compiler/rustc_metadata/src/rmeta/mod.rs

   1 use decoder::Metadata;
   2 use table::{Table, TableBuilder};
   3
   4 use rustc_ast::{self as ast, MacroDef};
   5 use rustc_attr as attr;
   6 use rustc_data_structures::svh::Svh;
   7 use rustc_data_structures::sync::MetadataRef;
   8 use rustc_hir as hir;
   9 use rustc_hir::def::CtorKind;
  10 use rustc_hir::def_id::{DefId, DefIndex, DefPathHash};
  11 use rustc_hir::definitions::DefKey;
  12 use rustc_hir::lang_items;
  13 use rustc_index::{bit_set::FiniteBitSet, vec::IndexVec};
  14 use rustc_middle::hir::exports::Export;
  15 use rustc_middle::middle::cstore::{CrateDepKind, ForeignModule, LinkagePreference, NativeLib};
  16 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportLevel};
  17 use rustc_middle::mir;
  18 use rustc_middle::ty::{self, ReprOptions, Ty};
  19 use rustc_serialize::opaque::Encoder;
  20 use rustc_session::config::SymbolManglingVersion;
  21 use rustc_session::CrateDisambiguator;
  22 use rustc_span::edition::Edition;
  23 use rustc_span::symbol::{Ident, Symbol};
  24 use rustc_span::{self, ExpnData, ExpnId, Span};
  25 use rustc_target::spec::{PanicStrategy, TargetTriple};
  26
  27 use std::marker::PhantomData;
  28 use std::num::NonZeroUsize;
  29
  30 use decoder::DecodeContext;
  31 pub use decoder::{provide, provide_extern};
  32 crate use decoder::{CrateMetadata, CrateNumMap, MetadataBlob};
  33 use encoder::EncodeContext;
  34 use rustc_span::hygiene::SyntaxContextData;
  35
  36 mod decoder;
  37 mod encoder;
  38 mod table;
  39
  40 crate fn rustc_version() -> String {
  41     format!("rustc {}", option_env!("CFG_VERSION").unwrap_or("unknown version"))
  42 }
  43
  44 /// Metadata encoding version.
  45 /// N.B., increment this if you change the format of metadata such that
  46 /// the rustc version can't be found to compare with `rustc_version()`.
  47 const METADATA_VERSION: u8 = 5;
  48
  49 /// Metadata header which includes `METADATA_VERSION`.
  50 ///
  51 /// This header is followed by the position of the `CrateRoot`,
  52 /// which is encoded as a 32-bit big-endian unsigned integer,
  53 /// and further followed by the rustc version string.
  54 crate const METADATA_HEADER: &[u8; 8] = &[b'r', b'u', b's', b't', 0, 0, 0, METADATA_VERSION];
  55
  56 /// Additional metadata for a `Lazy<T>` where `T` may not be `Sized`,
  57 /// e.g. for `Lazy<[T]>`, this is the length (count of `T` values).
  58 trait LazyMeta {
  59     type Meta: Copy + 'static;
  60
  61     /// Returns the minimum encoded size.
  62     // FIXME(eddyb) Give better estimates for certain types.
  63     fn min_size(meta: Self::Meta) -> usize;
  64 }
  65
  66 impl<T> LazyMeta for T {
  67     type Meta = ();
  68
  69     fn min_size(_: ()) -> usize {
  70         assert_ne!(std::mem::size_of::<T>(), 0);
  71         1
  72     }
  73 }
  74
  75 impl<T> LazyMeta for [T] {
  76     type Meta = usize;
  77
  78     fn min_size(len: usize) -> usize {
  79         len * T::min_size(())
  80     }
  81 }
  82
  83 /// A value of type T referred to by its absolute position
  84 /// in the metadata, and which can be decoded lazily.
  85 ///
  86 /// Metadata is effective a tree, encoded in post-order,
  87 /// and with the root's position written next to the header.
  88 /// That means every single `Lazy` points to some previous
  89 /// location in the metadata and is part of a larger node.
  90 ///
  91 /// The first `Lazy` in a node is encoded as the backwards
  92 /// distance from the position where the containing node
  93 /// starts and where the `Lazy` points to, while the rest
  94 /// use the forward distance from the previous `Lazy`.
  95 /// Distances start at 1, as 0-byte nodes are invalid.
  96 /// Also invalid are nodes being referred in a different
  97 /// order than they were encoded in.
  98 ///
  99 /// # Sequences (`Lazy<[T]>`)
 100 ///
 101 /// Unlike `Lazy<Vec<T>>`, the length is encoded next to the
 102 /// position, not at the position, which means that the length
 103 /// doesn't need to be known before encoding all the elements.
 104 ///
 105 /// If the length is 0, no position is encoded, but otherwise,
 106 /// the encoding is that of `Lazy`, with the distinction that
 107 /// the minimal distance the length of the sequence, i.e.
 108 /// it's assumed there's no 0-byte element in the sequence.
 109 #[must_use]
 110 // FIXME(#59875) the `Meta` parameter only exists to dodge
 111 // invariance wrt `T` (coming from the `meta: T::Meta` field).
 112 struct Lazy<T, Meta = <T as LazyMeta>::Meta>
 113 where
 114     T: ?Sized + LazyMeta<Meta = Meta>,
 115     Meta: 'static + Copy,
 116 {
 117     position: NonZeroUsize,
 118     meta: Meta,
 119     _marker: PhantomData<T>,
 120 }
 121
 122 impl<T: ?Sized + LazyMeta> Lazy<T> {
 123     fn from_position_and_meta(position: NonZeroUsize, meta: T::Meta) -> Lazy<T> {
 124         Lazy { position, meta, _marker: PhantomData }
 125     }
 126 }
 127
 128 impl<T> Lazy<T> {
 129     fn from_position(position: NonZeroUsize) -> Lazy<T> {
 130         Lazy::from_position_and_meta(position, ())
 131     }
 132 }
 133
 134 impl<T> Lazy<[T]> {
 135     fn empty() -> Lazy<[T]> {
 136         Lazy::from_position_and_meta(NonZeroUsize::new(1).unwrap(), 0)
 137     }
 138 }
 139
 140 impl<T: ?Sized + LazyMeta> Copy for Lazy<T> {}
 141 impl<T: ?Sized + LazyMeta> Clone for Lazy<T> {
 142     fn clone(&self) -> Self {
 143         *self
 144     }
 145 }
 146
 147 /// Encoding / decoding state for `Lazy`.
 148 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 149 enum LazyState {
 150     /// Outside of a metadata node.
 151     NoNode,
 152
 153     /// Inside a metadata node, and before any `Lazy`.
 154     /// The position is that of the node itself.
 155     NodeStart(NonZeroUsize),
 156
 157     /// Inside a metadata node, with a previous `Lazy`.
 158     /// The position is a conservative estimate of where that
 159     /// previous `Lazy` would end (see their comments).
 160     Previous(NonZeroUsize),
 161 }
 162
 163 // FIXME(#59875) `Lazy!(T)` replaces `Lazy<T>`, passing the `Meta` parameter
 164 // manually, instead of relying on the default, to get the correct variance.
 165 // Only needed when `T` itself contains a parameter (e.g. `'tcx`).
 166 macro_rules! Lazy {
 167     (Table<$I:ty, $T:ty>) => {Lazy<Table<$I, $T>, usize>};
 168     ([$T:ty]) => {Lazy<[$T], usize>};
 169     ($T:ty) => {Lazy<$T, ()>};
 170 }
 171
 172 type SyntaxContextTable = Lazy<Table<u32, Lazy<SyntaxContextData>>>;
 173 type ExpnDataTable = Lazy<Table<u32, Lazy<ExpnData>>>;
 174
 175 #[derive(MetadataEncodable, MetadataDecodable)]
 176 crate struct ProcMacroData {
 177     proc_macro_decls_static: DefIndex,
 178     stability: Option<attr::Stability>,
 179     macros: Lazy<[DefIndex]>,
 180 }
 181
 182 /// Serialized metadata for a crate.
 183 /// When compiling a proc-macro crate, we encode many of
 184 /// the `Lazy<[T]>` fields as `Lazy::empty()`. This serves two purposes:
 185 ///
 186 /// 1. We avoid performing unnecessary work. Proc-macro crates can only
 187 /// export proc-macros functions, which are compiled into a shared library.
 188 /// As a result, a large amount of the information we normally store
 189 /// (e.g. optimized MIR) is unneeded by downstream crates.
 190 /// 2. We avoid serializing invalid `CrateNum`s. When we deserialize
 191 /// a proc-macro crate, we don't load any of its dependencies (since we
 192 /// just need to invoke a native function from the shared library).
 193 /// This means that any foreign `CrateNum`s that we serialize cannot be
 194 /// deserialized, since we will not know how to map them into the current
 195 /// compilation session. If we were to serialize a proc-macro crate like
 196 /// a normal crate, much of what we serialized would be unusable in addition
 197 /// to being unused.
 198 #[derive(MetadataEncodable, MetadataDecodable)]
 199 crate struct CrateRoot<'tcx> {
 200     name: Symbol,
 201     triple: TargetTriple,
 202     extra_filename: String,
 203     hash: Svh,
 204     disambiguator: CrateDisambiguator,
 205     panic_strategy: PanicStrategy,
 206     edition: Edition,
 207     has_global_allocator: bool,
 208     has_panic_handler: bool,
 209     has_default_lib_allocator: bool,
 210     plugin_registrar_fn: Option<DefIndex>,
 211
 212     crate_deps: Lazy<[CrateDep]>,
 213     dylib_dependency_formats: Lazy<[Option<LinkagePreference>]>,
 214     lib_features: Lazy<[(Symbol, Option<Symbol>)]>,
 215     lang_items: Lazy<[(DefIndex, usize)]>,
 216     lang_items_missing: Lazy<[lang_items::LangItem]>,
 217     diagnostic_items: Lazy<[(Symbol, DefIndex)]>,
 218     native_libraries: Lazy<[NativeLib]>,
 219     foreign_modules: Lazy<[ForeignModule]>,
 220     impls: Lazy<[TraitImpls]>,
 221     interpret_alloc_index: Lazy<[u32]>,
 222     proc_macro_data: Option<ProcMacroData>,
 223
 224     tables: LazyTables<'tcx>,
 225
 226     exported_symbols: Lazy!([(ExportedSymbol<'tcx>, SymbolExportLevel)]),
 227
 228     syntax_contexts: SyntaxContextTable,
 229     expn_data: ExpnDataTable,
 230
 231     source_map: Lazy<[rustc_span::SourceFile]>,
 232
 233     compiler_builtins: bool,
 234     needs_allocator: bool,
 235     needs_panic_runtime: bool,
 236     no_builtins: bool,
 237     panic_runtime: bool,
 238     profiler_runtime: bool,
 239     symbol_mangling_version: SymbolManglingVersion,
 240 }
 241
 242 #[derive(Encodable, Decodable)]
 243 crate struct CrateDep {
 244     pub name: Symbol,
 245     pub hash: Svh,
 246     pub host_hash: Option<Svh>,
 247     pub kind: CrateDepKind,
 248     pub extra_filename: String,
 249 }
 250
 251 #[derive(MetadataEncodable, MetadataDecodable)]
 252 crate struct TraitImpls {
 253     trait_id: (u32, DefIndex),
 254     impls: Lazy<[(DefIndex, Option<ty::fast_reject::SimplifiedType>)]>,
 255 }
 256
 257 /// Define `LazyTables` and `TableBuilders` at the same time.
 258 macro_rules! define_tables {
 259     ($($name:ident: Table<DefIndex, $T:ty>),+ $(,)?) => {
 260         #[derive(MetadataEncodable, MetadataDecodable)]
 261         crate struct LazyTables<'tcx> {
 262             $($name: Lazy!(Table<DefIndex, $T>)),+
 263         }
 264
 265         #[derive(Default)]
 266         struct TableBuilders<'tcx> {
 267             $($name: TableBuilder<DefIndex, $T>),+
 268         }
 269
 270         impl TableBuilders<'tcx> {
 271             fn encode(&self, buf: &mut Encoder) -> LazyTables<'tcx> {
 272                 LazyTables {
 273                     $($name: self.$name.encode(buf)),+
 274                 }
 275             }
 276         }
 277     }
 278 }
 279
 280 define_tables! {
 281     kind: Table<DefIndex, Lazy<EntryKind>>,
 282     visibility: Table<DefIndex, Lazy<ty::Visibility>>,
 283     span: Table<DefIndex, Lazy<Span>>,
 284     ident_span: Table<DefIndex, Lazy<Span>>,
 285     attributes: Table<DefIndex, Lazy<[ast::Attribute]>>,
 286     children: Table<DefIndex, Lazy<[DefIndex]>>,
 287     stability: Table<DefIndex, Lazy<attr::Stability>>,
 288     const_stability: Table<DefIndex, Lazy<attr::ConstStability>>,
 289     deprecation: Table<DefIndex, Lazy<attr::Deprecation>>,
 290     ty: Table<DefIndex, Lazy!(Ty<'tcx>)>,
 291     fn_sig: Table<DefIndex, Lazy!(ty::PolyFnSig<'tcx>)>,
 292     impl_trait_ref: Table<DefIndex, Lazy!(ty::TraitRef<'tcx>)>,
 293     inherent_impls: Table<DefIndex, Lazy<[DefIndex]>>,
 294     variances: Table<DefIndex, Lazy<[ty::Variance]>>,
 295     generics: Table<DefIndex, Lazy<ty::Generics>>,
 296     explicit_predicates: Table<DefIndex, Lazy!(ty::GenericPredicates<'tcx>)>,
 297     // FIXME(eddyb) this would ideally be `Lazy<[...]>` but `ty::Predicate`
 298     // doesn't handle shorthands in its own (de)serialization impls,
 299     // as it's an `enum` for which we want to derive (de)serialization,
 300     // so the `ty::codec` APIs handle the whole `&'tcx [...]` at once.
 301     // Also, as an optimization, a missing entry indicates an empty `&[]`.
 302     inferred_outlives: Table<DefIndex, Lazy!(&'tcx [(ty::Predicate<'tcx>, Span)])>,
 303     super_predicates: Table<DefIndex, Lazy!(ty::GenericPredicates<'tcx>)>,
 304     mir: Table<DefIndex, Lazy!(mir::Body<'tcx>)>,
 305     promoted_mir: Table<DefIndex, Lazy!(IndexVec<mir::Promoted, mir::Body<'tcx>>)>,
 306     mir_abstract_consts: Table<DefIndex, Lazy!(&'tcx [mir::abstract_const::Node<'tcx>])>,
 307     unused_generic_params: Table<DefIndex, Lazy<FiniteBitSet<u32>>>,
 308     // `def_keys` and `def_path_hashes` represent a lazy version of a
 309     // `DefPathTable`. This allows us to avoid deserializing an entire
 310     // `DefPathTable` up front, since we may only ever use a few
 311     // definitions from any given crate.
 312     def_keys: Table<DefIndex, Lazy<DefKey>>,
 313     def_path_hashes: Table<DefIndex, Lazy<DefPathHash>>
 314 }
 315
 316 #[derive(Copy, Clone, MetadataEncodable, MetadataDecodable)]
 317 enum EntryKind {
 318     AnonConst(mir::ConstQualifs, Lazy<RenderedConst>),
 319     Const(mir::ConstQualifs, Lazy<RenderedConst>),
 320     ImmStatic,
 321     MutStatic,
 322     ForeignImmStatic,
 323     ForeignMutStatic,
 324     ForeignMod,
 325     ForeignType,
 326     GlobalAsm,
 327     Type,
 328     TypeParam,
 329     ConstParam,
 330     OpaqueTy,
 331     Enum(ReprOptions),
 332     Field,
 333     Variant(Lazy<VariantData>),
 334     Struct(Lazy<VariantData>, ReprOptions),
 335     Union(Lazy<VariantData>, ReprOptions),
 336     Fn(Lazy<FnData>),
 337     ForeignFn(Lazy<FnData>),
 338     Mod(Lazy<ModData>),
 339     MacroDef(Lazy<MacroDef>),
 340     Closure,
 341     Generator(hir::GeneratorKind),
 342     Trait(Lazy<TraitData>),
 343     Impl(Lazy<ImplData>),
 344     AssocFn(Lazy<AssocFnData>),
 345     AssocType(AssocContainer),
 346     AssocConst(AssocContainer, mir::ConstQualifs, Lazy<RenderedConst>),
 347     TraitAlias,
 348 }
 349
 350 /// Contains a constant which has been rendered to a String.
 351 /// Used by rustdoc.
 352 #[derive(Encodable, Decodable)]
 353 struct RenderedConst(String);
 354
 355 #[derive(MetadataEncodable, MetadataDecodable)]
 356 struct ModData {
 357     reexports: Lazy<[Export<hir::HirId>]>,
 358     expansion: ExpnId,
 359 }
 360
 361 #[derive(MetadataEncodable, MetadataDecodable)]
 362 struct FnData {
 363     asyncness: hir::IsAsync,
 364     constness: hir::Constness,
 365     param_names: Lazy<[Ident]>,
 366 }
 367
 368 #[derive(TyEncodable, TyDecodable)]
 369 struct VariantData {
 370     ctor_kind: CtorKind,
 371     discr: ty::VariantDiscr,
 372     /// If this is unit or tuple-variant/struct, then this is the index of the ctor id.
 373     ctor: Option<DefIndex>,
 374     is_non_exhaustive: bool,
 375 }
 376
 377 #[derive(TyEncodable, TyDecodable)]
 378 struct TraitData {
 379     unsafety: hir::Unsafety,
 380     paren_sugar: bool,
 381     has_auto_impl: bool,
 382     is_marker: bool,
 383     specialization_kind: ty::trait_def::TraitSpecializationKind,
 384 }
 385
 386 #[derive(TyEncodable, TyDecodable)]
 387 struct ImplData {
 388     polarity: ty::ImplPolarity,
 389     defaultness: hir::Defaultness,
 390     parent_impl: Option<DefId>,
 391
 392     /// This is `Some` only for impls of `CoerceUnsized`.
 393     // FIXME(eddyb) perhaps compute this on the fly if cheap enough?
 394     coerce_unsized_info: Option<ty::adjustment::CoerceUnsizedInfo>,
 395 }
 396
 397 /// Describes whether the container of an associated item
 398 /// is a trait or an impl and whether, in a trait, it has
 399 /// a default, or an in impl, whether it's marked "default".
 400 #[derive(Copy, Clone, TyEncodable, TyDecodable)]
 401 enum AssocContainer {
 402     TraitRequired,
 403     TraitWithDefault,
 404     ImplDefault,
 405     ImplFinal,
 406 }
 407
 408 impl AssocContainer {
 409     fn with_def_id(&self, def_id: DefId) -> ty::AssocItemContainer {
 410         match *self {
 411             AssocContainer::TraitRequired | AssocContainer::TraitWithDefault => {
 412                 ty::TraitContainer(def_id)
 413             }
 414
 415             AssocContainer::ImplDefault | AssocContainer::ImplFinal => ty::ImplContainer(def_id),
 416         }
 417     }
 418
 419     fn defaultness(&self) -> hir::Defaultness {
 420         match *self {
 421             AssocContainer::TraitRequired => hir::Defaultness::Default { has_value: false },
 422
 423             AssocContainer::TraitWithDefault | AssocContainer::ImplDefault => {
 424                 hir::Defaultness::Default { has_value: true }
 425             }
 426
 427             AssocContainer::ImplFinal => hir::Defaultness::Final,
 428         }
 429     }
 430 }
 431
 432 #[derive(MetadataEncodable, MetadataDecodable)]
 433 struct AssocFnData {
 434     fn_data: FnData,
 435     container: AssocContainer,
 436     has_self: bool,
 437 }
 438
 439 #[derive(TyEncodable, TyDecodable)]
 440 struct GeneratorData<'tcx> {
 441     layout: mir::GeneratorLayout<'tcx>,
 442 }
 443
 444 // Tags used for encoding Spans:
 445 const TAG_VALID_SPAN_LOCAL: u8 = 0;
 446 const TAG_VALID_SPAN_FOREIGN: u8 = 1;
 447 const TAG_INVALID_SPAN: u8 = 2;