); + + match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) { + // We have exactly one non-ZST field. + (Some((i, field)), None, None) => { + // Field fills the struct and it has a scalar or scalar pair ABI. + if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size + { + match field.abi { + // For plain scalars, or vectors of them, we can't unpack + // newtypes for `#[repr(C)]`, as that affects C ABIs. + Abi::Scalar(_) | Abi::Vector { .. } if optimize => { + abi = field.abi; + } + // But scalar pairs are Rust-specific and get + // treated as aggregates by C ABIs anyway. + Abi::ScalarPair(..) => { + abi = field.abi; + } + _ => {} + } + } + } + + // Two non-ZST fields, and they're both scalars. + (Some((i, a)), Some((j, b)), None) => { + match (a.abi, b.abi) { + (Abi::Scalar(a), Abi::Scalar(b)) => { + // Order by the memory placement, not source order. + let ((i, a), (j, b)) = if offsets[i] < offsets[j] { + ((i, a), (j, b)) + } else { + ((j, b), (i, a)) + }; + let pair = self.scalar_pair::(a, b); + let pair_offsets = match pair.fields { + FieldsShape::Arbitrary { ref offsets, ref memory_index } => { + assert_eq!(memory_index, &[0, 1]); + offsets + } + _ => panic!(), + }; + if offsets[i] == pair_offsets[0] + && offsets[j] == pair_offsets[1] + && align == pair.align + && size == pair.size + { + // We can use `ScalarPair` only when it matches our + // already computed layout (including `#[repr(C)]`). + abi = pair.abi; + } + } + _ => {} + } + } + + _ => {} + } + } + if fields.iter().any(|f| f.abi.is_uninhabited()) { + abi = Abi::Uninhabited; + } + Some(LayoutS { + variants: Variants::Single { index: V::new(0) }, + fields: FieldsShape::Arbitrary { offsets, memory_index }, + abi, + largest_niche, + align, + size, + }) + } + + fn layout_of_never_type(&self) -> LayoutS { + let dl = self.current_data_layout(); + let dl = dl.borrow(); + LayoutS { + variants: Variants::Single { index: V::new(0) }, + fields: FieldsShape::Primitive, + abi: Abi::Uninhabited, + largest_niche: None, + align: dl.i8_align, + size: Size::ZERO, + } + } + + fn layout_of_struct_or_enum<'a, V: Idx, F: Deref> + Debug>( + &self, + repr: &ReprOptions, + variants: &IndexVec>, + is_enum: bool, + is_unsafe_cell: bool, + scalar_valid_range: (Bound, Bound), + discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool), + discriminants: impl Iterator, + niche_optimize_enum: bool, + always_sized: bool, + ) -> Option> { + let dl = self.current_data_layout(); + let dl = dl.borrow(); + + let scalar_unit = |value: Primitive| { + let size = value.size(dl); + assert!(size.bits() <= 128); + Scalar::Initialized { value, valid_range: WrappingRange::full(size) } + }; + + // A variant is absent if it's uninhabited and only has ZST fields. + // Present uninhabited variants only require space for their fields, + // but *not* an encoding of the discriminant (e.g., a tag value). + // See issue #49298 for more details on the need to leave space + // for non-ZST uninhabited data (mostly partial initialization). + let absent = |fields: &[F]| { + let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited()); + let is_zst = fields.iter().all(|f| f.is_zst()); + uninhabited && is_zst + }; + let (present_first, present_second) = { + let mut present_variants = variants + .iter_enumerated() + .filter_map(|(i, v)| if absent(v) { None } else { Some(i) }); + (present_variants.next(), present_variants.next()) + }; + let present_first = match present_first { + Some(present_first) => present_first, + // Uninhabited because it has no variants, or only absent ones. + None if is_enum => { + return Some(self.layout_of_never_type()); + } + // If it's a struct, still compute a layout so that we can still compute the + // field offsets. + None => V::new(0), + }; + + let is_struct = !is_enum || + // Only one variant is present. + (present_second.is_none() && + // Representation optimizations are allowed. + !repr.inhibit_enum_layout_opt()); + if is_struct { + // Struct, or univariant enum equivalent to a struct. + // (Typechecking will reject discriminant-sizing attrs.) + + let v = present_first; + let kind = if is_enum || variants[v].is_empty() { + StructKind::AlwaysSized + } else { + if !always_sized { StructKind::MaybeUnsized } else { StructKind::AlwaysSized } + }; + + let mut st = self.univariant(dl, &variants[v], &repr, kind)?; + st.variants = Variants::Single { index: v }; + + if is_unsafe_cell { + let hide_niches = |scalar: &mut _| match scalar { + Scalar::Initialized { value, valid_range } => { + *valid_range = WrappingRange::full(value.size(dl)) + } + // Already doesn't have any niches + Scalar::Union { .. } => {} + }; + match &mut st.abi { + Abi::Uninhabited => {} + Abi::Scalar(scalar) => hide_niches(scalar), + Abi::ScalarPair(a, b) => { + hide_niches(a); + hide_niches(b); + } + Abi::Vector { element, count: _ } => hide_niches(element), + Abi::Aggregate { sized: _ } => {} + } + st.largest_niche = None; + return Some(st); + } + + let (start, end) = scalar_valid_range; + match st.abi { + Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => { + // the asserts ensure that we are not using the + // `#[rustc_layout_scalar_valid_range(n)]` + // attribute to widen the range of anything as that would probably + // result in UB somewhere + // FIXME(eddyb) the asserts are probably not needed, + // as larger validity ranges would result in missed + // optimizations, *not* wrongly assuming the inner + // value is valid. e.g. unions enlarge validity ranges, + // because the values may be uninitialized. + if let Bound::Included(start) = start { + // FIXME(eddyb) this might be incorrect - it doesn't + // account for wrap-around (end < start) ranges. + let valid_range = scalar.valid_range_mut(); + assert!(valid_range.start <= start); + valid_range.start = start; + } + if let Bound::Included(end) = end { + // FIXME(eddyb) this might be incorrect - it doesn't + // account for wrap-around (end < start) ranges. + let valid_range = scalar.valid_range_mut(); + assert!(valid_range.end >= end); + valid_range.end = end; + } + + // Update `largest_niche` if we have introduced a larger niche. + let niche = Niche::from_scalar(dl, Size::ZERO, *scalar); + if let Some(niche) = niche { + match st.largest_niche { + Some(largest_niche) => { + // Replace the existing niche even if they're equal, + // because this one is at a lower offset. + if largest_niche.available(dl) <= niche.available(dl) { + st.largest_niche = Some(niche); + } + } + None => st.largest_niche = Some(niche), + } + } + } + _ => assert!( + start == Bound::Unbounded && end == Bound::Unbounded, + "nonscalar layout for layout_scalar_valid_range type: {:#?}", + st, + ), + } + + return Some(st); + } + + // At this point, we have handled all unions and + // structs. (We have also handled univariant enums + // that allow representation optimization.) + assert!(is_enum); + + // Until we've decided whether to use the tagged or + // niche filling LayoutS, we don't want to intern the + // variant layouts, so we can't store them in the + // overall LayoutS. Store the overall LayoutS + // and the variant LayoutSs here until then. + struct TmpLayout { + layout: LayoutS, + variants: IndexVec>, + } + + let calculate_niche_filling_layout = || -> Option> { + if niche_optimize_enum { + return None; + } + + if variants.len() < 2 { + return None; + } + + let mut align = dl.aggregate_align; + let mut variant_layouts = variants + .iter_enumerated() + .map(|(j, v)| { + let mut st = self.univariant(dl, v, &repr, StructKind::AlwaysSized)?; + st.variants = Variants::Single { index: j }; + + align = align.max(st.align); + + Some(st) + }) + .collect::>>()?; + + let largest_variant_index = variant_layouts + .iter_enumerated() + .max_by_key(|(_i, layout)| layout.size.bytes()) + .map(|(i, _layout)| i)?; + + let all_indices = (0..=variants.len() - 1).map(V::new); + let needs_disc = |index: V| index != largest_variant_index && !absent(&variants[index]); + let niche_variants = all_indices.clone().find(|v| needs_disc(*v)).unwrap().index() + ..=all_indices.rev().find(|v| needs_disc(*v)).unwrap().index(); + + let count = niche_variants.size_hint().1.unwrap() as u128; + + // Find the field with the largest niche + let (field_index, niche, (niche_start, niche_scalar)) = variants[largest_variant_index] + .iter() + .enumerate() + .filter_map(|(j, field)| Some((j, field.largest_niche?))) + .max_by_key(|(_, niche)| niche.available(dl)) + .and_then(|(j, niche)| Some((j, niche, niche.reserve(dl, count)?)))?; + let niche_offset = + niche.offset + variant_layouts[largest_variant_index].fields.offset(field_index); + let niche_size = niche.value.size(dl); + let size = variant_layouts[largest_variant_index].size.align_to(align.abi); + + let all_variants_fit = variant_layouts.iter_enumerated_mut().all(|(i, layout)| { + if i == largest_variant_index { + return true; + } + + layout.largest_niche = None; + + if layout.size <= niche_offset { + // This variant will fit before the niche. + return true; + } + + // Determine if it'll fit after the niche. + let this_align = layout.align.abi; + let this_offset = (niche_offset + niche_size).align_to(this_align); + + if this_offset + layout.size > size { + return false; + } + + // It'll fit, but we need to make some adjustments. + match layout.fields { + FieldsShape::Arbitrary { ref mut offsets, .. } => { + for (j, offset) in offsets.iter_mut().enumerate() { + if !variants[i][j].is_zst() { + *offset += this_offset; + } + } + } + _ => { + panic!("Layout of fields should be Arbitrary for variants") + } + } + + // It can't be a Scalar or ScalarPair because the offset isn't 0. + if !layout.abi.is_uninhabited() { + layout.abi = Abi::Aggregate { sized: true }; + } + layout.size += this_offset; + + true + }); + + if !all_variants_fit { + return None; + } + + let largest_niche = Niche::from_scalar(dl, niche_offset, niche_scalar); + + let others_zst = variant_layouts + .iter_enumerated() + .all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO); + let same_size = size == variant_layouts[largest_variant_index].size; + let same_align = align == variant_layouts[largest_variant_index].align; + + let abi = if variant_layouts.iter().all(|v| v.abi.is_uninhabited()) { + Abi::Uninhabited + } else if same_size && same_align && others_zst { + match variant_layouts[largest_variant_index].abi { + // When the total alignment and size match, we can use the + // same ABI as the scalar variant with the reserved niche. + Abi::Scalar(_) => Abi::Scalar(niche_scalar), + Abi::ScalarPair(first, second) => { + // Only the niche is guaranteed to be initialised, + // so use union layouts for the other primitive. + if niche_offset == Size::ZERO { + Abi::ScalarPair(niche_scalar, second.to_union()) + } else { + Abi::ScalarPair(first.to_union(), niche_scalar) + } + } + _ => Abi::Aggregate { sized: true }, + } + } else { + Abi::Aggregate { sized: true } + }; + + let layout = LayoutS { + variants: Variants::Multiple { + tag: niche_scalar, + tag_encoding: TagEncoding::Niche { + untagged_variant: largest_variant_index, + niche_variants: (V::new(*niche_variants.start()) + ..=V::new(*niche_variants.end())), + niche_start, + }, + tag_field: 0, + variants: IndexVec::new(), + }, + fields: FieldsShape::Arbitrary { + offsets: vec![niche_offset], + memory_index: vec![0], + }, + abi, + largest_niche, + size, + align, + }; + + Some(TmpLayout { layout, variants: variant_layouts }) + }; + + let niche_filling_layout = calculate_niche_filling_layout(); + + let (mut min, mut max) = (i128::MAX, i128::MIN); + let discr_type = repr.discr_type(); + let bits = Integer::from_attr(dl, discr_type).size().bits(); + for (i, mut val) in discriminants { + if variants[i].iter().any(|f| f.abi.is_uninhabited()) { + continue; + } + if discr_type.is_signed() { + // sign extend the raw representation to be an i128 + val = (val << (128 - bits)) >> (128 - bits); + } + if val < min { + min = val; + } + if val > max { + max = val; + } + } + // We might have no inhabited variants, so pretend there's at least one. + if (min, max) == (i128::MAX, i128::MIN) { + min = 0; + max = 0; + } + assert!(min <= max, "discriminant range is {}...{}", min, max); + let (min_ity, signed) = discr_range_of_repr(min, max); //Integer::repr_discr(tcx, ty, &repr, min, max); + + let mut align = dl.aggregate_align; + let mut size = Size::ZERO; + + // We're interested in the smallest alignment, so start large. + let mut start_align = Align::from_bytes(256).unwrap(); + assert_eq!(Integer::for_align(dl, start_align), None); + + // repr(C) on an enum tells us to make a (tag, union) layout, + // so we need to grow the prefix alignment to be at least + // the alignment of the union. (This value is used both for + // determining the alignment of the overall enum, and the + // determining the alignment of the payload after the tag.) + let mut prefix_align = min_ity.align(dl).abi; + if repr.c() { + for fields in variants { + for field in fields { + prefix_align = prefix_align.max(field.align.abi); + } + } + } + + // Create the set of structs that represent each variant. + let mut layout_variants = variants + .iter_enumerated() + .map(|(i, field_layouts)| { + let mut st = self.univariant( + dl, + &field_layouts, + &repr, + StructKind::Prefixed(min_ity.size(), prefix_align), + )?; + st.variants = Variants::Single { index: i }; + // Find the first field we can't move later + // to make room for a larger discriminant. + for field in st.fields.index_by_increasing_offset().map(|j| &field_layouts[j]) { + if !field.is_zst() || field.align.abi.bytes() != 1 { + start_align = start_align.min(field.align.abi); + break; + } + } + size = cmp::max(size, st.size); + align = align.max(st.align); + Some(st) + }) + .collect::>>()?; + + // Align the maximum variant size to the largest alignment. + size = size.align_to(align.abi); + + if size.bytes() >= dl.obj_size_bound() { + return None; + } + + let typeck_ity = Integer::from_attr(dl, repr.discr_type()); + if typeck_ity < min_ity { + // It is a bug if Layout decided on a greater discriminant size than typeck for + // some reason at this point (based on values discriminant can take on). Mostly + // because this discriminant will be loaded, and then stored into variable of + // type calculated by typeck. Consider such case (a bug): typeck decided on + // byte-sized discriminant, but layout thinks we need a 16-bit to store all + // discriminant values. That would be a bug, because then, in codegen, in order + // to store this 16-bit discriminant into 8-bit sized temporary some of the + // space necessary to represent would have to be discarded (or layout is wrong + // on thinking it needs 16 bits) + panic!( + "layout decided on a larger discriminant type ({:?}) than typeck ({:?})", + min_ity, typeck_ity + ); + // However, it is fine to make discr type however large (as an optimisation) + // after this point – we’ll just truncate the value we load in codegen. + } + + // Check to see if we should use a different type for the + // discriminant. We can safely use a type with the same size + // as the alignment of the first field of each variant. + // We increase the size of the discriminant to avoid LLVM copying + // padding when it doesn't need to. This normally causes unaligned + // load/stores and excessive memcpy/memset operations. By using a + // bigger integer size, LLVM can be sure about its contents and + // won't be so conservative. + + // Use the initial field alignment + let mut ity = if repr.c() || repr.int.is_some() { + min_ity + } else { + Integer::for_align(dl, start_align).unwrap_or(min_ity) + }; + + // If the alignment is not larger than the chosen discriminant size, + // don't use the alignment as the final size. + if ity <= min_ity { + ity = min_ity; + } else { + // Patch up the variants' first few fields. + let old_ity_size = min_ity.size(); + let new_ity_size = ity.size(); + for variant in &mut layout_variants { + match variant.fields { + FieldsShape::Arbitrary { ref mut offsets, .. } => { + for i in offsets { + if *i <= old_ity_size { + assert_eq!(*i, old_ity_size); + *i = new_ity_size; + } + } + // We might be making the struct larger. + if variant.size <= old_ity_size { + variant.size = new_ity_size; + } + } + _ => panic!(), + } + } + } + + let tag_mask = ity.size().unsigned_int_max(); + let tag = Scalar::Initialized { + value: Int(ity, signed), + valid_range: WrappingRange { + start: (min as u128 & tag_mask), + end: (max as u128 & tag_mask), + }, + }; + let mut abi = Abi::Aggregate { sized: true }; + + if layout_variants.iter().all(|v| v.abi.is_uninhabited()) { + abi = Abi::Uninhabited; + } else if tag.size(dl) == size { + // Make sure we only use scalar layout when the enum is entirely its + // own tag (i.e. it has no padding nor any non-ZST variant fields). + abi = Abi::Scalar(tag); + } else { + // Try to use a ScalarPair for all tagged enums. + let mut common_prim = None; + let mut common_prim_initialized_in_all_variants = true; + for (field_layouts, layout_variant) in iter::zip(&*variants, &layout_variants) { + let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else { + panic!(); + }; + let mut fields = iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst()); + let (field, offset) = match (fields.next(), fields.next()) { + (None, None) => { + common_prim_initialized_in_all_variants = false; + continue; + } + (Some(pair), None) => pair, + _ => { + common_prim = None; + break; + } + }; + let prim = match field.abi { + Abi::Scalar(scalar) => { + common_prim_initialized_in_all_variants &= + matches!(scalar, Scalar::Initialized { .. }); + scalar.primitive() + } + _ => { + common_prim = None; + break; + } + }; + if let Some(pair) = common_prim { + // This is pretty conservative. We could go fancier + // by conflating things like i32 and u32, or even + // realising that (u8, u8) could just cohabit with + // u16 or even u32. + if pair != (prim, offset) { + common_prim = None; + break; + } + } else { + common_prim = Some((prim, offset)); + } + } + if let Some((prim, offset)) = common_prim { + let prim_scalar = if common_prim_initialized_in_all_variants { + scalar_unit(prim) + } else { + // Common prim might be uninit. + Scalar::Union { value: prim } + }; + let pair = self.scalar_pair::(tag, prim_scalar); + let pair_offsets = match pair.fields { + FieldsShape::Arbitrary { ref offsets, ref memory_index } => { + assert_eq!(memory_index, &[0, 1]); + offsets + } + _ => panic!(), + }; + if pair_offsets[0] == Size::ZERO + && pair_offsets[1] == *offset + && align == pair.align + && size == pair.size + { + // We can use `ScalarPair` only when it matches our + // already computed layout (including `#[repr(C)]`). + abi = pair.abi; + } + } + } + + // If we pick a "clever" (by-value) ABI, we might have to adjust the ABI of the + // variants to ensure they are consistent. This is because a downcast is + // semantically a NOP, and thus should not affect layout. + if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) { + for variant in &mut layout_variants { + // We only do this for variants with fields; the others are not accessed anyway. + // Also do not overwrite any already existing "clever" ABIs. + if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) { + variant.abi = abi; + // Also need to bump up the size and alignment, so that the entire value fits in here. + variant.size = cmp::max(variant.size, size); + variant.align.abi = cmp::max(variant.align.abi, align.abi); + } + } + } + + let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag); + + let tagged_layout = LayoutS { + variants: Variants::Multiple { + tag, + tag_encoding: TagEncoding::Direct, + tag_field: 0, + variants: IndexVec::new(), + }, + fields: FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] }, + largest_niche, + abi, + align, + size, + }; + + let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants }; + + let mut best_layout = match (tagged_layout, niche_filling_layout) { + (tl, Some(nl)) => { + // Pick the smaller layout; otherwise, + // pick the layout with the larger niche; otherwise, + // pick tagged as it has simpler codegen. + use cmp::Ordering::*; + let niche_size = |tmp_l: &TmpLayout| { + tmp_l.layout.largest_niche.map_or(0, |n| n.available(dl)) + }; + match (tl.layout.size.cmp(&nl.layout.size), niche_size(&tl).cmp(&niche_size(&nl))) { + (Greater, _) => nl, + (Equal, Less) => nl, + _ => tl, + } + } + (tl, None) => tl, + }; + + // Now we can intern the variant layouts and store them in the enum layout. + best_layout.layout.variants = match best_layout.layout.variants { + Variants::Multiple { tag, tag_encoding, tag_field, .. } => { + Variants::Multiple { tag, tag_encoding, tag_field, variants: best_layout.variants } + } + _ => panic!(), + }; + Some(best_layout.layout) + } + + fn layout_of_union<'a, V: Idx, F: Deref> + Debug>( + &self, + repr: &ReprOptions, + variants: &IndexVec>, + ) -> Option> { + let dl = self.current_data_layout(); + let dl = dl.borrow(); + let mut align = if repr.pack.is_some() { dl.i8_align } else { dl.aggregate_align }; + + if let Some(repr_align) = repr.align { + align = align.max(AbiAndPrefAlign::new(repr_align)); + } + + let optimize = !repr.inhibit_union_abi_opt(); + let mut size = Size::ZERO; + let mut abi = Abi::Aggregate { sized: true }; + let index = V::new(0); + for field in &variants[index] { + assert!(!field.is_unsized()); + align = align.max(field.align); + + // If all non-ZST fields have the same ABI, forward this ABI + if optimize && !field.is_zst() { + // Discard valid range information and allow undef + let field_abi = match field.abi { + Abi::Scalar(x) => Abi::Scalar(x.to_union()), + Abi::ScalarPair(x, y) => Abi::ScalarPair(x.to_union(), y.to_union()), + Abi::Vector { element: x, count } => { + Abi::Vector { element: x.to_union(), count } + } + Abi::Uninhabited | Abi::Aggregate { .. } => Abi::Aggregate { sized: true }, + }; + + if size == Size::ZERO { + // first non ZST: initialize 'abi' + abi = field_abi; + } else if abi != field_abi { + // different fields have different ABI: reset to Aggregate + abi = Abi::Aggregate { sized: true }; + } + } + + size = cmp::max(size, field.size); + } + + if let Some(pack) = repr.pack { + align = align.min(AbiAndPrefAlign::new(pack)); + } + + Some(LayoutS { + variants: Variants::Single { index }, + fields: FieldsShape::Union(NonZeroUsize::new(variants[index].len())?), + abi, + largest_niche: None, + align, + size: size.align_to(align.abi), + }) + } +} diff --git a/compiler/rustc_target/src/abi/mod.rs b/compiler/rustc_target/src/abi/mod.rs index fa6af2ed7f3a..b6972d914a0e 100644 --- a/compiler/rustc_target/src/abi/mod.rs +++ b/compiler/rustc_target/src/abi/mod.rs @@ -13,6 +13,7 @@ use std::num::{NonZeroUsize, ParseIntError}; use std::ops::{Add, AddAssign, Deref, Mul, RangeInclusive, Sub}; use std::str::FromStr; +use bitflags::bitflags; #[cfg(feature = "nightly")] use rustc_data_structures::intern::Interned; use rustc_index::vec::{Idx, IndexVec}; @@ -22,6 +23,127 @@ use rustc_macros::HashStable_Generic; #[cfg(feature = "nightly")] pub mod call; +mod layout; + +pub use layout::LayoutCalculator; + +bitflags! { + #[derive(Default)] + #[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))] + pub struct ReprFlags: u8 { + const IS_C = 1 << 0; + const IS_SIMD = 1 << 1; + const IS_TRANSPARENT = 1 << 2; + // Internal only for now. If true, don't reorder fields. + const IS_LINEAR = 1 << 3; + // If true, the type's layout can be randomized using + // the seed stored in `ReprOptions.layout_seed` + const RANDOMIZE_LAYOUT = 1 << 4; + // Any of these flags being set prevent field reordering optimisation. + const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits + | ReprFlags::IS_SIMD.bits + | ReprFlags::IS_LINEAR.bits; + } +} + +#[derive(Copy, Clone, Debug, Eq, PartialEq)] +#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))] +pub enum IntegerType { + Pointer(bool), + Fixed(Integer, bool), +} + +impl IntegerType { + pub fn is_signed(&self) -> bool { + match self { + IntegerType::Pointer(b) => *b, + IntegerType::Fixed(_, b) => *b, + } + } +} + +/// Represents the repr options provided by the user, +#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)] +#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))] +pub struct ReprOptions { + pub int: Option, + pub align: Option, + pub pack: Option, + pub flags: ReprFlags, + /// The seed to be used for randomizing a type's layout + /// + /// Note: This could technically be a `[u8; 16]` (a `u128`) which would + /// be the "most accurate" hash as it'd encompass the item and crate + /// hash without loss, but it does pay the price of being larger. + /// Everything's a tradeoff, a `u64` seed should be sufficient for our + /// purposes (primarily `-Z randomize-layout`) + pub field_shuffle_seed: u64, +} + +impl ReprOptions { + #[inline] + pub fn simd(&self) -> bool { + self.flags.contains(ReprFlags::IS_SIMD) + } + + #[inline] + pub fn c(&self) -> bool { + self.flags.contains(ReprFlags::IS_C) + } + + #[inline] + pub fn packed(&self) -> bool { + self.pack.is_some() + } + + #[inline] + pub fn transparent(&self) -> bool { + self.flags.contains(ReprFlags::IS_TRANSPARENT) + } + + #[inline] + pub fn linear(&self) -> bool { + self.flags.contains(ReprFlags::IS_LINEAR) + } + + /// Returns the discriminant type, given these `repr` options. + /// This must only be called on enums! + pub fn discr_type(&self) -> IntegerType { + self.int.unwrap_or(IntegerType::Pointer(true)) + } + + /// Returns `true` if this `#[repr()]` should inhabit "smart enum + /// layout" optimizations, such as representing `Foo<&T>` as a + /// single pointer. + pub fn inhibit_enum_layout_opt(&self) -> bool { + self.c() || self.int.is_some() + } + + /// Returns `true` if this `#[repr()]` should inhibit struct field reordering + /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr()`. + pub fn inhibit_struct_field_reordering_opt(&self) -> bool { + if let Some(pack) = self.pack { + if pack.bytes() == 1 { + return true; + } + } + + self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some() + } + + /// Returns `true` if this type is valid for reordering and `-Z randomize-layout` + /// was enabled for its declaration crate + pub fn can_randomize_type_layout(&self) -> bool { + !self.inhibit_struct_field_reordering_opt() + && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT) + } + + /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations. + pub fn inhibit_union_abi_opt(&self) -> bool { + self.c() + } +} + /// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout) /// for a target, which contains everything needed to compute layouts. #[derive(Debug, PartialEq, Eq)] @@ -622,7 +744,7 @@ impl AbiAndPrefAlign { /// Integers, also used for enum discriminants. #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)] -#[cfg_attr(feature = "nightly", derive(HashStable_Generic))] +#[cfg_attr(feature = "nightly", derive(Encodable, Decodable, HashStable_Generic))] pub enum Integer { I8, @@ -644,6 +766,16 @@ impl Integer { } } + /// Gets the Integer type from an attr::IntType. + pub fn from_attr(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(self, cx: &C) -> AbiAndPrefAlign { let dl = cx.data_layout(); @@ -1172,12 +1304,7 @@ pub enum TagEncoding { /// For example, `Option<(usize, &T)>` is represented such that /// `None` has a null pointer for the second tuple field, and /// `Some` is the identity function (with a non-null reference). - Niche { - untagged_variant: V, - #[cfg(feature = "nightly")] - niche_variants: RangeInclusive, - niche_start: u128, - }, + Niche { untagged_variant: V, niche_variants: RangeInclusive, niche_start: u128 }, } #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)] @@ -1568,3 +1695,13 @@ impl LayoutS { } } } + +#[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), +} diff --git a/compiler/rustc_traits/Cargo.toml b/compiler/rustc_traits/Cargo.toml index 9474e6df5677..a432498abcca 100644 --- a/compiler/rustc_traits/Cargo.toml +++ b/compiler/rustc_traits/Cargo.toml @@ -12,6 +12,7 @@ rustc_hir = { path = "../rustc_hir" } rustc_index = { path = "../rustc_index" } rustc_ast = { path = "../rustc_ast" } rustc_span = { path = "../rustc_span" } +rustc_target = { path = "../rustc_target" } chalk-ir = "0.87.0" chalk-engine = "0.87.0" chalk-solve = "0.87.0" diff --git a/compiler/rustc_traits/src/chalk/db.rs b/compiler/rustc_traits/src/chalk/db.rs index d15707e5cedd..344c8b93c170 100644 --- a/compiler/rustc_traits/src/chalk/db.rs +++ b/compiler/rustc_traits/src/chalk/db.rs @@ -9,9 +9,9 @@ use rustc_middle::traits::ChalkRustInterner as RustInterner; use rustc_middle::ty::{self, AssocKind, EarlyBinder, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable}; use rustc_middle::ty::{InternalSubsts, SubstsRef}; +use rustc_target::abi::{Integer, IntegerType}; use rustc_ast::ast; -use rustc_attr as attr; use rustc_hir::def_id::DefId; @@ -218,21 +218,21 @@ impl<'tcx> chalk_solve::RustIrDatabase> for RustIrDatabase<'t c: adt_def.repr().c(), packed: adt_def.repr().packed(), int: adt_def.repr().int.map(|i| match i { - attr::IntType::SignedInt(ty) => match ty { - ast::IntTy::Isize => int(chalk_ir::IntTy::Isize), - ast::IntTy::I8 => int(chalk_ir::IntTy::I8), - ast::IntTy::I16 => int(chalk_ir::IntTy::I16), - ast::IntTy::I32 => int(chalk_ir::IntTy::I32), - ast::IntTy::I64 => int(chalk_ir::IntTy::I64), - ast::IntTy::I128 => int(chalk_ir::IntTy::I128), + IntegerType::Pointer(true) => int(chalk_ir::IntTy::Isize), + IntegerType::Pointer(false) => uint(chalk_ir::UintTy::Usize), + IntegerType::Fixed(i, true) => match i { + Integer::I8 => int(chalk_ir::IntTy::I8), + Integer::I16 => int(chalk_ir::IntTy::I16), + Integer::I32 => int(chalk_ir::IntTy::I32), + Integer::I64 => int(chalk_ir::IntTy::I64), + Integer::I128 => int(chalk_ir::IntTy::I128), }, - attr::IntType::UnsignedInt(ty) => match ty { - ast::UintTy::Usize => uint(chalk_ir::UintTy::Usize), - ast::UintTy::U8 => uint(chalk_ir::UintTy::U8), - ast::UintTy::U16 => uint(chalk_ir::UintTy::U16), - ast::UintTy::U32 => uint(chalk_ir::UintTy::U32), - ast::UintTy::U64 => uint(chalk_ir::UintTy::U64), - ast::UintTy::U128 => uint(chalk_ir::UintTy::U128), + IntegerType::Fixed(i, false) => match i { + Integer::I8 => uint(chalk_ir::UintTy::U8), + Integer::I16 => uint(chalk_ir::UintTy::U16), + Integer::I32 => uint(chalk_ir::UintTy::U32), + Integer::I64 => uint(chalk_ir::UintTy::U64), + Integer::I128 => uint(chalk_ir::UintTy::U128), }, }), }) diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs index 5e77ad4054a5..0af8276b246c 100644 --- a/compiler/rustc_ty_utils/src/layout.rs +++ b/compiler/rustc_ty_utils/src/layout.rs @@ -13,13 +13,8 @@ use rustc_span::symbol::Symbol; use rustc_span::DUMMY_SP; use rustc_target::abi::*; -use std::cmp::{self, Ordering}; +use std::fmt::Debug; use std::iter; -use std::num::NonZeroUsize; -use std::ops::Bound; - -use rand::{seq::SliceRandom, SeedableRng}; -use rand_xoshiro::Xoshiro128StarStar; use crate::layout_sanity_check::sanity_check_layout; @@ -66,16 +61,6 @@ fn layout_of<'tcx>( Ok(layout) } -#[derive(Copy, Clone, Debug)] -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), -} - // Invert a bijective mapping, i.e. `invert(map)[y] = x` if `map[x] = y`. // This is used to go between `memory_index` (source field order to memory order) // and `inverse_memory_index` (memory order to source field order). @@ -89,37 +74,6 @@ fn invert_mapping(map: &[u32]) -> Vec { inverse } -fn scalar_pair<'tcx>( - cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, - a: Scalar, - b: Scalar, -) -> LayoutS { - let dl = cx.data_layout(); - let b_align = b.align(dl); - let align = a.align(dl).max(b_align).max(dl.aggregate_align); - let b_offset = a.size(dl).align_to(b_align.abi); - let size = (b_offset + b.size(dl)).align_to(align.abi); - - // HACK(nox): We iter on `b` and then `a` because `max_by_key` - // returns the last maximum. - let largest_niche = Niche::from_scalar(dl, b_offset, b) - .into_iter() - .chain(Niche::from_scalar(dl, Size::ZERO, a)) - .max_by_key(|niche| niche.available(dl)); - - LayoutS { - variants: Variants::Single { index: VariantIdx::new(0) }, - fields: FieldsShape::Arbitrary { - offsets: vec![Size::ZERO, b_offset], - memory_index: vec![0, 1], - }, - abi: Abi::ScalarPair(a, b), - largest_niche, - align, - size, - } -} - fn univariant_uninterned<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, ty: Ty<'tcx>, @@ -134,226 +88,7 @@ fn univariant_uninterned<'tcx>( return Err(LayoutError::Unknown(ty)); } - let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align }; - - let mut inverse_memory_index: Vec = (0..fields.len() as u32).collect(); - - let optimize = !repr.inhibit_struct_field_reordering_opt(); - if optimize { - let end = if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() }; - let optimizing = &mut inverse_memory_index[..end]; - let effective_field_align = |f: &TyAndLayout<'_>| { - if let Some(pack) = pack { - // return the packed alignment in bytes - f.align.abi.min(pack).bytes() - } else { - // returns log2(effective-align). - // This is ok since `pack` applies to all fields equally. - // The calculation assumes that size is an integer multiple of align, except for ZSTs. - // - // group [u8; 4] with align-4 or [u8; 6] with align-2 fields - f.align.abi.bytes().max(f.size.bytes()).trailing_zeros() as u64 - } - }; - - // If `-Z randomize-layout` was enabled for the type definition we can shuffle - // the field ordering to try and catch some code making assumptions about layouts - // we don't guarantee - if repr.can_randomize_type_layout() { - // `ReprOptions.layout_seed` is a deterministic seed that we can use to - // randomize field ordering with - let mut rng = Xoshiro128StarStar::seed_from_u64(repr.field_shuffle_seed); - - // Shuffle the ordering of the fields - optimizing.shuffle(&mut rng); - - // Otherwise we just leave things alone and actually optimize the type's fields - } else { - match kind { - StructKind::AlwaysSized | StructKind::MaybeUnsized => { - optimizing.sort_by_key(|&x| { - // Place ZSTs first to avoid "interesting offsets", - // especially with only one or two non-ZST fields. - // Then place largest alignments first, largest niches within an alignment group last - let f = &fields[x as usize]; - let niche_size = f.largest_niche.map_or(0, |n| n.available(cx)); - (!f.is_zst(), cmp::Reverse(effective_field_align(f)), niche_size) - }); - } - - StructKind::Prefixed(..) => { - // Sort in ascending alignment so that the layout stays optimal - // regardless of the prefix. - // And put the largest niche in an alignment group at the end - // so it can be used as discriminant in jagged enums - optimizing.sort_by_key(|&x| { - let f = &fields[x as usize]; - let niche_size = f.largest_niche.map_or(0, |n| n.available(cx)); - (effective_field_align(f), niche_size) - }); - } - } - - // FIXME(Kixiron): We can always shuffle fields within a given alignment class - // regardless of the status of `-Z randomize-layout` - } - } - - // inverse_memory_index holds field indices by increasing memory offset. - // That is, if field 5 has offset 0, the first element of inverse_memory_index is 5. - // We now write field offsets to the corresponding offset slot; - // field 5 with offset 0 puts 0 in offsets[5]. - // At the bottom of this function, we invert `inverse_memory_index` to - // produce `memory_index` (see `invert_mapping`). - - let mut sized = true; - let mut offsets = vec![Size::ZERO; fields.len()]; - let mut offset = Size::ZERO; - let mut largest_niche = None; - let mut largest_niche_available = 0; - - if let StructKind::Prefixed(prefix_size, prefix_align) = kind { - let prefix_align = - if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align }; - align = align.max(AbiAndPrefAlign::new(prefix_align)); - offset = prefix_size.align_to(prefix_align); - } - - for &i in &inverse_memory_index { - let field = fields[i as usize]; - if !sized { - cx.tcx.sess.delay_span_bug( - DUMMY_SP, - &format!( - "univariant: field #{} of `{}` comes after unsized field", - offsets.len(), - ty - ), - ); - } - - if field.is_unsized() { - sized = false; - } - - // Invariant: offset < dl.obj_size_bound() <= 1<<61 - let field_align = if let Some(pack) = pack { - field.align.min(AbiAndPrefAlign::new(pack)) - } else { - field.align - }; - offset = offset.align_to(field_align.abi); - align = align.max(field_align); - - debug!("univariant offset: {:?} field: {:#?}", offset, field); - offsets[i as usize] = offset; - - if let Some(mut niche) = field.largest_niche { - let available = niche.available(dl); - if available > largest_niche_available { - largest_niche_available = available; - niche.offset += offset; - largest_niche = Some(niche); - } - } - - offset = offset.checked_add(field.size, dl).ok_or(LayoutError::SizeOverflow(ty))?; - } - - if let Some(repr_align) = repr.align { - align = align.max(AbiAndPrefAlign::new(repr_align)); - } - - debug!("univariant min_size: {:?}", offset); - let min_size = offset; - - // As stated above, inverse_memory_index holds field indices by increasing offset. - // This makes it an already-sorted view of the offsets vec. - // To invert it, consider: - // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0. - // Field 5 would be the first element, so memory_index is i: - // Note: if we didn't optimize, it's already right. - - let memory_index = - if optimize { invert_mapping(&inverse_memory_index) } else { inverse_memory_index }; - - let size = min_size.align_to(align.abi); - let mut abi = Abi::Aggregate { sized }; - - // Unpack newtype ABIs and find scalar pairs. - if sized && size.bytes() > 0 { - // All other fields must be ZSTs. - let mut non_zst_fields = fields.iter().enumerate().filter(|&(_, f)| !f.is_zst()); - - match (non_zst_fields.next(), non_zst_fields.next(), non_zst_fields.next()) { - // We have exactly one non-ZST field. - (Some((i, field)), None, None) => { - // Field fills the struct and it has a scalar or scalar pair ABI. - if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size { - match field.abi { - // For plain scalars, or vectors of them, we can't unpack - // newtypes for `#[repr(C)]`, as that affects C ABIs. - Abi::Scalar(_) | Abi::Vector { .. } if optimize => { - abi = field.abi; - } - // But scalar pairs are Rust-specific and get - // treated as aggregates by C ABIs anyway. - Abi::ScalarPair(..) => { - abi = field.abi; - } - _ => {} - } - } - } - - // Two non-ZST fields, and they're both scalars. - (Some((i, a)), Some((j, b)), None) => { - match (a.abi, b.abi) { - (Abi::Scalar(a), Abi::Scalar(b)) => { - // Order by the memory placement, not source order. - let ((i, a), (j, b)) = if offsets[i] < offsets[j] { - ((i, a), (j, b)) - } else { - ((j, b), (i, a)) - }; - let pair = scalar_pair(cx, a, b); - let pair_offsets = match pair.fields { - FieldsShape::Arbitrary { ref offsets, ref memory_index } => { - assert_eq!(memory_index, &[0, 1]); - offsets - } - _ => bug!(), - }; - if offsets[i] == pair_offsets[0] - && offsets[j] == pair_offsets[1] - && align == pair.align - && size == pair.size - { - // We can use `ScalarPair` only when it matches our - // already computed layout (including `#[repr(C)]`). - abi = pair.abi; - } - } - _ => {} - } - } - - _ => {} - } - } - - if fields.iter().any(|f| f.abi.is_uninhabited()) { - abi = Abi::Uninhabited; - } - - Ok(LayoutS { - variants: Variants::Single { index: VariantIdx::new(0) }, - fields: FieldsShape::Arbitrary { offsets, memory_index }, - abi, - largest_niche, - align, - size, - }) + cx.univariant(dl, fields, repr, kind).ok_or(LayoutError::SizeOverflow(ty)) } fn layout_of_uncached<'tcx>( @@ -404,14 +139,7 @@ fn layout_of_uncached<'tcx>( } // The never type. - ty::Never => tcx.intern_layout(LayoutS { - variants: Variants::Single { index: VariantIdx::new(0) }, - fields: FieldsShape::Primitive, - abi: Abi::Uninhabited, - largest_niche: None, - align: dl.i8_align, - size: Size::ZERO, - }), + ty::Never => tcx.intern_layout(cx.layout_of_never_type()), // Potentially-wide pointers. ty::Ref(_, pointee, _) | ty::RawPtr(ty::TypeAndMut { ty: pointee, .. }) => { @@ -440,7 +168,7 @@ fn layout_of_uncached<'tcx>( }; // Effectively a (ptr, meta) tuple. - tcx.intern_layout(scalar_pair(cx, data_ptr, metadata)) + tcx.intern_layout(cx.scalar_pair(data_ptr, metadata)) } ty::Dynamic(_, _, ty::DynStar) => { @@ -448,7 +176,7 @@ fn layout_of_uncached<'tcx>( data.valid_range_mut().start = 0; let mut vtable = scalar_unit(Pointer); vtable.valid_range_mut().start = 1; - tcx.intern_layout(scalar_pair(cx, data, vtable)) + tcx.intern_layout(cx.scalar_pair(data, vtable)) } // Arrays and slices. @@ -677,677 +405,41 @@ fn layout_of_uncached<'tcx>( return Err(LayoutError::Unknown(ty)); } - let mut align = - if def.repr().pack.is_some() { dl.i8_align } else { dl.aggregate_align }; - - if let Some(repr_align) = def.repr().align { - align = align.max(AbiAndPrefAlign::new(repr_align)); - } - - let optimize = !def.repr().inhibit_union_abi_opt(); - let mut size = Size::ZERO; - let mut abi = Abi::Aggregate { sized: true }; - let index = VariantIdx::new(0); - for field in &variants[index] { - assert!(field.is_sized()); - align = align.max(field.align); - - // If all non-ZST fields have the same ABI, forward this ABI - if optimize && !field.is_zst() { - // Discard valid range information and allow undef - let field_abi = match field.abi { - Abi::Scalar(x) => Abi::Scalar(x.to_union()), - Abi::ScalarPair(x, y) => Abi::ScalarPair(x.to_union(), y.to_union()), - Abi::Vector { element: x, count } => { - Abi::Vector { element: x.to_union(), count } - } - Abi::Uninhabited | Abi::Aggregate { .. } => { - Abi::Aggregate { sized: true } - } - }; - - if size == Size::ZERO { - // first non ZST: initialize 'abi' - abi = field_abi; - } else if abi != field_abi { - // different fields have different ABI: reset to Aggregate - abi = Abi::Aggregate { sized: true }; - } - } - - size = cmp::max(size, field.size); - } - - if let Some(pack) = def.repr().pack { - align = align.min(AbiAndPrefAlign::new(pack)); - } - - return Ok(tcx.intern_layout(LayoutS { - variants: Variants::Single { index }, - fields: FieldsShape::Union( - NonZeroUsize::new(variants[index].len()).ok_or(LayoutError::Unknown(ty))?, - ), - abi, - largest_niche: None, - align, - size: size.align_to(align.abi), - })); + return Ok(tcx.intern_layout( + cx.layout_of_union(&def.repr(), &variants).ok_or(LayoutError::Unknown(ty))?, + )); } - // A variant is absent if it's uninhabited and only has ZST fields. - // Present uninhabited variants only require space for their fields, - // but *not* an encoding of the discriminant (e.g., a tag value). - // See issue #49298 for more details on the need to leave space - // for non-ZST uninhabited data (mostly partial initialization). - let absent = |fields: &[TyAndLayout<'_>]| { - let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited()); - let is_zst = fields.iter().all(|f| f.is_zst()); - uninhabited && is_zst - }; - let (present_first, present_second) = { - let mut present_variants = variants - .iter_enumerated() - .filter_map(|(i, v)| if absent(v) { None } else { Some(i) }); - (present_variants.next(), present_variants.next()) - }; - let present_first = match present_first { - Some(present_first) => present_first, - // Uninhabited because it has no variants, or only absent ones. - None if def.is_enum() => { - return Ok(tcx.layout_of(param_env.and(tcx.types.never))?.layout); - } - // If it's a struct, still compute a layout so that we can still compute the - // field offsets. - None => VariantIdx::new(0), - }; - - let is_struct = !def.is_enum() || - // Only one variant is present. - (present_second.is_none() && - // Representation optimizations are allowed. - !def.repr().inhibit_enum_layout_opt()); - if is_struct { - // Struct, or univariant enum equivalent to a struct. - // (Typechecking will reject discriminant-sizing attrs.) - - let v = present_first; - let kind = if def.is_enum() || variants[v].is_empty() { - StructKind::AlwaysSized - } else { - let param_env = tcx.param_env(def.did()); - let last_field = def.variant(v).fields.last().unwrap(); - let always_sized = tcx.type_of(last_field.did).is_sized(tcx, param_env); - if !always_sized { StructKind::MaybeUnsized } else { StructKind::AlwaysSized } - }; - - let mut st = univariant_uninterned(cx, ty, &variants[v], &def.repr(), kind)?; - st.variants = Variants::Single { index: v }; - - if def.is_unsafe_cell() { - let hide_niches = |scalar: &mut _| match scalar { - Scalar::Initialized { value, valid_range } => { - *valid_range = WrappingRange::full(value.size(dl)) - } - // Already doesn't have any niches - Scalar::Union { .. } => {} - }; - match &mut st.abi { - Abi::Uninhabited => {} - Abi::Scalar(scalar) => hide_niches(scalar), - Abi::ScalarPair(a, b) => { - hide_niches(a); - hide_niches(b); - } - Abi::Vector { element, count: _ } => hide_niches(element), - Abi::Aggregate { sized: _ } => {} - } - st.largest_niche = None; - return Ok(tcx.intern_layout(st)); - } - - let (start, end) = cx.tcx.layout_scalar_valid_range(def.did()); - match st.abi { - Abi::Scalar(ref mut scalar) | Abi::ScalarPair(ref mut scalar, _) => { - // the asserts ensure that we are not using the - // `#[rustc_layout_scalar_valid_range(n)]` - // attribute to widen the range of anything as that would probably - // result in UB somewhere - // FIXME(eddyb) the asserts are probably not needed, - // as larger validity ranges would result in missed - // optimizations, *not* wrongly assuming the inner - // value is valid. e.g. unions enlarge validity ranges, - // because the values may be uninitialized. - if let Bound::Included(start) = start { - // FIXME(eddyb) this might be incorrect - it doesn't - // account for wrap-around (end < start) ranges. - let valid_range = scalar.valid_range_mut(); - assert!(valid_range.start <= start); - valid_range.start = start; - } - if let Bound::Included(end) = end { - // FIXME(eddyb) this might be incorrect - it doesn't - // account for wrap-around (end < start) ranges. - let valid_range = scalar.valid_range_mut(); - assert!(valid_range.end >= end); - valid_range.end = end; - } - - // Update `largest_niche` if we have introduced a larger niche. - let niche = Niche::from_scalar(dl, Size::ZERO, *scalar); - if let Some(niche) = niche { - match st.largest_niche { - Some(largest_niche) => { - // Replace the existing niche even if they're equal, - // because this one is at a lower offset. - if largest_niche.available(dl) <= niche.available(dl) { - st.largest_niche = Some(niche); - } - } - None => st.largest_niche = Some(niche), - } - } - } - _ => assert!( - start == Bound::Unbounded && end == Bound::Unbounded, - "nonscalar layout for layout_scalar_valid_range type {:?}: {:#?}", - def, - st, - ), - } - - return Ok(tcx.intern_layout(st)); - } - - // At this point, we have handled all unions and - // structs. (We have also handled univariant enums - // that allow representation optimization.) - assert!(def.is_enum()); - - // Until we've decided whether to use the tagged or - // niche filling LayoutS, we don't want to intern the - // variant layouts, so we can't store them in the - // overall LayoutS. Store the overall LayoutS - // and the variant LayoutSs here until then. - struct TmpLayout { - layout: LayoutS, - variants: IndexVec>, - } - - let calculate_niche_filling_layout = - || -> Result, LayoutError<'tcx>> { - // The current code for niche-filling relies on variant indices - // instead of actual discriminants, so enums with - // explicit discriminants (RFC #2363) would misbehave. - if def.repr().inhibit_enum_layout_opt() + tcx.intern_layout( + cx.layout_of_struct_or_enum( + &def.repr(), + &variants, + def.is_enum(), + def.is_unsafe_cell(), + tcx.layout_scalar_valid_range(def.did()), + |min, max| Integer::repr_discr(tcx, ty, &def.repr(), min, max), + def.is_enum() + .then(|| def.discriminants(tcx).map(|(v, d)| (v, d.val as i128))) + .into_iter() + .flatten(), + def.repr().inhibit_enum_layout_opt() || def .variants() .iter_enumerated() - .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())) + .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())), { - return Ok(None); - } - - if variants.len() < 2 { - return Ok(None); - } - - let mut align = dl.aggregate_align; - let mut variant_layouts = variants - .iter_enumerated() - .map(|(j, v)| { - let mut st = univariant_uninterned( - cx, - ty, - v, - &def.repr(), - StructKind::AlwaysSized, - )?; - st.variants = Variants::Single { index: j }; - - align = align.max(st.align); - - Ok(st) - }) - .collect::, _>>()?; - - let largest_variant_index = match variant_layouts - .iter_enumerated() - .max_by_key(|(_i, layout)| layout.size.bytes()) - .map(|(i, _layout)| i) - { - None => return Ok(None), - Some(i) => i, - }; - - let all_indices = VariantIdx::new(0)..=VariantIdx::new(variants.len() - 1); - let needs_disc = |index: VariantIdx| { - index != largest_variant_index && !absent(&variants[index]) - }; - let niche_variants = all_indices.clone().find(|v| needs_disc(*v)).unwrap() - ..=all_indices.rev().find(|v| needs_disc(*v)).unwrap(); - - let count = niche_variants.size_hint().1.unwrap() as u128; - - // Find the field with the largest niche - let (field_index, niche, (niche_start, niche_scalar)) = match variants - [largest_variant_index] - .iter() - .enumerate() - .filter_map(|(j, field)| Some((j, field.largest_niche?))) - .max_by_key(|(_, niche)| niche.available(dl)) - .and_then(|(j, niche)| Some((j, niche, niche.reserve(cx, count)?))) - { - None => return Ok(None), - Some(x) => x, - }; - - let niche_offset = niche.offset - + variant_layouts[largest_variant_index].fields.offset(field_index); - let niche_size = niche.value.size(dl); - let size = variant_layouts[largest_variant_index].size.align_to(align.abi); - - let all_variants_fit = - variant_layouts.iter_enumerated_mut().all(|(i, layout)| { - if i == largest_variant_index { - return true; - } - - layout.largest_niche = None; - - if layout.size <= niche_offset { - // This variant will fit before the niche. - return true; - } - - // Determine if it'll fit after the niche. - let this_align = layout.align.abi; - let this_offset = (niche_offset + niche_size).align_to(this_align); - - if this_offset + layout.size > size { - return false; - } - - // It'll fit, but we need to make some adjustments. - match layout.fields { - FieldsShape::Arbitrary { ref mut offsets, .. } => { - for (j, offset) in offsets.iter_mut().enumerate() { - if !variants[i][j].is_zst() { - *offset += this_offset; - } - } - } - _ => { - panic!("Layout of fields should be Arbitrary for variants") + let param_env = tcx.param_env(def.did()); + def.is_struct() + && match def.variants().iter().next().and_then(|x| x.fields.last()) { + Some(last_field) => { + tcx.type_of(last_field.did).is_sized(tcx, param_env) } + None => false, } - - // It can't be a Scalar or ScalarPair because the offset isn't 0. - if !layout.abi.is_uninhabited() { - layout.abi = Abi::Aggregate { sized: true }; - } - layout.size += this_offset; - - true - }); - - if !all_variants_fit { - return Ok(None); - } - - let largest_niche = Niche::from_scalar(dl, niche_offset, niche_scalar); - - let others_zst = variant_layouts - .iter_enumerated() - .all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO); - let same_size = size == variant_layouts[largest_variant_index].size; - let same_align = align == variant_layouts[largest_variant_index].align; - - let abi = if variant_layouts.iter().all(|v| v.abi.is_uninhabited()) { - Abi::Uninhabited - } else if same_size && same_align && others_zst { - match variant_layouts[largest_variant_index].abi { - // When the total alignment and size match, we can use the - // same ABI as the scalar variant with the reserved niche. - Abi::Scalar(_) => Abi::Scalar(niche_scalar), - Abi::ScalarPair(first, second) => { - // Only the niche is guaranteed to be initialised, - // so use union layouts for the other primitive. - if niche_offset == Size::ZERO { - Abi::ScalarPair(niche_scalar, second.to_union()) - } else { - Abi::ScalarPair(first.to_union(), niche_scalar) - } - } - _ => Abi::Aggregate { sized: true }, - } - } else { - Abi::Aggregate { sized: true } - }; - - let layout = LayoutS { - variants: Variants::Multiple { - tag: niche_scalar, - tag_encoding: TagEncoding::Niche { - untagged_variant: largest_variant_index, - niche_variants, - niche_start, - }, - tag_field: 0, - variants: IndexVec::new(), - }, - fields: FieldsShape::Arbitrary { - offsets: vec![niche_offset], - memory_index: vec![0], - }, - abi, - largest_niche, - size, - align, - }; - - Ok(Some(TmpLayout { layout, variants: variant_layouts })) - }; - - let niche_filling_layout = calculate_niche_filling_layout()?; - - let (mut min, mut max) = (i128::MAX, i128::MIN); - let discr_type = def.repr().discr_type(); - let bits = Integer::from_attr(cx, discr_type).size().bits(); - for (i, discr) in def.discriminants(tcx) { - if variants[i].iter().any(|f| f.abi.is_uninhabited()) { - continue; - } - let mut x = discr.val as i128; - if discr_type.is_signed() { - // sign extend the raw representation to be an i128 - x = (x << (128 - bits)) >> (128 - bits); - } - if x < min { - min = x; - } - if x > max { - max = x; - } - } - // We might have no inhabited variants, so pretend there's at least one. - if (min, max) == (i128::MAX, i128::MIN) { - min = 0; - max = 0; - } - assert!(min <= max, "discriminant range is {}...{}", min, max); - let (min_ity, signed) = Integer::repr_discr(tcx, ty, &def.repr(), min, max); - - let mut align = dl.aggregate_align; - let mut size = Size::ZERO; - - // We're interested in the smallest alignment, so start large. - let mut start_align = Align::from_bytes(256).unwrap(); - assert_eq!(Integer::for_align(dl, start_align), None); - - // repr(C) on an enum tells us to make a (tag, union) layout, - // so we need to grow the prefix alignment to be at least - // the alignment of the union. (This value is used both for - // determining the alignment of the overall enum, and the - // determining the alignment of the payload after the tag.) - let mut prefix_align = min_ity.align(dl).abi; - if def.repr().c() { - for fields in &variants { - for field in fields { - prefix_align = prefix_align.max(field.align.abi); - } - } - } - - // Create the set of structs that represent each variant. - let mut layout_variants = variants - .iter_enumerated() - .map(|(i, field_layouts)| { - let mut st = univariant_uninterned( - cx, - ty, - &field_layouts, - &def.repr(), - StructKind::Prefixed(min_ity.size(), prefix_align), - )?; - st.variants = Variants::Single { index: i }; - // Find the first field we can't move later - // to make room for a larger discriminant. - for field in st.fields.index_by_increasing_offset().map(|j| field_layouts[j]) { - if !field.is_zst() || field.align.abi.bytes() != 1 { - start_align = start_align.min(field.align.abi); - break; - } - } - size = cmp::max(size, st.size); - align = align.max(st.align); - Ok(st) - }) - .collect::, _>>()?; - - // Align the maximum variant size to the largest alignment. - size = size.align_to(align.abi); - - if size.bytes() >= dl.obj_size_bound() { - return Err(LayoutError::SizeOverflow(ty)); - } - - let typeck_ity = Integer::from_attr(dl, def.repr().discr_type()); - if typeck_ity < min_ity { - // It is a bug if Layout decided on a greater discriminant size than typeck for - // some reason at this point (based on values discriminant can take on). Mostly - // because this discriminant will be loaded, and then stored into variable of - // type calculated by typeck. Consider such case (a bug): typeck decided on - // byte-sized discriminant, but layout thinks we need a 16-bit to store all - // discriminant values. That would be a bug, because then, in codegen, in order - // to store this 16-bit discriminant into 8-bit sized temporary some of the - // space necessary to represent would have to be discarded (or layout is wrong - // on thinking it needs 16 bits) - bug!( - "layout decided on a larger discriminant type ({:?}) than typeck ({:?})", - min_ity, - typeck_ity - ); - // However, it is fine to make discr type however large (as an optimisation) - // after this point – we’ll just truncate the value we load in codegen. - } - - // Check to see if we should use a different type for the - // discriminant. We can safely use a type with the same size - // as the alignment of the first field of each variant. - // We increase the size of the discriminant to avoid LLVM copying - // padding when it doesn't need to. This normally causes unaligned - // load/stores and excessive memcpy/memset operations. By using a - // bigger integer size, LLVM can be sure about its contents and - // won't be so conservative. - - // Use the initial field alignment - let mut ity = if def.repr().c() || def.repr().int.is_some() { - min_ity - } else { - Integer::for_align(dl, start_align).unwrap_or(min_ity) - }; - - // If the alignment is not larger than the chosen discriminant size, - // don't use the alignment as the final size. - if ity <= min_ity { - ity = min_ity; - } else { - // Patch up the variants' first few fields. - let old_ity_size = min_ity.size(); - let new_ity_size = ity.size(); - for variant in &mut layout_variants { - match variant.fields { - FieldsShape::Arbitrary { ref mut offsets, .. } => { - for i in offsets { - if *i <= old_ity_size { - assert_eq!(*i, old_ity_size); - *i = new_ity_size; - } - } - // We might be making the struct larger. - if variant.size <= old_ity_size { - variant.size = new_ity_size; - } - } - _ => bug!(), - } - } - } - - let tag_mask = ity.size().unsigned_int_max(); - let tag = Scalar::Initialized { - value: Int(ity, signed), - valid_range: WrappingRange { - start: (min as u128 & tag_mask), - end: (max as u128 & tag_mask), - }, - }; - let mut abi = Abi::Aggregate { sized: true }; - - if layout_variants.iter().all(|v| v.abi.is_uninhabited()) { - abi = Abi::Uninhabited; - } else if tag.size(dl) == size { - // Make sure we only use scalar layout when the enum is entirely its - // own tag (i.e. it has no padding nor any non-ZST variant fields). - abi = Abi::Scalar(tag); - } else { - // Try to use a ScalarPair for all tagged enums. - let mut common_prim = None; - let mut common_prim_initialized_in_all_variants = true; - for (field_layouts, layout_variant) in iter::zip(&variants, &layout_variants) { - let FieldsShape::Arbitrary { ref offsets, .. } = layout_variant.fields else { - bug!(); - }; - let mut fields = iter::zip(field_layouts, offsets).filter(|p| !p.0.is_zst()); - let (field, offset) = match (fields.next(), fields.next()) { - (None, None) => { - common_prim_initialized_in_all_variants = false; - continue; - } - (Some(pair), None) => pair, - _ => { - common_prim = None; - break; - } - }; - let prim = match field.abi { - Abi::Scalar(scalar) => { - common_prim_initialized_in_all_variants &= - matches!(scalar, Scalar::Initialized { .. }); - scalar.primitive() - } - _ => { - common_prim = None; - break; - } - }; - if let Some(pair) = common_prim { - // This is pretty conservative. We could go fancier - // by conflating things like i32 and u32, or even - // realising that (u8, u8) could just cohabit with - // u16 or even u32. - if pair != (prim, offset) { - common_prim = None; - break; - } - } else { - common_prim = Some((prim, offset)); - } - } - if let Some((prim, offset)) = common_prim { - let prim_scalar = if common_prim_initialized_in_all_variants { - scalar_unit(prim) - } else { - // Common prim might be uninit. - Scalar::Union { value: prim } - }; - let pair = scalar_pair(cx, tag, prim_scalar); - let pair_offsets = match pair.fields { - FieldsShape::Arbitrary { ref offsets, ref memory_index } => { - assert_eq!(memory_index, &[0, 1]); - offsets - } - _ => bug!(), - }; - if pair_offsets[0] == Size::ZERO - && pair_offsets[1] == *offset - && align == pair.align - && size == pair.size - { - // We can use `ScalarPair` only when it matches our - // already computed layout (including `#[repr(C)]`). - abi = pair.abi; - } - } - } - - // If we pick a "clever" (by-value) ABI, we might have to adjust the ABI of the - // variants to ensure they are consistent. This is because a downcast is - // semantically a NOP, and thus should not affect layout. - if matches!(abi, Abi::Scalar(..) | Abi::ScalarPair(..)) { - for variant in &mut layout_variants { - // We only do this for variants with fields; the others are not accessed anyway. - // Also do not overwrite any already existing "clever" ABIs. - if variant.fields.count() > 0 && matches!(variant.abi, Abi::Aggregate { .. }) { - variant.abi = abi; - // Also need to bump up the size and alignment, so that the entire value fits in here. - variant.size = cmp::max(variant.size, size); - variant.align.abi = cmp::max(variant.align.abi, align.abi); - } - } - } - - let largest_niche = Niche::from_scalar(dl, Size::ZERO, tag); - - let tagged_layout = LayoutS { - variants: Variants::Multiple { - tag, - tag_encoding: TagEncoding::Direct, - tag_field: 0, - variants: IndexVec::new(), - }, - fields: FieldsShape::Arbitrary { offsets: vec![Size::ZERO], memory_index: vec![0] }, - largest_niche, - abi, - align, - size, - }; - - let tagged_layout = TmpLayout { layout: tagged_layout, variants: layout_variants }; - - let mut best_layout = match (tagged_layout, niche_filling_layout) { - (tl, Some(nl)) => { - // Pick the smaller layout; otherwise, - // pick the layout with the larger niche; otherwise, - // pick tagged as it has simpler codegen. - use Ordering::*; - let niche_size = |tmp_l: &TmpLayout| { - tmp_l.layout.largest_niche.map_or(0, |n| n.available(dl)) - }; - match ( - tl.layout.size.cmp(&nl.layout.size), - niche_size(&tl).cmp(&niche_size(&nl)), - ) { - (Greater, _) => nl, - (Equal, Less) => nl, - _ => tl, - } - } - (tl, None) => tl, - }; - - // Now we can intern the variant layouts and store them in the enum layout. - best_layout.layout.variants = match best_layout.layout.variants { - Variants::Multiple { tag, tag_encoding, tag_field, .. } => Variants::Multiple { - tag, - tag_encoding, - tag_field, - variants: best_layout.variants, - }, - _ => bug!(), - }; - - tcx.intern_layout(best_layout.layout) + }, + ) + .ok_or(LayoutError::SizeOverflow(ty))?, + ) } // Types with no meaningful known layout. diff --git a/src/tools/clippy/clippy_lints/src/casts/cast_possible_truncation.rs b/src/tools/clippy/clippy_lints/src/casts/cast_possible_truncation.rs index 88deb4565eb2..adbcfd3189b7 100644 --- a/src/tools/clippy/clippy_lints/src/casts/cast_possible_truncation.rs +++ b/src/tools/clippy/clippy_lints/src/casts/cast_possible_truncation.rs @@ -2,12 +2,11 @@ use clippy_utils::consts::{constant, Constant}; use clippy_utils::diagnostics::span_lint; use clippy_utils::expr_or_init; use clippy_utils::ty::{get_discriminant_value, is_isize_or_usize}; -use rustc_ast::ast; -use rustc_attr::IntType; use rustc_hir::def::{DefKind, Res}; use rustc_hir::{BinOpKind, Expr, ExprKind}; use rustc_lint::LateContext; use rustc_middle::ty::{self, FloatTy, Ty}; +use rustc_target::abi::IntegerType; use super::{utils, CAST_ENUM_TRUNCATION, CAST_POSSIBLE_TRUNCATION}; @@ -122,7 +121,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, let cast_from_ptr_size = def.repr().int.map_or(true, |ty| { matches!( ty, - IntType::SignedInt(ast::IntTy::Isize) | IntType::UnsignedInt(ast::UintTy::Usize) + IntegerType::Pointer(_), ) }); let suffix = match (cast_from_ptr_size, is_isize_or_usize(cast_to)) { diff --git a/src/tools/clippy/clippy_lints/src/lib.rs b/src/tools/clippy/clippy_lints/src/lib.rs index b481314abedc..601990cd6a31 100644 --- a/src/tools/clippy/clippy_lints/src/lib.rs +++ b/src/tools/clippy/clippy_lints/src/lib.rs @@ -26,7 +26,6 @@ extern crate rustc_arena; extern crate rustc_ast; extern crate rustc_ast_pretty; -extern crate rustc_attr; extern crate rustc_data_structures; extern crate rustc_driver; extern crate rustc_errors;